Browsing by Subject "ecological stoichiometry"

The shallow bays and inlets of the coastal Baltic Sea consist of a patchy seafloor with different sediment types that are affected by anthropogenic pressure, such as organic matter loading. Benthic macrofauna affects the carbon and nutrient stock capacity of such coastal areas by storing these elements in their body tissues and thus working as a temporary carbon and nutrient pool. These nutrient stocks are especially stable when the animals are large and long-lived. Fluctuations in organic input have been suggested to modify the diversity, abundance, and biomass of the benthic communities and therefore affect the nutrient reserves bound within the fauna. However, there is little information on how stress, in form of increasing sediment organic matter content, change the stocks and stoichiometric ratios of benthic macrofaunal communities. This thesis investigates if the changes in sediment organic matter affect benthic community composition and organism size and its ability to function as a carbon (C), nitrogen (N) and phosphorous (P) pool by measuring: 1) how the benthic faunal diversity, abundance, and biomass composition and 2) the C:N:P content and ratios of the benthic fauna change between three different sediment categories. A significant difference was found between sandy and muddy sediments in terms of benthic biomass and abundance, as well as the carbon and phosphorus stocks. Large long-living bivalves were found in sandy sediments, but overall organism size was not significantly different between the sediment categories. In general, the results show that higher sediment organic matter content resulted in fewer individuals, biomass, and thus a smaller storage capacity of carbon and nutrients. No statistical differences were found between the C:N and N:P and C:P ratios along the three sediment types. However, somewhat more P was bound within the fauna at sites with more organic matter, compared to the sandy and mixed sediments. The results highlight the importance of macrofauna in the functional performance of the ecosystem function and their potential for shifts with increasing disturbance. In conclusion, the increase in sediment organic matter can significantly change the capacity of macrofaunal communities to bind carbon and nutrients and this might have implications for the coastal nutrient filter. More research regarding the fauna's ability to adapt to the changing environment is needed.