In many intertidal habitats dead seaweeds are washed up on the sediment and buried in soft substrata. The amounts and frequency of deposition are increasing, partially as an effect of eutrophication. This can alter the biochemistry of sediments and, in turn, may influence the species composition of assemblages and increase their susceptibility to the next disturbance. Furthermore, bioturbation and mechanical breakdown by animals can contribute to mineralise and transfer (as energy and nutrients) the algal detritus up to the highest levels of food-webs. Such effects can be expected to vary according to the physical and chemical characteristics of the environment (e.g. organic content, grain-size), to the local tolerance to organic enrichment and to the activities of animals. In this project, the effect of the burial of seaweeds on the benthic system will be analysed and the response of macrofauna will be combined with a functional approach. In particular, I will analyse the release of nutrients from algal mats, the changes in macrofaunal composition due to the increase of nutrients and the physical disturbance of the algal mats and the pathway and the fate of the algal detritus in the food-web.
These patterns will be analysed and compared in sandy, organically poor and muddy, organically rich habitats, using manipulative experiments in the field. Sediments will be enriched with dead seaweeds and inorganic nutrients. At selected sites, added algae will be isotopically labelled with ^13C and/or ^15N. The work will provide, for the first time, the opportunity to study more explicitly the influence of macro-algal blooms on macrofauna and on the benthic food-webs using different methods. The use of manipulative experiments can provide real cause-effect explanations. The use of stable isotope tracers is a new, powerful approach for in-situ characterisation of the cycling of food and nutrients. This will positively affect both the applicant and the host institution. The measurements from experimental plots will provide critical tests for models about sedimentary biogeochemistry developed in the host institution. The applicant will improve her professional and research skills in an institution specialized in coupling and modelling biological and biogeochemical data for coastal habitats. Publication of results will be in peer-reviewed journals.