The Impact of Tide Pool Size on Species Richness and Diversity on Hurricane Island, Maine. Elsa Nierenberg and Yulin Holder

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1 The Impact of Tide Pool Size on Species Richness and Diversity on Hurricane Island, Maine Elsa Nierenberg and Yulin Holder Chapter 2 May 17-25th, 2017

2 The Impact of Tide Pool Size on Species Richness and Diversity on Hurricane Island, Maine Using approximations of percent coverage, we calculated the diversity and species richness of varying sized tide pools in two different areas. Our goal was to determine if larger size indicated greater diversity. Ultimately, we created a baseline of what tide pools in this area look like. Our data suggests that larger tide pools indicate greater species richness and possibly more diversity. This is important because it means that looking at these tide pools over time could show the effects of climate change and other factors on this habitat and the species that occupy it. More data is needed for more definitive conclusions. Introduction Tide pools in the rocky, intertidal zone in Maine are often very diverse. This diversity affects access to food, competition, species richness, and many other aspects of the miniature and isolated ecosystem that is the common tide pool. Our objective was to determine the impact of size on diversity and species richness, ultimately answering questions about the health of the marine life on Hurricane Island, creating a baseline study and a reference list of species found in tide pools in this area. Increased diversity has been correlated with increased size (specifically surface area) in past studies, however none have been on the specific tide pools on Hurricane Island. One such study, performed by Western Washington University in an unspecified tropical area found that species number increases with habitat diversity, and larger areas tend to contain more kinds of habitats ( Project 7: Species Richness in Tidepools, 2010). A second study by the University of Minnesota in the Bahamas determined that surface area of the tide pools was best at determining abundance (meaning that larger pools had more organisms living in it and that larger size encouraged more growth). They also noted that intermediate intertidal zones had greater species diversity because of the balance between food and competition as well as other factors such as ph and temperature (University of Minnesota, 2008). Given that these warmer climates are very different from the shores and tide pools off the coast of Maine, other studies and background information were used to better predict the patterns of diversity. One such study (taking place in Washington state at Tatoosh Island) primarily focused on behavior in tide pools and found that tide pool size correlates with population size. The study noted that the increase in species diversity with an increase in island or insular habitat area is well documented ( Pfister, 1998). There s also evidence that suggests that tidepools separate from inflow of ocean water have a different environment than those that are not isolated. A study of tide pools in the Carrigathorna and Barlogie Creek regions (Mt. Hood National Forest, Oregon) noted that the isolation of tide pools can heavily impact their diversity; much greater changes in flora and fauna may be expected in those pools which are continuously separated from the sea (Diamond, 1988). However, some of the most valuable information came from past student projects on Hurricane Island. These projects helped define the norms of an intertidal zone famous for its Chapter 2. Page 1

3 variation and helped lay the groundwork for creating methods of testing that would be effective in this area. In 2016, a study on location of tide pools in relation to diversity was conducted. Some of the most relevant information was that lower intertidal regions were found to be more diverse, areas with greater disturbance had more diversity, and Littorina littorea were the most dominant species in intertidal at the time of the study (Kenney, 2016). Another study looked at coralline algae and periwinkles in tide pools and noted that the snail population was lower in areas with more algae (Sfiat, 2014). This added another element to consider in our study: the interconnectedness of tide pool species. All of the past studies looking at tide pools on Hurricane Island used similar methods of measurement-- averaging depth measurements and using percent covered to determine species presence. Several of these studies also took base measurements for things like temperature and ph in order to compare tide pools and isolate the factors they were studying. Kenney and Sfiat both thought that their findings might be related to factors such as intertidal height and disturbance. The bottom line was that different areas of Two Bush Island had different tide pools and varied significantly. This would be something we would have to take into account when comparing tide pools. Given the background information that supports our hypothesis, and the overlaps of findings in past studies on Hurricane Island, we hypothesized that tide pools larger in size (specifically surface area because our research suggests that this is more significant than depth) would have both greater species diversity and species richness. We believe that this will be true because more area allows for more niches and for different creatures that affect diversity to thrive. We believe that finding data that supports our hypothesis could ultimately answer questions about the health and diversity on Hurricane Island, create a baseline study and a reference list of species found in tide pools in this area, and offer the potential of a future impact study looking at climate change and tide pool diversity. Materials and Methods Computer with excel Meter stick (for measuring depth) Compass Meter tape (for measuring height and width of tidepools) Notebooks w/pens or pencils (to record data) Field guide: A Field Guide to the Atlantic Seashore by Kenneth L. Gosner Thermometer ph meter Refractometer Pipette Stadia and phone with Sea Level app Waterproof camera (to photograph tidepools) GPS (to get location of each tidepool) Plastic beaker (for bringing specimens back to identify) Locations of studied tide pools Chapter 2. Page 2

