A variety of mammals suppress reproduction when they experience poor physical condition or environmental harshness. In many marine mammal species, reproductive impairment has been correlated to ...polychlorinated biphenyls (PCBs), the most frequently measured chemical pollutants, while the relative importance of other factors remains understudied. We investigate whether reproductively active females abandon investment in their foetus when conditions are poor, exemplified using an extensively studied cetacean species; the harbour porpoise (Phocoena phocoena). Data on disease, fat and muscle mass and diet obtained from necropsies in The Netherlands were used as proxies of health and nutritional status and related to pregnancy and foetal growth. This was combined with published life history parameters for 16 other areas to correlate to parameters reflecting environmental condition: mean energy density of prey constituting diets (MEDD), cumulative human impact and PCB contamination. Maternal nutritional status had significant effects on foetal size and females in poor health had lower probabilities of being pregnant and generally did not sustain pregnancy throughout gestation. Pregnancy rates across the Northern Hemisphere were best explained by MEDD. We demonstrate the importance of having undisturbed access to prey with high energy densities in determining reproductive success and ultimately population size for small cetaceans.
Organochlorine (OC) pesticides and the more persistent polychlorinated biphenyls (PCBs) have well-established dose-dependent toxicities to birds, fish and mammals in experimental studies, but the ...actual impact of OC pollutants on European marine top predators remains unknown. Here we show that several cetacean species have very high mean blubber PCB concentrations likely to cause population declines and suppress population recovery. In a large pan-European meta-analysis of stranded (n = 929) or biopsied (n = 152) cetaceans, three out of four species:- striped dolphins (SDs), bottlenose dolphins (BNDs) and killer whales (KWs) had mean PCB levels that markedly exceeded all known marine mammal PCB toxicity thresholds. Some locations (e.g. western Mediterranean Sea, south-west Iberian Peninsula) are global PCB "hotspots" for marine mammals. Blubber PCB concentrations initially declined following a mid-1980s EU ban, but have since stabilised in UK harbour porpoises and SDs in the western Mediterranean Sea. Some small or declining populations of BNDs and KWs in the NE Atlantic were associated with low recruitment, consistent with PCB-induced reproductive toxicity. Despite regulations and mitigation measures to reduce PCB pollution, their biomagnification in marine food webs continues to cause severe impacts among cetacean top predators in European seas.
Neisseria animaloris is considered to be a commensal of the canine and feline oral cavities. It is able to cause systemic infections in animals as well as humans, usually after a biting trauma has ...occurred. We recovered N. animaloris from chronically inflamed bite wounds on pectoral fins and tailstocks, from lungs and other internal organs of eight harbour porpoises. Gross and histopathological evidence suggest that fatal disseminated N. animaloris infections had occurred due to traumatic injury from grey seals. We therefore conclude that these porpoises survived a grey seal predatory attack, with the bite lesions representing the subsequent portal of entry for bacteria to infect the animals causing abscesses in multiple tissues, and eventually death. We demonstrate that forensic microbiology provides a useful tool for linking a perpetrator to its victim. Moreover, N. animaloris should be added to the list of potential zoonotic bacteria following interactions with seals, as the finding of systemic transfer to the lungs and other tissues of the harbour porpoises may suggest a potential to do likewise in humans.
The North Sea is an ecologically rich habitat for marine wildlife which has also been impacted by industrial developments and anthropogenic emissions of contaminants such as mercury. Marine mammals ...are particularly susceptible to mercury exposure, due to their trophic position, long lifespan, and dependence on (increasingly contaminated) aquatic prey species. To mitigate impact, marine mammals can detoxify methylmercury by binding it to selenium-containing biomolecules, creating insoluble mercury selenide granules. Here, liver, kidney, muscle, and brain samples from an adult male bottlenose dolphin (Tursiops truncatus) with known elevated mercury concentrations were analysed through scanning electron microscopy (SEM). Tiemannite (HgSe) deposits were identified in all organs, ranging from 400 nm to 5 μm in diameter, with particle size being organ-dependent. Although reported in other studies, this is the first time that the three-dimensional nature of tiemannite is captured in marine mammal tissue.
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•First high-resolution SEM images of HgSe in marine mammal organs.•Indicates complex pathways of HgSe formation and transport between organs.•Organ-specific size of primary nanoparticles recorded.
Climate change is predicted to have profound consequences for marine ecosystems. Due to the growing political and social drive to address its impacts, monitoring and mitigating climate change is a ...priority in marine policy in the UK. Cetaceans have been proposed as informative sentinel species for monitoring ocean health. Here, strandings data from four UK cetacean species were assessed for their use as a tool to aid policy makers monitoring climate change in marine environments. Data on stranded cetaceans were collected from 1990 to 2018 and differences in the proportions of stranded cold water adapted and warm water adapted species assessed using Generalised Linear Models (GLM), with 6-year periods and four regions of the UK included as explanatory variables. This modelling approach showed an increase in the proportion of stranded warm water adapted species over time across the UK and that differences in proportion of strandings between cold water and warm water adapted species can be detected between regions and 6-year periods, chosen as metrics to coordinate with reporting cycles for policy assessment needs. As such, these results show the potential for utilising strandings data to identify changing oceanic trends at the appropriate spatial and temporal scales for policy reporting in the UK. However, development of these analyses with a more detailed examination of these data at a finer resolution, incorporating other data sources, such as distribution trends and dietary stable isotope data, may be required before it is applicable as an indicator for trends in changes in climate.
