Assessment of cytochrome P450 1A in harbour seals (Phoca vitulina) using a minimally-invasive biopsy approach

Biomarkers of organochlorine exposure, such as the induction of cytochrome P450 1A (CYP1A), can be used to assess the impact of environmental contaminants on the health of free-ranging marine mammal populations. The objective of the present study was to measure CYP1A in skin and liver biopsies obtained from live harbour seals (Phoca vitulina). Twelve harbour seal pups, aged three to five weeks, were captured from the Fraser River estuary, British Columbia, Canada, and temporarily held in captivity. Skin ( approximately 60 mg) and liver ( approximately 40 mg) biopsies, obtained while seals were under general anaesthesia, yielded sufficient tissue for the measurement of CYP1A by immunoblot analysis and ethoxyresorufin O-deethylase activity. A short-term exposure experiment, in which harbour seals (n=3) were treated orally with beta-naphthoflavone (BNF), resulted in increased hepatic and cutaneous CYP1A protein levels, consistent with observations in other mammals. This study is the first to measure CYP1A in skin and liver biopsies from live harbour seals and to report in vivo BNF-associated CYP1A induction in a marine mammal. The results demonstrate that microsamples collected using minimally-invasive techniques can provide toxicologically-relevant information form marine mammals.     

On the potential impact of harbour seal predation on the cod population in the eastern North Sea

Increasing Scandinavian harbour seal populations during the last decades coincide in time with the collapse of the cod fishery. Assumptions of a causal relationship have led to claims favouring re-introduction of seal hunting. Proposals for ‘adaptive management’ often assume that decimating seal populations will automatically favour the fishery. This argument presupposes seal predation to be sufficiently large to have a measurable impact on the fish population. The potential magnitude of the cod-seal interaction was analysed using data on harbour seal abundance, feeding habits and compiled information on cod life history and cod landing statistics. A size-structured life history matrix for the cod population was applied and the size-specific prey preferences of harbour seals were taken into account. Estimated seal predation was small compared to both the landings by the fishery, and to minimum estimates of the total cod population. Furthermore, since the size classes of cod targeted by seals have low reproductive values, the impact of seal predation on cod production will be further reduced. Our analyses suggest harbour seals have a negligible impact on the cod fishery.     

Contaminant exposure and effects in Baltic ringed and grey seals as assessed by biomarkers

The Baltic Sea ecosystem has suffered from a heavy pollutant load for more than three decades. Persistent organic pollutants (POPs) and heavy metals have been of most concern due to their persistence and toxic properties. Ringed seals (Phoca hispida baltica) and grey seals (Halichoerus grypus) living in the Baltic Sea have been suffering from pathological impairments, including reproductive disturbances, which have resulted in a depressed reproductive capacity. We investigated several biochemical parameters as potential biomarkers for exposure to and effects of the contaminant load in the Baltic seals. Seals from less polluted areas were used as reference material in terms of the pollution load. In both Baltic seal populations, the levels of some biochemical parameters diverged from those in the reference seals, and some of these showed a clear correlation with the individual contaminant load. Of the potential bioindicators, we propose cytochrome P4501A activity and vitamin E levels, in blubber or plasma, as exposure biomarkers for polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in both species. The arylhydrocarbon receptor-mediated chemical-activated luciferase gene expression (CALUX) response reflects the whole PCB and DDT burden in ringed seals. Retinyl palmitate (vitamin A) levels showed a negative correlation with the individual POP load, and is proposed as potential effect biomarkers for the depletion of the vitamin A stores. As the nutritional levels of both vitamin A and E have an impact on the vitamin levels in the seals, more information on the dietary vitamin levels is needed before any conclusions can be drawn. As the relationship between biochemical parameters and contaminants varied between the two species, species-specific characteristics has to be considered when monitoring the health status and possible toxic effects of the contaminant load in ringed and grey seals.     

