David T. Specht

Predicting bioaccumulation potential: A test of a fugacity-based model

Clams (Macoma nasuta) from an unpolluted site in Yaquina Bay, Oregon were exposed in the laboratory for 28 days to 6 field-contaminated sediments (treatments) which varied widely in concentration of 10 organic pollutants. Mean accumulation factors (AF = (concentration in tissue/lipid, %/100)/(concentration in sediment/total organic carbon, %/100)) of 8 neutral organic compounds (DDE [p,p′], 2,2′,3,5′6-pentachlorobiphenyl, 2,3′,4,4′,5-pentachlorobiphenyl, Aroclor® 1254, pyrene, chrysene, benzo[a]pyrene, benzo[b,(k)]fluoranthene) were homogeneous across treatments. Statistically significant differences were detected between some treatment AFs for ODD [p,p′] and benz[a]anthracene, and between some chemicals within treatments (experimentwise a=0.05). Accumulation factors were less than 2 and less variable in highly polluted, organically enriched sediments (total organic carbon > 3.69 ± 0.044%), but sometimes exceeded 2 in clams exposed to surficial (0–2 cm deep) sediments with low pollutant concentration and low organic carbon content (⩽ 0.86 ±0.037%). These results suggest that the AF model may provide reasonable estimates of bioaccumulation potential of hydrophobic neutral organic compounds in organically enriched, polluted sediments.

Accumulation factors for eleven polychlorinated biphenyl congeners

According to the fugacity approach pollutant uptake by an organism is determined by the chemical fugacity differential between the organism and its environment. The Accumulation Factor (AF) is a simple, fugacity-based model which has been shown to be useful for predicting the bioaccumulation potential of hydrophobic neutral organic compounds in sediment dwelling animals. Previously, the constancy of AFs for ten hydrophobic neutral organic compounds were tested by exposing clams (Macoma nasuta) in the laboratory for 28 days to six field-collected sediments varying widely in C{sub S}, TOC, and other chemical and physical characteristics. Sediment and tissue samples from that study were achieved and later analyzed for 11 polychlorinated biphenyl (PCB) congeners. In this paper the authors report mean and maximum AFs (AF{sub max}) for 11 PCB congeners and test the constancy of the AFs across 5 sediments (treatments) by congener and across the 11 congeners by treatment.

Efficiency of uptake of hexachlorobenzene from water by the tellinid clam, Macoma nasuta

Abstract A study was undertaken to determine the efficiency with which a marine deposit-feeding clam ( Macoma nasuta ) extracted hexachlorobenzene (HCB) from water (EPW). An exposure chamber (clambox) was designed that separated the inhalant and exhalant siphons, allowing the collection of ventilated water. Seawater dosed with 14 C-labeled HCB was pumped into the inhalant chamber of the clambox. Clams were exposed to three temperatures (12, 17, 22°C) to vary weight-specific ventilation volume ( Vg ). Loss of HCB from the exhalant chamber precluded determination of EPW from the difference in HCB concentrations between the inhalant and exhalant chambers. Instead, gross EPW was calculated by dividing the HCB tissue residues by the amount of HCB to which the clam was exposed (water ventilated × the HCB concentration). Gross EPW averaged 82%. Correcting for non-gill uptake (surface sorption of HCB), gill EPW averaged 64–66%, and did not decrease with increasing Vg . In M. nasuta, Vg varied less than two-fold, which may explain the lack of a ventilation effect on EPW. HCB tissue residues were linearly related ( R 2 = 0.93) to gill exposure. The linear relationship between tissue residues and exposure supports a bioenergetics-based bioaccumulation model and indicates that factors that increase Vg , such as low oxygen concentrations, would result in more rapid uptake and a greater body burden.

