langzi's Journal

Authors: Maya Rink, Taylor Byrd, Sarah-Rose Nicolson, and Jayden Kaptein
Survey Dates: July 31-August 1, 2024
Location: Pa’ea Lagoon, Tahiti Nui, French Polynesia

Algae Research of Pā’ea Fish Pond - French Polynesia Summer 2024

Authors: Maya Rink, Sarah Nicolson, Jadyn Kaptein, Taylor Byrd

Survey Dates: July 31 - August 1

Locations: Pa’ea Lagoon, Tahiti Nui, French Polynesia

INTRODUCTION

This survey studied the types of algae species inside of and on the rock walls of the Paea Lagoon Auai’a fish pond in Pā’ea, Tahiti, French Polynesia on August 1st, 2024. This type of fish pond was historically used by Polynesians to collect fish to eat within its walls (a rock barrier), however, the practice fell out after French colonization and large-scale fishing became more widespread.

The Paea Lagoon Auai’a fish pond is one of the original historical fish ponds, however it underwent restoration four years ago, and is now only used for scientific observation, not for harvesting fish.

The team has been hired by a private client to identify all of the types of algae observed in the fish pond and on all sides of the rock barrier. The barrier is a structure of large uneven rocks. Currently, the client knows there is some algae present in the fish pond, especially along the walls, but is uncertain of the species richness and percent cover of algae present.

This research is building upon previous Wildland Studies programs’ projects from August 2023 and May 2024 who also surveyed algae presence within the pond. This comparison will answer the given research question: how has the richness and percent cover of algae in the Paea Lagoon Auai’a fish pond changed over time since Summer 2023. The team will use the previously collected data to develop a trend analysis to address this question.

The research will differ from previous surveys as it will emphasize the development of a complete species list of algae present in the fish pond, where previous surveys have grouped their data by agal families.

Furthermore, the surveyors collaborated with another research team that is analyzing the substrate present in the same fish pond. Our teams will compare algae relationships with substrate cover.

METHODS

Fish Pond Survey
The team began by taking a preliminary survey of the area. Two swimmers measured the fish pond and scanned the area to gauge an understanding of the quantity and general types of algae that would be studied.

The 15.25m*15.25m fish pond was then divided into five transects. Three transects were used to study the fish pond’s rock barrier walls (Transect 1, 4, and 5). The other two were dedicated to the inner pond (Transect 2 and 3). Each cross-shore transect was spaced 5.1m apart. The transects were then split into five survey points which occurred every three meters. The quadrat method was utilized to conduct the survey. Starting at 0m, a 50*50cm quadrat was placed with its top right corner (when facing the ocean) on the survey point, with the first quadrat measuring the first 50cm of sand following the shore.

The same transect lines as the substrate research group type were used to obtain complementary data.

The method for the rock barrier and surrounding area was slightly altered to obtain more representative data of the algae cover. Two quadrats were used at each specified marker on the transect. One quadrat was used from the center of the rock barrier to the left side, and the other quadrat was used from the center of the rock barrier to the right side. The quadrat’s length was extended an extra 25 cm (making the total length 75 cm) to include the area surrounding the wall.

Start: 8/1/2024, 12:15pm, beaufort 2, 23°C, partly cloudy 30%, wind blowing from SE.
End: 8/1/2024 4:00pm, beaufort 4, 22°C, partly cloudy 40%, wind blowing from SE.

The four person team assigned two people to hold the transects and the other two to be swimmers, collecting the data using quadrats. The first observation of each species of algae was sampled and stored in a numbered plastic bag to be studied and identified after the survey. Ten bags of samples were collected, some of which were revealed to contain repeat species.

Beach Survey
From 2:50pm to 3:00pm, the team completed a terrestrial survey, sampling the 15.5m of beach adjacent to the fish pond to study the species richness of washed up algae. This survey was done opportunistically with all four team members collecting as many unique species of algae as possible.

Following the surveys, the team separated the samples to identify each species. A microscope was utilized to closely observe smaller species of algae. Identification was completed through the use of an algae identification book: Algae of French Polynesia (Payri et al., 2000).

RESULTS

see Figure 2. Species Index: https://docs.google.com/document/d/e/2PACX-1vT4dP08Q0ozwChf3HqfIb2_oDwA5l-xTakvLPqUiBLrflnHBzW9SEa3cL-wt3aEOrXBTR68FB-MOjuX/pub

see Data Set: https://docs.google.com/spreadsheets/d/1lgfq4BT0JQU3NYPJq31JUx_b4gDFCwIZgzQo0q153DM/edit?gid=0#gid=0

see Figure 4. Percent Coverage Comparison of Algal Species: https://docs.google.com/document/d/e/2PACX-1vT4dP08Q0ozwChf3HqfIb2_oDwA5l-xTakvLPqUiBLrflnHBzW9SEa3cL-wt3aEOrXBTR68FB-MOjuX/pub

INTERPRETATIONS

When examining the collected data from various transects, several key trends and observations emerged:

1. Species Distribution and Dominance:
   The accumulation of the data collected found 15 different species in total ranging between family rhodophyta, chlorophyta, and paethaedae. The survey found the dominant algal species in the fish pond to be Microdictyon umbilicatum, a type of microalgae or turf, representing 68.6% of all algal species.

When comparing algal presence across all transects, there is a clear increase in abundance along the walls as compared to the inner pond, represented by transect two and three. Here, the substrate consists of artificial rock. Turf algae, specifically Microdictyon umbilicatum, was the most prevalent species on these rocks. This suggests a positive correlation between the artificial rock substrate and the abundance of turf algae, indicating that substrate type significantly influences algae distribution.

When comparing algal presence on the inner and outer sides of the walls, percent cover is consistently higher on the inner sides of the wall. This could be alluded to several potential reasons including possible increased herbivory by adult fish on the outside of the pond or rougher condition on the outer walls preventing algae from growing. More research should be done to make a conclusion.

Algae coverage was compared with another research group focusing on substrate type using two of the same transects, 2 and 3. Both teams also collected data from the area surrounding the pond’s walls (transect 1, 4, and 5). The quadrats within the fish pond that exhibited the highest algae coverage primarily contained white fine sand and black fine sand.

Conversely, the data collected by the substrate group indicated that the primary substrate on the walls, where algae coverage was the most abundant, consisted of artificial rock, with some white and black fine sand present.

1. Comparison with Historical Data

In previous years, data was collected on the general algae coverage in the fish pond quadrats. During the Summer 2023 assessment, the algae coverage was found to be 28% with a standard deviation of 0.2614, with seven genuses observed. In Spring 2024, the average algae coverage dropped to 23.87% mean coverage with a standard deviation of 0.12572084, with five species observed. These previous studies examined quadrants both on the walls of the fish pond and within the pond itself. Our data from this year revealed a 27% algae coverage in the fish pond our standard deviation was 0.1144220727.

Our Summer 2024 findings identified a greater variety of algae types which originally totalled seven genuses. We identified 15 algae species, with 13 total genus, indicating potential yearly variations in algae diversity. However, more data should be collected over an extended period of time to make this conclusion.

DISCUSSION

Potential for Error
During the team's trials, several errors were encountered. Two transects broke, affecting the overall trial duration due to the additional time needed to replace them. Strong currents impacted the linearity of the transect lines.

Human error, including misidentification is also possible to have occurred. Additionally, issues with gear, such as leaking snorkels and masks, should be noted, potentially affecting species observation. It's important to highlight, also, that the identification book, Algae of French Polynesia, was published in 2000, meaning there could have been revisions to the taxonomy of the algae since its release.

In addition, some of the algae collected required a microscope for identification. It was not possible to use a microscope for every site in the field, so microalgae and germlings of macroalgae could have possibly been looked over.

For future studies, the team recommends using high-quality transects and gear capable of withstanding unexpected weather, given the cold and windy conditions encountered during the trials. Additionally, conducting more trials would make the data even more accurate.

Authors: Maria Miller, Alex Lombardi, Diya Sterling
Survey Dates: July 31 - August 1
Location: Pa'ea Lagoon, Tahiti Nui, French Polynesia

Introduction

Wildlands Studies research teams have surveyed the Pā’ea Lagoon Aua i’a over Winter and Spring seasons for the past year to document substrate variety and abundance. Throughout this time, changes in substrate have been observed, and have been used as a basis for future observations. Continuing this research we intend to focus specifically on mineral content to thoroughly represent the mineral cover within the fish pond.

As Tahiti enters the winter season, new data is significant in determining if there is a correlation between dominant substrate groups and their location within the fish pond, as opposed to other seasons and data collections. As our methods and focus vary from past surveys, we will only be comparing their inside substrate data, and not focusing on specific species of algae, but instead categorizing algae as a substrate type.
Our client is most interested in understanding the collection of sand around the North and South walls, and a general mapping of where different substrates are located within the fish pond. In order to develop a hypothesis as to why the collection of sand is allocated, it is necessary to first get a strong understanding of where these collections of sand are located along the walls. For the purpose of this survey, we will be using the term channel to describe the openings in the north and south rock walls that are likely developed from erosion. We hypothesize that these channels in the rocks are resulting in the deposition of sand along the walls. Overall, our study aims to determine mineral substrate cover of the fish pond, with a focus on sediment deposition along the North and South walls.

