Long-term temporal and spatial trends in phytoplankton biomass and class-level taxonomic composition in the hydrologically variable Neuse-Pamlico estuarine continuum, North Carolina, U.S.A.

Abstract

Phytoplankton diagnostic photopigments in near-surface waters (<0.5 m) were identified and quantified by high-performance liquid chromatography beginning in April 1994 in the Neuse River Estuary and in October 1999 in the Pamlico Sound, North Carolina. Photopigment concentrations were analyzed using ChemTax to determine the class-specific biomass of the dominant phytoplankton groups. Long-term annual and seasonal trends in phytoplankton biomass and composition were characterized along the river-estuarine continuum and compared to river flow rates, which were variable because of droughts, uncharacteristic seasonal rainfall patterns, and, since 1996, an increase in the frequency of tropical storms and hurricanes. We tested the hypothesis that temporal and spatial patterns of phytoplankton biomass and composition were largely controlled by changes in river flow rate through associated changes in salinity and residence time or through physical transport and advection of phytoplankton classes with river flow along the estuary. Significant interannual, seasonal, and spatial variability in phytoplankton biomass and composition was observed and coincided with variability in river flow rates. The five dominant phytoplankton classes (Chlorophyceae, Cryptophyceae, Cyanobacteria, Bacillariophyceae, and Dinophyceae) were physically displaced downstream during periods of elevated river flow. Dinoflagellates were reduced in abundance during high flow conditions, especially in the upper Neuse River Estuary. The abundance of cyanobacteria was also reduced throughout the system during elevated river flow conditions, although chlorophytes were more abundant. Changes in hydrology can be a useful indicator of seasonal phytoplankton distribution and higher level compositional changes along hydrologic gradients in these and similar systems.

Estuarine Phytoplankton Responses to Hurricanes and Tropical Storms with Different Characteristics (Trajectory, Rainfall, Winds)

“…Picocyanobacteria and nanoflagellates usually dominate phytoplankton community biomass during the summer at mesohaline locations, accounting for >60% of the phytoplankton community biomass, followed by diatoms and dinoflagellates (Valdes-Weaver et al 2006;Paerl et al, unpublished size-fractionated HPLC data). The dominant N sources for the summer phytoplankton are ammonium and DON supplied by water column regeneration and diffusion out of sediments (Rizzo et al 1992;Twomey et al 2005).…”

“…Biological and Chemical Measurements Chlorophyll a and diagnostic phytoplankton photopigments (chlorophylls and carotenoids) were determined using high-performance liquid chromatography (HPLC) coupled to an inline photodiode array spectrophotometer (Shimadzu SPD M10av; see Valdes-Weaver et al 2006 for complete details on sample processing). Photopigment concentrations were analyzed using the ChemTax matrix factorization program to determine the relative contribution of each of five phytoplankton taxonomic groups (chlorophytes, cryptophytes, cyanobacteria, diatoms, dinoflagellates) to total chlorophyll a (Mackey et al 1996).…”

Environmental Factors Contributing to the Development and Demise of a Toxic Dinoflagellate (Karlodinium veneficum) Bloom in a Shallow, Eutrophic, Lagoonal Estuary

“…Water temperature (∼20°C) and the prevailing mesohaline conditions were conducive for K. veneficum growth (Nielsen 1996;Li et al 2000;Fensin 2004;Goshorn et al 2004). Prior studies have shown that algal blooms are common in the region of the estuary where this bloom developed (Valdes-Weaver et al 2006;Waggener 2006). One explanation is that the estuary widens in this region, increasing the residence time with respect to riverine discharge (Luettich et al 2000).…”

Limnological characterisation and phytoplankton seasonal variation in a subtropical shallow lake (Guaiba Lake, Brazil): a long-term study

“…A study conducted across Brazil showed that the conditions in most of its inland water bodies ranged from mesotrophic to eutrophic (Abe et al, 2006) due to population and economic growth in their corresponding watersheds, which has compromised the quality of water supplies and of water for other uses, mainly due to the occurrence of cyanobacterial blooms (Sant'Anna et al, 2008). Despite its significance for predicting events and the identification of environmental changes, such as those related to climate, hydrology, eutrophication and oligotrophication (Barbosa and Padisák, 2004;Valdes-Weaver et al, 2006), long-term limnological studies in inland waters are scarce in Brazil (Seeliger et al, 2002).The aim of this study was to provide a longterm limnological characterisation of a subtropical shallow lake from southern Brazil (Guaiba Lake), in addition to verifying seasonal differences, including the influence of quali-quantitative phytoplankton variation. …”