Benthic marine pollution around McMurdo Station, Antarctica: A summary of findings

McMurdo Station is the United States Antarctic Research Program's (USARP) centre for scientific and logistical support for most of the continent and is the largest settlement in Antarctica. Over 30 years of human presence with shipping, air-transport, scientific, and municipal activities have resulted in severe but localized nearshore marine benthic pollution. This review will summarize the results of 3 years of research which has documented concentrations of chemical contaminants, changes in community patterns, and the toxicity of sediments to invertebrate species and infaunal communities. The primary contaminants are petroleum hydrocarbons in the sediments of Winter Quarters Bay, the site of shipping activities and a former dumpsite. Total hydrocarbon levels in sediments in Winter Quarters Bay were comparable to the most polluted harbours in temperate latitudes. However, a steep gradient of pollution existed: stations less than 1 km away were nearly pristine. Benthic invertebrate communities changed dramatically along this contamination gradient. The results of both field and laboratory bioassay experiments with contaminated sediments found that biological changes observed in benthic communities around McMurdo Station were most likely caused by hydrocarbons, PCBs, and PCTs. A primary goal of polar pollution research is to determine the response and tolerance of Antarctic biota to physical and chemical anthropogenic disturbance, and the mitigation of negative effects. To this end, future work should include continued monitoring of changes in chemical and community patterns, studies of the physiological responses of Antarctic invertebrates to chemical contamination, and further comparisons of anthropogenic and natural disturbances to benthic communities.     

Benthic changes at McMurdo Station, Antarctica following local sewage treatment and regional iceberg-mediated productivity decline

McMurdo Station, the largest research station in Antarctica, ceased on-site garbage dumping in 1988 and initiated sewage treatment in 2003. In 2003-2004 its sea-ice regime was altered by the massive B-15A and C-19 iceberg groundings in the Ross Sea, approximately 100 km distant. Here we follow macrofaunal response to these changes relative to a baseline sampled since 1988. In the submarine garbage dump, surface contaminants levels have declined but associated macrofaunal recolonization is not yet evident. Although sewage-associated macrofauna were still abundant around the outfall nearly 2 yr after initiation of treatment, small changes downcurrent as far as 434 m from the outfall suggest some community recovery. Widespread community changes in 2003-2004, not seen in the decade previously, suggests that the benthos collectively responded to major changes in sea-ice regime and phytoplankton production caused by the iceberg groundings.     

Distribution of the McMurdo Station sewage plume

The spatial distribution and movement of the sewage plume from McMurdo Station, Antarctica, was investigated in the ocean under the early summer ice. Samples of seawater were obtained via holes drilled through the ice and analysed for coliform bacteria. Ocean currents were also examined to determine their effect on the movement of the plume. High densities of coliform bacteria were found along the ca. 1 km shoreline of McMurdo Station and the plume extended 200–300 m seaward. The relocation of the outfall from a surface configuration to the subsurface (11 m deep) had little influence on the distribution of the plume that sometimes reached the seawater intake station, 400 m to the south. Ocean current measurements in the study area confirmed that, while the prevailing advection was to the north and away from the intake area, episodic reversals of flow at some current meter stations coincided with pulses of sewage that moved into the intake. These findings support the use of bacterial indicators as one means to map the distribution and movement of recent sewage contamination in cold (−1.8°C) seawater and provides evidence that the disposal and movement of domestic wastes in coastal polar environments deserves attention.     

Reducing sewage pollution in the Antarctic marine environment using a sewage treatment plant

Despite Antarctica being the largest pristine wilderness on Earth, many coastal Antarctic research stations release untreated sewage waste into the marine environment, which may have negative effects on local wildlife. In February 2003 a sewage treatment plant was installed at Rothera Research Station (Adelaide Island, Antarctic Peninsula). After one year of operation the sewage treatment plant had dramatically reduced the microbiological pollution in the near-shore marine environment around the outfall and seawater quality conformed to European Union Bathing Water Standards.     

Changes in the composition and structure of Mediterranean rocky-shore communities following a gradient of nutrient enrichment: descriptive study and test of proposed methods to assess water quality regarding macroalgae

Changes in the species composition and structure of Mediterranean macroalgal-dominated communities from the upper sublittoral zone are described along a gradient of nutrient enrichment coming from a urban sewage outfall. Ulva-dominated communities only appear close to the sewage outfall. Corallina-dominated communities replace ulvacean algae at intermediate levels of nutrient enrichment. Cystoseira-dominated communities thrive in the reference site but already appear at nutrient levels that are threefold higher than those reported from unpolluted sites. Assemblage variability of Cystoseira-dominated communities decreases along the gradient of nutrient enrichment. Methods based on the functional-form groups of macroalgae to assess the water quality provide equivocal results at intermediate levels of nutrient enrichment because species belonging to the same group can display a completely different response to pollution. Alternatively, methods based on indicator species showed correlated evidence among species abundances and pollution levels and seem to have better performances in water quality assessment.     

