Topical Area: Water Quality

Frank J. Millero, University of Miami/RSMAS, Miami, FL

Eutrophication and red tides in Florida Bay have been both an economic and environmental concern for many years. High nutrient concentrations resulting from agriculture runoff, industrial effluent and other sources have been considered to be the causes for the degradation of water quality as evidenced by algal blooms and the mass mortality of turtle grass. Nutrients, such as phosphate, are critical to the onset and sustainment of phytoplankton blooms.

To better understand the relationship between nutrients and the carbonate system in the Florida Bay, several cruises were completed in 1997 to survey the water quality. During these cruises, our group measured carbonate system parameters (including total alkalinity (TA), pH, total carbon dioxide (TCO₂), and partial pressure of carbon dioxide (pCO₂)), as well as salinity and nutrients. In addition to the cruises, several other groups have collected samples that have been measured in the laboratory. TA, pH, TCO₂, and pCO₂ measurements have been used in an effort to characterize the carbonate system in Florida Bay. This analysis will help to contribute to the determination of the saturation state of calcite and aragonite particles that can absorb phosphate as well as to the examination of the uptake of inorganic carbon by phytoplankton. Surface nutrient data was collected continuously on cruises via a flowing multi-parameter nutrient system, developed in our laboratory. This system measures the concentrations of nitrate, nitrite, silicate, and phosphate from a flowing seawater line onboard a research vessel. The continuously flowing nutrient system has the advantage of providing real-time data and a greater density of measurements than discrete sampling. This greater density of measurements can, for instance, help to identify changes in nutrient concentrations due to circulation patterns of water masses or frontal movements. Chlorophyll-a data were also collected during a cruise to evaluate primary production in Florida Bay waters. The nutrient data has also been compared with the carbonate system data to help identify changes in nutrient concentrations related to degradation of plant material.