Health biomarkers in marine mammals

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Biomonitoring of marine pollution

Biomonitoring uses organisms and their biological responses to detect pollutant exposure and harmful biological effects, including effects of substances or mixtures that may escape chemical monitoring.

The Coastal Wiki articles on this subject provide complementary perspectives:


Effects of diverse toxic substances on different marine animals are described in articles in the category ecotoxicology.



Introduction

Figure 1. The health of the Harbour Seal as top predator is an important biological parameter of the Trilateral Monitoring and Assessment Program (TMAP). This program was founded by The Netherlands, Denmark and Germany, for the protection and conservation of the Wadden Sea. It includes management, monitoring and research, as well as political matters.
Figure 2. Overview of immunological investigations using blood samples of marine mammals.

Marine mammals can serve as sentinel species for changes in marine ecosystems. Their long lifespan, often high trophic position and capacity to accumulate persistent contaminants make them particularly useful for detecting some forms of environmental stress. However, marine-mammal health is influenced by many interacting environmental and biological factors, and changes in health cannot generally be attributed to a particular ecosystem pressure without additional evidence.

The present article describes physiological and immune biomarkers used to investigate the health status of marine mammals, with emphasis on studies of harbor seals. Pollutants can alter immune function, resulting in immune suppression or inappropriate immune activation and potentially increasing susceptibility to disease. Measurements such as lymphocyte proliferation, cytokine expression and acute-phase proteins can therefore provide information on immune and general health status. Their interpretation requires consideration of other factors that affect immune function, including age, infection, nutritional condition and stress.[1]

Health and immune biomarkers

Figure 3. Directly after arrival at the Seal Station, lymphocytes of newborn harbor seals were particularly susceptible to the toxic effects of several tested metals, including beryllium, lead and cadmium, which inhibited lymphocyte proliferation (value <0.1). This susceptibility decreased during rehabilitation.

Blood samples allow several aspects of immune and physiological condition to be measured in living marine mammals (Fig. 2). Commonly investigated health parameters include lymphocyte proliferation, expression of cytokines and other immune-related genes, concentrations of acute-phase proteins and hematological parameters. These biomarkers can be quantified using techniques such as reverse transcriptase polymerase chain reaction (RT-PCR) for gene expression and mass spectrometry for selected proteins. Results can be compared with contaminant concentrations to investigate possible associations between exposure and altered physiological or immune function.

Lymphocytes proliferate when activated as part of an immune response. Their capacity to proliferate after standardized stimulation therefore provides a measure of cellular immune competence. Reduced proliferation can indicate immunosuppression, whereas unusually strong responses to particular substances may indicate sensitization or hypersensitivity (Fig. 3).

Figure 4. Cytokine index of IL-2 mRNA from the blood samples of two harbor porpoises living in captivity (Pp1, Pp2) and four accidentally caught animals (Pp3-Pp6) From: Fonfara et al. (2007[2])

Protein blood concentrations of APPs such as haptoglobin (Hp), C-reactive protein (CRP) or transferrin are influenced by inflammation and disease and might therefore be useful parameters to monitor health. Long-term studies are needed to establish baseline or reference ranges, because APP concentrations are influenced by many factors other than pollutant exposure.[3]

Persistent organic pollutants, particularly PCBs and organochlorine pesticides, are among the contaminants most extensively studied in relation to marine-mammal health. Associations have been reported with altered immune responses, reproductive impairment and pathological changes. Because these compounds are persistent and lipophilic, they can reach high concentrations in long-lived marine mammals through food-web accumulation.[4][5]

Metal pollution – effects on the immune system

Exposure to metal pollution occurring in many industrialized coastal zone has been associated with altered immune function in marine mammals. The effect depends on the metal, its chemical form, concentration and bioavailability, and may involve either suppression or stimulation of immune responses.[6]

Experimental studies with pinnipeds have shown that exposure to some metals can alter lymphocyte responses, including suppression or hypersensitivity. The response depends on the metal, its chemical form and concentration, and the age and physiological condition of the animal.[7][8]

Pups can be exposed to metals through transplacental transfer, maternal milk and, at a later stage, contaminated prey. Kakuschke et al. (2008[9]) reported that lymphocytes of newborn seal pups were particularly susceptible to the toxic effects of metals, with susceptibility subsequently decreasing with age (Fig. 3).

Factors affecting biomarker interpretation

Several factors unrelated to pollution can alter marine-mammal health biomarkers. The following studies illustrate the effects of stress, infection and development on immune parameters.

Cytokine mRNA expression from two harbor porpoises living in captivity and four accidentally caught wild living porpoises were compared. A stress-induced modulation of the cytokine expression was suspected in the accidentally caught wild animals (Fig. 4)[2][10]. Furthermore, cytokine and acute phase proteins transcription varied in harbor seal pups during rehabilitation in the seal station Friedrichskoog, Germany, suggesting that these parameters might be useful to assess the health status, maturation of the immune system, and the ability to handle stress in these animals (Fig. 5)[11].

