B5: Bioenergetics-mediated effects of multiple stressors on marine bioturbators in shallow coastal ecosystems
supervised by Sokolova, Forster
Our aim is to understand the interactive effects of multiple stressors on behavior, physiology and ecologically important of marine bioturbators (mollusks and polychaetes). We will determine the effects of stress-induced physiological and behavioral changes on ecologically important functional traits (bioirrigation and biorturbation) and develop a predictive bioenergetically-based model to assess the long-term population-level consequences of coping with multiple stressors in shallow water Baltic ecosystems.
State of the art
Coastal shallow habitats play a key role in ecosystem processes at the sea-land interface of the Baltic Sea. Due to their shallow depth and proximity to the land, these habitats experience high levels of abiotic stress such as fluctuations of temperature, salinity, CO2 and oxygen content. Furthermore, the global sea level rise as well as the local wetland management may result in the permanent flooding of low-lying coastal land creating novel habitats characterized by high nutrient content, unique sediment characteristics and high susceptibility to periodic hypoxia . These factors can strongly affect the resident biota including marine invertebrates (such as mollusks and polychaetes) that serve as bioturbators and ecosystem engineers in the soft-bottom communities of the Baltic Sea. Sediment bioturbation is an extremely energy-demanding activity, so that energetic stress resulting from exposure to fluctuating salinity, temperature or oxygen levels can impair bioturbation and/or bioirrigation potential of the coastal benthic biota. Furthermore, high energy demand caused by multiple stressors may push the already stressed populations of bioturbators into the bioenergetically unsustainable state thereby negatively impacting their survival and critical ecological functions. To date, the combined effects of multiple stressors on energy homeostasis of marine bioturbators have not been studied. The proposed study aims to close this important gap in our knowledge using bioenergetics as a tool to integrate the effects of multiple stressors on marine bioturbators and develop a mechanistic model to determine the bioenergetic “tipping points” beyond which the survival, growth and/or ecological functions of bioturbators become impaired in the shallow water ecosystems of the Baltic Sea.
We will conduct laboratory studies to assess the bioenergetic trade-offs between organismal activities (such as burrowing, ventilation and filtration) and homeostatic functions (including metabolic and osmotic homeostasis, and cellular stress protection) in the soft-shell clam Mya arenaria and a polychaete Hediste diversicolor. We will also determine the effects of the multiple stressor scenarios on bioturbation and bioirrigation potential of clams and polychaetes in laboratory mesocosms using different oxygen, temperature and salinity regimes representative of the present-day conditions and future scenarios of global climate change and coastal flooding. These data will be later used to develop a quantitative model based on the dynamic energy budget (DEB) to predict survival, growth and ecological functions (bioirrigation and bioturbation) of M. arenaria and H. diversicolor under different salinity, temperature and oxygen regimes, which will be tested and validated in field studies.
The proposed studies involve a close collaboration with subproject B4 focusing on animal-sediment interactions as well as subprojects B3 and G3 studying sediment biogeochemistry of shallow coastal habitats and newly flooded soils. The proposed studies will also be integrated with the project H1, H3 and H4 that determine hydrological and salinity regimes in the coastal shallow waters near the common study sites.