Methods

The materials used include a transect that reached 20 meters, snorkel gear with fins, neoprene socks, an underwater slate, one 50 centimeter by 50 centimeter quadrant, a camera, and 24 plastic cups labeled by quadrant points. Before the survey commenced, a preliminary survey was conducted to get a general idea of the surface area and to determine the best way to separate transects.
We began our survey by allocating roles between three group members. Two members held the transect, one on each end, and one member swam along the transect surveying the substrate cover within a 50 centimeter by 50 centimeter quadrant. We measured the dimensions of the fishpond and found it to be a 15.25 meter by 15.25 meter area. With this, cross-shore transects were separated by 5 meters from the inside part of both the North and South walls, creating two transects inside of the pond. Three more transect areas were placed at the center of the perimeter wall of the pond. Two of these were cross-shore along the North and South walls. The West wall had a longshore transect to close off our sampling universe within the fishpond.
At each transect, a quadrant was placed every 3 meters five times, starting at 0 meters, with the top left of the quadrant placed on each point on the left side of the transect. For the two transects inside the pond, we only surveyed the left side of the transect. For the transects lining the perimeter, we surveyed both the left and right side of the transects to gain insight on the immediate outside of the pond to fulfill our client’s interest. At each site, sand portions were lightly dusted through to uncover the possibility of different sized sand particles under the first layer.
For the transects inside the pond, once the left side was surveyed at all five points, the swimmer went back to shore to immediately take a picture of the data gathered and switch out the slate and quadrant for 5 plastic cups labeled for each survey point. Once again moving every 3 meters starting at 0 meters, the swimmer scooped the top layer of sand at each of the five points. For the perimeter transects, this was only done on the inner wall at each of the five points. Once we completed the entire survey, two swimmers were designated to get 2 samples of the top layer of sand right outside of the North and South walls of the fishpond where the large piles of white sand were found in order to more deeply analyze the sediment per request of our client.
For data analysis, we used a Google Sheet to create a table for each of the transects and substrate types which included fine white sand, fine black sand, coarse white sand, coarse black sand, rubble, rock, artificial stone, algae, live coral, and dead coral. We differentiated fine and coarse sand by individual particle size, provided by the spring research group. The spring research group concluded that fine sand was particles less than 1 mm, while coarse sand was particles over 1 mm on average. We had overlapping substrate cover, so each area summed up to a percentage over 100%. From this, we were able to make pie charts for each of the transects which used ratios for each of our percentages so that they could be a total of 100%. We then created a second table that took the average coverage of all the substrate types overall transects and found the standard deviations for each group. A pie chart was formed out of this table as well. Once this data was analyzed, a map was formulated showing each of the dominant substrate types in each quadrant area to encapsulate the variation across the fishpond floor for our client.

Results
Figures and Data: https://docs.google.com/spreadsheets/d/1aaYnemKM8PBG3YQlgV00L5wFx-vuUwom1tuDsJfMhdA/edit

Discussion

An overall average of 18.4% of fine black sand and 17.5% white fine sand cover dominated the sampling universe. Fine and coarse grain (white/black) sand was the main type of substrate cover throughout the fish pond. Our client was specifically interested in the piles of fine-grain white sand accumulating on both North and South walls. It was unclear as to how these piles occur, postulating whether it was current direction, biological erosion, or holes in the fish pond wall causing sand to pile up in these two areas. Upon further observations, our team discovered that these substrate piles consisted of a sediment deposition of fine black sand on the outer south wall, with fine white sand on the inner south wall. Fine white sand dominated the outer north wall, and fine black sand dominated the inner north wall. These findings may suggest that waves are being refracted as they travel through the North and South walls, accumulating fine black sand on the South sides of the walls and depositing fine white sand on the opposite side.
Though we had different methods for surveying and conducting calculations, we were still able to compare our data with the Spring data through the dominant substrate found inside the fishpond and directly outside. In the Spring, it was found that coarse sand was the dominant substrate inside of the pond and fine sand was dominant outside of the pond. For our current data conducted this Winter, the dominant substrate found both inside the pond and directly outside the North and South walls was fine white sand. This differs between the seasons. Despite the Spring group not including their survey conditions, we can infer that winds are stronger during the Winter in Tahiti, likely increasing the level of erosion and sifting sand substrate in the channel regions of the fishpond. Colder temperatures may also increase nutrients in the water attracting more bioeroders and increasing algae composition. Halimeda algae also disintegrates fairly quickly and adds to the fine white sand substrate content, as mentioned by our client. We suggest that future research projects should collaborate with another team observing Bathymetry to get a deeper understanding as to why the sediment depostion and wave current sieves out the white and black sand this particular way in the channel. Something to note is the wave direction was traveling from the South, with some wave interference from strong winds possibly impacting these filtrations.

Areas for Improvement/Suggestions to Future Groups:

For this survey, we separated algae substrate from mineral substrate to ensure a further in-depth analysis of each substrate cover as suggested by past groups. This worked very well for us, so we suggest continuing this in future surveys. We also adjusted the methods by using systematic sampling along transects instead of random coordinates to gain a more accurate area cover and standardization.
We did have areas for improvement. Once we analyzed our data, we realized some points in the fishpond weren’t accounted for, so we recommend allocating transects in a way that reaches all corners of the fishpond. For example, the entrance to the fishpond was missed in our data and could be significant when looking at the channel on the sides of the pond. For samples taken, it is important to ensure saving them for future further analysis done by the client. Also, ensure a scale is included for comparison in any photos taken of the sand samples for a better visual of the differing sand sizes and context. During the survey, we faced some opportunities for human error. When we entered the water, the Beaufort scale reached a 2. While in the water, we found the Beaufort scale changed to a 4 and stayed this way until we exited the water. In combination with the Southern winds, this created difficulties as the transect moved with the strong current and the quadrant placed had to be held firmly to keep it from drifting. There is also the likely occurrence of bias due to having only one person surveying the substrate cover and only having the ability to use human vision which is limited. For the future, we recommend having multiple swimmers surveying the quadrants to ensure a lower likeliness of bias. We were unable to do this due to time constraints and limited participants.

Conclusion

Our studies show the collections of sand around the North and South walls were a result of sediment deposition from filtration through the fish pond walls. We designed a general map of substrate cover in the fish pond to visually display the variation of substrate cover, as well as the location of the sand piles in the channel. The North wall accumulated fine black sand on the inside of the wall, with fine white sand on the outside. The South wall had accumulated fine black sand on the outer wall, with fine white sand on the inside. We suggest that this pattern of accumulation may be due to wave refraction as the current hits different parts of the wall, and the influence of the 1m hole in the West wall causing a stronger current within the pond. Further studies need to focus on the North and South wall channels to analyze the sediment deposition and mineral content in order to predict future erosion patterns of the fish pond substrate. This could also raise the question of how this impacts species abundance and behavior in the fishpond.

Authors: Abby Nestor, Kendall Bangert, Lily Silverstein

Introduction
The objective of this monitoring project was to establish a baseline beach profile and a comparison of the varying current speeds in and around the perimeter of the Paea Lagoon fish pond. The expected outcome was a higher beach profile on the inside of the south wall due to sediment accumulation resulting from the current that flows south to north. The bathymetry of the beach from the back wall of the property to the back wall of the fish pond was mapped using cross-shore transects along the inside and outside of the pond walls and in the center of the pond. The current speeds were measured in these same areas to evaluate the possible influence of the current and the sediment accumulation it causes on the bathymetry of the beach.

Methods
To create a profile of the beach's changing elevation, 5 cross-shore transects were used: 1 transect 1 meter from the outside of the south wall, 1 transect 1 meter from the inside of the south wall, 1 transect 1 meter from the outside of the north wall, 1 transect 1 meter from the inside of the north wall, and 1 transect down the center of the pond. Along the transects, any change in the slope of the beach was measured using the Emery Method, which uses two rods, each with a marker noting the eye level of the observer, a tape measure to measure the distance between the two rods, and a protractor apparatus to measure the change in angle of the slope. To begin, the 0 m point was defined as the apex of the angle at the base of the back wall under the fourth diving board from the stairs. For each transect, the distance between the 0 m point and the starting point was measured and recorded using the two marked rods and a tape measure. One rod was placed at the 0 m point and one rod was placed at the starting point of the transect, which was at the back wall of the house. The distance between the two walls was measured using a tape measure. The change in angle between the two points was also measured and recorded using an apparatus made of a protractor with a straw taped parallel to the flat side and a string tied through the hole of the protractor with a weight attached to the end. The string fell along the 90 degree mark when the protractor was held flat side up. The protractor was held flat side up at the marker point on the rod at the starting point and the observer looked through the straw, shifting the end of the straw on the protractor to point up or down until the marker on the rod at the 0 m point was in view. A second observer recorded the angle at which the string fell on the protractor in relation to the 90 degree line. The difference between this measured angle and 90 degrees is the change in angle between the 0 m point and the starting point. The rod at the starting point was kept in place, while the team member holding the rod at the 0 m point moved the rod to the point directly before the first change in the slope of the beach that occurs directly in front of the rod at the starting point. The process used to measure the distance between the 0 m point and the starting point was repeated between the starting point and the point directly before the first change in slope. The same technique used to measure the change in the slope of the beach between the 0 m point and the starting point was also used to measure the slope of the beach between the starting point and the point before the first change in slope. The rod at the starting point was then moved to the point directly before the next change in slope, and the techniques for measuring the distance between the rods and the slope of the beach between the two rods was used again. This process is repeated for each change in slope until the back wall of the fish pond is reached.

