The Gulf of Finland, in the northeastern Baltic Sea, is experiencing ongoing adverse effects due to human activities, leading to a decline in the quality of the marine environment [
1]. The current emphasis in environmental monitoring and assessment lies in chemical and ecological measurements, with little attention given to the connection between these measurements and their biological effects. The neglect of examining biological effects hampers our understanding of the overall influence that various contaminants have on marine organisms, which results from complex combinations of multiple effects. We have collected sediments from moderately to highly contaminated offshore and coastal areas with subsequent analyses of selected chemicals (
Figure 1). Where available, clams (
M. balthica) were collected for biological effects measurements. From seven sites, whole-sediment bioassays with amphipods (
M. affinis) were conducted to determine the effect of contaminants with the registration of the mortality rate and activity of three biochemical biomarkers. In the sediment biotest, the mortality rate was mostly uniformly low (around 8%). The comparison of the amphipod and clam biomarker data revealed that the amphipod, which was exposed to sediments from Narva Bay, did not exhibit significant changes in biomarker activities, except for catalase (CAT), which indicates oxidative stress (
Figure 2). In clams, peaks and falls in enzymatic activities primarily reflect in situ exposure to harmful compounds and conditions. The lowest glutathione S-transferase (GST) activity in clams might be related to the impact of contaminants, as high levels of mercury registered simultaneously in the sediments near the Narva river mouth, while near Kunda harbour, the normalised content of PAH anthracene exceeded more than five times the HELCOM threshold. The highest GST in Narva bay clams might be related to the mixed impact of toxic biocide TBT, which exceeded the GES threshold by almost ten times, and moderate contamination by PAHs and non-dioxin-like PCBs was found in the sediments there. According to the calculated integrated biomarker response index, the highest value at the Sillamäe harbour reflects the most stressful conditions within the studied area. In addition, the elevated level of oxidative stress hints at the unfavourable hydrophysical and chemical conditions in this location.
Author Contributions
Conceptualization, I.K.; methodology, I.K., N.K., M.L. and K.K.L.; formal analysis, I.K.; investigation, I.K., N.K. and M.L.; writing—original draft preparation, I.K.; writing—review and editing, I.K. and K.K.L.; supervision, I.K. and K.K.L.; project administration, I.K.; funding acquisition, I.K., N.K. and K.K.L. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by the European Neighbourhood Instrument and co-financed by the European Union (HAZLESS, NarBaltAware) (grant numbers: ER90/194), by the European Biodiversity Partnership Biodiversa + (D2P) (grant number: 2021-473), and the Environmental Investment Centre (KIK 17253).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Available on request.
Acknowledgments
We want to thank our colleagues from the Department of Marine Systems (TalTech), namely, Urmas Lips, Fred Buschmann, Oliver Sammlas, and the crew of the R/V Salme, for their comprehensive support in the organization and conduction of the fieldworks.
Conflicts of Interest
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results. The content of this publication is the sole responsibility of authors and can under no circumstances be regarded as reflecting the position of the Programme-participating countries or the European Union.
Reference
- Kuprijanov, I.; Väli, G.; Sharov, A.; Berezina, N.; Liblik, T.; Lips, U.; Kolesova, N.; Maanio, J.; Junttila, V.; Lips, I. Hazardous substances in the sediments and their pathways from potential sources in the eastern Gulf of Finland. Mar. Pollut. Bull. 2021, 170, 112642. [Google Scholar] [CrossRef]
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