Linking microbial communities and macrofauna functional diversity with benthic ecosystem functioning in shallow coastal sediments, with an emphasis on nitrifiers and denitrifiers.
Nitrogen (N) is most often implicated as the nutrient limiting primary production in the coastal ocean. Sediments are important sites for N cycling in coastal ecosystems. Nearly half of the produced primary production is eventually deposited onto the shallow continental shelf seafloor, where benthic activities (bioturbation, bio-irrigation) play a fundamental role in the recycling of nutrients needed by primary producers back into the water column. However, it is well-known that the nutrient cycle is resulting from the activity of microorganisms (bacteria and archaea) . Hence, the activity of macrofauna has an indirect effect on benthic nutrient cycling through its direct affect on microbial communities. Recent studies have shown that macrofaunal functional diversity indeed affects the structure and activity of benthic microbial communities in experimental settings. However, field studies, linking macrofaunal functional diversity, microbial diversity and nutrient cycling have not been conducted so far. Here, we do such an attempt from shallow North Sea sediments. Our objectives are 1- To assess spatially and temporally the community structure of total microbial communities (Bacteria and Archaea) based on ribosomal DNA; and of metabolically active nitrifiers (ammonium-oxidizing archaea and bacteria) in detail based on functional genes. 2- To investigate the relationships between microbial diversity (in general and detail) and different environmental factors with N-cycle processes (Nitrification, denitrification and N mineralization) . 3- To assess how macrofaunal functional diversity directly affects the benthic environment, and how this cascades in the abundance and composition of benthic microbial communities involved in nitrification and denitrification. DGGE (Denaturant Gradient Gel Electrophoresis) and next-generation sequencing are also the methods used to survey different microbial communities.
