Connecting Clams to Seagrass Resilience

Among the most productive ecosystems on earth, seagrass communities use carbon, provide habitat and food, cycle nutrients, and anchor the sediment bottom, providing an extensive range of services. Regions with historically extensive seagrass cover have been experiencing ongoing die-offs in recent years, which have negative cascading effects on recreational fisheries, grazers such as manatees and marine turtles, and other important resources.

Diana Chin, Ph.D., a National Science Foundation Postdoctoral Research Fellow in Biology, is working in Pine Island Sound and Biscayne Bay to understand drivers and mitigating factors surrounding seagrass ecosystem declines.  

Diana Chin, Photo by Tracey Vlasak

Her focus is on understanding how lucinid clam metabolism responds to human nutrient (nitrogen and phosphorus) pollution in the coastal zone, and what implications this may have for seagrass health. Florida seagrass beds are often home to one or more species of lucinid clam, which have bacteria that can benefit seagrass in at least two ways.

First, the bacteria use sulfide from sediment to feed themselves and their host clams, removing naturally occurring sulfide from around seagrass roots that can become fatally toxic to the plants when they are stressed by low light availability, high water temperatures, extreme salinity variations, or other increasingly common problems.  

Diana Chin, Photo by Shane Antalick

Second, the bacteria are capable of fixing nitrogen, or making atmospheric nitrogen biologically usable. Some of that nitrogen could be taken up by seagrass, or lucinid clams can supplement their diets by filter-feeding on phytoplankton and taking up usable nitrogen that is already in the water rather than making it themselves.

Both processes may be more likely where there is more available phytoplankton and usable nitrogen – for example, nutrient-polluted coastal areas – and neither process is as beneficial to seagrass. Chin is working to determine if coastal nutrient pollution could be weakening the beneficial relationship between lucinid clams and seagrasses.

Chin has been working with colleagues from the CCS and from the Sanibel-Captiva Conservation Foundation, whose facilities were heavily impacted by Hurricane Ian, to collect data. If conditions allow, she will conduct one last, post-hurricane sampling in December, which could yield interesting clues about how the effects of an extreme environmental event might cascade from microbes to animals to plants in an ecosystem.