Barry T. Hargrave

Arctic contaminants: sources, occurrence and pathways

Potentially toxic organic compounds, acids, metals and radionuclides in the northern polar region are a matter of concern as it becomes evident that long-range transport of pollution on hemispheric to global scales is damaging this part of the world. In this review and assessment of sources, occurrence, history and pathways of these substances in the north, the state of knowledge of the transport media--the ocean and atmospheric circulation--is also examined. A five-compartment model of the northern region is developed with the intent of assessing the pathways of northern contaminants. It shows that we know most about pathways of acids, metals and radionuclides and least about those of complex synthetic organic compounds. Of the total annual inputs of anthropogenic acidic sulphur and the metals lead and cadmium to the Arctic via the atmosphere, an estimated 10-14% are deposited. A water mass budget for the surface layer of the Arctic Ocean, the most biologically active part of that sea, is constructed to examine the mass budget for one of the major persistent organochlorine compound groups found in remote regions, hexachlorocyclohexanes (HCH), one isomer of which is lindane. It is concluded that both the atmosphere and the ocean are important transport media. Even for the HCH substances which are relatively easily measured and simple in composition compared to other synthetic organics, we know little about the occurrence and environmental physical/chemical characteristics that determine pathways into the food chain. More environmental measurements, chemical characterization studies and environmental chemical transport modelling are needed, as is better knowledge of the circulation of the Arctic Ocean and the marine food web.

Spatial and temporal trends and effects of contaminants in the Canadian Arctic marine ecosystem: a review

Recent studies have added substantially to our knowledge of spatial and temporal trends of persistent organic pollutants and heavy metals in the Canadian Arctic marine ecosystem. This paper reviews the current state of knowledge of contaminants in marine biota in the Canadian Arctic and where possible, discusses biological effects. The geographic coverage of information on contaminants such as persistent organochlorines (OCs) (PCBs, DDT- and chlordane-related compounds, hexachlorocyclohexanes, toxaphene) and heavy metals (mercury, selenium, cadmium, lead) in tissues of marine mammal and sea birds is relatively complete. All major beluga, ringed seal and polar bear stocks along with several major sea bird colonies have been sampled and analysed for OC and heavy metal contaminants. Studies on contaminants in walrus are limited to Foxe Basin and northern Québec stocks, while migratory harp seals have only been studied recently at one location. Contaminant measurements in bearded seal, harbour seal, bowhead whale and killer whale tissues from the Canadian Arctic are very limited or non-existent. Many of the temporal trend data for contaminants in Canadian Arctic biota are confounded by changes in analytical methodology, as well as by variability due to age/size, or to dietary and population shifts. Despite this, studies of OCs in ringed seal blubber at Holman Island and in sea birds at Prince Leopold Island in Lancaster Sound show declining concentrations of PCBs and DDT-related compounds from the 1970s to 1980s then a levelling off during the 1980s and early 1990s. For other OCs, such as chlordane, HCH and toxaphene, limited data for the 1980s to early 1990s suggests few significant declines in concentrations in marine mammals or sea birds. Temporal trend studies of heavy metals in ringed seals and beluga found higher mean concentrations of mercury in more recent (1993/1994) samples than in earlier collections (1981-1984 in eastern Arctic, 1972-1973 in western Arctic) for both species. Rates of accumulation of mercury are also higher in present day animals than 10-20 years ago. Cadmium concentrations in the same animals (eastern Arctic only) showed no change over a 10-year period. No temporal trend data are available for metals in sea birds or polar bears. There have been major advances in knowledge of specific biomarkers in Canadian Arctic biota over the past few years. The species with the most significant risk of exposure to PCBs and OC pesticides may be the polar bear which, based on comparison with EROD activity in other marine mammals (beluga, ringed seal), appears to have elevated CYP1A-mediated activity. The MFO enzyme data for polar bear, beluga and seals suggest that even the relatively low levels of contaminants present in Arctic animals may not be without biological effects, especially during years of poor feeding.

Towards a classification of organic enrichment in marine sediments based on biogeochemical indicators.

A nomogram is developed to show that pH, redox potentials (Eh(NHE)) and measures of dissolved sulfides (H2S + HS(-) + S(2-))(total free S(2-)) can be used to classify organic enrichment impacts in marine sediments. The biogeochemical cycle of sulfur in marine sediments is described to show that changes in macrobenthic infauna community structure associated with high levels of organic matter supply result from stress due to oxygen deficiency (hypoxia and anoxia) and toxic effects of S(2-). The changes reflect enhancement of microbial sulfate reduction under conditions of high organic matter sedimentation and the progressive formation of hypoxic-anoxic conditions measured by decreased Eh NHE and increased concentrations of S(2-). The nomogram provides a basis for classification of the oxic status of marine sediments based on changes in inter-related biological and biogeochemical variables along an organic enrichment gradient.

