Work Package 9
A system model approach to the response of the BUS to variable physical forcing
Regional ecosystem models can simulate variability and changes of complex food webs in response to variable external physical forcing. They allow the interplay of the ecosystem components to be quantified and the role of single processes for the whole ecosystem to be resolved. As such, these models can be used to assess and predict variability of the ecosystems productivity and services. The regional ecosystem model of Schmidt and Eggert (2016) includes major food web components including a sediment component with benthic sulfide oxidizing bacteria (Schulz et al., 1999). The model shows the importance of sediment and benthic-pelagic coupling for the nitrogen, oxygen and carbon budget of the BUS. It has also identified significant knowledge gaps on physiological properties of the microbial community in response to highly variable environmental conditions. This leads to uncertain model results with respect to carbon and phosphate retention in the sediment, denitrification, frequency and intensity of sulfidic events and the emission of climate relevant gases (Nagel et al., 2013, Emeis et al., 2016).
General Questions and Research topics:
The aim of this work package is to enhance the predictive capability of a regional ecosystem model. Assess trends and variability of ecosystem state and services in response to varying physical forcing. The data from the other SPs will allow a sophisticated development and validation of the BUS ecosystem model. The focus will be on
- the role of sulfide oxidizing bacteria for oxygen consumption and sulfide removal in the bottom water and for phosphate retention in the sediments
- the shaping of benthic bacterial community provinces by circulation patterns, small scale processes and the interplay of hydrographic and microbial time scales
- changing denitrification in sediments as result of varying hydrographic conditions
- pattern and variability of greenhouse gas emissions in relation to circulation
- frequency and intensity of environmental threats by sulfide release from sediments
The modeling work will rely on the diagenetic model for benthic fluxes from SP8 and the multi-layer sediment model developed in the BMBF-project SECOS. The model will be integrated over decades. Distribution patterns of benthic bacteria, nutrient, oxygen and carbon budgets and spans of variability, turnovers, thresholds and feedbacks between organisms and their ambient conditions will be analyzed in relation to a varying physical forcing.