| Abstrakt: |
Worldwide, shallow bay systems are impacted by altered freshwater inflows and nutrient loading. To facilitate predictions of phytoplankton abundance and dissolved oxygen responses to altered inflows, we develop a spatially explicit, multi-nutrient, multi-species model (MUMPS) for shallow bay systems, then use data from the San Antonio Bay System (SABS), USA, for training. Through sensitivity and simulation analyses, we found that the phytoplankton biomass of SABS, under historically averaged conditions, is likely controlled by a combination of cell loss through hydraulic displacement and light limitation. However, modest reductions in river discharge diminished hydraulic displacement of cells, allowing for increased phytoplankton biomass. It also led to increases in the yearly dissolved oxygen minimum, which was associated with the greater phytoplankton biomass. Additionally, decreasing river discharge altered how river nutrient concentrations influenced phytoplankton biomass in SABS, resulting in a state where nutrient reductions became more effective with decreasing discharge. Importantly, reduced inflows led to a regional shift in phytoplankton biomass from the lower bay towards the middle bay. Regional shifts in phytoplankton biomass in SABS arising from altered river discharges, such as suggested by our model, may be impactful to sessile organisms (e.g., oysters), organisms of limited dispersal (e.g., juvenile blue crabs), and the organisms that feed on these (e.g., endangered whooping cranes for the case of blue crabs). [ABSTRACT FROM AUTHOR] |
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