On the potential impact of harbour seal predation on the cod population in the eastern North Sea

Increasing Scandinavian harbour seal populations during the last decades coincide in time with the collapse of the cod fishery. Assumptions of a causal relationship have led to claims favouring re-introduction of seal hunting. Proposals for ‘adaptive management’ often assume that decimating seal populations will automatically favour the fishery. This argument presupposes seal predation to be sufficiently large to have a measurable impact on the fish population. The potential magnitude of the cod-seal interaction was analysed using data on harbour seal abundance, feeding habits and compiled information on cod life history and cod landing statistics. A size-structured life history matrix for the cod population was applied and the size-specific prey preferences of harbour seals were taken into account. Estimated seal predation was small compared to both the landings by the fishery, and to minimum estimates of the total cod population. Furthermore, since the size classes of cod targeted by seals have low reproductive values, the impact of seal predation on cod production will be further reduced. Our analyses suggest harbour seals have a negligible impact on the cod fishery.     

Time-course evaluation of ROS-mediated toxicity in mussels, Mytilus galloprovincialis, during a field translocation experiment

Harbours can be considered as model environments for developing and validating field monitoring procedures and to investigate mechanistic relationships between different biological responses. In this study several biomarkers were investigated in marine mussels caged for 4 weeks (June-July 2001) into an industrialized harbour of NW Italy. Organisms were collected at different time-intervals to better characterize the sensitivity, temporal variations and interactions of analysed responses. Besides single antioxidants the total oxyradical scavenging capacity (TOSC) assay was used to analyse the capability of the whole antioxidant system to neutralize specific forms of radicals: these data were further integrated by measurement of DNA integrity, oxidized bases and the impairment of lysosomal membrane stability in haemocytes. Results showed a biphasic trend for single antioxidants and TOSC, with an increase during the first 2 weeks of exposure to the polluted site followed by a progressive decrease up to a severe depletion in the final part of the experiment.     

Prioritising range-wide scientific monitoring of the Cape fur seal in southern Africa

The range of the Cape fur seal Arctocephalus pusillus pusillus population largely coincides with the region of the cold, nutrient-rich Benguela Current Large Marine Ecosystem (BCLME) adjoining the west coast of South Africa, Namibia and Angola. Range-wide scientific monitoring of the seal population was initiated in the 1970s to inform on population management questions related to commercial seal harvesting and seal–fishery interactions. Since the 1970s, seal-related management goals have changed, especially in South Africa where seal harvesting ceased in 1990 and government has conformed to scientific advice against the culling of seals for the intended benefit of fisheries. However, renewed impetus has been provided to seal research and monitoring through the expansion of the ‘ecosystem-based management’ concept in the region, as well as improved international cooperation in the management of marine resources. Together with wide-scale ecosystem changes in the marine environment, and forecast effects of global climate changes, this has justified the continuation and improvement of range-wide scientific monitoring of Cape fur seals. We prioritised seal monitoring based on cost, effort, and relevance to monitoring objectives that have been identified for the region, with consideration given to the conservation status of top predators, interspecific and predator-fishery interactions and the potential use of Cape fur seals as indicators of ecosystem health. An integrated approach incorporating a suite of life-history attributes of seals is recommended, useful monitoring tools are discussed and the need for coordinated monitoring effort and standardisation of sampling techniques is emphasised.     

Time-course evaluation of ROS-mediated toxicity in mussels, Mytilus galloprovincialis, during a field translocation experiment

Harbours can be considered as model environments for developing and validating field monitoring procedures and to investigate mechanistic relationships between different biological responses. In this study several biomarkers were investigated in marine mussels caged for 4 weeks (June–July 2001) into an industrialized harbour of NW Italy. Organisms were collected at different time-intervals to better characterize the sensitivity, temporal variations and interactions of analysed responses. Besides single antioxidants the total oxyradical scavenging capacity (TOSC) assay was used to analyse the capability of the whole antioxidant system to neutralize specific forms of radicals: these data were further integrated by measurement of DNA integrity, oxidized bases and the impairment of lysosomal membrane stability in haemocytes. Results showed a biphasic trend for single antioxidants and TOSC, with an increase during the first 2 weeks of exposure to the polluted site followed by a progressive decrease up to a severe depletion in the final part of the experiment.     