Bioaccumulation of polychlorinated biphenyls (PCBs) in the marine pelagic food web, based on a seasonal study in the southern Gulf of St. Lawrence, 1976−1977

Copyright (c) 1996 Elsevier Science B.V. All rights reserved. Polychlorinated biphenyls (PCBsr were quantified in bulk seawater (3.1p1.0 ng l −1 , N=3r in 1976, in plankton (2.9p3.3 ng g −1 wet weight, N=176r in 1976 and 1977 and in fish (155p194 ng g −1 wet weight, N=135r in 1977 collected from St. Georges Bay in the southern Gulf of St. Lawrence. PCB concentrations in the plankton of the entire water column varied seasonally by ten times, with the highest values occurring in spring, lowest during summer and variable levels in late fall. The lower PCB levels in the total summer community coincide with a reduced biomass in certain size fractions in the Bay rather than a decrease in PCB concentration of the plankton. PCBs were concentrated in the middle-sized fractions of the planktonic community and this is attributed to the greater biomass present in these categories. PCB concentrations in plankton were most highly correlated with their lipid content at the time of sampling. Seasonal reductions of lipid in the plankton per m 3 resulted in a higher concentration of PCB per unit lipid in the remaining community. Planktonic PCB concentrations, expressed on a lipid basis, are found to be correlated with cumulative rainfall 21 d before sampling for both years combined. Adult fish were more contaminated by PCBs than either their egg or juvenile stages. Mature gaspereau, herring and smelt had higher concentrations of PCB contamination than mackerel, capelin, white hake and silversides. No difference was found between PCB contamination of the sexes of fish species analyzed. PCBs were transferred from mother to offspring in fish, but at lower levels than the level present in the parent; and the maximum accumulation from the environment occurred between immature and adult fish. The best predictors of PCB contamination in fish in St. Georges Bay are lipid content followed by size and age. PCB concentrations in plankton, normalized to lipid content, did not increase with size or trophic level. PCB concentrations in fish increased with size and on average were ten times the levels found in plankton. Marine mammals collected by other researchers in the region during the 1970s had accumulated up to several orders-of-magnitude higher concentrations than those found in fish, with a more gradual increase with size of organism. Lipid content and age or exposure period appear to be the main factors which determine PCB concentrations in the marine food chain in the southern Gulf of St. Lawrence.

In situ feeding and absorption responses of sea scallops Placopecten magellanicus (Gmelin) to storm-induced changes in the quantity and composition of the seston

Time-series of hourly clearance, ingestion and absorption rates and absorption efficiency were measured over 48 h for adult sea scallops (Placopecten magellanicus) held in situ in a coastal embayment in Nova Scotia, Canada, during a wind-induced resuspension event. Temporal variations in oceanographic variables, and seston quantity and composition (organic matter, organic carbon, nitrogen, chlorophyll a, and inorganic particle size spectra) were monitored during the study with moored instruments and hourly water sampling. Resuspension of bottom materials during the storm resulted in large changes in the amount (1 to 30 mg l−1 total particulate matter) and nutritional quality (25 to 50% organic content) of seston. High sedimentation rates after the storm were accelerated by flocculation, resulting in the rapid settling of resuspended particles and an increase in seston quality. Observed short-term (hourly) fluctuations in clearance rate were not related to storm- or tide-induced changes in seston characteristics but were directly related to flow velocity. Significantly lower clearance rates were observed at relatively low ( 9 cm s−1) flow speeds. The overall reduction in ingestion rates after the storm resulted from decreased food availability. Hourly absorption efficiency (AE) measurements were closely related to seston quality (total organic, organic C and N content) and AE declined exponentially with decreasing seston quality. Reductions in AE during the resuspension event were offset by the increased ingestion rate, resulting in no significant changes in absorption rates for organic matter, C, or N over the sampling period. As the low food quality of the resuspended matter was balanced by increased availability, any physiological regulation of food acquisition (i.e. clearance rate regulation) would have been irrelevant to maintaining food intake constant.

Estimates of oil in aquatic sediments by fluorescence spectroscopy

Abstract Aromatic substances extracted with n -hexane from various sediments were analysed by fluorescence spectroscopy. Contour diagrams of fluorescence intensity at various excitation and emission wavelengths were used to compare fluorescence spectral patterns of sample extracts and standard oils. Similarities in spectral contour diagrams confirmed the presence of petroleum residues in Bermuda beach sand, intertidal sand and sedimenting material from an inlet near an oil refinery in Nova Scotia, and in sand from Chedabucto Bay contaminated by the Arrow stranding in 1970. Total oil concentrations ranged from 10–3000 μg/g wet sediment with highest concentrations occurring in sedimenting particles. Fluorescence patterns in many sample extracts did not resemble any standard oil, indicating the presence of fluorescing material not originating from fresh petroleum.