4 Tide pool number 1A 2A 3A 4A 5A 6A 7A 1B 2B 3B 4B 5B 6B 7B Coordinates 19T / UTM 19T / UTM 19T / UTM 19T / UTM 19 T / UTM 19T / UTM 19T / UTM 19 T / UTM 19 T / UTM 19 T / UTM 19T / UTM n/a (GPS was not available) n/a n/a Study Site All of the tide pools observed were directly in the sun, with little to no shade. Set B of the tide pools was closer to the ocean and had a more constant and direct inflow of water. As the tide came in, the Set B of the tide pools would combine and no longer be isolated; however, when we studied them, they were all isolated or almost isolated. The amount of shell hash varied from tide pool to tide pool, with Set A of the tide pools having a considerable amount more than Set B. Set A was also located in an area with more Rockweed and Bladder Wrack inside of or surrounding the tide pools. All of the tide pools were formed either in small depressions between rocks or in the cavity of one rock Chapter 2. Page 3

The blue dots are approximations for set B.

5 Image of the area between Two Bush and Hurricane Island where the tide pools are located (google maps street view feature). Note that the red dots are approximations for set A locations. The blue dots are approximations for set B. For orientation, the trees at the backdrop are on Hurricane Island. Tide pool 6A-- one of our largest and most irregularly shaped pools Chapter 2. Page 4

6 Procedure 1. Identify an area that has a large number of tidepools relatively close to each other and approximately at the same intertidal height but varying in size 2. Choose one tidepool to analyze 3. Walk around the tidepool (not in it, as to avoid disturbing the organisms inside or scaring them into hiding) and identify and record all of the species inside the tide pool (this includes every species that is submerged in water, if only a part of the species is submerged, use only the submerged part in your estimation. Keep this consistent with every tide pool,) use a field guide to do this, with trickier species that can t be immediately identified, place a sample in the plastic beaker with seawater to bring back to the lab and identify there 4. After identifying all of the species in the tidepool, spending at least 5 minutes moving seaweed and looking into crevices, start approximating percent coverage of the species out of 100%, looking at the entire pool. Do this with a partner, with each person coming up with their own approximation and then average the two or compromise until a percentage is agreed upon. 5. Repeat Step 4 for each species in the pool. Do not worry about making sure the percentages add up to 100% because species overlap. 6. Pick three random points to measure depth in the pool, placing the meter stick upright in those locations, then average the 3 depths and record this average as the depth. 7. Take the thermometer and submerge the end into the tidepool until it appears that the reading has stabilized, almost touching the bottom but avoid touching the thermometer with anything else, (when picking the place to submerge the thermometer, try to choose an area that is close to the average depth of the tide pool) and record the temperature 8. Take the ph meter and place the tip into the water, wait for ten seconds and then press the hold button and record the reading 9. Take the pipette and fill it with water from the tidepool by squeezing the end, then empty it by squeezing the end again, do this three times (we did this to ensure that our salinity reading would not be contaminated with water from any previous tide pools), then fill up the pipette, flip open the end of the refractometer and squeeze a drop onto the glass surface, (make sure to wipe off the surface after each use) flip the cover back on and look through the eyepiece, turning toward the light. Look at the line between the blue and white areas and the dashes labeled with numbers. See which number the line fits with (look at the right hand column of numbers) and record this as the salinity reading in ppt. 10. Use the GPS and record the exact coordinates of the tidepool. Stand towards the center of the tide pool when taking the coordinates. 11. Measure the length and width of the tide pool using the meter tape, picking the widest points. The measurement of the length should be taken perpendicular to the width measurement. 12. Have one person stand in the middle of the tidepool holding the stadia upright. Have another person identify the high tide line (usually indicated by the top row of barnacles) Chapter 2. Page 5

