Shellfish are harvested from estuaries around the Florida coast. The shells of clams, scallops, and oysters are vulnerable to dissolution when the calcium carbonate saturation state is lowered. Photo credit: E. Raabe, U.S. Geological Survey. [larger version]
Temperate and subtropical ocean regions are home to a diverse range of environmental conditions, habitats, species, and fisheries. Scientists at the U.S. Geological Survey St. Petersburg Center are monitoring seawater chemistry associated with ocean acidification and benthic habitats on the West Florida Shelf. One of the goals is to fill data gaps in the Gulf of Mexico for carbon flux (pCO2) and air-sea flux. Global models have neglected this marginal, but highly productive sea. Existing data do not sufficiently address the spatial and temporal variability in this temperate to sub-tropical ocean.
Calcium carbonate mineralization is essential in shell formation and in the structure of many marine organisms such as shellfish, plankton, and algae. Calcium carbonate is also a major component in limestone and carbonate sands. The basic result of ocean acidification (lowering of pH) is that fewer carbonate ions are available for calcium carbonate mineralization processes. If the carbonate mineral saturation state is low (less than 1), minerals such as aragonite and calcite readily dissolve into the water column.
USGS research is aimed at addressing data gaps in coastal waters and to increase our understanding of how ocean acidification affects estuarine and shallow shelf marine waters. Shallow water cruises conducted by the USGS will provide regional information on the saturation state and pCO2 fluctuation at the seawater/air boundary using a Multi-parameter Inorganic Carbon Analyzer (MICA). Data from the State of Florida shellfish harvest areas are being evaluated for changes in estuarine water chemistry over the last two decades. Laboratory experiments are currently underway to investigate the effect of ocean acidification on the growth of marine calcifying algae that produce calcium carbonate sediments in temperate, subtropical and tropical marine ecosystems.