Polybrominated diphenyl ethers (PBDEs) in seal populations from eastern and western Canada: an assessment of the processes and factors controlling PBDE distribution in seals

Polybrominated diphenyl ether (PBDE) concentrations were measured in the blubber of five mother-pup pairs of grey seals (Halichoerus grypus) from Sable Island, Nova Scotia (NS) sampled in 1995 and in 20 harbour seals (Phoca vitulina) from British Columbia (BC) sampled in 1991-1992. Concentrations in maternal grey seals from Sable Island averaged 112+/-55.2 ng/g lipid (mean+/-s.d.) and were over twice the concentrations measured in their pups; higher brominated PBDEs showed a distinct decline in PBDEs transfer efficiency in mother-pup pairs as a function of increasing K(o/w). Hepta-BDEs and higher molecular weight (MW) congeners appear not to be transferred efficiently from the grey seals mother to pup during lactation on the basis of lipid/water partitioning (as indicated by ln K(o/w)) and this may be a consequence of molecular size (MW>600 Da) which may limit diffusion and partitioning. PBDE concentrations in blubber from harbour seals from the Strait of Georgia averaged 319+/-132 ng/g lipid (mean+/-s.d., n=13), while those from the more remote and less contaminated Quatsino Sd. averaged 27.8+/-11.8 ng/g (mean+/-s.d., n=7). Tri- to hexa-BDEs were appreciably enriched in Strait of Georgia harbour seals relative to those from Quatsino Sd, suggesting that the former were closer to PBDE sources. The main congeners identified in all samples were BDEs 47, 99, 100, 153 and 154. Data were compared to those in ringed seals sampled from Holman, North West Territories (NWT), in 1996. The Holman samples had a higher proportion of lower bromination congeners, and a lower proportion of higher bromination congeners, than did the Sable Island and BC seal samples, consistent with selection in favour of more volatile compounds during atmospheric transport to the Arctic.     

Polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs) in livers of harbor seals (Phoca vitulina) from San Francisco Bay,California and Gulf of Maine

Bioaccumulation of endocrine disruptors in marine mammals positioned at the top of the food chain is of toxicological concern. Livers from four pups and ten adult harbor seals (Phoca vitulina) stranded in San Francisco Bay (SFB) and the Gulf of Maine (GOM) were analyzed for polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs). We used GC–ECD and GC–NCI/MS to investigate the presence of 28 PCBs and 8 OH-PCB metabolites, respectively. Σ₂₈PCB concentrations (di- to octa-CBs) ranged from 1.81 to 35.9 μg/g lipid with a median of 6.53 for the seal pups and 2.31 to 249 μg/g lipid with a median of 28.9 for the adult seals. Σ₈OH-PCB concentrations (penta- to hepta-OH-PCBs) ranged from 0.02 to 0.69 μg/g lipid with a median of 0.04 for the adult seals, i.e., at much lower concentrations than those for PCBs. Ratios of OH-PCBs to PCBs (0.24% on average) were comparable to those in beluga whale, but were lower than ratios in human livers. The OH-PCB profiles were slightly different between SFB and GOM seal livers, although similar PCB congener patterns were observed. Generally, 4-OH-CB107 was found predominantly in seal livers and was the only OH-PCB detectable in most of seal pup livers. This study provides information on OH-PCBs in seals, adding to the scarce exposure data for these chemicals.     

Net dispersal of harbour seals within the Wadden Sea before and after the 1988 epizootic

Harbour seals in the Wadden Sea (The Netherlands, Germany and Denmark) have been monitored by aerial surveys since the 1980s. Annual maximum figures reported in the various regions (38 separate tidal basins) and the number of pups counted were used to estimate vital population parameters and to quantify the net migration of harbour seals within the Wadden Sea before (1980–1987) and after an epizootic (1990–1994). The total pre-whelping population increased at a mean annual rate of 9 and 14%, respectively, and varied considerably among the various regions of the Wadden Sea. The overall mean annual survival was found to increase from 0.88 during the pre-epizootic period to 0.93 during the post-epizootic period. The distribution of pups and of older seals over the 38 separate sub-areas was highly uneven. Based on between-year population changes and the number of pups reported, net dispersal fluxes among the four regions of the Wadden Sea were estimated for the two time intervals. During the pre-epizootic period, only Schleswig-Holstein, Germany, produced a surplus of animals which counter-balanced the low recruitment of the other regions. During the post-epizootic period, the net dispersal fluxes were at a much lower level. Nevertheless, in The Netherlands, a continuous influx of seals was required because the recruitment was insufficient to explain the observed numerical increase. At the level of the 38 separate tidal basins, the actual pattern of dispersal showed that the majority of sub-areas were not self-supporting with respect to the local pup production and thus dependent on the influx of animals. More than 65% of all immigrants originated from only 7 sub-areas, which are considered `key areas' of vital importance for the Wadden Sea harbour seal population.     

