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Research theme 1: Biotic and abiotic factors affecting community composition of the rocky shores of Saltӧ.

This study will determine if community composition in the rocky shores of Sweden is affected by a range of abiotic and biotic factors. Abiotic factors of particular interest are depth, substrate type, and wave action. An interesting feature of Tjärnö’s coastline is the markedly low tidal range. This could reduce the width of the shoreline, blurring the boundaries of zonation. To combat this problem, a survey design characterized by reduced quadrat sizes and sampling distance intervals will be used. To quantify depth, the distance from each quadrat to the low tide line will be recorded. For substrate type, size classification will be employed. To take into account wave action, two sampling sites on the Western face of Saltö will represent exposed rocky shores. In contrast, rocky beaches facing the East will represent sheltered rocky shores. Macrobenthic organisms will be identified and counted. This data will be analyzed to determine if clusters occur. Statistical methods such as anosim, simper, and bioenv will finally be used to determine if the communities/clusters significantly differ, which organisms are dominant in each community/zone, and which environmental variables cause the zonation/clustering.

Biotic factors of interest include predation and competition for food and space. As a dominant occupant of local rocky shores, Littorina saxatilis will be used in an experimental set-up to determine how predation from crabs and the availability of two different habitats - macroalgae and rocks - factor into its distribution along the coast. In order to assess habitat choice in the presence and absence of the predator Carcinus maenas, a Two Way Anova will be conducted. Correlation between the abundances of dominant species will be evaluated to determine the significance of competition as a biotic factor.

Contributors:
Sara De Clerck – Vé De Koninck – Dominic Duncan – Samantha Stott –  Uthesh Umapathy - Angeline Z. Lacson

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