The function tan (θ) = H/D was used to solve for the change in height (H) between each change in slope, using the angle of the slope of the beach measured using the protractor (θ) and the distance between the two rods (D). The cumulative height was calculated for each of the 5 transects and graphed with the cumulative distance from the starting point.

To measure the current speed, 10 points were first chosen in and around the fish pond where a tape measure, buoy, and stopwatch were used to record how many seconds it took the buoy to travel a given distance. One point was 5.5 m from the shoreline, 1 m outside of the north wall, one point was 10.5 m from the shoreline, 1 m outside of the north wall, one point was 5.5 from the shoreline, 1 m inside of the north wall, and one point was 10.5 m from the shoreline, 1 m inside of the north wall. On the south wall, 4 points with these same distances from the shoreline and the wall as used for the north Wall were chosen as well. The last 2 points were 5.5 m from the shoreline, directly down the middle of the pond, and 10.5 m from the shoreline directly down the middle of the pond. At each point, two team members held each end of a tape measure and one of these two team members dropped a buoy at the end of the tape measurer at which they stood. A 1 m buffer was used to allow the buoy to reach a constant speed, and once the buoy traveled 1 m, a third team member started a stop watch and stopped the stop watch once the buoy traveled a given distance. For the 4 points outside of the pond, a distance of 5 m was used and for the 6 points inside of the pond, a distance of 3 m was used. This was repeated 5 times at each of the 10 points, and the average time it took to travel the given distance was calculated. The amount of meters traveled was divided by the average time to calculate the average current speed in m/s at each chosen point.

Results
Figure 1. Beach profiles of 1 meter to the right or left of the respective wall and the center of the fish pond.
https://docs.google.com/document/d/18pQvFWGDjtg89jIlTOwIRssvCENwRNFxEPDVx1oRX_w/edit?usp=sharing

The outside of the south wall had the lowest beach profile of all 5 sites. The shoreline was reached at around 9.27 meters with a total distance of 34.6 meters. As seen in Figure 1, this profile lies significantly below the other sites sampled and reaches its steepest slope at 22.31 meters. It briefly increases in height before reaching the back wall of the pond. This profile had an overall slope of -0.115. This was the steepest slope of all sites.
The profile of the inside of the south wall was a total of 37.89 meters in length. The bathymetry showed a gradual decline in height with a significant increase in slope steepness at 32.46 meters. The profile has an overall slope of -0.0908.
The middle of the pond had a fairly high profile that was 35.5 m in length. The slope fluctuated between increasing and decreasing steepness until 17.73 m where it significantly increased in steepness. The profile had an overall slope of -0.0903, which is similar to that of the inside of the south wall.
The inside of the north wall had the highest profile overall and was 38.67 m in length. The slope decreased before flattening out and increasing slightly at 3.65 m. The slope then decreased gradually before a slight rise in elevation approximately 5.89 meters from the wall where there is a patch of rocky substrate. The overall slope was -0.0911, similar to that of the south wall and middle of the pond.
The profile of the outside of the north wall had a length of 35.37 m. The slope of the beach decreased gradually before flattening out at ~21 m and then fluctuated in steepness for the rest of the profile, with a final increase 2.11 away from the back wall where a rocky portion lies.
The overall slope was -0.0996.

Figure 2. The current speed is measured along the outside and inside of the walls and middle of the fish pond within two distances from the shoreline.
https://docs.google.com/document/d/1A05Mk31mAPxufpbUG6dC-EWkxcY2xQxDEcnoFefgBZs/edit?usp=sharing

Figure 3. The standard deviation of each measured current speed with a gradient depicting highest to lowest deviation value.
https://docs.google.com/document/d/1AlyQYfcdaSQjspsW31pykuVYXOHchfmQ0UlB-1LQC0g/edit?usp=sharing

As clear in Figure 2, current speed was relatively consistent with a range of 0.118-0.267 m/s. The slowest speed occurred 5.5 m from the shoreline on the inside of the south wall. The fastest speed occurred 10.5 m from the shoreline on the inside of the south wall. Figure 3 displays the standard deviations for each current speed. The lowest standard deviation was 0.025 and occurred 5.5 m from the shoreline on the outside of the south wall. The highest standard deviation was 0.125 and occurred 5.5 m from the shoreline on the inside of the south wall.

Discussion
Due to constantly changing currents, a correlation cannot be determined from this limited data set. The beach profiles and current speeds serve as a baseline to build upon in future surveys. The overall slopes of the profiles were relatively consistent between the five sites. The outside of the south wall had the steepest overall slope of -0.115 indicating a lack of sediment accumulation. This outcome was expected due to the current flowing south to north which pushes sediment over the wall to the inside, displacing sediment from the outside. The current speed complimenting this data shows small scale changes due to a heterogenous wall varying in height. The slopes of the profiles of the other sites were all relatively consistent.
The fastest current speed was 10.5 meters away from shoreline on the inside of the south wall and was 0.45 m/s faster than the outside. This was unexpected because the wall was thought to slow the current speed and therefore the speed should be higher on the outside of the south wall. These results could be explained by the changing wind speed which caused a large standard deviation of 0.125 occuring 5.5 meters away from the shoreline on that same side of the wall. Also, the tide was higher than usual so the rocks were deeper in the water which may have interfered with the usual current dynamics. As the current continues to flow northward, it would typically pick up speed due to scouring which makes the current stronger as it approaches the inside of the north wall. It loses speed when it passes through the wall resulting in a higher speed on the inside of the north wall compared to the outside of the north wall. This is shown in our results with 0.055 m/s decrease in speed.
During data collection, wind speeds varied between 2 to 4 on the Beaufort scale. This wind may have led to potential errors as in order to obtain an accurate angle measurement, the string needed to hang straight down and it was often blown by the wind. Furthermore, these wind variations caused fluctuations in speed at which the buoy traveled throughout each trial, leading to large deviations between measured current speeds at given location. Lastly, current speeds were measured at different distances from the inside and outside of the fish pond to reduce overlapping currents.

Proposal for Future Studies
In future studies, the accuracy would be improved with the survey being performed over several days, in differing conditions, and over different seasons to account for temporal changes in this fish pond’s bathymetry. Although potential errors have been accounted for in our data, it can be assumed that improvements can be made in order to effectively compare changes in these beach profiles. Substrate type in different areas of the pond may also be compared to its current speed.

Metadata
Beach Profile Data:
31 July, 2024
1 PM- 6 PM
Beaufort 4
Cloud Cover 90%

Current Speed Data:
1 August, 2024
11 AM-2 PM
Beaufort 2-4
Cloud Cover 65%

Authors- Sierra Nunis, Taylor English, and Ryan del Rosario

Introduction
Our project was focused on recording the species richness in a transitional fish pond in Pa'eam Tahiti. Species or taxonomic richness is defined as the amount of different species in an area. Our sampling universe was the area encompassing the fishpond from shore to the furthest wall, as well as two areas 15 meters adjacent to the pond. We specifically decided to expand on a previous years research on species diversity, with our focus on the specific sizes of two target families: the butterflyfish and damselfish. Our aim is to compare the abundance of juvenile butterfly and damsel fishes inside the fish pond compared to areas outside, which could indicate how effective the pond is as a nursery, the recruitment rate, or the fitness of individuals that use the pond for shelter.

Methods
We used the same methods as the prior group as follows. We separated into two phases; monitoring the inside of the fish pond (including a special survey of the central rock formation), and then monitoring the outer rock walls and a transect 15 meters longshore from the outer walls to provide comparisons. The first swimmer did one pass to record the species richness three meters away from the transect to make sure to not disturb the fish. They then waited 2 minutes at the end of the transect to allow fish to return before swimming back over the transect to make additional records. After a minimum of 2 minutes, we would repeat the same methods but would instead record the abundance of juvenile and adult target families of butterfly and damselfish. Juveniles were calculated as being under a designated range. We classified butterfly juveniles as 4 cm or under and Damsel juveniles were 3 cm or under. This was repeated by two researchers with a total of four complete laps. The same methods were repeated for the other two transects surrounding the inside of the fish pond,as well as the exterior and 15 m away.
In relation to the prior groups we decided to change the methods to surveying the inner fish pond. In past years they designated a researcher to swim for 10 minutes around the exterior and then 10 minutes observing the interior. We believe being inside the small interior would frighten the fish so we just surveyed the exterior. When surveying the exterior we concluded that the swimming around the exterior would scare fish so we decided to have one researcher stationary about ½ a meter away to record any fish richness and size of damsel/butterfly for a total of 10 minutes. To best estimate the size, a small rock prior to entering the water was measured out to be approximately 3 cm and was placed on the rock structure to precisely know if the fish is within our juvenile range when swimming past it. This was a total of 10 minutes of patrolling and made exact by an underwater watch.