Early post-release survival of stranded Cape fur seal pups at Black Rocks,Algoa Bay,South Africa

The small and isolated Cape fur seal Arctocephalus pusillus pusillus rookery at Black Rocks, Algoa Bay, South Africa, is an important component of the marine biota of the Addo Elephant National Park. Although little is known of the demographics of this rookery, it is believed to be declining in abundance. The pupping season for this population coincides with summer storms that often wash pups from Blacks Rocks. In the past, many that washed up on the mainland were rescued and returned to their colony. However, the necessity and value of this exercise has been questioned. The displacement of 200 pups from their rookery following a severe storm in December 2008 presented an opportunity to follow the early survival of rescued pups that were returned to Black Rocks. Tag resightings of those that were adequately tagged (n = 52) were obtained during five visits to Black Rocks over a period of 3½ months. The results indicated that about one-quarter of tagged pups survived. This is the first study to demonstrate substantial short-term survival of otariid pups following rehabilitation and return to the wild.     

Measuring lysosomal stability as an effective tool for marine coastal environmental monitoring

The use of lysosomal stability in the mussel, Mytilus galloprovincialis, as a potential biomarker of environmental contamination has been evaluated along the Portuguese coast. To this end, the neutral red retention (NRR) time was measured in mussel haemocytes gathered from nine different locations reflecting different degrees of anthropogenic contamination. Mussels collected in the vicinity of industrial and urban areas showed the lowest lysosomal stability. Additionally, no significant seasonal variability (winter-spring/summer) for NRR time was observed. In order to further support the usefulness of this method as an integrated tool for monitoring marine coastal environments, we compared the levels of xenobiotics in mussel tissues with the obtained NRR values. The results highlighted a consistent pattern, with the lowest lysosomal stability intimately correlated with the higher contaminant concentrations. In summary, this integrated approach further demonstrated that the NRR assay can provide useful and objective indications of the real health status of organisms subjected to different stress agents, being a valid option for environmental monitoring.     

Cytochrome P450 in seals: monooxygenase activities, immunochemical cross-reactions and response to phenobarbital treatment

Cytochrome P450 monooxygenase activities, reflecting the expression of various subfamilies of P450, were measured in liver samples of harp and hooded seal. Differences in some of the investigated parameters were observed between the two species, between sexes, and between pups and adults. Treatment of single female pups from each species with phenobarbital (i.v. 45 mg/kg), resulted in increased levels of EROD and estradiol 2-hydroxylase activities in both species, whereas MCOD, ECOD and PROD activities were induced only in the harp seal sample. Antibodies against a dog P450 2B form (anti-dog PBD-2 IgG) gave a single band around 52kD in both species, strongest in male pups. This band seemed elevated in the PB-treated harp seal pup. Based on the single treated pup of each species, the results suggest that seals respond to PB-type treatment with a weaker response, and with different enzyme patterns, that most terrestrial mammals. Antibodies against cod P450 IAI cross-reacted with two bands in liver samples from adult seals of both species (about 54 and 52kD), but this was strongest in the hooded seal. The intensity of the bands reflected the EROD activities in the samples, suggesting the application of immunodetection in screening marine mammals for effects of environmental contamination.     

Environmental management of ports and harbours — implementation of policy through scientific monitoring

Recent legislation aimed specifically at protecting the marine environment has had a direct impact on the environmental management of port and harbour operations. Effective implementation of suitable policies requires options and responses based on scientific data derived from appropriate technology and methodology. UK ports, operating under an increasingly European regime in terms of legislation, have responded to the environmental challenge through a series of organisational and research initiatives. Fundamental to the notion of sustainable port development is the ability to characterise environmental performance through appropriate monitoring and mapping protocols. Monitoring, the systematic and repeated measurement of the direct or indirect effect of our activity or contaminant on the environment, can play a crucial role in verifying implementation of port policy and evaluating the effectiveness of the management option. Aspects such as adherence to specific regulatory standards, investigation of pollution trends, provision of research data, measurements for the development of standards and early warning of critical changes in certain parameters are all facilitated by an appropriate monitoring protocol. The long established techniques of monitoring physical and chemical parameters to assess environmental quality are increasingly being supplemented by ecological monitoring programmes. By mapping marine habitats with their associated communities and species, the vulnerability and sensitivity of the habitats to port operations can be found and biological indicators such as the occurrence of particular species, species richness and diversity indices can be identified to assist decision making on environmental protection issues.     

