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Title:
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Phytoplankton Responses to Nutrient Loading in Galveston Bay |
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Scholar:
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Amanda Thronson |
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School:
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Texas A&M University at Galveston |
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Mentor:
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Dr. Antonietta Quigg |
[View Presentation ( 299 KB)] |
Galveston Bay, Texas is a large shallow estuary that acts as a drainage basin for 60% of the major industrial facilities in Texas. Due to the predictions of a 50% population increase along the Texas coast, the demand on freshwater supplies before entering Galveston Bay are set to rise exponentially. This will lead to mitigation strategies that control freshwater inflows, and with them, the major source of nutrient loading into Galveston Bay. Because of this, the impacts of nutrient loadings to phytoplankton communities in Galveston Bay need to be better understood.
Guillen (1999) surveyed databases of nitrogen, phosphorus, and chlorophyll a levels in Galveston Bay and proposed that phytoplankton populations are most likely regulated by fluctuations in phosphorus levels. Örnólfsdóttir et al. (2004), on the other hand, performed a series of nutrient addition experiments and found that phytoplankton in Galveston Bay were generally N limited. They predicted that pulsed nitrate inputs will favor increased phytoplankton biomass, particularly diatoms.
The present study shows that nitrogen is indeed the limiting nutrient in Trinity Bay, Christmas Bay, West Bay, Rollover Pass, Smith Point and Offatt's Bayou. Diatoms dominated water samples in all locations and showed the biggest response to N additions. Our findings agree with those of Örnólfsdóttir et al. (2004) but not Guillen (1999). In addition, this study reveals that physiologically, the diatoms are the most adapt to respond to nitrogen inputs into Galveston Bay. Hence, changes to freshwater inflows into Galveston Bay, and so nutrient loading, will impact phytoplankton community composition. It is important to understand how this will affect higher trophic levels.