7 and stand at that height holding a meter stick upright. Use the See Level app, tilting the phone until all of the lines are level with the top of the stadia. Record the height of the top of the phone. Subtract this from the height of the stadia and record the result as the intertidal height. 13. Record observations of shading, direction of water flow and anything else that sets each tide pool apart from the other. Use a compass to determine the direction from which the ocean flows into the tide pool if possible. Also note the time of day and weather. 14. Repeat this procedure for each tide pool, analyzing as many tide pools as possible and aiming to analyze tide pools of varying sizes. If needed, move to a new area with more tide pools and note the differences in areas. 15. When graphing the relationship between area and species diversity as well as area and species richness, (scatter plot graphs) use the Pearson Correlation Coefficient to find the R value. Then use the R score to calculate the P value. We used We used the Pearson test because it takes into account the size of the data set. When comparing the average percent coverage of a species in shallow versus deep tide pools, run a T Test to determine if the difference is significant (if the p value is less than.05, the difference is significant). Definitions Species Diversity - Species diversity relates to the number of species in the community and the relative abundance (evenness) of each species. Species Richness - Species Richness is the number of species an area contains (simply a count of species, does not take abundance into account). Shannon Index Formula H = - [p i * ln(p i )] Where, = Summation p i = Number of individuals of species/total number of samples Results Figure 1. Table of species found in observed tide pools Gastropods Common periwinkle (Littorina littorea) Smooth periwinkles (Littorina obtusata) Waved whelk (Buccinum undatum) Tortoiseshell limpet (Tectura testudinalis) Dog whelk (Nucella lapillus) Algae Brown algae Red algae (Hildenbrandia) Rockweed (Ascophyllum nodosum Bladder wrack (Fucus vesiculosus) Cord weed (Chorda tomentosa) Chapter 2. Page 6

8 Common Atlantic slipper snail (Crepidula fornicata) Sea lettuce (Ulva lactuca) Coralline algae Bivalves Irish moss (Chondrus crispus) Bushy red weed (Cystoclonium Blue mussels (Mytilus edulis) purpureum) Spongomorpha Crustaceans Common Southern Kelp Green crab (Carcinus maenas) Dulse (Rhodymenia palmata) Northern rock barnacles (Semibalanus balanoides) Aphidic algae Amphipod Unidentified encrusting green algae Unidentified crab Coral weed (Corallina officinalis) Atlantic rock crab (Cancer irroratus) Sea Potato (Leathesia difformis) Long wrist hermit crab (Pagurus longicarpus) Soft sour weed (Desmarestia viridis) Crumb of bread sponge (Halichondria panicea) Polychaete Spirorbis (worm) Unidentified worm Echinoderm Green Sea Urchin (Strongylocentrotus droebachiensis) Vertebrates Fish Larvae Chapter 2. Page 7

9 Figure 2. Species richness increases over all as tide pool area increases. Pearson P value is This trend is significant. Note: Area is in quotations because we calculated surface area by measuring the widest and longest parts of the tide pools (most of which were irregularly shaped) and so the area is an approximation Chapter 2. Page 8

10 Figure 3. There is greater diversity in larger tide pools, however this trend is not significant. Pearson P value of Chapter 2. Page 9

11 Figure 4. There is greater diversity in larger tide pools. This trend is significant. Pearson P value of Figure 5. There is greater diversity in larger tide pools, however the trend is not significant. Pearson P value of Chapter 2. Page 10

12 Figure 6. The average percent coverage of coralline algae was significantly higher in deep tide pools compared to shallow ones. The average amount of coral weed was significantly lower in deep tide pools compared to shallow ones. (P value from T test is 0.02 for Coralline algae and 0.02 for Coral weed. The other species are not significant.) Note: Deep tide pools were determined as pools larger than 10 cm in average depth. Discussion Our data partially supports the research findings that we used to create our hypothesis. Overall, our data suggests that larger surface area in a tide pool does correlate with species richness (Figure 2) and that species diversity could possibly correlate, however more research and data is needed (Figure 5). This trend could be explained by the fact that larger tide pools provide a more varied environment, so a greater number of different species could thrive there. We also found that the data from tide pool Set B suggests that species diversity increases as size increases (Figure 4). As we will discuss more below, this could be because the difference in depth allows for a greater range of species or because of the greater inflow of water. However, Set A, alone, was not significantly related to diversity (Figure 3). When considering Set A and B as a whole, compared with diversity, the trend is not significant (Figure 5). Based on our findings, we believe that with more data from surveying larger tide pools, a stronger correlation Chapter 2. Page 11