Coprostanol as sewage tracer in McMurdo Sound, Antarctica

Sediment cores from the vicinity of sewage outfalls off McMurdo Station as well as surface grab samples from different locations in the McMurdo Sound, Antarctica were analysed for coprostanol (5β-cholestan-3β-ol) and epicoprostanol (5β-cholestan-3-ol) to assess the degree of sewage addition to the Sound. Sediment samples close to the point source contain as much as 3 mg g⁻¹ dry sediment of coprostanol, whereas samples farther from the source, for example from New Harbour and Granite Harbour, contain only trace levels to 40 ng g⁻¹. Coprostanol in the sediments of latter locations most likely originates from seals rather than from sewage outfalls. It appears that sewage particles are very quickly incorporated into the sediment layers close to the discharge point in the eastern Sound. However, significant levels (930 ng g⁻¹) of fecal sterols were detected in Cape Armitage surface sediments, indicating that the sewage plume could also have reached the seawater intake station, situated in between the outfall and Cape Armitage sampling site. These results suggest the need for a sound environmental monitoring and assessment of the existing wastewater practices in the region.     

The effects of domestic sewage effluent on marine communities at Coffs Harbour, New South Wales, Australia

Studies of the impact of secondary treated domestic effluent have been conducted at Coffs Harbour, NSW, Australia for the last 8 years. During that time, monitoring has shown that impacts are restricted to within approximately 300 m of the outfall for most variables (e.g. algal species richness, changes to the structure of invertebrate communities living in kelp holdfasts) but that the ephemeral green alga Ulva lactuca has significantly greater cover than at reference sites for a distance of 500 m from the point of discharge. Based on the results of this study, a new outfall proposed for the northern area of Coffs Harbour was predicted to have effects over a much smaller spatial scale. It is suggested, therefore, that the recent decision to abandon the plans for the new outfall reflects growing public concern over issues other than cost minimization and biological impact in the use of ocean disposal as an option for the management of human sewage waste.     

Delta13C and delta15N shifts in benthic invertebrates exposed to sewage from McMurdo Station, Antarctica

In an effort to identify biomonitors for contamination of Antarctic marine benthos by sewage, this study determines whether the US Antarctic Program’s McMurdo Station produces a benthic sewage footprint and whether resident megafauna are assimilating sewage-derived material. We identified strong C and N isotopic gradients in benthic sediment as a function of downstream distance from McMurdo Station’s point-source sewage addition. Sediment C and N isotope ratios approached marine background levels at the sampling end-point 612 m downcurrent. Based on isotope abundances in their tissues, at least some sewage C and N were assimilated by the sedentary, suspension feeding soft coral Alcyonium antarcticum, ascidian Cnemidocarpa verrucosa and bivalve Laternula elliptica. However, as inferred by tissue-sediment differences in downstream isotope trends, such assimilation was not in proportion to sewage exposure and input, therefore implying non-generalist feeding behavior by these species. In contrast, the motile, generalist feeding sea urchin Sterechinus neumayeri, sea star Odontaster validus and ribbon worm Parborlasia corrugatus showed isotopic evidence of sewage C and N assimilation roughly in proportion to sewage input. We recommend these generalist feeders for further use as biomonitors at this site now that sewage treatment has been implemented. As these species are circumpolar in distribution, they may also prove useful elsewhere in the Antarctic.     

Constraints on spatial variability in soft-sediment communities affected by contamination from an Antarctic waste disposal site

A small-scale (<500 m length) transect-based survey was conducted in December 1998 to examine the spatial distribution of soft-sediment communities and of concentrations of heavy metals and hydrocarbons in sediments in Brown Bay, adjacent to an abandoned waste dump, at Casey Station, Antarctica. Samples were taken along three transects at increasing distances (nine stations) from the shore-line waste dump. A gradient of contamination was detected, but concentrations of contaminants were very variable with "hotspots" or high levels of contaminants at some stations. Multivariate analysis revealed that the distribution of soft-sediment communities was distinctly different between the inner, middle and outer stations. Abundances of most taxa were very variable with few patterns apparent, but some fauna displayed an abundance gradient from the inner to the outer part of the bay. Many taxa had maximum abundances at outer stations and minimum at inner stations. Multivariate correlations between environmental variables and soft-sediment communities indicated that combinations of some metals (Cd, Cu, Sn, Pb) and grain size (mainly finer fractions, fine sands and coarse silts) were the variables that best "matched" the community patterns within Brown Bay. This study indicated that there were significant correlations between the presence of contaminants and the distribution and composition of soft-sediment communities over very small spatial scales.     

