Patterns of phytoplankton primary productivity in the Neuse River estuary, North Carolina, USA

• Published in: Marine ecology. Progress series (Halstenbek) 1993, Vol.97 (3), p.287-297
• Main Authors: Boyer, Joseph N., Christian, Robert R., Stanley, Donald W.
• Format: Article
• Language: English
• Subjects: Biomass; Biomass production; Brackish; Estuaries; Linear regression; Nitrogen; Phytoplankton; Primary productivity; Productivity; Salinity; Statistical median
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps097287

Phytoplankton primary productivity in the Neuse River estuary (North Carolina, USA) was assessed for spatial and temporal patterns over 4 yr as a function of associated influential factors, especially biomass (chlorophyll a, chl a) and light. From 14CO2-uptake assays maximum photosynthetic rates (Pmax), photosynthesis versus irradiance relationships, daily primary productivity (Pd), and annual primary productivity (Py) for the system were calculated. Both physical and chemical characteristics of the estuary were profoundly influenced by river flow; this became especially apparent during the near record high flow events of spring 1987. Salinity was depressed throughout the estuary while average photic depth declined. A significant 'washout' of chl a occurred as a result of freshwater input upstream. The effects of this high flow persisted for months after the events and influenced the spatial pattern of primary productivity in the estuary. For the 4 yr period, daily primary productivity ranged from 0.002 to 4.84 g C m−2 d−1 and unlike many estuaries, correlated poorly with chl a. However, the product of biomass (chl a), photic depth, and surface incident light, In (B Zp Io), was found to explain 66 % of the variance in In Pd. Pooled data from estuarine stations had a significantly lower slope of the regression line and higher y-intercept than riverine stations. This may have been due to the increased biomass specific production (PmB) of the phytoplankton in the mesohaline zone relative to the river species. No significant differences in the relationship of In Pd to In (B Zp Io) were found between seasons or years. There was no better relationship between Pd and any other measured parameters. The 1985 to 1988 annual primary productivity estimates for the Neuse River estuary were 395, 455, 491, and 493 g C m−2 yr−1 with the mean being 456 g C m−2 yr−1.