R-05-02 Phytoplankton Carrying Capacity in the Damariscotta River Estuary

Mary Jane Perry
School of Marine Sciences and Darling Marine Center

University of Maine
193 Clark's Cove Road
Walpole, ME 04573-3307
207.563.3146
perrymj@maine.edu
http://optics.dmc.maine.edu

The Damariscotta River Estuary is home to the most intensive shellfish farming in Maine, a result of the river's excellent water quality and ideal temperature conditions. Oyster farms on the Damariscotta lease about 100 acres of surface and bottom waters. Recently, questions have been raised about how many farms can be supported by the estuary.

Oysters depend on phytoplankton for food; therefore assessing the sustainability of aquaculture in the Damariscotta River Estuary requires an understanding of phytoplankton dynamics. Perry's research examined variability of phytoplankton biomass using a high-frequency time series study of phytoplankton, nutrients, light, and physical conditions in the estuary. Perry observed strong spatial gradients in temperature, salinity, and phytoplankton, with the largest biomass occurring in the upper estuary. Phytoplankton cells <20 μm were the dominant fraction of phytoplankton biomass throughout most of the shellfish growing season, which has important implications for the shellfish industry because oysters typically feed on cells that size. The high concentration of cells < 20 μm diameter in the surface waters of the upper estuary during the late spring and early summer provides rationale for using floating grow-out enclosures for juvenile oysters in this section of the estuary. Continued monitoring of phytoplankton variability can help oyster and mussel farmers decide when to sow, maintain, and harvest.

1-year project: 2005-2006
Total: $52,721

Associated publications
Thompson, B., and M. Perry. 2007. Phytoplankton in the Damariscotta River Estuary. Research in Focus Fact Sheet. Orono, ME: Maine Sea Grant.