Investigating epifauna community assembly in shallow bays using traits

Sammanfattning: Ecological studies are often performed to investigate ecosystems from a taxonomic point of view (e.g. species richness or species composition). However, investigating variations in organism traits, rather than variations based on taxonomy, can yield higher mechaninistic understanding of the ecosystem. Invertebrate communities in shallow bays have not been subject for extensive investigations of traits. Thus, this study aimed to assess impacts on trait composition of invertebrates in shallow bays by five factors: (i) topographic openness, (ii) nitrogen load, (iii) filamentous algae, (iv) submerged plants, and (v) predatory fish. In order to investigate these connections, a large-scale field sampling of shallow bay ecosystems in the Swedish part of the Baltic Sea was conducted. Statistical analysis was performed using permutational multivariate analysis of variance (PERMANOVA) based on distance matrices, and the results were visualized with nonmetric multidimensional scaling (nMDS). The results show that topographic openness and submerged plants in shallow bays structure invertebrate trait composition. Topographic openness was shown to impact the traits of invertebrate communities slightly more (19 %) than submerged plants (14 %). Several traits are shown to be the drivers behind these results. However, not all effects on traits by the factors seem to be direct effects; some effects are likely seen due to indirect effects. The lack of effect of predatory fish is discussed and may be due to artifacts. Furthermore, different elements of trait-based studies are briefly discussed and recommendations for future trait studies are given.