Abstract
BackgroundThe harbour porpoise is exposed to increasing pressure caused by anthropogenic activities in its marine environment. Numerous offshore wind farms are planned or under construction in the North and Baltic Seas, which will increase underwater noise during both construction and operation. A better understanding of how anthropogenic impacts affect the behaviour, health, endocrinology, immunology and physiology of the animals is thus needed. The present study compares levels of stress hormones and mRNA expression of cytokines and acute-phase proteins in blood samples of harbour porpoises exposed to different levels of stress during handling, in rehabilitation or permanent human care.Free-ranging harbour porpoises, incidentally caught in pound nets in Denmark, were compared to harbour porpoises in rehabilitation at SOS Dolfijn in Harderwijk, the Netherlands, and individuals permanently kept in human care in the Dolfinarium Harderwijk and Fjord & Belt Kerteminde, Denmark. Blood samples were investigated for catecholamines, adrenaline, noradrenaline and dopamine, as well as for adrenocorticotropic hormone (ACTH), cortisol, metanephrine and normetanephrine. mRNA expression levels of relevant cell mediators (cytokines IL-10 and TNFα, acute-phase proteins haptoglobin and C-reactive protein and the heat shock protein HSP70) were measured using real-time PCR.ResultsBiomarker expression levels varied between free-ranging animals and porpoises in human care. Hormone and cytokine ranges showed correlations to each other and to the health status of investigated harbour porpoises. Hormone concentrations were higher in free-ranging harbour porpoises than in animals in human care. Adrenaline can be used as a parameter for the initial reaction to acute stress situations; noradrenaline, dopamine, ACTH and cortisol are more likely indicators for the following minutes of acute stress. There is evidence for different correlations between production of normetanephrine, metanephrine, cortisol and the expression of IL-10, HSP70 and haptoglobin.ConclusionsThe expression patterns of the selected molecular biomarkers of the immune system are promising to reflect the health and immune status of the harbour porpoise under different levels of stress.
Highlights
The harbour porpoise is exposed to increasing pressure caused by anthropogenic activities in its marine environment
The harbour porpoise (Phocoena phocoena) is the only reproducing cetacean species in the Baltic Sea and eastern North Sea [1,2,3]. These waters are highly exposed to anthropogenic impacts as an increasing number of human activities are conducted in these areas, including shipping, construction of offshore wind farms, fisheries, seismic and military operations
Blood chemistry revealed that only two investigated individuals showed increased liver enzymes alkaline phosphatase (ALP) from 424 to 471 U/L and glutamic pyruvic transaminase (GPT) from 109 to 143 U/L compared to reference values of harbour porpoises in human care and from the wild [42]
Summary
The harbour porpoise is exposed to increasing pressure caused by anthropogenic activities in its marine environment. The harbour porpoise (Phocoena phocoena) is the only reproducing cetacean species in the Baltic Sea and eastern North Sea [1,2,3] These waters are highly exposed to anthropogenic impacts as an increasing number of human activities are conducted in these areas, including shipping, construction of offshore wind farms, fisheries, seismic and military operations. These activities cause underwater noise which results in disturbance of and stress in the marine fauna [3,4,5,6,7,8,9]. It has a broad spectrum of metabolic and immunemediating effects mainly associated with stress reactions [11,20,21]
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