Research

T. Harder, F. Esser, Z. Sebesvari

Influence of biogeochemical sediment parameters on infaunal colonization of spionids in tidal flats (wadden sea, Germany)

Surface-associated microorganisms have been demonstrated to act as localized signposts in colonization patterns of benthic invertebrates on hard substrata. The analysis of sediment cores along a transect in tidal flat sediments of the Wadden Sea (East Frisian North Sea coast, Germany) revealed distinctive abundance patterns of sessile, infaunal macroorganisms, many of which disperse via a pelagic larval stage. To test the potential of microorganisms, sediment TOC content and texture to mediate larval settlement, we developed laboratory-based cultures of the infaunal polychaetes Streblospio benedicti and Polydora cornuta, identified the criteria of larval competence, and designed a larval settlement bioassay. Based on this model system the influence of physical (particle size, flow, surface boundary layer thickness) and biochemical parameters (viable vs. non-viable surface associated microorganisms and individual bacterial isolates, TOC) on the preference or rejection of sediment treatments by competent larvae was analyzed in laboratory studies. We present results and methodologies (bioassays, molecular tools, chemical and biogeochemical analytical techniques) currently used and optimized in our laboratory to analyze potential feedbacks and interactions between microbial settlement cues and biogeochemical sediment characteristics.