We did further research on the direct outside of the right and left walls of the fish pond. We did this by using the same methods as the inside rather just a meter from the edge going to the outer lagoonside. We also conducted two further transects 15 meters away from the center of each right and left wall. These transects were also going 15 m crossshore and the same methods were used.

Results
​When looking at our graph, the x-axis indicated the areas surveyed, the bars indicate the classification of fish including their family and estimated age (of juvenile or adult), and the y-axis is number of individuals of each observed in their respective sampling universe. The adult damsel fish were the most observed, followed by adult butterfly, then juvenile damsel, and the least observed being juvenile Butterfly.The only location where neither were seen was the far right transect. The main locations for the juveniles were most abundant in the inner fish pond but juvenile damsel were seen in all but the far right, and juvenile butterfly were only observed in the inner fish pond, far left and inside right. But when taking richness survey data we used the highest number of observations and when taking the size data we used a small rock 3cm in size and placed it on the nursery so as to estimate size; and we classified them opportunistically so standard deviation isn’t necessary.
Data
https://docs.google.com/document/d/1LmZSOaD4YEh7sJmy8pC6VnOkvRDZvcdIu7gYCr1re3s/edit?usp=sharing

Discussion
Species richness was highest in the fish pond, particularly, inside of the central structure which was home to a variety of juvenile butterflyfish, gregories, and surgeonfish. Outside the fish pond, the majority juvenile observed were those of previously mentioned dusky gregories that made their home in tiny rock shelters.
Richness was much lower outside comparatively. There was a mix of both juvenile and adult fish of many families present, interestingly including a juvenile snowflake moray eel adult yellow boxfishm a meter and a half long flutemouth that was swimming among the fish pond’s interio, and an adult orange-lined triggerfish lodged within a solitary rock. In total, the fish pond was home to 15 different families of reef fish. In comparison directly outside of the fish pond there were 7 families on the right exterior and 5 on the left exterior.
The left area of the pond was notably more abundant in life than the right side. We propose this could possibly be due to the current going from south (left) to north (right) causing more sediment deposits on the left side. But further research is required to determine this hypothesis. On the left we observed 7 raccoon butterflyfish, three juvenile scissortail sergeants, and a solitary peacock damselfish. The right exterior meanwhile was relatively barren. Notably, however, it was one of the only locations where lagoon triggerfish were observed. Three juveniles that used the rock holes on the bottom for shelter.
In terms of abundance the Dusky gregories were by far the most abundant species in the area, living in practically every facet of the rock walls. Most were large, 6-7 cm adults that guarded their territories fiercely. Dusky gregories were observed constantly fighting back against other fish, including one scaring off an entire shoal of grazing sharpnose mullets. Furthermore, the presence of predatory fish like the flutemouth or eels could indicate attempts at predation which may be of interest to understanding the fish pond’s ecosystem. Butterflyfish like the vagabond and raccoon were spotted most often with a few speckled butterflyfish and a single threadfin butterflyfish being observed.
We would like to note that during our first day of surveying, there was a high in current due to the wind and weather conditions making the water have low visibility. The current also pushed surveyors so it was hard to maintain the set meter distance from our transects. The second day was better in visibility but current still posed a problem and we would recommend further research done on better weather conditions.
The fish pond’s diversity is certainly above that of the adjacent areas, being home to even large adult fish species. The presence of juvenile butterflyfish and damselfish indicates that it’s functioning as intended as a nursery for these species, indicating that it’s recruiting and maintaining young fish sufficiently well. For future surveys, we suggest broadening the scope of surveyed families to include all types of fish. Juvenile surgeonfish, eels, flutemouths, and emperor angelfish were also found in and around the fish pond. Looking further into their quantities compared to outside the pond will better quantify what thrives and relies on this miniature ecosystem. Furthermore, the behavior of specimens within the fish pond could be of potential interest. How often are they feeding? What is their alert and flight distance? How territorial are they? Compare all this to like specimens outside. Perhaps those in the fish pond feed more and are more territorial due to the limited space. It’s clear the fishpond is providing a unique and valued service for the coral reef community, and focusing on the behaviors and physiology of its inhabitants may yield valuable information regarding the function of fish ponds.

By Elyse Hartmann, Madeleine Yang, and Marina Thompson
Survey dates: 5/19/24 - 5/21/24
Location: Paea, Tahiti, French Polynesia

Introduction
In this study we started a beach profile to monitor how the beach elevation changes over time. The objective given was to measure the degree of which the terrain slopes by looking at transects going through the Paeanfish pond and outside of it, by our client Thomas. Our monitoring reveals information on the relationship between current and sand deposition, as well as documenting erosion.

Methods
We started by measuring the dimensions of the fish pond. Each wall of the fish pond and the opening on the beach were measured to the outermost part.
In order to get a representative profile of the beach’s elevation, we split the area into four, parallel, 32 meter transects with 5 measurements taken within. Two transects went through the fish pond and two were on either side of the fish pond walls.

To gather the measurements, we used the south most noni tree in front of the pond as a fixed point to standardize the starting point for measurements. In the future if this tree is no longer there, start measurements 0.34m to the left of the southern mist metal pole in front of Thomas’ property. To calculate the slope of the beach, tape lines 120cm high on two sticks were used in conjunction with a protractor: we recorded the angle from the higher stick to the lower stick by looking at the other tape mark through a straw on a protractor. The protractor had a string with a weight attached to it, so one team member could read the angle indicated by the string, while one was looking through the straw. This was repeated to get the angle and hypotenuse 20 times around the fish pond in a systematic manner. Then the height from the original (horizontal point near noni tree) was calculated using cosine.

In order to measure the speed of the current we strategically choose five spots around and within the fish pond, making sure to intercept all the previous four transect lines. We took measurements on each side of the fish pond’s interior (north and south), two outside the fish pond’s walls (north and south), and one west of the fish pond outside the walls. At the spot, one team member held each side of the tape measure and the third team member recorded the time of when the buoy went past the designated marks. The buoy was dropped at 0m and floated downstream to pick up speed, once it reached 3m a stopwatch was started. When the buoy reached 7m (a distance of 4m recorded) the stopwatch was stopped and the time was recorded. The data was then averaged to find the speed in meters per second (m/s).
Safety precautions such as wearing shoes were taken when walking in the lagoon to avoid complications with venomous benthic animals.

Results
NOTE: Our depth measurements are not correct. We have determined that our measurements are proportional to each other and the beach slopes and current speeds are correct. (Therefore, figures 2-3 and 5 are all correct). However, the depth measurements do not reflect the real depths from point zero, so figure 1 is visually correct, but numerically incorrect. This is due to an unknown error in methods or calculation. We suggest future groups look further into this.

The measurements of the fish pond walls were 14.5m in the South wall, 17.1m for the East opening, 15.7m for the North wall, and 16.8m for the West wall.

Figure 1 shows cross sections of the beach along four different lines. It shows that the southmost line (site 1) has the lowest depth at the start and highest depth before the waterline. Whereas, the part of this beach cross section that is below the waterline has the second largest depth from point zero. If you look at site 2, the opposite is happening, the depth is the 3rd largest before the waterline and the shallowest after the waterline. Site 3 on the northern side inside the fishpond has the greatest depth throughout the whole transect line with the deepest part at 5.32 meters below the wall of the property.

These results correspond with calculations of the slopes showing that site 3 has the greatest negative slope overall of -0.22 and Site 2 has the lowest negative slope of -0.13. All of the slopes within each transect line had standard deviations between 0.08 and 0.15 showing a large amount of variation in slope within each site line. Though, transect 3 had the most slope variation.

In addition, the ocean currents at each location along the transect line sites differed. The current speed was highest deeper into the water west of westward fish pond wall where the current speed was 0.36 m/s. This is to be expected since the measurement was taken much deeper into the water. Location 1 was the next greatest along transect one (south most outside the fish pond) with a speed of 0.17 m/s. The lowest current speed was measured at site 2, where the average slope was the lowest as seen in figure 2. T-tests showed that there was a significant difference between the current speed between sites 1 and 2 with a P-value of 0.072.

Figures: https://docs.google.com/document/d/1s2taUzmCdVAy7Pd_E-1flnjZBLYdMdLJDsTSKIdLg3o/edit

Figure two represents the average slopes of our four transect lines. Site 3 had the greatest slope and figure two had the smallest. These were both the transects within the fish pond.

Figure 3 depicts the different current speeds at 5 locations, three outside of the fish pond and two within. Locations 1, 2, 3, and 4 each intercept the corresponding depth transect perpendicularly. Site 5 is parallel to the west wall, and had the highest current speed.

Figure 4 is useful in visualizing the different depths from the starting spot at different points in and around the fish pond. The depths ranged from .3 to 5.32 meters. The scale of colors goes from white/yellow (shallow change), to red/purple (deep change).

In order to establish long term visuals of how the fish pond changes shape and the walls shift, we took a photo standing from a perch on the bathroom wall. Future photos can be compared to this baseline- 5/21/24.