Health biomarkers in marine mammals are generally not specific to a particular pollutant. Immune and physiological responses can also be influenced by infection, age, sex, nutritional condition, reproductive status, capture and handling stress, and other environmental pressures. Biomarker measurements should therefore be interpreted together with contaminant concentrations, clinical observations and other information on the animals and their environment.[1]

Long-term monitoring is particularly valuable because it can establish normal ranges, reveal temporal changes in contaminant exposure and health parameters, and help distinguish persistent trends from natural variation.[5]


Related articles

Biomonitoring of pollution impacts in the marine environment
Biomarkers for assessing marine pollution effects
Endocrine disruption by marine pollutants
Coastal pollution and impacts
Biomarker
Bioindicator
Endocrine disrupting compounds
Endocrine system
Elemental mass spectrometry - a tool for monitoring trace element contaminants in the marine environment
Passive acoustic monitoring (PAM) of marine mammals
Environmental risk assessment of marine activities
Portal:Ecotox
Threats to Coral Reefs: the Effects of Chemical Pollution



References

  1. ↑ 1.0 1.1 Desforges, J.P., Sonne, C., Levin, M., Siebert, U., De Guise, S. and Dietz, R. 2016. Immunotoxic effects of environmental pollutants in marine mammals. Environ Int. 86: 126-39
  2. ↑ 2.0 2.1 Fonfara S., Siebert, U. Prange, A. and Colijn, F. 2007. The impact of stress on cytokine and Haptoglobin mRNA expression in blood samples from harbour porpoises (Phoconea phocoena). Journal of the Marine Biological Association of the United Kingdom 87, 305-311
  3. ↑ Kakuschke, A., Erbsloeh, H.-B., Griesel, S. and Prange, A. 2010. Acute phase protein haptoglobin in blood plasma samples of harbour seals of the Wadden Sea and of the isle Helgoland. Comparative Biochemistry and Physiology, Part B 155: 67–71
  4. ↑ Jepson, P.D., Bennett, P.M., Allchin, C.R., Law, R.J., Kuiken,T., Baker, J.R., Rogan, E. and Kirkwood, J.K. 1999. Investigating potential associations between chronic exposure to polychlorinated biphenyls and infectious disease mortality in harbor porpoises from England and Wales. Science of the Total Environment 244: 339-348
  5. ↑ 5.0 5.1 Sonne, C., Siebert, U., Gonnsen, K., Desforges, J-P., Eulaers, I., Persson, S., Roos, A., Bäcklin, B-M., Kauhala, K., Olsen, M.T., Harding, K.C., Treu, G., Galatius, A., Andersen-Ranberg, E., Gross, S., Lakemeyer, J., Lehnert, K., Lam, S.S., Peng, W. and Dietz, R. 2020. Health effects from contaminant exposure in Baltic Sea birds and marine mammals: A review. Environment International 139, 105725
  6. ↑ Bennett, P. M., Jepson, P.D., Law, R.J., Jones, B.R., Kuiken, T., Baker, J.R., Rogan, E. and Kirkwood, J.K. 2001. Exposure to heavy metals and infectious disease mortality in harbour porpoises from England and Wales. Environmental Pollution 112: 33-40.
  7. ↑ Kakuschke, A., Valentine-Thon, E., Griesel, S., Fonfara, S., Siebert, U. and Prange, A. 2005. The immunological impact of metals in Harbor Seals (Phoca vitulina) of the North Sea. Environmental Science & Technology 39: 7568-7575
  8. ↑ Kakuschke, A., Valentine-Thon, E., Griesel, S., Fonfara, S., Siebert, U. and Prange, A. 2011. Are metal-induced hypersensitivities in harbor seals associated with liver function? Marine Pollution Bulletin 62: 1891-1894
  9. ↑ Kakuschke, A., Valentine-Thon, E., Fonfara, S., Griesel, S., Siebert, U. and Prange, A. 2008. Metal-Induced Impairment of the Cellular Immunity of Newborn Harbor Seals (Phoca Vitulina). Archives of Environmental Contamination and Toxicology 55: 129-136
  10. ↑ Fonfara S., Siebert, U. and Prange, A. 2007. Cytokines and acute phase proteins as markers for infection in harbour porpoises (Phoconea phocoena). Marine Mammal Science 23: 931-942
  11. ↑ Fonfara, S., Kakuschke, A., Rosenberger, T., Siebert, U. and Prange, A. 2008. Changes of cytokine and acute phase protein expression in blood samples of harbour seal pups during their first months of life. Marine Biology 155: 337-345


The main authors of this article are Kakuschke, Antje, Kramer, Katharina and Fonfara, Sonja
Please note that others may also have edited the contents of this article.
Citation: Kakuschke, Antje; Kramer, Katharina; Fonfara, Sonja ; (2026): Health biomarkers in marine mammals. Available from http://www.coastalwiki.org/wiki/Health_biomarkers_in_marine_mammals [accessed on 2-09-2026]
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