Distribution of PACs in surficial sediments and bioavailability to mussels, Mytilus edulis of Halifax Harbour

Surficial sediments and blue mussels were collected around the perimeter of Halifax Harbour. Samples were analysed for the levels and fingerprint of polycyclic aromatic compounds (PACs). The objective was to explore the relationship between contaminant profiles in sediments and in mussels and to explore the possibility of deducing their sources, pattern of deposition and circulation in the harbour. Combustion derived compounds predominated in both sets of samples, with more variability observed in the level of petroleum derived hydrocarbons in mussel samples. Biota-sediment accumulation factors (BSAF, dry/dry wt.) varied throughout the harbour, ranging from means of 0.006 to 1.26, where generally fluoranthene displayed the highest BSAF. Sediments and mussels give complementary views of the geographical distribution of contaminants, they reflect the state of benthic and pelagic habitats. Results observed for Halifax Harbour are discussed from the perspective of published data.     

海域使用活动对海湾生态环境的压力评估——以莱州湾为例

以莱州湾为例,基于GIS和地理空间模拟框架,结合海洋生态红线区分布,建立了海域使用活动对海洋生态环境的潜在压力评估模型,空间量化评估多种海域使用活动对海洋生态环境的潜在影响。结果显示,多种海域使用活动的潜在压力总体呈近岸高于远岸、湾顶>东部>西部的分布特征;压力高值区集中于距岸10 km以内海域和5 m水深以内海域;海洋特别保护区、海洋自然保护区及重要河口生态系统等类型的海洋生态红线区受到开放式养殖、围海养殖、盐业用海活动的压力较大,需要对其进行重点监控。研究揭示了莱州湾海域使用活动对海洋生态环境潜在压力的空间分布格局,为海洋生态红线落地实施和海域使用管理提供决策依据。     

The influence of underwater data transmission sounds on the displacement behaviour of captive harbour seals (Phoca vitulina)

To prevent grounding of ships and collisions between ships in shallow coastal waters, an underwater data collection and communication network (ACME) using underwater sounds to encode and transmit data is currently under development. Marine mammals might be affected by ACME sounds since they may use sound of a similar frequency (around 12 kHz) for communication, orientation, and prey location. If marine mammals tend to avoid the vicinity of the acoustic transmitters, they may be kept away from ecologically important areas by ACME sounds. One marine mammal species that may be affected in the North Sea is the harbour seal (Phoca vitulina). No information is available on the effects of ACME-like sounds on harbour seals, so this study was carried out as part of an environmental impact assessment program. Nine captive harbour seals were subjected to four sound types, three of which may be used in the underwater acoustic data communication network. The effect of each sound was judged by comparing the animals' location in a pool during test periods to that during baseline periods, during which no sound was produced. Each of the four sounds could be made into a deterrent by increasing its amplitude. The seals reacted by swimming away from the sound source. The sound pressure level (SPL) at the acoustic discomfort threshold was established for each of the four sounds. The acoustic discomfort threshold is defined as the boundary between the areas that the animals generally occupied during the transmission of the sounds and the areas that they generally did not enter during transmission. The SPLs at the acoustic discomfort thresholds were similar for each of the sounds (107 dB re 1 microPa). Based on this discomfort threshold SPL, discomfort zones at sea for several source levels (130-180 dB re 1 microPa) of the sounds were calculated, using a guideline sound propagation model for shallow water. The discomfort zone is defined as the area around a sound source that harbour seals are expected to avoid. The definition of the discomfort zone is based on behavioural discomfort, and does not necessarily coincide with the physical discomfort zone. Based on these results, source levels can be selected that have an acceptable effect on harbour seals in particular areas. The discomfort zone of a communication sound depends on the sound, the source level, and the propagation characteristics of the area in which the sound system is operational. The source level of the communication system should be adapted to each area (taking into account the width of a sea arm, the local sound propagation, and the importance of an area to the affected species). The discomfort zone should not coincide with ecologically important areas (for instance resting, breeding, suckling, and feeding areas), or routes between these areas.     