Discussion
Our results present a couple different patterns and findings that could be relevant to continue monitoring overtime.
The south side of the fish pond interior has a shallower depth and slope than the north side interior. Correlating this finding with lagoon current strength and direction can tell us about the possible future of deposition of sediment and changes of depth within the fish pond. The measurement can be used as a baseline measurement and repeated in the future to compare and quantify changes occurring within the fish pond.
Specifically, we found that the current is traveling northward, and we recorded a 0.6 meters per second slow down after the water crossed the south wall of the fish pond. Therefore, the higher elevation on site 2 can be correlated to sediment deposition due to slowed current speed after the fish pond wall.
Additionally, we want to note the relationship between the largest depths (at site 3), and the hole in the fish pond’s west wall, which overlaps with site 3. We observed that when a buoy was placed in a few meter’s radius of the opening, it would float towards that exit, slowly increasing in velocity, exemplifying this as an outflow spot for currents. This could help explain why the north interior side of the fish pond is deeper than the south, because of sediments being carried with currents leaving the pond at this exit (and other cracks and crevices along the north wall).
Numerically we recorded an average 0.3 meters per second increase in current speed on site three compared to site 2. But it’s relevant to note that we did not calculate current velocity specifically at the mouth of the west wall opening - which is where it would have been even faster, as observed visually by buoy movement. This solidifies the relationship between current direction, velocity, and deposition of sediment in and around the fish pond, especially when considering different physical features.
In the future we suggest groups do more measurements around the hole in the west wall. These could be current, depth, or sediment related to learn more about the erosion and deposition occurring in the fish pond and around the opening.

Errors
As this is the first beach profile there were a couple of human errors that can be addressed. One error would be that when measuring the dimensions of the fish pond we were at the water level. This may cause error as we may have not been aligned with the fish pond walls.
During the days that data was collected there were varying wind speeds between 3 and 5 on the Beaufort scale. We recorded the wind speeds at the time of each current trial in order to include a more accurate depiction of what was happening and why.
The wind made it difficult to fully straighten long transects and made it difficult to use the string method on our protractor when calculating angles of the topography’s slope. To reduce error, one person would look through the protractor while another person ensured the weight at the end of the string was indeed oriented downwards.
The large swell two weeks ago and other temporal weather could have affected the depth of the sediment and the current speeds.
In addition, there was an unknown error during data collection and processing, influencing the accuracy of our data.

SURVEY DATES: 05/19/2024 - 05/21/2024
SURVEY LOCATION: Paea Lagoon Aua i’a Fish Pond
AUTHORS: Jessie Segnitz, Uma Pant, Nicole Pianalto, and S. Tara Grover

INTRODUCTION:
In this survey, we observed the substrate inside, on top, and outside the Paea Lagoon Aua i’a Fish Pond. The fish pond is a Polynesian traditional practice of small scale fish collection that fell into disuse over time due to the effects of European colonization, commercial fishing, and globalization. We are building upon the previous studies done by Wildlands students in 2022 and 2023 in order to meet the needs of our client, a private individual interested in species and land conservation who owns a marine observatory on Tahiti.

The objective of our study is to determine the sea floor substrate and algae covers on the inside and outside of the fishpond, and top of the rock wall top itself. Further objectives of the research team were to establish measurement definitions for the average particle sizes of both "fine" and "coarse" sand to set a standard for future use, and second, evaluate the presence of patterns on the seafloor of fine and coarse sand areas. There is a current along the shore running south to north through the fishpond and our client is specifically interested in the influence of this current and how the rock wall may act as a sieve or filter, changing the concentration of the sand types on the different sides of the wall. Earlier studies concluded that there was no statistically significant difference in substrate coverages outside and inside the fishpond, however, they did not account for the difference between fine and coarse sand, which is the knowledge gap we addressed with our survey.

We hypothesized that there would be a significant difference in the coverage of the different sand types on the south and north side of the wall. We further hypothesized that there would be a difference in overall substrate coverage inside and outside of the fish pond walls because of the barrier effects of the wall on the current's ability to move and transport substrate types through the area.

METHODS:

FIRST SURVEY — INSIDE FISH POND
We used a 50 x 50 cm quadrant to survey percent coverage of different substrate and algae types. We used a random number generator to generate 10 coordinates within the size of the fish pond which is roughly 15 x 15 meters. Using the bottom right corner of the fish pond (Northern corner) as our (0,0) origin point, we used a transect to measure out the predetermined coordinate points to the South along the shore (x-axis) and out into the water (y-axis) and placed the bottom right corner of the quadrat at each point. Our randomly-generated coordinates were (8, 12), (5, 1), (2, 7), (10, 9), (14, 3), (9, 11), (6, 12), (7, 9), (12, 9), (13, 2).

For this survey as well as Survey #2, we evaluated percent coverage of the following categories: fine sand (with the majority under 1mm length of grain on average), coarse sand (over 1mm length of grain on average), bare rubble (chunks of substrate between 2.5-10 cm, including stone, dead coral, shells), bare rock (over 10 cm with no algae cover), and five types of algae. These types were turf algae (under 1 cm), and the macroalgae genuses: Halimeda, Padina, Turbinaria, and Dictyota. Two researchers both independently estimated the coverage of each type and then double verified with each other.

We made sure to step lightly to avoid disturbing substrates or moving any particles into or out of the quadrats. We also exercised a high level of caution to avoid contact with dangerous benthic species including the stonefish, by wearing neoprene boots and swimming when possible without touching the floor.

SECOND SURVEY —OUTSIDE FISH POND
Starting from the north fish pond edge at the point closest to the shore, we measured out 5 meters parallel to the shore. That would be our starting point of our survey line of 15 meters to the end of the fish pond walls. We did systematic sampling, so every 5 meters starting from 0 meters on the transect we would sample using a 50 x50 cm quadrat, putting the quadrat on the left side of the transect with the bottom right corner at the starting point. We did this for the north, west and south walls of the fish pond. We evaluated percent coverage of the same categories and methods as for Survey #1 (above).

THIRD, FOURTH, AND FIFTH SURVEY — SEDIMENT TRANSECT
In this survey we used line intercept sampling by using a transect adjacent to the interior and exterior wall, which we identified as the area on the seafloor closest to the rock wall that did not include any large rocks that made up the foundation of the wall. We evaluated percent sediment coverage of the following categories: fine sand (under 1mm length of grain on average), coarse sand (over 1mm length of grain on average), rubble (2.5-10 cm), rock (greater than 10 cm), and alive coral, all regardless of any algae cover on top. By looking at what sediment lay directly underneath the transect line we classified what sediment was present and the length of the section it created, for the entire 14.5 meters. We conducted this survey for the north, west and south side walls of the fishpond on both the inside and outer side of walls.

SIXTH SURVEY—- ON TOP OF WALL
For this survey we used systematic sampling using the 50 x50 cm quadrat and a transect laid out from the start of the rock wall for all three walls. We placed the bottom of the quadrant at 0m, 5, and 10 meters for each wall. The quadrat was placed in the very center of the wall, and at all survey points, the wall was thicker in width than 50 cm so the quadrat consisted completely of substrate from the wall itself. We looked down from an aerial view and measured the same substrate and algae types as previously mentioned in the other surveys. We repeated this method for all three walls for a total of 9 survey points.

SEVEN SURVEY — SAND MEASUREMENT
For this survey a team of two took samples of fine and coarse sand from inside the fishpond, scooping only the surface layer of sediment. We collected approximately 20 mm of sand and water for each. The samples were chosen based on visual differentiation, where the fine sand was scooped
from the left wall delta closest to shore inside the fishpond, and coarse sand from the center of the fish pond. The sand was laid out on a paper towel and a randomization method was used to choose 50 grains of sand to measure from each sample. Calipers were used to measure out the various particles in millimeters.

IMPROVEMENTS/ CHANGES FROM PREVIOUS SURVEYS

We used a 50 x 50 centimeter quadrat instead of the previous group's 1x1 m. This allowed us to take more accurate and detailed data on the coverage within our survey areas while still being a large enough surveyed area to be generalizable to the entire pond.

We know that the algae species and concentration can change due to seasonal and climate patterns. We did our own preliminary analysis of what types of macroalgae genuses were present when we got in the water, and created our own list of them to measure instead of using the previous groups. This was the same as the previous groups except for one exclusion, Sargassum, which was not present at this time, and one new inclusion, Dyctyota, which was present.

We did a randomized point intersect method for the inside of the fishpond instead of the previous groups' strategic sampling method because the fishpond is a big enough sample universe to benefit from a random sample to eliminate bias or accidental disproportionate inclusion or exclusion of substrate patterns.

We continued the original method of strategic sampling for the outside fish pond sampling universe, and for the walltop itself, because we felt that the narrow range of these areas would be better represented by consistent sampling. A visual analysis of the general substrate cover of the entire survey area confirmed that we were not overlooking any patterns due to this sampling method.
Surveying the wall top itself was also a new addition to this survey project that was not present in previous years. This allows us to set a baseline time zero (t=0) standard for wall composition which gives insight into the structural integrity of the stones based on how close together they are, and what substrate types are present among the cracks..
Another new addition was the specific line-intercept survey along the outer and inner walls that focused on determining patterns of sand dispersal through the walls.