Benthic Metabolism and the Quality of Sediment Organic Carbon

AbstractWe have used changes in oxygen uptake of sediment cores incubated in the laboratory and receiving no particulate input to examine the utilization of labile organic carbon by the benthos. A model is described that predicts a decline in sediment oxygen consumption after primary labile organic carbon (G01) is depleted. Oxygen consumption by cores taken from an intertidal sandflat in Nova Scotia and incubated in darkness (11–13°C) declined after about two months. G01 organic carbon was estimated as ∼8% of total sediment carbon (GT) in the upper 1 cm of sediment. Anaerobic metabolism (based on CO2 production), a significant portion of community metabolism, increased rather than declined during the incubations. Similar calculations were performed using published data on cores from Narragansett Bay. At this location, organic matter in the G01 fraction was 5% of GT. A less labile organic carbon fraction (G02) was estimated to be 44% of GT based on declining oxygen consumption after 27 days. Refractory car...

Toxaphene in amphipods and zooplankton from the Arctic Ocean

Lysianassid amphipods (Eurythenes gryllus) trapped at abyssal depths in the Arctic Ocean over the Alpha Ridge contained higher concentrations of toxaphene (polychlorinated camphenes, PCCs) (mean ± S.D. = 2300 ± 960 ng g−1 wet weight, 16500 ± 7900 ng g−1 lipid) than smaller species (Anonyx, Tmetonyx, Onisimus) (143 ± 135 ng g−1 wet weight, 1730 ± 1240 ng g−1 lipid) captured on the continental shelf adjacent to Axel Heiburg and Ellef Ringnes Islands. Zooplankton collected over the shelf contained PCC concentrations more than an order-of-magnitude lower than amphipods (3.6 ± 2.0 ng g−1 wet weight, 67 ± 45 ng g−1 lipid). Heavier PCCs containing eight and nine chlorines were selectively accumulated by both amphipods and zooplankton. The data are combined with previously published observations to construct a hypothetical food web and to calculate bio-magnification factors for PCCs between probably predator-prey links.

Rapid digestion and assimilation of bait by the deep-sea amphipod Eurythenes gryllus

Scavenging lysianassoid amphipods (Eurythenes gryllus) were collected with a newly designed trap to measure digestion rates with timed exposure to bait in the Canada Basin of the Arctic Ocean (2075 m) and in the Nares (3521 m) and Sohm Abyssal (4978 m) Plains, northeast Atlantic Ocean. In feeding experiments up to 157 h long, water and organic matter content were not significantly different in anterior, central and hind gut regions of individual amphipods, showing that digestion in E. gryllus conforms to the batch reactor feeding model. Ingested bait was rapidly solubilized and water content increased from 90% within 69 h. Digestion rates, calculated from exponential curves fitted to decreases in gut contents for dry matter and various organic components, were very high (2.1–6.5% loss h−1) for sardines ingested during short (6–11 h) incubation periods in the Canada Basin. Mackerel ingested by amphipods trapped in the Nares and Sohm Abyssal Plains were digested at lower rates (0.4-1.0% loss h−1) in in situ experiments up to 123 h. Allometric regressions described relationships between body length and calories potentially available for assimilation from one meal by male and female instars. Rapid digestion in opportunistic scavengers like E. gryllus makes gut capacity available for additional feeding when food supply is unpredictable.

Benthic oxygen consumption on continental shelves off eastern Canada

The consumption of phytoplankton production by the benthos is an important component of organic carbon budgets for continental shelves. Sediment texture is a major factor regulating benthic processes because fine sediment areas are sites of enhanced deposition from the water column, resulting in increased organic content, bacterial biomass and community metabolism. Although continental shelves at mid- to high latitudes consist primarily of coarse relict sediments (Piper, Continental Shelf Research, 11, 1013–1035), shelf regions of boreal and subarctic eastern Canada contain large areas of silt and clay sediments (Fader, Continental Shelf Research, 11, 1123–1153). We collated estimates of benthic oxygen consumption in coarse (<20% silt-clay, <0.5% organic matter) and fine sediments (20% silt-clay, 0.5% organic matter) for northwest Atlantic continental shelves including new data for Georges Bank, the Scotian Shelf, the Grand Banks of Newfoundland and Labrador Shelf. Estimates were applied to the areal distribution of sediment type on these shelves to obtain a general relationship between sediment texture and benthic carbon consumption. Mean benthic oxygen demand was 2.7 times greater in fine sediment than in coarse sediment, when normalized to mean annual temperature. In terms of carbon equivalents, shelf regions with minimal fine sediment (Georges Bank, the Grand Banks of Newfoundland-northeast Newfoundland) consumed only 5–8% of annual primary production. Benthos of the Gulf of Maine (100% fine sediment) and the Scotian Shelf (35% fine sediment) utilized 16–19% of primary production. Although 32% of the Labrador Shelf area contained fine sediments, benthic consumption of pelagic production (8%) was apparently limited by low mean annual temperature (2°C). These results indicate that incorporation of sediment-specific oxygen uptake into shelf carbon budgets may increase estimates of benthic consumption by 50%. Furthermore, respiration and production by large macrofauna allow an even greater proportion of primary production to enter benthic pathways. Fine sediment areas (shelf basins or “depocenters”) are postulated to be sites of enhanced biological activity which must be considered in the modelling of shelf carbon budgets and the role of the benthos in demersal fisheries.