Der Einfluss von Kläranlagenabwässern auf benthische Wirbellose im Zürichsee

In 1981–83 sublittoral macroinvertebrates were collected by means of SCUBA diving from artificial substrates submerged near the outfalls from eight sewage treatment plants in Lake Zürich. Pollution around the outfall resulted on the one hand in a reduction of pollution intolerant benthic invertebrates, on the other hand in a considerable increase in the relative abundance of pollution tolerant taxa such as leeches, flatworms and crustaceans. Changes in the faunal composition were related to nutrient enrichment and changes in the nature of the substratum due to sedimentation of sewage sludge. Species diversity (Simpson index) showed low values near the outfall from some plants, high values near the outfall from others. Low species diversity did not always mark the sites where greatest pollution has been observed.      

Lidar observations of the stratospheric aerosol during 1993 above McMurdo Station,Antarctica

Scattering ratios of stratospheric aerosol obtained by lidar at McMurdo Station, Antarctica (78°S, 167°E), during February–December 1993, have been analysed in relation to the stratospheric polar vortex. Seasonal changes in their properties are used to infer dynamic processes occurring in the Antarctic stratosphere during the year. Descent rates are calculated and compared to values obtained with different studies. Our analysis suggests that the apparent springtime cleansing of the Antarctic stratosphere is the result of subsidence of air masses inside the vortex and of sedimentation of larger particles. Below 20 km of height, an enhancement of the aerosol descent rates during July was associated with high occurrence of Polar Stratospheric Cloud events above McMurdo Station in that period. A synoptic approach using potential vorticity values at 425 K above the station has been employed to figure out the behaviour of the aerosol across the vortex boundary during its early formation.     

Carbon and nitrogen stable isotopes in coastal benthic populations under multiple organic enrichment sources

In a dispersive coastal area under multiple organic enrichment sources, stable isotopes were used to trace organic sources of carbon and nitrogen in sediments and benthic macrofauna. The Bivalve Abra alba and the Polychaetes Nephtys sp. and Pectinaria (Lagis) koreni were reliable indicators of the input of terrestrial-derived organic matter into this coastal area, either originated in outfall sewage discharges or estuarine outflow. An isotopic depletion was observed up to 250 m from the outfall branches, much stronger in the biota than in the sediments. An enrichment of 2‰ in the sediments, and 2-6‰ in the species was noticed in sites located farther than 1500 m from the outfall. Depositivores and carnivores/omnivores gave the best picture of the extension of the sewage dispersion and incorporation into the food web.     

Australia''s first deepwater sewage outfalls: Design considerations and environmental performance monitoring

The discharge of sewage to the ocean can be an issue of public and scientific concern. Such has been the case in Sydney over at least the past 25 years. In this paper, the history of Sydney's sewage discharge is outlined, and the decisions taken to address concerns about the environmental effects of shoreline discharge of large volumes of primary treated sewage effluent are described. Design criteria are described for deepwater outfall systems that, since 1990–1991, have discharged 80% of Sydney's sewage after primary treatment at North Head, Bondi and Malabar Sewage Treatment Plants (STP). The integrated elements of a comprehensive five year Environmental Monitoring Programme (EMP) are set out. Other papers in this volume describe the result of EMP component studies. The five year EMP was designed to provide the basis to assess the environmental performance of the new deepwater outfall systems during the first two years of their operation and to provide a baseline against which further change may be measured.     

Sediment disturbance off the Tagus Estuary, Western Portugal: chronic contamination, sewage outfall operation and runoff events

Sediment disturbance patterns in the coastal area off the Tagus Estuary (Portugal) have been assessed using a set of combined techniques. The potential sources of disturbance in the area include chronic contamination of the fine sediments originating from the estuary, a local input from a long-sea sewage outfall and occasional high runoff episodes following torrential rain. The Sediment Quality Triad approach, combining environmental chemistry (namely organic contaminants), macrofaunal benthic communities and laboratory sediment toxicity assays, was performed on sediment samples from 20 sites. The samples were collected before the outfall commenced operation and four years after commissioning, in order to evaluate the relative magnitudes of the three potential sources of disturbance. The sediment contamination created by the estuary was identified as the most important cause of reduced sediment quality, as disturbance in all three components of the Sediment Quality Triad were only found in a site located near the estuary.     