RESULTS:

Please copy and paste the link below into your browser to view data sheets with graphical analysis

https://docs.google.com/document/d/1296DmEP9zlzIvRDUheGtx5jx7ANnlSfT8JGAyNMvuSI/edit

DISCUSSION:

Survey one data illustrates that the substrate cover inside the fish pond is mostly coarse sand and a scattering of rubble across the area. While the dominant algae inside the fish pond was Halimeda. In the survey two data, it portrays that the sediment composition outside the fishpond was mostly made up of fine sand and some coarse sand, while the algae was mostly turf. The differential sediment composition inside and outside the pond demonstrates that the fish pond creates a different sediment environment, which is reflected by the dominant algae that is growing in the area.

The survey three, four, and five data show sand patterns that are representative of the current flowing through the pond. The currents are coming from the south going north, parallel to the shore. Outside the southern wall there was a larger section of fine sand, while the interior of the fishpond there were three distinct sections of fine sand. This illustrated that the southern wall is filtering the fine sand into the pond at a relatively slow rate, with most of it concentrated on three sections that correlate with thinner and lower wall sections. While on the other hand, the opposite was reflected by the north wall, by the sand filtering out of the pond. The exterior of the wall substrate consisted of more fine sand than the interior of the wall reflecting that there is a large rate the fine sand is leaving the fish pond. With the influx of fine sand coming in at a slower rate and the outflux leaving at a greater rate, the inventory of the fine sand in the fish pond would be lower. This is also reflected in the data from survey one, the sediment coverage inside the fish pond, portraying that there was very little fine sand within the sampling sites that is a portrayal of the entire pond. Then with the west wall the sediment makeup of the interior and exterior was fairly similar with the percent of fine sand being around 30 percent. This similarity illustrates their is not that much if any sand movement between this wall.

For Survey 6 looking at substrate composition on top of the wall itself, we found that the turf (algae less than 1mm long on top of rock/rubble) dominated the bulk of the substrate available in this location, at 83%, as expected. The wall is composed of large rocks, and can resist wave action more so than coarse or fine sand, which can be washed away. Since the stones here are the original foundation of the fishpond from whare our client rebuilt it many years ago, it makes sense that turf covers almost all of the present stone content. The coverage of bare rock with no turf is only the parts of stones that are still above water even at high tide, so there was no ability for turf to settle and grow there. The areas that were not turf or stone are what is visible between the rocks when looking from an aerial view, ad thus they represent the cracks between the rocks which allow a view of algae content below and occasionally all the way down to the sand on the floor.

During Survey 7, we revealed key information about classifying the difference between the size of coarse and fine sand. We found that the coarse sand had a median of more than 1mm in particle size, and the fine sand had a median size of less than 1mm in particle size. We used this understanding to clarify our data for both types of sand during the other survey collections, where we used visual markers to identify each type. This classification can also be used for future studies as a standardization of the monitoring project.

It's important to note there was an ocean swell a couple weeks ago that washed away different substrate from the location that may have previously been present in the area. For example, certain algae species and fine sand may have been washed away, influencing the current composition of the inside and outside of fishpond wall barriers. This may contribute to significant differences between this survey and the previous ones, although other factors such as seasonal differences and simply the regular wave and wind action of many months will also produce these differences.

Overall, there are noticeable trends in the differences with sand cover on the inside versus the outside of the fishpond.
The higher concentration of fine sand outside could be due to current and wave action pushing coarser, heavier sand particles inside the fishpond that has nowhere to go, whereas Fine sand can be lifted away by wave action. The fact that turf on rock substrate covered most of the fish wall shows how the stones have been present long enough to accumulate turf cover.
Another explanation for the lack of other types of substrate and algae coverage may be due to the nature of intertidal zone harsh conditions, which only support life for the most hardy species that can survive high and low temperatures, water and salinity levels, and have increased mechanical wave action that make it difficult to establish a presence on the rocks and moves sediment rather quickly, not allowing for settlement.

We also noted an interesting observation from this year's data versus last year's projects. Halimeda is the most common algae found in and around the pond, which is different from the rest of the coral reef areas that the research team has seen across Tahiti and Moorea.

PROPOSALS FOR FUTURE METHODS:

We propose that future projects continue to differentiate between fine and coarse sand, so that a standard can be maintained for data collection over time in consideration of factors such as current speed and wave action.
A proposal for future groups is to analyze the structure of the wall to determine what qualities exactly lead specific sections to allow more fine sand through the stones.
The line-intercept survey of sand cover along the sides of the walls should be repeated to track change over time.
We also recommend separating the data collection between algae biodiversity (different genuses) and mineral substrates (coral, sand types, rock, rubble) as separate surveys, where the mineral substrate survey does not regard algae coverage.
The algae biodiversity survey should also include a difference between turf on rock vs. turf on rubble, to make sure that it is clear to differentiate the preferential turf substrate.

We also recommend continuing data collection on specific algae types over time, or making sure to note if there is a decrease in a specific population during that year to maintain standard measurements, just to keep a clear comparison of the different populations in the fish pond over time.

Authors: Payton Curley, Evan Gray, Jasmine Rosado, Julianna Evinski
Introduction:
The objective of this monitoring project was to collect data on the richness of fish families and invertebrates both within and in areas surrounding the fish pond. We were tasked with creating a cumulative list of all the species found in four locations: inside the refuge, within the fish pond in general (excluding the refuge), directly outside of the fish pond’s borders, and further away from the pond in the reef area. Species richness—or species count—in an area is important because it can be an indication of biodiversity. We analyzed species richness in the fishpond and made comparisons to the outside, calculating the number of species per square meter for every area in the process. This information can be used to compare to past years and analyze changes in diversity. We can draw conclusions about overall health and activity of the fishpond, as well as changes over time based off this information. The monitoring of this pond officially began 2 years ago and our group is excited to contribute to this monitoring project.

Methods:
Our areas of focus consisted of inside the fish pond, the exterior of the fishpond wall, the outer coral reef, and the new refuge in the fishpond. For the inside of the fishpond we decided to conduct a preliminary simple floating survey to get a gauge of what species we should be looking for. The next day we decided to use the transect beam method to quantify the number of species in the pond. We used 3 transects--one for each wall--each 15 meters long. We began by measuring 1 meter away, perpendicular to the wall, to establish the start point on the transect and staked it down in the sand with a rock. A researcher then ran it parallel to the wall and swam an extra few meters past the other end so as not to bother fish directly in the 15 meter survey area. After waiting 2 minutes, another researcher would then swim along the transect, recording any pelagic fish seen 1 meter on each side of the transect below, covering a total of 30 square meters per transect. After swimming the length of the transect, the researcher would then wait another 2 minutes and then swim back over the transect, this time recording benthic fish and invertebrates.
To survey the outer border of the fish pond, we used the same method, instead measuring 1 meter away from each wall on the outside of the pond. We then ran each 15 meter transect parallel to the wall and recorded pelagic and benthic species, as well as invertebrates.
To survey the outer reef away from the fish pond, we used three different areas. The first area we measured was 15 meters away from the left wall of the fishpond. We laid a transect out parallel to the wall, repeating the same methods to measure fish species. We then measured 15 meters away from the border wall and laid out another transect parallel to the fishpond and repeated the survey methods. We then measured 15 meters away from the right wall and laid out another transect, repeating the same methods for measuring fish species.
We also measured the fish species in the newly built refuge. One researcher started a 10 minute timer, watched the fish swimming in and out of the rocks surrounding the refuge, and took note of the different species. After the first 10 minutes were up, the researcher then started another 10 minute timer and watched the fish that were inside the refuge and in the boulder.
In conducting this survey, there were a couple changes from the previous year's group that observed fish biodiversity. Although we used the same methods for surveying the inside of the pond and on the border of the wall, we changed the method for the outer reef survey. The previous group decided to use coordinates and do 3 transects parallel to shore at that location. We decided instead to survey 3 different locations, each parallel to one of the walls of the fishpond. We changed this because we believe that surveying different locations for the outer reef would give a more accurate depiction of the greater lagoon that the fishpond is a part of. We wanted to eliminate possible confounding variables as factors like the strength of the current and depth vary based on where you are in relation to the fishpond. This is why we decided to include two areas off the beach on either side of the fishpond as well as one further into the water from the outside wall. This way we could see how the fishpond affects the greater ecosystem.
In addition to these changes, we also decided to focus solely on species richness rather than richness and abundance due to the fact that our client was most interested in which species were present rather than the amount of individuals we saw. Another addition to our methods in comparison to the previous year was focusing on invertebrate species as well. The method that we chose for surveying fish species works for invertebrates, which our client was interested in seeing in addition to the fish species.

