Estuarine Processes Eutrophication

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Increased loadings of nutrients to estuaries have altered ecosystem function by encouraging growth of phytoplankton and macroalgae while inducing large swings in dissolved oxygen and threatening the sustainability of seagrass meadows. We are measuring and modeling these processes to understand the future trajectory of estuarine ecosystems.

The past several decades have seen a massive increase in eutrophication of estuaries globally, leading to widespread hypoxia and anoxia, habitat degradation, alteration of food web structure, loss of biodiversity, and increased frequency, spatial extent, and duration of harmful algal blooms. A majority of estuaries in the USA are degraded as a result. Shallow seagrass dominated lagoons appear to be particularly sensitive. In many of these ecosystems, endemic species such as seagrass are lost as benthic algae and phytoplankton dominate under increased nutrient supply.  

Our research of eutrophication began with developing methods to estimate nutrient loading from groundwater. Those methods integrated continuous monitoring as well as numerical modeling. Monitoring of nitrogen levels, salinity, chlorophyll, dissolved oxygen, and light attenuation have led to a better understanding of the mechanisms and timescales of eutrophication. We have now begun enhancing biogeochemical models to represent estuarine processes such as hypoxia, benthic fluxes, and seagrass kinetics. These models can then be used to simulate future scenarios of nutrient loading and sea-level rise, while also exploring biophysical feedbacks such as decreased sediment resuspension due to increased seagrass biomass.