13 could be found in future projects. As part of our data analysis we were able to study five types of interesting species and compare their presence in tide pools of various depths (Figure 6). We found that coralline algae and coral weed were significantly different in shallow and deep tide pools. Interestingly, these two species are related, however the coralline algae was much more prevalent in deeper pools and the coral weed in shallower pools. We also found that species can vary significantly in their presence depending on how close the tide pool is to the ocean and if there is an inflow of ocean water. This could be because the more direct inflow causes differences in salinity, temperature, and the movement of the water (disturbance). This could also be because the tide pools in Set B were deeper, creating an almost entirely different environment under the surface. A potential future project could consider the factors of distance from the ocean and intertidal height. It is important to note that we found these trends after collecting data which could mean we were biased in trying to find a significant difference and we could be reporting a false relationship. Future projects should hypothesize about species and how their presence may vary based on depth before gathering data. Our sources of error include our approximations in percent coverages, which we tried to counteract by individually approximating and then taking the average of our approximations. However, we could not completely eliminate bias and our quick approximations vary in accuracy. A grid system could also be used to estimate percent coverage more accurately. Future projects could try other ways to enumerate species perhaps by only focusing on species richness, counting individuals rather than approximating or possibly measuring the space each species occupies based on the size of an individual. We also had limited access to larger tide pools which would be needed in future studies to establish a significant trend. To address this problem, future studies could perhaps try a new location outside of Two Bush Island. Another source of error is that we surveyed tide pools on different days and at different times, meaning that our measurements of salinity, temperature, ph and intertidal height could all have been affected by changes in weather and tide. Future studies could take measurements at a fixed time after the start of low tide in order to regulate this more. We also had to assume that all of our tide pools were relatively similar in our baseline measurements which could also affect the number and amount of species in the tide pools. Our measurements of depth also were not exactly random as we chose spots in the tide pools without using a die or calculator; we would recommend using a die or calculator in the future to take random samples. Additionally, our two sets of data were taken in different intertidal heights, with different inflows of water, so comparing tide pools across sets means we disregarded these differences which could impact diversity. Thus, our experiment is not truly controlled so we cannot make definitive conclusions (aside from needing more data). To fix this, future studies could try to pick only one area or pick areas that are at a similar intertidal height (ours varied by 63 cm) and distance away from the ocean. The most influential errors are inaccuracy of approximations and the differences in intertidal heights between tide pools. Potential future projects could include studies that look at other factors related to tide pool diversity, as above mentioned, location including intertidal height or different parts of the island. There is also the potential for a more long term impact study that analyzes tide pool diversity on Hurricane Island and how it is affected by global warming or other human impacts Chapter 2. Page 12

14 Using the reference sheet of species we found, a future project could also expand on this list to create a field guide of species in tide pools in this area. There is also the possibility of a project looking more in-depth at the differences in tide pools in Set A and Set B, more specifically analyzing what diversity looks like when an inflow of water is present versus in an isolated pool. The goal of our study was to create a baseline and a snapshot in time of tide pools in this area and show a correlation in size to diversity and species richness. If our hypothesis could be proven then that would mean areas with more tide pools create more environments for a wider range of species and indicates the health of that environment. References Diamond, Jared. Factors Controlling Species Diversity: Overview and Synthesis. Annals of the Missouri Botanical Garden, vol. 75, no. 1, 1988, pp , Goss-Custard, Susan, et al. Tide Pools of Carrigathorna and Barloge Creek. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, vol. 287, no. 1016, 1979, pp , Gosner, Kenneth L. A Field Guide to the Atlantic Seashore: Invertebrates and Seaweeds of the Atlantic Coast from the Bay of Fundy to Cape Hatteras ; Text and Illustrations. Boston: Houghton Mifflin, Print. Kenney, Noah Effect of Location on Tidepool Diversity Study. Working paper. N.p.: n.p., n.d. Print. Project 7: Species Richness in Tidepools (n.d.): n. pag. Department Of Environmental Sciences, Western Washington University, 28 Feb Web. < >. Pfister, Catherine A. Extinction, Colonization, and Species Occupancy in Tidepool Fishes. Oecologia, vol. 114, no. 1, 1998, pp , Sfiat Coralline algae and periwinkles in tidepools. Working paper. N.p.: n.p., n.d. Print. "Tide Pools." University of Minnesota Duluth. University of Minnesota, 02 May Web. 12 May < >. Williams, Jennah. "The Correlation between Rock Pool Size and Species Diversity." Journal of Aquaculture & Marine Biology 2.4 (2015): n. pag. Web Chapter 2. Page 13

Chapter 1: The Rocky Intertidal: Disturbance and Diversity Pirates of the Intertidal: On stranger Tides. By: Connor Rooks and Austin Grace.

Chapter 1: The Rocky Intertidal: Disturbance and Diversity Pirates of the Intertidal: On stranger Tides By: Connor Rooks and Austin Grace Introduction Abstract In our study, we investigated the intermediate