Results:
INSIDE
It consisted of 16 different species making up 9 families. Damsel, Soldier, Surgeon, Cardinal, Lizardfish, Wrasse, Butterfly, Trigger and Goat. The main families were Butterfly, Wrasse, and Damsel. There were also a few invertebrates in the pond that were recorded, which were burrowing urchins and cone snails.
BORDER
We found 12 species and 6 families. The families we saw were wrasse, damselfish, butterflyfish, goatfish, triggerfish, and snapper. The dominant fish families in that area were the wrasse, damselfish, and butterflyfish. On the border there were invertebrates like urchins, sea cucumbers and snails.
OUTER
We found 8 species and 6 families outside of the pond. Those families were wrasse, triggerfish, damselfish, butterflyfish, goatfish, and blenny. The dominant fish families were wrasse and damsel. The invertebrates that were seen were sea cucumbers and urchins
Species per square meter:
In the outside of the pond the fish species per sq meter is 0.267 and the family per sq meter is 0.2. The border of the fish pond species per sq meter is 0.4 and the family per sq meter is 0.2. Inside the fish pond the species per sq meter is 0.533 and the family per sq meter is 0.3.
REFUGE
The refuge has a 5.26M^2 area and the species found in the refuge were convict surgeonfish, vagabond butterflyfish, dusky gregory damselfish, scribbled rabbitfish, and shrimpgoby. The species per meter squared is 0.95.

Excel Sheet of Fish species and families in the areas we surveyed and the refuge: https://docs.google.com/file/d/1m8wKrIt85X0fUAqYR5jy4uCnl2dJ0mCe/edit?usp=docslist_api&filetype=msexcel

Graphs of the Dominant fish families in each area surveyed: https://docs.google.com/document/d/1-TLTvTTL0N2qam0O5UhaSUtxwH7bV46unkOpq7_5_dE/edit

Discussion:
After the survey, it was determined that there was a greater diversity of fish species inside the pond versus near the pond and 15 meters away from the pond. The diversity of the fish species gradually decreases as you get farther away from the pond within the area that we surveyed. This is different from last year's findings where there was a higher diversity of fish species outside the fish pond. However, it is important to note that our locations outside the fishpond were in similar depth of water to the fishpond itself, and it is possible that last year surveyed a deeper area of the lagoon which would have affected the fish species they saw. In addition to this, we saw a overall increase of families of fish in all of the sites compared to last year
Compared to previous years, this year our client was less concerned with abundance and wanted to focus more on species richness. With the list of species we have curated at the request of our client, we have categorized them into families. This can be helpful to know because we have learned previously that members of different families exhibit different behaviors and it can be telling of the nature of the ecosystem interactions between fish and their environments. Ultimately with the species list, we hoped to create a bigger picture regarding species interactions. We ended up finding there was an increase in the number of species present using the same transects inside of the fish pond as last year. This increase in species richness could be occurring because of a number of reasons, including the recent swell. Our client mentioned there had been a buildup of algae and sediment in the area, and the swell washed some of these materials out to some degree. We imagine this event cleaned up some of the area, thus increasing the health of the fish pond, bringing more species back into it. Additionally, as time goes on naturally, the fish pond will gain popularity among the fish. As the ecosystem becomes more established, more species will be drawn into the pond. When juveniles come in, this attracts bigger fish and causes a cascade effect of abundance. If conditions in this area remain the same, diversity will likely continue to increase over time. We hypothesize that if the survey was to be repeated next year, the species richness will continue to increase.
We are considering our measurements as time zero for the refuge since it was only established a few weeks ago. Our client was interested in seeing how smaller, more sheltered areas would affect the biodiversity of fish in the location. We have already noticed a variety of different species and families within the refuge and within a meter of the perimeter wall. We calculated a high species per square meter value which is telling of the importance of micro-habitats and how they foster fish biodiversity.
The limitations of our experiment mostly had to do with the physical constraints of the ocean. During our first day of data collection, the tide was low and thus the water level in the fish pond was abnormally low. Still, we stuck to our methods and continued to use the transect to allocate our two meter wide survey area. As a result, some areas were too shallow for fish to be located in–namely the left and right transects inside the fish pond which ran perpendicular to the shoreline. If we had more time to collect data, we would have waited until the tide was higher. Additionally, the current in the area was strong–especially on the first day of data collection–so the transact lines may not have been completely parallel to the walls of the fish pond. Like with our first limitation, if we were given more time, we would have waited for ideal current conditions. Our final limitation is due to the nature of observing fish in the wild. As shown in our data table, some of the species were not fully identified due to the limited amount of data we had—fully relying on memory recollection while collecting data. Therefore, both the stonefish and the shrimpgoby were identified solely by their family name instead of being more specific and identifying their species. Going forward, we would recommend to future researchers to either invest in waterproof identification guides so as to be able to identify species while still in the field or bring a camera along with them while surveying.

Authors: Erick Morales Oyola, Rudy Paddock, Daniel Hirata, and Ezra Bergson-Michelson.

Introduction:
In this survey, we observed the cover of algae both inside and outside of a reconstructed fish pond in Pā’ea, Tahiti, French Polynesia. Fish ponds, as you all know, were traditionally used by the Polynesians as a form of aquaculture. The rock barriers were used to trap adult fish within the fish pond, providing a regular supply of fish when ocean fishing was not possible. Through this survey, we hoped to further understand the ecology of the fish pond, focusing on how the microhabitat created within the rock walls would affect the marine life that the fish pond was supposed to attract. In this survey, the proposed research question was whether or not there was a difference in algae cover and genus abundance inside versus outside the fish ponds.

Methods:
We began by measuring the total area of the fish pond, which was found to be 15 meters by 15 meters. Then, we divided each length into quarters, with markings at 0, 5, 10, and 15 meters. The 0 and 15 meter marks include the area of sand directly adjacent to the rock walls of the fish pond. We laid one transect along the shoreline, labeling it as our x-axis. We laid another transect perpendicular to the shore along the fish pond wall, labeling it the y-axis. Due to limited transect availability, the x-axis points were marked with rocks for reference while in the water. Then, the bottom right corner of the quadrat was laid at each point of intersection. For example, a quadrat was laid at (0,0), then (0,5), (0,10), and (0,15). In each quadrant we estimated the total percent coverage of all algae and recorded the incidence of different algal genus’. The same process was repeated for a 15x15m square that was 15m north away from the fishpond. It was in at the same position out from the shore.

Data:
Our findings were not statistically significant, given that we obtained a P-value of 0.7413. Within the fish pond, there was a 28.00% mean coverage, whereas the control site had a mean algal coverage of 25.13%. The standard deviations for algal coverage for the fish pond and control sites were 26.14 and 22.54, respectively. Our 95% confidence gave us intervals of 28.00+/-12.808 and 25.13+/-11.044 for the fish pond and control sites. Further, the observed instance rates of genus Turbinaria, encrusting algae, genus Halameda, and the ”Other” category were higher in the fish pond. On the other hand, brown turf algae, genus Padina, and genus Sargassum were more common in the control site. Additionally, on the rock walls of the fish pond, brown turf algae was the most common algae found. There were small sporadic patches of various other algae types, including genus Halameda and encrusting algae in addition to branching and encrusting coral. The Shannon diversity index using quadrat instances for algae genuses gives the fish pond site an index of 1.55. The species evenness was found to be 0.866 with a species richness of 6. The total number of individuals was 35, and the average population size was 5.83. The Shannon diversity index for the control site was also 1.55 with a species evenness of 0.863 and a species richness of 6. The total number of individuals was 31 with an average population size of 5.17.

Discussion:
As our results were not statistically significant, we found there was no significant difference between the algal coverage between the fish pond and control sites. However, there were varying trends within each site. In both sites, algal coverage increased with depth. However, in the fish pond site, the underlying substrate was a significant factor in addition to the evident trend of depth and algal coverage. In the fish pond, genus Halimeda and genus Turbinaria were only present on rocky substrates in addition to being more common at deeper depths. Outside of the fish pond at the control site, genus Turbinaria and genus Padina were prevalent at deeper depths, with encrusting algaes being much less common. Turf algae was also less common outside of the fish pond. These observations led us to believe that the fish pond is accurately simulating the natural algal cover of the coastal ecosystems in Pā’ea. However, with only one control site, randomness in choosing the location of this site may have been a factor.

There are a few potential sources of error:

A small sampling size in terms of number of sites.
Proximity of the second site to the fish pond.

Potential areas for improvement:

More sites spread out over a greater area and variety of substrate types.
More sampling sites within the fish pond.

Conclusion:
In conclusion, we found no statistical difference between the algae coverage inside and outside the fish pond. Nonetheless, more research could be conducted to understand more about the microhabitats found within fish ponds.

INTRODUCTION:
The objective of our fish pond monitoring project was to collect data on the behavior and biodiversity of fish families that are found inside the pond, near the pond. as well as in outer regions of the reef. Since the topic and goal for the monitoring project was already given by the previous group, we altered their methods to increase accuracy and precision of the study.

METHODS:
Our methods changed slightly from the past years. To conduct our experiment we measured 3 sites: the inner fish pond, the exterior of the fish pond, and the outer coral reefs. We used transects to collect our data and had two researchers hold the transects at 15m of length while the other 2 researchers swam on either side of the transect, observing the area below them that went 1m out from the line (therefore 30m^2). Three of these transects were taken per site. The recorders swimming noted different fish species, amount of fish per species, as well as the behavior the fish performed when first spotted on the recorder’s swim. Each transect swim took about 3 mins.
To place the transects in the inner pond when facing the water, one transect was along the left wall, one along the right wall, and one at the centerline of the fish pond, also perpendicular to the shore.
The transect of the outer pond simply lined the outer section on the pond going 2m beyond the fish pond structure along the left, back, and right wall.
The outer coral reef collection site was at 328, 05 according to Tomas’ camera determined by a buoy placement that was swam out through the use of a scuba jet. The buoy was placed at approximately 17° 42' 27" South 149° 35' 11" West. Three transect lines were placed perpendicular to the shore mimicking the inner pond formation (each line being 6.5m apart with the center line starting directly on the buoy).

