Diana Chin, Ph.D., a National Science Foundation Postdoctoral Research Fellow in Biology at the University of Florida, recently collaborated with SCCF staff to complete the first of several quarterly surveys of lucinid clams in seagrass beds in western Pine Island Sound. Chin will link these surveys to water quality data collected by SCCF and other Charlotte Harbor agencies to determine whether the clams’ metabolism is responding to nutrient levels in the bay, and what implications this has for the health of Pine Island Sound’s seagrass.

Lucinid clams are common underneath seagrass beds worldwide and feature an unusual metabolism. Though they can digest microscopic algae that they filter from seawater, lucinid clams get most of their energy from symbiotic bacteria in their gills, which use naturally occurring sulfide (the chemical that creates the low tide “rotten egg” smell) from sediment to make their own food. The clams can change the proportion of nutrition they obtain from their bacteria or from filter-feeding, depending on how much microscopic algae is available in their environment at the time. Recent studies also suggest that the clams’ symbiotic bacteria may be able to convert inert atmospheric nitrogen into a form of nitrogen that can be used by other living things for growth. As with feeding, the clams likely alter how much nitrogen is converted depending on how much usable nitrogen is already available from the environment. The more food and nitrogen the clams get from their symbiotic bacteria relative to external sources, the more likely they are to benefit the health of the seagrass where they live: Sediment sulfide buildup is toxic to seagrasses, and seagrasses tend to compete with algae more effectively when they can take up nitrogen from sediment as well as from water. 

Ultimately, Chin hopes to understand whether coastal nutrient pollution can break up this beneficial clam-seagrass relationship. The Charlotte Harbor region has been experiencing more frequent and severe algal blooms and fish kills as nutrients from aging septic and sewage infrastructure, fertilizer runoff, and other sources fuel the growth of bacteria and algae to abnormal levels. By measuring ratios of particular carbon and nitrogen atoms in lucinid clam tissues, as well as the expression of key metabolic genes, Chin will establish whether the clams are switching their metabolism in a way that would reduce or eliminate their beneficial effects on seagrass.