Temporal and Spatial Variation in the Phytoplankton Community and Relationships with Environmental Conditions in Barnegat Bay-Little Egg Harbor, New Jersey

Abstract:

The Barnegat Bay-Little Egg Harbor Estuary (BB-LEH) is a shallow, poorly flushed system bordered by a highly developed watershed. It is therefore very susceptible to nutrient enrichment. The Estuary is classified as a highly eutrophic system with episodic recurrences of brown tides and other microalgal blooms, loss of submerged aquatic vegetation, and decline of hard clam stock and harvest. A recent USGS report showed that TN and TP loading from surface runoff increased nearly 90% from 1995 to 2010 in BB-LEH, with the northern most developed embayment accounting for more than 60% of annual load. Understanding the relationships between the ongoing nutrient input and phytoplankton community change is essential for water quality assessment and management in the BB-LEH Estuary. We investigated the phytoplankton community in BB-LEH from September 2011 to August 2013. Monthly and biweekly samples were collected by the NJDEP Water Quality Monitoring program from 9 sites in the first year, and 6 of those same sites in the second year. Analysis of phytoplankton included species identification and enumeration, and calculation of cell density and biovolume. Notable seasonal and spatial variation in species composition and succession were observed in both years. Picoplankton was dominant during summer in both years and appeared more persistent in northern Barnegat Bay (June to October) compared to southern sites (June-August). Brown tide alga, Aureococcus anophagefferens, was detected from southern Barnegat Bay and Little Egg Harbor at cell densities of 10⁵ to 10⁶ L^-1, relatively low compared to other picoplankton. Species similarity analysis using 2011-2012 data identified three segments from north to south: northern Barnegat Bay, southern Barnegat Bay and Little Egg Harbor. Noticeable year-to-year differences in phytoplankton assemblages and species succession were observed in all segments. The particular year to year change in phytoplankton in this study may have been affected by the strong impact of Hurricane Sandy. Multivariate analyses are underway to assess the patterns in the phytoplankton community, including spatial-temporal variations and the extent to which measured environmental variables can explain the observed phytoplankton assemblage changes.