Fantasia, R.L.; Bricelj, V.M., and Ren, L., 2017. Phytoplankton community structure based on photopigment markers in a mid-Atlantic U.S. coastal lagoon: Significance for hard-clam production. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey.

Phytoplankton community structure at four contrasting sites in the Barnegat Bay-Little Egg Harbor (BB-LEH) Estuary was determined microscopically and by photopigment-CHEMTAX analysis. It was related to temperature, salinity, and weekly growth rates of juvenile hard clams, Mercenaria mercenaria, deployed at these sites during the summer in 2012 and 2013, pre- and post-Hurricane Sandy. Results indicated distinct differences in phytoplankton composition among sites, with a greater contribution of chlorophytes and cyanobacteria at the northernmost site, Island Beach State Park (IBSP). Photopigment analysis was useful in improving upon the taxonomic assessment of pico-coccoid (<3 μm) algae that are difficult to identify microscopically. The presence of the brown tide alga, Aureococcus anophagefferens, was confirmed by immunofluorescence during both years, with peak densities of 4.4 × 10⁵ cells ml⁻¹ in June 2013 at Sedge Island, in a Marine Conservation Zone that supports clam seeding. Concentrations of 19′but-fucoxanthin and A. anophagefferens showed a strong linear relationship, suggesting that this pigment is a good indicator of this pelagophyte in BB-LEH. The occurrence of brown tide was important to consider in CHEMTAX analysis as it affected the estimated contribution of diatoms to chl a, given that A. anophagefferens is also characterized by a relatively high fucoxanthin:chlorophyll a ratio. Generally, hard-clam tissue-growth rates were greatest at Sedge Island and Tuckerton, LEH, and least at IBSP, a lower salinity site, and off Harvey Cedars, a more developed site along a bulkheaded shoreline. Significant linear relationships were found between clam growth rate and diagnostic photopigments, with positive relationships for indicators of diatoms and negative relationships for those of cyanobacteria and chlorophytes.