Predation within the intertidal zone, specifically regarding the predator-prey interaction between sea stars in Class Asteroidea and their food source, contributes to a large biodiversity of organisms. In this experiment, we compared the percent coverage of algae and shelled organisms within a quadrat surrounding three types of predatory sea stars (Pisaster ochraceus, Dermasterias imbricata, and Lepasterias hexactis) to determine their habitat based on predatory behavior. Our data showed a significant difference in algae and shelled organism coverage between different species of sea star; shelled organism percent coverage was less than algae percent coverage in all species of sea stars. The niche, or role and position a species plays in its environment, of each star ultimately influenced the frequency and diversity of other recorded organisms

Farzadpour, Shayan

Lott, Jana

Smith, Desa

Williams, Savannah

English

Digital Commons@Humboldt State University (HSU)

IdeaFest: Interdisciplinary Journal of Creative Works and Research from Humboldt State University Volume 4 IdeaFest Journal Article 5 2020 Differences in Algal, Gastropod, and Arthropod Coverage Surrounding Pisaster Ochraceus and Other Asteroids in Humboldt County, California Desa Smith Humboldt State University Jana Lott Humboldt State University Savannah Williams Humboldt State University Shayan Farzadpour Humboldt State University Follow this and additional works at: https://digitalcommons.humboldt.edu/ideafest  Part of the Marine Biology Commons Recommended Citation Smith, Desa; Lott, Jana; Williams, Savannah; and Farzadpour, Shayan (2020) "Differences in Algal, Gastropod, and Arthropod Coverage Surrounding Pisaster Ochraceus and Other Asteroids in Humboldt County, California," IdeaFest: Interdisciplinary Journal of Creative Works and Research from Humboldt State University: Vol. 4 , Article 5. Available at: https://digitalcommons.humboldt.edu/ideafest/vol4/iss1/5 This Article is brought to you for free and open access by the Journals at Digital Commons @ Humboldt State University. It has been accepted for inclusion in IdeaFest: Interdisciplinary Journal of Creative Works and Research from Humboldt State University by an authorized editor of Digital Commons @ Humboldt State University. For more information, please contact kyle.morgan@humboldt.edu. Differences in Algal, Gastropod, and Arthropod Coverage Surrounding Pisaster Ochraceus and Other Asteroids in Humboldt County, California Acknowledgements We wanted to give a big thanks to Humboldt State's biology department for supplying us with the tools necessary to complete this experiment. Also thank you to Adrian Macedo for guiding us through this project. This article is available in IdeaFest: Interdisciplinary Journal of Creative Works and Research from Humboldt State University: https://digitalcommons.humboldt.edu/ideafest/vol4/iss1/5 Differences in Algal, Gastropod, and Arthropod Coverage Surrounding Pisaster Ochraceus and Other Asteroids in Humboldt County, California Biological SciencesideaFestJournalDesa Smith (Humboldt State University), Jana Lott (Humboldt State University), Savannah Williams (Humboldt State University), Shayan Farzadpour (Humboldt State University)AbstractPredation within the intertidal zone, specifically regarding the predator-prey interaction between sea stars in Class Asteroidea and their food source, contributes to a large biodiversity of  organisms. In this experiment, we compared the percent coverage of  algae and shelled organisms within a quadrat surrounding three types of  predatory sea stars (Pisaster ochraceus, Dermasterias imbricata, and Lepas-terias hexactis) to determine their habitat based on predatory behavior. Our data showed a significant difference in algae and shelled organism coverage between different species of  sea star; shelled organism percent coverage was less than algae percent coverage in all species of  sea stars. The niche, or role and position a species plays in its environment, of  each star ultimately influenced the frequency and diversity of  other recorded organisms. Keywords: asteroids, algae coverage, gastropod, arthropod, intertidal, Pisaster ochraceusIntroductionThe beaches in Northern California consist of  rocky intertidal shores, which are inhabited by various marine invertebrates and a wide selection of  algae (Foster et al. 1988). The intertidal zone can be broken up into four smaller zones, described by the species that inhabit those zones (Foster et al. 1988). The two lowest zones, the Splash Zone and the Barnacle Zone, are mostly comprised of  kelp, sea stars, mussels, and barnacles. One of  the most common inhabitants in Northern California is the ochre star Pisaster ochraceus, accompanied by the leather star (Dermasterias imbricata) and six-rayed star (Lepasterias hexactis). Asteroids are carnivorous, and their diet consists mostly of  shelled organisms, such as mussels (Paine 1976, Penchaszadeh and Lera 1983, Monteiro and Pardo 1994). These sea stars are often found near areas of  dense mussel beds or other food sources (Paine 1976). Differences in algal, gastropod, and arthropod coverage surrounding Pisaster ochraceus 39ideaFestJournalSea stars play an important role in the inter-tidal zone, they are described as a keystone species based on how their presence increases biodiversity due to their predation on mussels (Manzur et al 2009). Biodiversity is crucial to keeping an ecosys-tem functioning, as each species has their own role in the productivity of  that ecosystem. In this study, we looked at different species of  sea stars and the habitats immediately surrounding them by mea-suring algae coverage and animal coverage in that area. Animals that were observed in this area in-cluded gastropods such as marine snails and lim-pets, and arthropods such as hermit crabs. With the impending threat of  climate change, intertidal species are at a greater risk of  desiccation, or dry-ing out, which can threaten the species survival. Tracking sea star’s prey selection can help scien-tists to measure the health of  this keystone species. We hypothesize that shelled organisms should be more abundant than algae near sea stars because sea stars are more likely to be found in dense areas of  food sources, such as mussel beds. MethodsWe measured algae and shelled percentage coverage among 51 P. ochraceus and a combined 31 D. imbricata and L. hexactis. We collected data three separate times at Patrick’s Point State Park (41.1298° N, 124.1651° W) and Baker Beach (41.0477° N, 124.1236° W) at low tide during the week of  November 10th-17th, 2019 (Fig 1). The low tide levels ranged from -0.3 ft to 2.6 ft. Percent coverage was determined using a 0.50 x 0.50 meter quadrat with 100 squares, each square representing 1% coverage. We centered the quadrat on the sea star and counted squares occupied by algae or shelled organisms. Percent coverage of  algae and shelled organisms between P. ochraceus and other stars was analysed using the statistical program R. Three tests were run: the Shapiro-Wilk normality test to determine data normalcy, an F-test to compare variances, and a Wilcoxon rank sum test with continuity correc-tion for determining significance of  differences seen in the data. ResultsThe average quadrat makeup differed be-tween the groups of  sea stars we compared. Re-sults from F- and the Shapiro-Wilk test indicated that most data sets did not meet statistical stan-dards for equal variance and normality (Table 1, Table 2); this led us to run a Mann-Whitney test to determine significance (Table 3).  Algae was the most abundant group through-out the duration of  the experiment, no matter the asteroid we measured (Fig 2). Even with this, the Mann-Whitney test showed significant differences between algae percent coverage of P. ochraceus com-pared to other sea stars in the intertidal zone; there Table 1. Summary of  F test comparing the variance between the different groups (F = f  distribution factor, df  = degrees of  freedom). Comparison Groups F Num df Denom df P-valueAlgae: Pisaster v Other 1.2661 49 37 0.458Shelled: Pisaster v Other 5.1344 33 22 0.0001675Pisaster: Algae v Shelled 284.7 49 33 < 2.2e-16Other: Algae v Shelled 1154.6 37 22 < 2.2e-1640 Smith, Lott, Williams, FarzadpourideaFestJournalis significantly more algae surrounding D. imbricata and L. hexactis than P. ochraceus (p-value 2.47e-05, Table 4). When comparing shelled organisms, we see a different pattern arise. The mean percent coverage of  shelled organisms is significantly dif-ferent, but with a majority of  shelled organisms surrounding P. ochraceus (p-value 0.0004525).By looking at the data, it is apparent that there was a difference in shelled and algae coverage within each sea star group. There is significantly more algae in both groups compared to shelled organisms (p-value < 2.2e-16, Table 4).DiscussionOur data and measurements provided our re-search group with indications that did not support our hypothesis, namely, that if  sea stars predomi-nantly feed on shelled organisms, then the percent coverage of  shelled organisms would surpass that of  algae within each quadrat sample. We recog-nized that the opposite was true; the percent cov-erage of  algae actually exceeded that of  all sea stars and shelled organisms in almost every quad-rat that was sampled. Although the experiment we conducted did not cater to our initial hypothesis, the frequency of  our measurements provided us with a better understanding regarding the differ-ences, similarities, and patterns between percent coverage of  shelled organisms and algae in rela-tion to the different sea stars. Average percent coverage of  algae was great-er among L. hexactis and D. imbricata than that of P. ochraceus. However, the average percent coverage of  shelled organisms was greater among P. ochra-ceus. This is most likely due to the protection that the algae may provide for smaller sea stars, such as L. hexactis; Leptasterias spp., which are noted to Fig 1.  