The conservation of seals in Irish waters: How research informs policy

Ireland's waters represent a valuable resource encompassing productive fishing grounds and important oil and gas reserves. As a species rich marine environment, Ireland's waters are also an important habitat for many species of marine mammal. Specifically, grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina) are widespread in Irish coastal waters and at least 24 species of cetacean have been reported at sea. The coastal zone represents critical habitat for many of these species, in particular seals that use both terrestrial and aquatic coastal habitat and are vulnerable to habitat degradation. Increasing exploitation of marine resources has increased their exposure to a range of anthropogenic effects including pollution and habitat loss. As top predators seals interact with commercial fisheries both directly and indirectly for resources and conflicts arise. The relatively recent move towards ‘greener’ resource exploitation such as marine renewable energy does not come without negative consequences for marine mammals including seals, which are afforded protection under national and international conservation legislation, highlighting the difficulties faced by resource managers. The sustainable exploitation of resources whilst conserving biodiversity is a challenging task and effective management implementation depends on appropriate policy informed by reliable scientific data. This paper outlines the conservation needs of seals in Irish waters, reviews our current knowledge of these species in Irish water, provides a critical analysis of the existing legislative framework and describes how research outputs can inform present and future policy decisions.     

Marine mammals from northeast Atlantic: relationship between their trophic status as determined by delta13C and delta15N measurements and their trace metal concentrations

The relationship between trophic position through delta13C and delta15N and trace metal concentrations (Zn, Cd, Cu and Hg) was investigated in the tissues of six marine mammal species from the Northeast Atlantic: striped dolphin Stenella coeruleoalba, common dolphin, Delphinus delphis, Atlantic white-sided dolphin Lagenorhynchus acutus, harbour porpoise Phocoena phocoena, white beaked-dolphin Lagenorhynchus albirostris, grey seal Halichoerus grypus stranded on French Channel and Irish coasts. White-beaked dolphins, harbour porpoises, white-sided dolphins, common and striped dolphins display the same relative and decreasing trophic position, as measured by delta15N values, along both the Irish and French channel coasts, reflecting conservative trophic habits between these two places. Hepatic and renal Cd concentrations were significantly correlated to muscle delta13C and delta15N values while Hg, Zn and Cu did not. These results suggest that Cd accumulation is partly linked to the diet while other factors such as age or body condition might explain Hg, Zn or Cu variability in marine mammals. Combined stable isotope and trace metal analyses appear to be useful tools for the study of marine mammal ecology.     

Effects of nanoparticles in Mytilus edulis gills and hepatopancreas - a new threat to marine life?

Every day new extraordinary properties of nanoparticles (a billionth of a meter) are discovered and worldwide millions are invested into nanotechnology and nanomaterials. Risks to marine organisms are still not fully understood and biomarkers to detect health effects are not implemented, yet. We used the filter feeding blue mussel as a model to analyse uptake and effects of nanoparticles from glass wool, a new absorbent material suggested for use in floating oil spill barriers. In both, gills and hepatopancreas we analysed uptake of nanomaterials by transmission electronmicroscopy (TEM) in unstained ultrathin sections over a period of up to 16 days. Lysosomal stability and lipofuscin content as general indicators of cellular pathology and oxidative stress were also measured. As portals of uptake, diffusion and endocytosis were identified resulting in nanoparticle accumulation in endocytotic vesicles, lysosomes, mitochondria and nuclei. Dramatic decrease of lysosomal membrane stability occurred after 12h of exposure. Lysosomal damage was followed by excessive lipofuscin accumulation indicative of severe oxidative stress. Increased phagocytosis by granulocytes, autophagy and finally apoptosis of epithelial cells of gills and primary and secondary digestive tubules epithelial cells indicated progressive cell death. These pathological responses are regarded as general indices of toxic cell injury and oxidative stress. By the combinational use of biomakers with the ultrastructural localisation of nanoparticle deposition, final evidence of cause-effect relationships is delivered.