To analyze our data we compared behaviors in the different sites through percentage breakdown and also used a Shannon’s index to find differences in fish species diversity.

Compared to last year (what changes and why)
-Using transects to swim across to count fish and observe their behavior instead of a 20 minute floating survey of a given area to avoid fish recount and for unbiased collection
-The location of observations that were analyzed outside of the fish pond because we wanted to have a better scope of the area between the shore and the wave breaks. Going to the farther reef was also requested since the fish pond ecosystem is supposed to mirror that of a reefs
-The use of statistical analysis to support any anecdotal observation (ie Shannon’s index and percentage comparisons) because beforehand there wasn’t much data we could go off of and compare to, just general observations. Data collection provides a concrete comparison for people who will replicate the experiment in the future

RESULTS

General fish spread
We saw mostly damselfish, wrasse, and Butterfly fish. In both the outer and inner pond damselfish were the dominant family while wrasse was the majority in the outer reef with damselfish second. We saw a wider variety of fish families in the outer reef where we saw 11 families compared to the inner and outer pond which had 7 and 5 families respectively.

Shannon’s index
The calculated Shannon's index in the outer reef was 1.63, 1.26 in the outer pond, and 1.19 in the inner pond. This supports the fact that diversity was highest in the outer reef compared to the inner pond.

Fish per square meter
In the outer reef, we found 2.23 fish per square meter, outside the fish pond there were 1.104 fish per square meter, and inside the pond there was less than 1 fish per square meter. This information shows that the outer reef also had higher abundance than the other two sample sites.

Behaviors in each area: Top percentages of each behavior

Lagoon- 44.3% were freely swimming, 19.9% were territorial, and 16.4% were eating coral

Outer pond- 41% were freely swimming, 25.6% were territorial, and 12.8% escaped

Inner pond- 47.2% were territorial, 33% were freely swimming, and 10.4% were eating algae

Which behaviors were done by fish families: Top percentages

Lagoon:
Territorial fish - 100% were damselfish
Swimming fish - 58.4% were wrasse and 20.2% were damsel
Coral eaters - 81.8% was an unidentified fish that we think is a juvenile parrot fish

Outer pond：
Swimming fish - 40% were damsel, 28.6% were goat fish
Territorial - 92% were damsel, 6% were soldier
Escaped, 90% were damsel, 10% were butterfly

Inside pond:
Territorial - 100% were damsel fish
Swimming - 56.2% were damsels
Algae eaters - 100% were wrasse

Discussion

Overall, our group found that there was a higher diversity in the outer reef than the inner pond as well as the two meter perimeter surrounding the pond, which was also observed by last years group.This is reflected by our Shannon’s index values, where the outer reef value was greater by 0.44. Additionally, we observed a higher abundance of fish in the outer reef, which is seen in our data concerning fish per square meter, where the outer reef had about 4.5 times more fish per square meter than the inner pond.

We hypothesize that biodiversity is greater in the outer reef because there’s a significant difference in coral abundance, which acts as a resource for food and habitat. Next, we saw the the most predominant behavior was freely swimming except for in the pond where the top behavior was territorial. Territorial was the next most common behavior in the other areas as well. Damsel fish were most predominant in the territorial behavior category. A notable thing we noticed was that there was a high amount of damsel fish inside the pond made up of Gregory and the banded sergeant. We saw a disproportionately large amount of territorial behavior inside the pond compared to outside the pond where we sampled more wall space which tended to host territorial behavior.

We hypothesize that higher territorial behaviors in the pond could be related to the size of the pond. The smaller space may cause competition for resources and habitat.

Our biggest take awaysys were that damsel fish were a dominant family inside of the pond leading to high levels of territorial behaviors. This is a similar finding as last years group. Additionally, we noticed a higher percent of damsel fish inside the pond compared to outside the pond and the outer reef also similar to last years group.

https://docs.google.com/document/d/1-lte3bJXD-KZUitAeGB48uavjCKzf1KFa8uRnnCQIVM/edit?usp=sharing

Bella Suhr, Olivia Berman, Bailey Wallace, Lucy Baker
Wildlands French Polynesia 2023
8/2/23

Fish Pond Substrate Composition Survey
https://docs.google.com/document/d/1-_xiPjURRbfSaKJYJ18934KN3xzoPCz9PMNh0XWtimo/edit?usp=sharing
(Click the link for figure and data tables)

Introduction:

We began this experimental survey as a follow-up to the Wildlands 2022 French Polynesia group whom conducted a substrate composition survey of a locally owned traditional fish pond in Taverea, Tahiti, on the Western side of the island. The owner of the fish pond requested insight regarding the main composition and type of substrate cover occurring in his pond. The previous research indicated the highest composition to be sand at 49.4%, then microalgae at 27.3%. This previous study had a sampling universe that included the pond and a 1-meter buffer around the pond's rock barrier and used randomly selected sample sites. This resulted in placing the inside and outside of the fish pond in one data set rather than separate resulting values that would allow for the comparison of the two. This previous survey provided a good basis for our prospective substrate composition but after further discussion with the owner of the pond. We decided to complete a new survey to observe any differences between the substrate within the fish pond, the region left of the fish pond, and the right of the fish pond. These are observed looking at the fish pond from the shore. This is due to the fact that a channel in the lagoon causes the current to flow South to North, or left to right when looking at the fish pond from the shore. This means the water flows through the left side, then through the rock barrier of the pond, and out to the right side. This produced our research question; If the fish pond is acting as a barrier or filter for the South to North current in the lagoon, what effect does the fish pond have on the substrate composition along the shore? To investigate this we decided to formulate our own methods that allowed us to compare the fish pond substrate composition to its surrounding areas.

Methods:

We began by taking measurements with a tape measure of the inner wall of the fish pond and found it to be 14.1x13 m (width x depth). The image above demonstrates our sampling universe, with the black square representing the fish pond, the red square showing our sample area to the left of the pond, and the green square showing our sample area to the right of the fish pond. Using 2 transects we laid out a 14.1x13m grid in each of our three locations. We determined the x-axis to be 14.1 m (horizontal to the beach) and the y-axis to be 13 m (vertical to the beach). With a random number generator, we determined 10 random coordinates on the x-axis and y-axis for each location, thus adding up to a total of 30 coordinates for the whole sampling universe. The bottom left corner of each box was deemed the (0,0) coordinate and a grid was formed. At each coordinate we used a 1 meter by 1 meter quadrat to assess the percent coverage on the grid, only considering the uppermost primary substrate layer. We classified the substrate by alive coral, sand, dead coral, rock, microalgae, and macroalgae. For this study, we considered microalgae to encompass algae less than 1cm and macroalgae to be larger than 1cm. One person held the quadrat down in place, another person recorded the values, and the final two people acted as observers of the substrate type. The two observers would look into the water with snorkel masks and estimate the percent of each substrate within the quadrat. The two agreed on the percentages for each sample quadrat and reported them to the recorder. When assessing percent coverage we did not go over 100%, we recorded only the topmost layer of the substrate. The values were recorded on waterproof slates and this sampling method was repeated for each of the 30 random coordinates, keeping the data for each of the left, fish pond, and right areas separate from each other.

Results:

The data collected throughout our study is represented in the tables in the Google doc linked above.

Analysis:

Upon comparing the mean substrate coverages with independent sample t-tests between the left and fishpond, fishpond and right, and left and right sample areas for each substrate category, we found that there is no statistically significant difference in mean substrate coverage in all 3 sample universes.

In regards to our research question (if the fish pond is acting as a barrier or filter for the South to North current in the lagoon, what effect does the fish pond have on the substrate composition along the shore?), our results suggest that the fish pond has a negligible impact on the substrate coverage on the area immediately surrounding the fish pond.

This could indicate that, in terms of substrate, the fish pond is not significantly altering the substrate coverage directly surrounding the fish pond thus the substrate environment is similar inside the fish pond as it is directly to the right and left of it.

When comparing this year's data to last year's, we did notice that the substrate coverage of sand has increased (2022 - 49% sand, 2023 - 77% sand inside the fish pond. We are not able to determine statistical significance between these averages due to the differences in the sampling universe, but it is a noticeable difference that could be due to various factors. One factor could be that last year's sample universe included the rock barrier of the fish pond itself. Another factor could be that the sand substrate coverage did actually increase, but we cannot determine that for sure with the data we collected.

As an anecdotal observation, we did notice that the particle size of the sand varied between the three sample sights and in smaller microhabitats. We did not have the instruments, resources, or time to properly investigate this observation.

In a future study, a possible endeavor could be the investigation and analysis of the substrate depth and its relation to the size of sand particles. As the current could be pushing sediment through the fish pond and acting as a sieve that only allows smaller particles to pass through. Meaning a build-up of sand could be occurring and the substrate could be affected in that way rather than a substrate coverage alteration.

Therefore there is room for more investigation of the substrate within and around the fish pond and we look forward to future results. Thank you.