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Discharge of dissolved organic matter (DOM) provides an important source of strong Cu-complexing ligands to the coastal ocean waters of Long Bay off the southeast coast of North Carolina. Concentrations of strong Cu ligands (∑Li at fixed KCuL′=1013.5), measured using competitive ligand equilibration-cathodic stripping voltammetry with 8-hydroxyquinoline (8-HQ) as the competing ligand, were linearly correlated with dissolved organic carbon (DOC) concentrations (∑Li=0.23DOC-14, r2=0.81, p≪0.01, n=9) in Long Bay transect samples. The relationship between ∑Li and DOC measured in this study was very similar to that measured in a previous study for Cape Fear estuarine sites. The Cape Fear provides 1.8×106 mol of strong Cu ligands annually to Long Bay with a ratio of ligand/DOC of 1.7×10-5 mol g-1 C. For South Atlantic Bight (SAB) shelf waters, yearly discharge from organic-rich rivers may provide up to 1.7×107 mol of strong Cu ligands. A river flux of this magnitude could support 1.6 nM strong Cu-complexation capacity throughout the SAB water column, or up to 50% of the total pool of strong Cu-complexing ligands. Estimates for the worldwide river discharge of terrestrial DOM indicate this source could support 0.03–0.2 nM strong Cu complexation capacity, or a maximum of 20% of the global ocean reservoir of strong Cu ligands. [Copyright &y& Elsevier]

River input of allochthonous organic matter dominates the strong complexation capacity of dissolved copper in the organic-rich Cape Fear River (CFR) estuary, North Carolina. This slightly stratified estuary is characterized by conservatively mixed dissolved organic carbon (DOC=200–1200 μM C), high river flow, and low biological productivity. Copper speciation data measured using competitive ligand equilibration–cathodic stripping voltammetry (CLE–CSV with 8-hydroxyquinoline (8-HQ)) for seven Cape Fear estuarine transects revealed that strong (mean detection window αCu8HQ=105.2) Cu-complexing ligands range in concentration from 7 to >200 nM (at fixed KCuL′=1013.5), are conservatively mixed below the turbidity maximum zone (S∼5), and exist in substantial excess of dissolved Cu levels (3–25 nM). Strong ligand and DOC concentrations exhibited strong linear correlations among transect samples at DOC concentrations <1000 μM C (r2=0.93, p≪0.01) and among all size fractions of ultrafiltered estuarine samples (r2=0.94, p≪0.01). A 300 μM C solution of Cape Fear River humic substances isolated using C18 extraction exhibited a strong Cu ligand concentration of 143 nM (at fixed KCuL′= 1013.5). Comparison with speciation data from estuarine transects indicates C18 isolated humics could account for 100% of the typical strong Cu-complexation capacity in the Cape Fear estuary. [Copyright &y& Elsevier]

Benthic fluxes were evaluated as a source of strong Cu-complexing ligands (K′CuL>1011) to the water column of the organic-rich Cape Fear River estuary along the North Carolina coast. A core incubation technique was used to measure sediment-water exchange of strong Cu-complexing ligands, as well as total dissolved Cu and dissolved organic carbon, at two sites within the estuary. Substantial ligand fluxes were observed only during summer experiments (850±610 nmol m-2 d-1 in June 2001 at lower estuarine site and 870±580 nmol m-2 d-1 in June 2002 at upper estuarine site). Strong ligand fluxes were correlated with DOC fluxes only for the June 2002 experiment. The ratio of strong Cu ligand:DOC fluxes among all cores from the June 2002 incubation (3×10-5 mol g-1 C) was nearly equivalent to the ratio measured in the water column in an earlier study of the Cape Fear estuary (2×10-5 mol g-1 C). Fluxes of TDCu were not statistically significant during any experiment and were not related to the behavior of strong Cu ligands. Although fluxes of strong Cu ligands were large during the summer months, short estuarine residence times (<1 week) and a large ambient water column pool of ligands (30–200 nM) limit the importance of sediment-water exchange as a major source to Cape Fear estuarine waters. However, the fluxing ligands are experimentally indistinguishable from those in the water column, suggesting that benthic fluxes may provide an important source to estuaries with long residence times or lower ambient ligand levels. [Copyright &y& Elsevier]

Phytoplankton nutrient limitation experiments were performed from 1994 to 1996 at three stations in the Cape Fear River Estuary, a riverine system originating in the North Carolina piedmont. Nutrient addition bioassays were conducted by spiking triplicate cubitainers with various nutrient combinations and determining algal response by analyzing chlorophyll a production and 14C uptake daily for 3 d. Ambient chlorophyll a, nutrient concentration, and associated physical data were collected throughout the estuary as well. At a turbid, nutrient-rich oligohaline station, significant responses to nutrient additions were rare, with light the likely principal factor limiting phytoplankton production. During summer at a mesohaline station, phytoplankton community displayed significant nitrogen (N) limitation, while both phosphorus (P) and N were occasionally limiting in spring withsome N + P co-limitation. Light was apparently limiting during fall and winter when the water was turbid and nutrient-rich, as well as during other months of heavy rainfall and runoff. A polyhaline station in the lower estuary had clearer water and displayed significant responses to nutrient additions during all enrichment experiments. At this site N limitation occurred in summer and fall, and P limitation (with strong N + P co-limitation) occurred in winter and spring. The data suggest there are two patterns controlling phytoplankton productivity in the Cape Fear system: 1) a longitudinal pattern of decreasing light limitation and increasing nutrient sensitivity along the salinity gradient, and 2) a seasonal alternation of N limitation, light limitation, and P limitation in the middle-to-lower estuary. Statistical analyses indicated upper watershed precipitation events led to increased flow, turbidity, light attenuation, and nutrient loading, and decreased chlorophyll a and nutrient limitation potential in the estuary. Periods of low rainfall and river flow led to reduced estuarine turb [ABSTRACT FROM AUTHOR]

We tracked a swine waste spill (4.13 x 107 L) into a small receiving river and estuary. After 2 d, a 29-km freshwater segment that the wastes had traversed was anoxic, with ca. 4000 dead fish floating and hung in shoreline vegetation. Suspended solids, nutrients, and fecal coliforms were 10- to 100-fold higher at the plume's edge (71.7 mg SS/L, 39.6 mg NH+4-N/L, and >1 x 106 cfu/100 mL, respectively; cfu, colony forming units, SS; suspended solids) than in unaffected reference sites. Elevated nutrientsand an oxygen sag from the plume reached the main estuary after ca. 5 d. Increased phytoplankton production was contributed by noxious algae, synechococcus aeruginosa and Phaeocystis globosa (108and 106 cells/mL, respectively) after 7 to 14 d. The toxic dinoflagellates, Pfiesteria piscicida and a second Pfiesteria-like species, increased to potentially lethal densities (103 cells/mL) that coincided with a fish kill and ulcerative epizootic. After 4 d, water-column fecal coliforms generally were at 102to 103 cfu/ 100 mL. But where the plume had hovered for the first 5 d, surface sediments mostly yielded =/>104 cfu/100 mL slurry, and after 61 d densities in surficial sediments were still at 103 to l04 cfu/100 mL. Dinoflagellate and euglenoid blooms developed and moved down-estuary, where they were detected after 61 d. This study documented acute impacts to surfacewaters from a concentrated swine operation, and examined some environmental policies affecting the intensive animal operation industry. [ABSTRACT FROM AUTHOR]