Biomonitoring of pollution impacts in the marine environment
Two approaches can be followed for monitoring the impact of pollutants on marine organisms. One approach is through chemical monitoring, by measuring the concentration of pollutants present in tissues of exposed organisms. The second approach is through biomonitoring, by evaluating the response of an organism exposed to a chemical pollutant. This response can be measured through biomarkers at the molecular, biochemical, cellular, physiological or behavioral level. Common biomarkers are described in the article Common biomarkers for the assessment of marine pollution. The organisms that are chosen for biomonitoring are so-called bioindicators. Bioindicators are organisms which are particularly suited to evaluate the impact of pollutants on marine ecosystems. Biomonitoring complements the information on the health status of the environment provided by the chemical approach.
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Response of marine organisms to toxic contaminants
Toxic pollutants (e.g. metals and synthetic chemicals) can accumulate in marine organisms causing wide-ranging physiological effects which can eventually threaten the entire ecosystem. Organismal stress responses have been observed at different biological levels, such as oxidative damage, activation of antioxidant defenses (cellular level), DNA damage, neurotoxicity (molecular level), impaired filtration or feeding activities, histological damage, growth, development, and reproduction of individuals (physiological level). [1]
During the exposure of an organism to toxic contaminants, the first measurable events take place at the molecular level. As a next step, cells are affected in their integrity, then the tissues and finally the organism as a whole. If exposure to a toxic substance is sufficiently high (by dose or duration of exposure), it can lead to a decrease in the abundance of the exposed species locally, or even to the disappearance of the population. If this species plays an important role in the functioning of the ecosystem, the entire ecological community may be affected and eventually collapse. It is therefore of great importance to identify the impact of a pollutant at the molecular level at an early stage, prior to possible repercussions on the entire ecosystem. [2] Biomonitoring focuses on the first levels of exposure impact, which can be detected via a range of biomarkers described in the article Common biomarkers for the assessment of marine pollution. Biomonitoring can further reveal what the physiological targets of the toxins are, and what their significance is for the homeostasis of organisms.
Interpretation of biomarkers requires knowledge of the toxic pollutants present and their concentrations, and of the adaptation of the bioindicator organism to other environmental factors. This knowledge must allow the impact of contaminants to be distinguished from responses to natural environmental variability and other factors such as rising ocean temperatures, changing salinities and shifts in nutrient-rich currents, as well as ocean acidification.[2]
Passive sampling: measuring the contaminant exposure
Biomarkers provide an indication of the time-integrated effect of an organism's exposure to pollutants. Interpretation of biomarker observations therefore requires knowledge of the average concentration of pollutants over a certain period. Passive sampling is a technique designed to estimating the average concentration of pollutants to which bio-accumulating organisms are exposed. Passive sampling devices collect pollutants from the environment over a set period of time without the need of external power sources or active sampling procedures. Several devices have been developed capable to collect contaminants such as persistent organic pollutants and heavy metals from flowing seawater, using sorbent substances with affinity to the targeted contaminants[3].
Related articles
References
- ↑ Rochman, C.M., Browne, M.A., Underwood, A.J., Van Franeker, J.A., Thompson, R.C. and Amaral-Zettler, L.A. 2016. The ecological impacts of marine debris: unraveling the demonstrated evidence from what is perceived. Ecology 97: 302–312
- ↑ 2.0 2.1 Chahouri, A., Yacoubi, B., Moukrim, A. and Banaoui, A. 2023. Bivalve molluscs as bioindicators of multiple stressors in the marine environment: Recent advances. Continental Shelf Research 264, 105056
- ↑ Vrana, B., Allan, I.J., Greenwood, R., Mills, G.A., Dominiak, E., Svensson, K., Knutsson, J. and Morrison, G. 2005. Passive sampling techniques for monitoring pollutants in water. TrAC Trends in Analytical Chemistry 24: 845-868
