Nutrient dynamics mediated through turbulence and plankton interactions (NTAP)

Problem to be solved
The level of eutrophication and the number of harmful algal bloom events keep increasing in European coastal waters, affecting industries, fisheries, tourism, ecosystem health, and overall quality of life. Nutrient and organic matter load and dynamics play a key role in those processes. Our inability to fully predict eutrophication or harmful algal bloom events derives from the present lack of an integral understanding of the influence of critical variables, such as small-scale turbulence, on the interaction between plankton and nutrient dynamics.

Scientific objectives and approach
Turbulence effects on plankton can strongly modulate nutrient and organic matter dynamics in coastal areas. However, data at present show that effects may be non-linear, depend on initial environmental conditions, and/or may be specific to certain sizes of organisms or specific taxa. In models of marine systems, turbulence is accounted for as affecting the transport of chemicals and organisms, but rarely as affecting biological processes, since biological effects appear complex and little is known about their dynamics. The overall objective is to provide a unified conceptual framework for nutrient dynamics as modulated by the interaction of turbulence and plankton and to use this information to aid in implementing and modifying legislation on coastal water quality and management. The specific objectives are a) to build a database on turbulence effects by gathering existing scattered data, b) to produce experimental data on key organisms, interactions and mass transfer rates, c) to develop a sensor for laboratory measurement of small-scale turbulence, and d) to produce a dynamical model at community level with exploratory and predictive capabilities.
The research strategy for fulfilling the specific objectives as well as building the overall framework consists of using multi-level approaches and levels of observation. Existing data from both experiments and field observations is analysed to guide the design of new experiments and preliminary modelling efforts. New experimental data on the effects of turbulence on plankton, ranging from organism to net community responses, is produced. A microsensor to measure flow in small containers is developed to overcome current size constraints. Modelling efforts are conducted to incorporate small-scale turbulence effects into a microbial food web model.

Expected impacts
Project output will permit improved assessment of nutrient and mass transfer behaviour and variability in coastal pelagic communities and thus be of value to environmental managers and in the formulation of water quality regulations.