Evaluation of short-term fallowing as a strategy for the management of recurring organic enrichment under salmon cages

Rotation of cages within fish farm leases and the subsequent fallowing of areas of seabed is commonly used to allow recovery of infaunal communities following periods of organic enrichment. To investigate the effect of different background environmental conditions on recovery response, two Atlantic salmon (Salmo salar) fish farm sites in southeast Tasmania were sampled over two commercial fallowing cycles. Despite similar stocking levels and feed input there were significant differences in the way in which sediment at each farm responded to the cessation of fish stocking. Sediments at both farms showed some improvement in the community structure over a three month fallow period, but the community structure only recovered to that present before stocking not to that at the reference sites. The similarity of the impact sites to the reference sites increased from ca. 25% to 31% at one site and 11% to 27% at the other after fallowing. Rate and extent of recovery were affected by farm location, initial impact of the sediments, and length of fallow period. Initial recovery was faster at the more sheltered site than at the more exposed site, possibly reflecting differences in environmental resilience with the more sheltered location better able to assimilate organic inputs. Accordingly general fallowing management protocols may need to be adapted to reflect differences between sites. The findings of this study suggest that the recovery response of benthic communities can be predicted once baseline conditions are understood.     

Changes in macroalgal communities in the vicinity of a Mediterranean sewage outfall after the setting up of a treatment plant

Benthic macroalgal communities of the upper rocky sublittoral were studied in 1995-1996 in the vicinity of the Marseille (Mediterranean, France) sewage outfall, 8 years after the setting up of a wastewater treatment plant and compared to a previous study carried out in 1972-1974. The number of taxa has increased, a clear stational and seasonal gradient of differentiation of the vegetation appeared, and a turf of ephemeral species is taking place of Corallina elongata at sites close to the outfall. These changes may be due to a decrease in pollutant load, the discharge of ferric chlorates used in the treatment process. However, the overall change is much less conspicuous than that described for deeper soft bottom communities, in particular the Cystoseira amantacea community is not still restored. Biological traits of this species (short distance dispersal) and the nature of most pollutants removed from the effluent (solids and organic matter) may explain this phenomenon.     

Subtidal assemblages on rocky reefs at a cliff-face sewage outfall (North Head, Sydney, Australia): What happened when the outfall was turned off?

For many years, sewage was continuously discharged via inshore outfalls into shallow subtidal habitats around Sydney (New South Wales). In 1990, deepwater ocean outfalls were commissioned and inshore discharge ceased. This study examined the assemblage of organisms found on subtidal cliffs at one inshore outfall to examine differences in, or recovery by, the biota when sewage was no longer discharged. This assemblage was primarily composed of filter-feeding animals (sponges, ascidians, bryozoans, anthozoans) and encrusting algae. Differences and changes in the assemblages at a number of different spatial scales, relative to the assemblages at two reference locations, were examined four times over a 20 month period. Although most taxa showed significant changes over the study period, most of these were unpredictable and varied interactively according to the taxon, plot, depth and location. For most measures, however, the location where sewage had been released lay within the natural variability shown by the reference locations. The implications of these findings are discussed with respect to other studies on the effects of sewage on intertidal and shallow subtidal habitats.     

Spatial and temporal patterns of the infaunal community near a major ocean outfall in Southern California

Effects of waste water discharge from a major ocean outfall in Southern California to the benthic infaunal community were examined during a 5-year monitoring programme. Natural features, primarily water depth, accounted for 82% of the variability in the infaunal community, while discharge-related effects represented less than 8% of the variability. The area immediately adjacent to the diffuser had the strongest outfall effects. Infaunal abundance showed a pattern of enhancement centred at the outfall. Diversity was also high, indicating that the area was not characterized by a degraded community.     

Use of physiological responses in Mytilus trossulus as integrative bioindicators of sewage pollution

Mussels, Mytilus trossulus (average shell length 43+/-0.8 mm), were sampled from a beach in Alaska that received untreated sewage for several years, a second beach adjacent to a secondary wastewater outfall, and two nearby reference beaches. Survival time in air, byssal thread production rate, and prevalence of trematode parasites were determined for each group. Tolerances to aerial exposure was significantly lower (P<0.05) at both sewage outfall sites than at the reference sites. Mussels exposed to untreated sewage produced fewer byssal threads and had a significantly higher prevalence of encysted trematodes than mussels from the other beaches, including the secondary wastewater site. Survival in air, byssal thread production, and trematode prevalence in mussels may be useful indicators in evaluating the longterm health of beaches exposed to sewage.