Project ISOFUN - Relationship between functional and isotopic diversity of coastal benthic communities

Benthic invertebrates affect many processes essential for the proper functioning of marine
ecosystems. The functional diversity of benthic animals, associated with their biological
characteristics, like feeding behavior, way of movement, as well as body size, affect e.g. sediment
mixing, which enhance the oxygen supply to sediments, and modify the exchange of nutrients at the
sediment-water interface. Coastal zones of the seas are characterized by high biodiversity of
benthos, as well as diverse sources of food for animals. The food (organic matter) in the form of
microalgae (phytoplankton) and plant debris (detritus) is produced directly in the sea or transported
to the sea by rivers. It is well known, that the source and the amount of food shape marine food
webs and biochemical structure of animals consuming it, and in particular their isotopic
composition of carbon and nitrogen. In consequence, relations among animals and organic matter
shape the trophic (isotopic) diversity of benthic communities. However, little is known about how
these relations influence the functional diversity of benthos. Thus, the main aim of this project is to
study the relationship of isotopic and functional diversity and to answer the question of how
different sources and amounts of organic matter (among other environmental gradients) influence
this relationship on the example of the southern coast of the Baltic Sea.
The main hypothesis of the project assumes that in the area with lower food availability (open
Polish coast near Łeba), benthic community will be characterized by greater diversity, caused by
competition for limited food. In turn, in the area with greater access to food (Gulf of Gdańsk near
the Vistula outflow), invertebrates population will be larger, while due to lack of interspecies
competition, it will also be relatively less diversified. Because in temperate regions, the amount of
organic matter changes seasonally, samples were collected in two contrasting seasons (winter and
late summer). To address the research questions, an innovative approach of combining both
functional and isotopic indices of diversity will be used. Furthermore, we will assess the influence
of organic matter properties among other environmental variables (depth, water mass
characteristics, sediment characteristics) on the diversity and structure of coastal benthic
communities. The results of the study will improve our understanding of organic matter influence
on benthic biodiversity and functioning of marine coastal ecosystems and will be an important
contribution to science in the face of climate change and eutrophication of marine environments,
caused by humans.