Manganese and suspended matter in the Yaquina Estuary, Oregon

The longitudinal distribution of total suspended matter and total, dissolved, and particulate manganese in a small coastal plain estuary is described. The distribution of manganese is a consequence of estuarine circulation; a within-estuary maximum is inversely correlated with river flow, and is a function of residence time in the estuary, resuspension in the upper estuary, and desorption from particles introduced from within the estuary or from the river. The turbidity maximum is similarly most pronounced during low river flows. The upper estuary (salinity <15‰), comprising a small percentage of the total estuary volume during low flow, receives material from the river and along the bottom from the lower estuary; this material is returned to the water column by resuspension and desorption from estuarine and riverine particles. The lower estuary tends to damp out these processes because of the greater volume and (residence) time available for mixing.

Dissolved silicon in the Yaquina Estuary, Oregon

Abstract The longitudinal distribution of dissolved silicon in the Yaquina Estuary is described in surface and bottom waters. Non-conservative behaviour is a function of high insolation and low runoff; residence time is the primary controlling factor.

Monitoring the expanding distribution of nonindigenous dwarf eelgrass zostera japonica in a pacific northwest USA estuary using high resolution digital aerial orthophotography

The paper describes a method of mapping the intertidal distribution of the nonindigenous seagrass Zostera japonica in a Pacific Northwest (PNW) USA estuary from color infrared aerial orthophotography using a hybrid digital classification technique. A random ground survey indicated an overall accuracy exceeding 80 percent for this procedure in the lower estuary, where this invasive species may interfere with mudflat foraging of the commercially important Dungeness crab. Knowledge of the areal distribution of Z. japonica from this digital classification will aid in planning studies to evaluate impacts of expansion of the nonindigenous seagrass in PNW estuaries.

Depuration kinetics of hexachlorobenzene in the clam, Macoma nasuta

1. The depuration rate constant for [14C]hexachlorobenzene (HCB) in the clam, Macoma nasuta, was determined following a short-term exposure to HCB contaminated seawater. 2. Depuration was not correlated with ventilation volume, nor did the amount of sediment ingested during depuration have a significant effect. 3. The half-life for HCB in M. nasuta was estimated to be 16 days with a bioconcentration factor of 3490 (wet weight basis).

Mapping intertidal eelgrass (Zostera marina L.) in three coastal estuaries of the Pacific Northwest USA using false colour near-infrared aerial photography

This study describes a hybrid technique of digitally classifying aerial photography used for mapping the intertidal habitat of eelgrass (Zostera marina L.) in Pacific Northwest USA estuaries. The large tidal range (2–3 m) in this region exposes most of this seagrass community at low tide, permitting the use of false colour near-infrared film that provides good contrast in imaging vegetated intertidal habitats. Three Oregon coastal estuaries in the USA were surveyed in 2004 or 2005 at photoscales of 1:10 000 or 1:20 000. Spatial resolution was 0.25 m and the minimum mapping unit was 2.5 × 2.5 m. Spatial accuracy was within 1.5 m. Comparison of the image classification and ground survey results yielded overall classification accuracies of 83% to 97%. This appears to be an effective technique for mapping intertidal eelgrass distributions in turbid coastal estuaries with large tidal ranges.

A Strategy for Protecting Circulating Seawater Systems from Oil Spills1

ABSTRACT A strategy is described for establishing a simple, inexpensive monitoring program for determining approximate levels of petroleum hydrocarbons in ambient water collected near intake structures of circulating seawater systems. The ambient water is obtained from the depth of intake using a submersible pump, which delivers the sample stream to a dockside partitioning chamber that provides instantaneous grab samples for analysis. A common hand-operated fluorometer equipped for measuring the oil content of a fluid was standardized using a locally-obtained No. 2 marine diesel fuel; oil concentrations in water samples were quantified as Marine Diesel Equivalents (MDE) in parts-per-billion. Surveys conducted along the central Oregon coast following the March 1999 beaching of the drifting freighter New Carissa off Alsea Bay were conducted in that bay, and in Yaquina Bay about 20 km to the north. No evidence of oil contamination from the beached ship was found. The highest MDE levels occurred within the es...