Petrowski, Sina (2013) Do bioturbators affect Arctic soft bottom communities?. (Master thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 57 pp.

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Abstract

A general understanding of drivers influencing biodiversity and the functioning of ecosystems is a central focus in ecology, especially in times of global change. Marine soft-bottom habitats as important food sources for higher trophic levels are expected to react to these global changes with alterations in composition and structure of benthic flora and fauna. However, little is known about the functioning of these habitats in high latitudes such as Arctic sedimentary environments. Bioturbation in a broad sense is the biological reworking of soils and sediments by all kinds of organisms. This process is, as well as consumption, an important driver of benthic species occurrence and dynamics. This study has determined the effects of bioturbation on benthic assemblages in a shallow Arctic soft-bottom habitat. A manipulative field experiment was conducted in l<ongsfjorden, Svalbard (79° N, 10° E), in summer 2012. Species composition in this fjord was dominated by crustaceans (50 %), polychaetes (32 %) and mollusks (13 %). The effects of bioturbation were determined using three bioturbation treatments, accomplished in an in-situ experiment: (i) exclusion of bioturbating animals by burying a plastic mesh into the sediment, (ii) procedural control treatments without a mesh but with the same disturbance as in areas with mesh, and (iii) un-treated areas as controls. Additionally, different cage treatments were installed at bioturbation areas to test for consumption effects, apart and combined with bioturbation. Exclusion of bioturbators showed significant effects on species richness, number of individuals and dry mass of benthic organisms, as well as on species composition, while predation had no effects. lt is suggested that bioturbation is a main driver shaping community patterns in Arctic softbottom environments, while predation seems to be of minor importance.

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