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NUTRIENT LIMITATION OF PHYTOPLANKTON GROWTH AND PHYSIOLOGY IN A SUBTROPICAL ESTUARY (PENSACOLA BAY, FL)
Citation:
JUHL, A. R. AND M. C. MURRELL. NUTRIENT LIMITATION OF PHYTOPLANKTON GROWTH AND PHYSIOLOGY IN A SUBTROPICAL ESTUARY (PENSACOLA BAY, FL). BULLETIN OF MARINE SCIENCE 82(1):59-82, (2008).
Impact/Purpose:
Measurement of nutrient limitation over seasons in Pensacola Bay, FL
Description:
Phytoplankton nutrient limitation was studied in a sub-estuary of lower Pensacola Bay using several techniques. Results for <5 um and . 5 um phytoplankton were similar. Nutrient-addition bioassays indicated year-round nutrient limitation, in contrast to seasonal patterns often described for higher latitude estuaries. N-limitation dominated although dissolved inorganic N:P ratios were always above the Redfield ratio. However, combined N and P additions enhanced growth more than single nutrients. Variability of in-situ alkaline phosphatase (Pase) activity was not clearly related to ambient nutrient concentrations or nutrient bioassay resuls. However, changes in Pase activity after nutrient additions also indicated persistent N-limitation Despite the evidence for nutrient limitation, the maximum quantum yield of photosystem II photochemistry (Fv/Fm) was generally high and nutrient additions caused only minor changes in Fv/Fm, indicating that nutrient limitation did not reduce photosynthetic efficiency. techniques like Pase activity and Fv/Fm measure the physiological state of the extent phytoplankton community while nutrient-addition bioassays test whether community production and yield could change with additional nutrient inputs. This distinction explains why phytoplankton showed nutrient limitation in Pensacola Bay without apparent physiological impairment. Incrased nutrient inputs to Pensacola Bay would likely incrase phytoplankton production and yield with potentially negative consequences.