Map of  Humboldt County showing the locations of  data collection (Baker Beach and Patrick’s Point State Park). Adapted from Ashton et al. 200641ideaFestJournalDifferences in algal, gastropod, and arthropod coverage surrounding Pisaster ochraceus Table 2. Summary of  Shapiro-Wilk test for normality in each data set (W = W-value). Data sets W P-valueAlgae (Pisaster) 0.86301 3.549e-05Algae (Other) 0.93393 0.02672Shelled (Pisaster) 0.86395 0.0005831Shelled (Other) 0.81916 0.0007892Table 3. Summary of  Wilcoxon rank sum test comparing differences within the two groups of  sea stars and between the two groups of  sea star (W= rank totals) Comparison Groups W P-valueAlgae: Pisaster v Other 449.5 2.47e-05Shelled: Pisaster v Other 605 0.0004525Pisaster: Algae v Shelled 1662 1.255e-13Other: Algae v Shelled 874 7.621e-11reside in mussel beds or in nearby pools, usually in contact with sea grass or algae (Jaffe et al. 2019) We observed that P. ochraceous  were found more often attached to bare rock, while other sea stars were found more submerged in water. Our data also shows that a variety of  other organisms such as anemones, urchins, and nudibranchs were re-corded within L. hexactis and D. imbricata quadrat samples, while P. ochraceus was often seen only in the presence of  algae or some shelled organisms. The niche of  each star ultimately influenced the fre-quency and diversity of  other recorded organisms. Identifying diet according to each individual species would strengthen this study and may pro-vide more conclusive results in the future, as well as recording data in control quadrats that did not contain sea stars. Understanding the prey selection of  sea stars and their location within the intertidal zone drives the understanding of  the ecosystem as a whole; a change in sea star behavior would cause catastrophic change in the structure of  the inter-tidal zone. This was observed during the seastar wasting disease outbreak in 2014, when the pop-ulation of  sea stars on the West Coast, specifical-ly P. ochraceus, was impacted by the disease. This caused a significant reduction in predation rates of  mussel beds (Menge et al. 2016), which results in decreased biodiversity and community struc-ture (Paine 1976). Studying the habitat selection of  different sea stars provides future scientists with a basic understanding that is necessary to protect these keystone species in our intertidal zone. With 42 Smith, Lott, Williams, FarzadpourideaFestJournalTable 4. Summary of  the averages of  algae coverage and shelled organisms organized by type of  sea star it was surrounding; group “Other” is a combination of  six rayed stars (L. hexactis) and leather stars (D. imbricata).Group Pisaster ochraceusMeanPisaster ochraceusSTDOtherMeanOtherSTDMean % Algae coverage 31 24 49 21Mean % Shelled organ-isms1.9 1.4 0.74 0.62Mean % Anemone 2.1 1.7 0.80 0.40Mean % Nudibranch 0 N/A 0.31 0.19Mean % Chiton 0 N/A 8.0 2.8Mean % Sea Urchin 0 N/A 6 0Fig 2. Comparison of  mean percent cover of  sea star, algae, shelled organisms, and anemones between Ochre stars (P. ochraceus) and the Other group (L. hexactis and D. imbricata)43ideaFestJournalDifferences in algal, gastropod, and arthropod coverage surrounding Pisaster ochraceus the impending threat of  climate change, species higher in the intertidal zone, such as the ones we observed, are at a greater risk of  desiccation. The temperatures the sea stars experience determine where in the intertidal zone they are located, which in turn could affect their foraging abilities (Helmuth and Wethey 2009). This stress causes shelled organisms to grow slower, and moving through the food chain would result in less nutri-ents for the sea stars. The risks of  climate change are only growing; knowing how sea stars rely on their prey can help us track the survival of  this keystone species. ReferencesAshton, Don & Marks, Sharyn & Welsh, Hartwell. (2006). 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PLos ONE. 11(5). doi.org/10.1371/journal.pone.0153994Manzur, Tatiana et al. (2009). Ontogenetic chang-es in habitat use and diet of  the sea-star He-liaster helianthus on the coast of  central Chile. Journal of  the Marine Biological Association of  the United Kingdom, 90, 537-546. Monteiro, A. M. G. & Pardo, E. V. (1994). Food diet of  Astropecten marginatus and Luidia senegal-ensis (Echinodermata-Asteroidea). Revista Bra-sileira de Biologia, 54, 49-54. Paine, R. T. (1976). Size-limited predation: An ob-servational and experimental approach with the Mytilus-Pisaster interaction. Ecological Soci-ety of  America, 57, 858-873. Pechenik, J. A. (2015). The Echinoderms. Biology of  the Invertebrates, 2, 497-527.Penchaszadeh, P .E. & Lera, M. E. (1983). Diet of  3 tropical Luidia-spp Echinodermata As-teroidea in Golfo Triste Venezuela. Caribbean Journal of  Science, 19, 1-6. 

Differences in Algal, Gastropod, and Arthropod Coverage Surrounding Pisaster Ochraceus and Other Asteroids in Humboldt County, California

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Differences in Algal, Gastropod, and Arthropod Coverage Surrounding Pisaster Ochraceus and Other Asteroids in Humboldt County, California

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