Bioavailability and trophic transfer of humic-bound copper from bacteria to zooplankton

ABSTRACT: The effect of humic acid (HA) on uptake and transfer of Cu by selected marine organisms from the microbial loop was determined. Bacteria grown with and without 15 µg Cu l-1 and with and without 10 mg Suwannee River Humic Acid (SRHA) l-1 were fed to Uronema sp. The Uronema were subsequently fed to Acartia tonsa to determine the effect of humic acid on the uptake and transfer of Cu from bacteria to copepods. The presence of 10 mg SRHA l-1 reduced Cu uptake in A. tonsa by an average of 54% and significantly reduced the negative effects of Cu on reproductive success ofA. tonsa. The percentage of the total Cu residues in A. tonsa resulting from feeding was estimated by exposing A. tonsa to the same conditions with and without pre-exposed Uronema as food. The results indicate that approximately 50% of the Cu residue is due to feeding. Thus, SRHA seems to affect Cu uptake in A. tonsa through binding of free Cu in the water at the same rate as through the food chain. This study demonstrates the importance of complexation of metals by organic matter and trophic transfer processes for organisms critical to estuarine food webs

Spatial and Temporal Variability in Zooplankton Community Dynamics in Three Urbanized Bayous of the Pensacola Bay System, Florida, USA

Spatial and temporal patterns in zooplankton community composition and abundance in coastal areas of the Gulf of Mexico are not well understood. Spatial and temporal differences in zooplankton community composition and abundance from 10 stations located in four sites are presented (Pensacola Bay and Bayou Texar, Bayou Chico, and Bayou Grande, three adjacent mesohaline-tidal bayous affected by urban and industrial development). Statistically significant differences (P \u3c 0.05) were found in log-biovolume among sites. The mean biovolume of zooplankton was highest in Pensacola Bay (0.38 ml m-3) followed by Bayou Grande (0.21 ml m-3), Bayou Chico (0.14 ml m-3), and Bayou Texar (0.06 ml m-3). Mean zooplankton abundances (organisms m-3) in Pensacola Bay (3,100 m-3) and Bayou Grande (3,000 m-3) were more than double the abundances in Bayou Texar (1,400 m-3) and Bayou Chico (1,100 m-3). The calanoid copepod Acartia tonsa Dana was the dominant species in the study area. The observed differences in the zooplankton community may be attributable to either one or a combination of factors such as water quality (toxicity), predation, and nutrient availability. Zooplankton abundance increased following two hurricanes that impacted the study area

Benthic Nutrient Flux in a Small Estuary in Northwestern Florida (USA)

Benthic nutrient fluxes of ammonium (NH4+), nitrite/nitrate (NO2- + NO3-), phosphate (PO4-3), and dissolved silica (DSi) were measured in Escambia Bay, an estuary within the larger Pensacola Bay system of northwestern Florida (USA). Our study occurred during a severe drought which reduced riverine inputs to Escambia Bay. Laboratory incubations of field-collected cores were conducted on 8 dates between June and October 2000 to estimate nutrient flux, and cores were collected from locations exhibiting a range of sediment organic matter content. NH4+ flux ranged from – 48.1 to 110.4 μmol m-2 h-1, but the mean flux was 14.6 μmol m-2 h-1. Dissolved silica (DSi) fluxes were also variable (-109. 3 to 145.3 μmol m-2 h-1), but the mean net flux (9.3 μmol m-2 h-1) was from the sediment to the water column. Bay sediment fluxes for NO2-+ NO3- and PO4-3 were less variable during this period (– 7.93 to 28.73 and – 1.74 to 3.29 μmol m-2 h-1 for NO2-+ NO3- and PO4-3, respectively). Low NH4+ fluxes were similar to published estimates from lagoonal Gulf of Mexico (GOM) estuaries, possibly due to the reduced freshwater input. Diminished regeneration of phosphate relative to inorganic nitrogen observed during the study period was consistent with previous research in Pensacola Bay suggesting phytoplankton phosphorus limitation. Finally, the estimated residence time of Escambia Bay and the mean turnover times for NH4+ and NO2-+ NO3- suggested that benthic flux significantly influenced nitrogen concentrations in overlying water

Mapping and Monitoring of Submerged Aquatic Vegetation in Escambia-Pensacola Bay System, Florida

