Variability in phytoplankton biomass and community composition in Corpus Christi Bay, Texas

Corpus Christi Bay is a shallow, wind-driven lagoon located on the semi-arid South Texas coast that has a rapidly urbanizing watershed. Projections indicate that this region will become warmer and drier and will support an increasing urban population over the next several decades. Here, a 27-month field study was undertaken to quantify phytoplankton biovolume, community composition, and relationships with environmental drivers. Phytoplankton biovolume varied unimodally with a peak in biovolume from spring through summer followed by a decline into fall and winter. Phytoplankton growth was related to nutrient availability during the spring and summer, while water temperature and factors affecting flushing were important during the fall and winter. Regions with more restricted circulation patterns (i.e., man-made canals) were found to support higher standing crops of phytoplankton and the occurrence of high biovolume blooms. Diatoms were dominant during the winter and spring, dinoflagellates were dominant during the summer and fall, and picophytoplankton groups were important during spring, summer, and fall. These results suggest that nutrient and physical conditions interact to determine phytoplankton biomass and community composition and contribute to our ability to project potential impacts of future increases in human populations in the watershed, decreasing precipitation due to climate change, and increasing frequency of short-lived flood events.