The proposed part of the project will focus on organic matter exchange with three major objectives:

1) Recruitment of phyto- and zooplankton resting stages linked to macrofauna composition and physicochemical habitat characteristics.

Many phyto- and zooplankton species overwinter as benthic resting stages and reemerge when conditions are favorable. For Baltic Sea management, it is of particular interest to understand the processes involved in the initiation of blooms, such as harmful cyanobacteria and dinoflagellates as well as zooplankton blooms. While blooms are a common feature in the Baltic Sea, the specific factors determining bloom magnitude and distribution are still not fully understood.

This study will estimate recruitment of species in situ from the water collected by the benthic lander above the benthic surface layer and identify early phyto- and zooplankton life stages. Sediment will be collected, macrofauna and resting stages identified. Intact sediments and overlaying bottom water of the sampling site will also be sampled and incubated for hatched zoo-and phytoplankton species. For anoxic habitats, one part of the incubated sediment will be manipulated with air bubbling to understand if oxygenation triggers hatching of resting stages.

2) Linking benthic community composition to small-scale physicochemical conditions

Previous studies showed that macro- and meiofauna enhance inorganic nutrient fluxes by advective fluid flow and bioturbation. However, these measurements have been done primarily in laboratory experiments. This study will measure in situ physicochemical conditions at fine scale and link the dynamics with benthic fauna abundance and composition. Macrofauna (and potential meiofauna) community will be identified microscopically from collected sediments of the sampling sites and linked to physicochemical processes.

3) Identify organic matter fluxes from the pelagial to the benthos

Settling of organic matter is the major energy source to the benthos, which affects benthic production and metabolisms. However, settling of organic material has not yet been measured at near-bottom surface. Settlement of organic matter fluxes will be estimated based on particulate organic material (POM) and oxygen measurements from sediment traps and seasonal dynamics identified over the sampling period.

Researchers and departments:
Monika Winder, Department of Ecology, Environment and Plant Science
Volker Bruchert, Department of Geological Sciences