Recently, the distribution and changes in submerged aquatic vegetation (SAY) in the Escambia-Pensacola Bay System in northeastern Florida were monitored by two techniques. One technique used divers to measure changes in the deepwater margin of beds and provided horizontal growth measurements to the nearest centimeter, the other used a differential global positioning system (DGPS) on a small boat to map the perimeter of SAY beds in shallow water. Current distribution of SAY in Escambia Bay shows that most of the SAY losses that occurred during the 1950s to 1970s have been recovered. In Santa Rosa Sound and Pensacola Bay, SAY showed significant increased growth with horizontal growth rates of some beds averaging more than 50 em over the past year. In Big Lagoon, however, SAY has declined an average of 10 em in horizontal coverage along the deepwater edge. Water quality and photosynthetically active radiation light measurements from the Escambia-Pensacola Bay System suggest that increased light availability was associated with the increased seagrass coverage in Santa Rosa Sound and Pensacola Bay, and elevated nutrient concentrations were associated with the seagrass declines in Big Lagoon

The effect of salinity on binding of Cd, Cr, Cu and Zn to dissolved organic matter

Abstract Salinity can affect binding of metals to humic acid and thus affect bioavailability, however, the effects are poorly understood. The fraction of Cu, Zn, Cd and Cr (at 100 μg/L) complexed with Suwannee River Humic Acid (SRHA) was measured at salinities of 0, 1, 3, 10, and 15 psu using 1000 Dalton ultrafiltration membranes. In distilled water, 10 mg SRHA/L bound at least 40% of each metal. Except for Cu, metal binding decreased to less than 20% at salinities between 1 and 15 psu. Copper binding decreased to 27% at 3 psu, but increased to approximately 60% bound at 15 psu. Copper complexation with natural dissolved organics from a local estuary was also measured and ranged from 25 to 100

The effect of humic acid on uptake/adsorption of copper by a marine bacterium and two marine ciliates

Abstract The effect of humic acid (HA) on Cu uptake by a bacterium and two bacterivorus ciliates was investigated. The presence of HA resulted in a statistically significant (p\u3c0.001) decrease in Cu associated with bacteria that were exposed to 67 μg Cu L−1. Complexation of Cu appears to lower the availability of Cu with respect to bacterial cell surface binding and uptake. For ciliates, 10 mg HA L−1 significantly reduced uptake of Cu by Uronema, but did not reduce uptake of Cu by Pleuronema. Uronema exposed to 67 μg Cu L−1 accumulated 54% less Cu when 10 mg HA L−1 was present (0.50 pg ciliate−1 vs 0.23 pg ciliate−1). Uronema feeding on V. natriegens, took up less than half as much Cu as unfed Uronema when exposed to Cu without HA (0.41 pg Cu fed ciliate−1 vs 0.86 pg Cu unfed ciliate−1, but only 40% less when exposed to Cu and HA (0.31 pg Cu fed ciliate−1 vs 0.51 pg Cu unfed ciliate−1). The lower % reduction attributable to fed ciliates in the presence of HA suggests that some of the Cu associated with HA is available through trophic processes

Benthic nutrient flux in a small estuary in northwest Florida (USA)

Benthic nutrient fluxes of ammonium (NH₄⁺), nitrite/nitrate (NO₂⁻ + NO₃⁻), phosphate (PO₄⁻³), and dissolved silica (DSi) were measured in Escambia Bay, an estuary within the larger Pensacola Bay system of northwestern Florida (USA). Our study occurred during a severe drought which reduced riverine inputs to Escambia Bay. Laboratory incubations of field-collected cores were conducted on 8 dates between June and October 2000 to estimate nutrient flux, and cores were collected from locations exhibiting a range of sediment organic matter content. NH₄⁺ flux ranged from – 48.1 to 110.4 μmol m⁻² h⁻¹, but the mean flux was 14.6 μmol m⁻² h⁻¹. Dissolved silica (DSi) fluxes were also variable (– 109. 3 to 145.3 μmol m⁻² h⁻¹), but the mean net flux (9.3 μmol m⁻² h⁻¹) was from the sediment to the water column. Bay sediment fluxes for NO₂⁻ + NO₃⁻ and PO₄⁻³ were less variable during this period (– 7.93 to 28.73 and – 1.74 to 3.29 μmol m⁻² h⁻¹ for NO₂⁻ + NO₃⁻ and PO₄⁻³, respectively). Low NH₄⁺ fluxes were similar to published estimates from lagoonal Gulf of Mexico (GOM) estuaries, possibly due to the reduced freshwater input. Diminished regeneration of phosphate relative to inorganic nitrogen observed during the study period was consistent with previous research in Pensacola Bay suggesting phytoplankton phosphorus limitation. Finally, the estimated residence time of Escambia Bay and the mean turnover times for NH₄⁺ and NO₂⁻ + NO₃⁻ suggested that benthic flux significantly influenced nitrogen concentrations in overlying water.Journal ArticleFinal article publishe