Polychlorinated biphenyls (PCBs) are toxic, persistent, and lipophilic chemical compounds that accumulate to high levels in harbor porpoises (Phocoena phocoena) and other cetaceans. It is important ...to monitor PCBs in wildlife, particularly in highly exposed populations to understand if concentrations are declining and how levels relate to toxicological thresholds and indices of health like infectious disease mortality. Here we show, using generalized additive models and tissue samples of 814 U.K.-stranded harbor porpoises collected between 1990 and 2017, that mean blubber PCB concentrations have fallen below the proposed thresholds for toxic effects. However, we found they are still associated with increased rates of infectious disease mortality such that an increase in PCB blubber concentrations of 1 mg kg–1 lipid corresponds with a 5% increase in risk of infectious disease mortality. Moreover, rates of decline and levels varied geographically, and the overall rate of decline is slow in comparison to other pollutants. We believe this is evidence of long-term preservation in the population and continued environmental contamination from diffuse sources. Our findings have serious implications for the management of PCB contamination in the U.K. and reinforce the need to prevent PCBs entering the marine environment to ensure that levels continue to decline.
Effective management of natural resources involves a multidisciplinary perspective to address complex issues in data poor-environments. With mobile species that do not conform to human-defined ...borders a cross-boundary approach is essential. There is a continuing concern of ecological sustainability of marine environments, which demands monitoring of ecosystem indicators. Such indicators are increasingly derived from monitoring sentinel species. Harbour porpoises (Phocoena phocoena) are included as indicator species in several national and international agreements. Increasing exposure to anthropogenic stressors may impact harbour porpoise populations. To investigate these risks, a better understanding of threats and their effect is required. This study aimed to identify current knowledge gaps, to predict future pressures or threats, and to define useful conservation indicators to facilitate future research on harbour porpoises in the North Sea, through expert elicitation gained in a two-round Delphi approach. The three most important knowledge gaps addressed were bycatch, population dynamics, and the cumulative effects of multiple stressors. Bycatch was predicted as the highest concern for porpoises in the next 20 years, followed by chemical and noise pollution, respectively. A list of essential indicators aiming to increase understanding of harbour porpoises’ health status was established and studying causes of death, distribution, abundance, habitat use and diet composition were scored as most relevant. These results should guide research focus and management objectives of harbour porpoise populations and the study design could be translated to serve managers in other geographical areas aiming to identify knowledge gaps and defining research priorities for other wildlife species.
•Cross-boundary approaches are essential when monitoring ecosystem indicators.•Increasing exposure to anthropogenic stressors may impact harbour porpoise populations.•Knowledge gaps identified are bycatch, population dynamics and cumulative effects.•Research focus should include studying causes of death, abundance and distribution.•The Delphi approach can help managers to define research focus and priorities.
With global increases in anthropogenic pressures on wildlife populations comes a responsibility to manage them effectively. The assessment of marine ecosystem health is challenging and often relies ...on monitoring indicator species, such as cetaceans. Most cetaceans are however highly mobile and spend the majority of their time hidden from direct view, resulting in uncertainty on even the most basic population metrics. Here, we discuss the value of long-term and internationally combined stranding records as a valuable source of information on the demographic and mortality trends of the harbour porpoise (Phocoena phocoena) in the North Sea. We analysed stranding records (n = 16,181) from 1990 to 2017 and demonstrate a strong heterogeneous seasonal pattern of strandings throughout the North Sea, indicative of season-specific distribution or habitat use, and season-specific mortality. The annual incidence of strandings has increased since 1990, with a notable steeper rise particularly in the southern North Sea since 2005. A high density of neonatal strandings occurred specifically in the eastern North Sea, indicative of areas important for calving, and large numbers of juvenile males stranded in the southern parts, indicative of a population sink or reflecting higher male dispersion. These findings highlight the power of stranding records to detect potentially vulnerable population groups in time and space. This knowledge is vital for managers and can guide, for example, conservation measures such as the establishment of time-area-specific limits to potentially harmful human activities, aiming to reduce the number and intensity of human-wildlife conflicts.
•International data synthesis to understand wildlife mortality and demographic trends•We demonstrate the value of long-term surveillance exemplified by stranding records.•Our analyses indicate potential vulnerable population groups in time and space.•Analytical methods allow establishment of robust baseline of spatiotemporal variation.•Results guide conservation measures aiming to reduce human-wildlife conflicts at sea.
In August 2021, a large-scale mortality event affected harbor porpoises (Phocoena phocoena) in the Netherlands. Pathology and ancillary testing of 22 animals indicated that the most likely cause of ...death was Erysipelothrix rhusiopathiae infection. This zoonotic agent poses a health hazard for cetaceans and possibly for persons handling cetacean carcasses.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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