Little creature, big impact: How oyster feeding sustains Florida’s coasts
Member spotlight – Carrie Schuman, PhD student in Fisheries and Aquatic Sciences
Oysters at first glance are not beautiful. However, these shellfish are one of the multi-taskers of the coastal world, providing many “ecosystem services”. Masses of oyster reefs along coastlines serve to protect against the battering of many storms that pass through Florida or the gradual erosion that cuts away at local shorelines. They sequester carbon by locking it away in their bodies and, more permanently, into the structure of their shells. They may serve as refuge and habitat for many small creatures, which may in turn feed larger organisms like fish and dolphins.
But some of the more important functions of oysters relate to their role as filter feeders. Their ability to positively affect water quality has led to their use in many restoration projects. Oyster filtration often contributes to controlling phytoplankton – masses of microscopic plants whose populations wax and wane with a variety of environmental factors, but whose growth can boom substantially when excess nitrogen and phosphorus are present. When phytoplankton experience a sudden population increase, or bloom, they may rapidly use up nutrients, consume dissolved oxygen, and block light from sea grasses and other submerged vegetation. This can result in a sub-par or even toxic environment for other aquatic life. In some regions, the role oysters play in keeping this growth in check is significant.
I am interested in quantifying the link between oysters and phytoplankton blooms within the St. Augustine area in Florida, more specifically in the Guana Tolomato Matanzas National Estuarine Research Reserve (GTM NERR) which stretches from above Ponta Vedra down to Palm Coast. However, to do this I need to know how much and how fast oysters in the region are filtering, as well as how fast phytoplankton biomass turns over within the system. Oyster filtration rates estimated from previous lab studies may not have captured the complexity of filtration in the natural environment. To obtain more accurate, meaningful results, I am measuring these rates in field using a biodeposition method. Biodeposits refer to oyster production of faeces and psuedofaeces (food particles rejected before ingestion). These can be collected by sediment traps constructed inexpensively from buckets and netting and then compared to inorganic matter in the water column to determine how quickly oysters are filtering. By applying this method in the reserve, I am able to generate an effective clearance rate (ECR), which estimates the weight of particles removed from the water column per oyster per hour under natural conditions. This research will guide management decisions as well as restoration projects that aim to maximize oyster filtration.
Lastly, because I am an interdisciplinary ecology student, I am also incorporating economics into my work. Many of the ecosystem services that oysters provide have value that is hard to express in dollars. For example, an oyster’s role as habitat for organisms that alternately feed commercially and recreationally attractive fish species is certainly worth something, but we might have to use a variety of creative and indirect methods to suggest a monetary value for this function. This also means it may be difficult to come up with ways to convince governments, agencies, and communities to financially support those services. Another complication is the fact that oysters are public goods, so there is no easy way to keep those who haven’t paid for services from still benefitting. Though challenging, I am assessing possible payment mechanisms for oyster-provided services. In addition to previously suggested ideas such as the inclusion of oysters in water quality credit trading programs, I am examining approaches used for similar public good resources such as mangroves, sea grasses, and coral reefs.
More about Carrie
Carrie originally hales from New England, and is currently an Interdisciplinary Ecology PhD candidate with a focus in Fisheries and Aquatic Sciences at UF. She is also pursuing a certificate in Tropical Conservation and Development. She has an M.S. in Marine Science and Technology, and a B.S. in Marine and Freshwater Biology. She has had an eclectic list of past professional experiences including graduate work involving a right whale ecology cruise, an internship with the New Hampshire Coastal Program, and a stint as an assistant curator at a phytoplankton culture collection. Besides her interest in creating practical solutions for natural resource issues, she is passionate about education and outreach and bridging the communication gap between scientists and the public.