Adam Sokołowski

Human pharmaceuticals are considered ”emerging pollutants” within the Arctic environment. While their impacts have been studied extensively in other regions of the world, their effects on native Arctic organisms remain poorly understood. To address this knowledge gap, we investigated the effects of the pharmaceutical pollution by carbamazepine, which has been detected in the Arctic marine ecosystem, on the Icelandic scallop Chlamys islandica. This research, as part of a series of studies, investigates the histopathological effects of carbamazepine on C. islandica following exposure to environmentally relevant concentrations (50 and 1000 ng L⁻¹). Histological assessments were conducted using haematoxylin and eosin (H&E) and Alcian Blue Periodic Acid–Schiff (AB-PAS) staining methods, followed by image analysis using image-processing techniques. These approaches provide quantitative measurements from traditionally semi-quantitative histopathological assessments and represent an underutilised approach within environmental toxicology. The results demonstrated that carbamazepine exposure induced tissue-level impairments in gonadal, gill, and digestive tissues of the scallop. Increased mucus production in gill and digestive tissues, atrophy of the digestive system, variations in sperm cell morphology, and a substantial reduction in vitellin envelope thickness within oocytes were observed. This study demonstrates that even short-term carbamazepine exposure can alter functional tissue characteristics in C. islandica, potentially affecting physiological performance and contributing to population-level consequences within Arctic marine ecosystems.

Calcifying bivalves account for > 80% of the total macrozoobenthic biomass in the southern Baltic Sea. Salinity declines from around 30 in the western Kattegat to 7 in the central Baltic Proper providing a natural gradient along which to investigate the impact of lowering salinity on shelled organisms. Low salinity conditions constrain biomineralisation with limited calcification substrates and periods of aragonite undersaturation. For species with wholly aragonitic shells like the cockle, Cerastoderma glaucum , shell maintenance and production can be challenging. While studies have investigated the corrosive effects of ocean acidification on calcifying organisms, few have considered the long-term consequences of low salinity. This study investigated the shell characteristics of C. glaucum sampled in 2016 and 2024–25 along the southern Baltic salinity gradient to examine variations in shell thickness, shape and condition. Comparisons were made with populations sampled from coastal lagoons in 2024–25 (UK and France) where seasonal salinity fluctuations are significant (< 20 to > 40). This comparative study revealed Baltic populations of C. glaucum exposed to salinities of < 10 to produce shells that are up to 85.2% thicker than populations in more variable environments. However, their size is limited to lengths of 20 mm, around 58% of the usual length achieved by individuals in salinities of > 10. Integral to survival, the shell offers protection from predation and adverse ambient conditions. Ocean freshening poses significant threats to biomineralisation and understanding the response of calcifying species to low salinity is fundamental for assessing their adaptive capacity to future projections of declining salinity.

1. ABSTRACT Human pharmaceuticals are ‘emerging pollutants’ within the Arctic, yet their impacts on native organisms are scarcely studied. One such pharmaceutical, carbamazepine (a Na+ channel blocker), has recently been detected in the Arctic marine ecosystem. Thus, within this paper we investigate the impacts of carbamazepine on the scallop Chlamys islandica through a short term exposure experiment conducted in Ny-Ålesund, Svalbard. We investigated changes in conditional, cellular and histological biomarkers within the gill tissue of the Icelandic scallop Chlamys islandica to assess the oxidative stress scallops experience due to the exposure of environmentally relevant concentrations of carbamazepine. We further investigate the impacts of carbamazepine on Ca2+ concentration of the tissue, which has been theorised but not empirically proven. The study addresses these impacts through free cytosolic Ca2+ analysis, histopathological analysis amended by image processing techniques, and enzymatic/non-enzymatic biomarkers analyses. The study found a novel impacts of carbamazepine on Chlamys islandica’s gill tissue. We observed an increase in calcium deposition within the tissue and a decrease in the tissue calcium concentration. The study also shows that the scallop’s enzymatic response has been negatively impacted by exposure of carbamazepine. Enzymatic biomarkers, acetylcholinesterase and malondialdehyde showed the highest concentration-dependent impact on the gill tissues. In summary, the results of this study show that impacts of carbamazepine are not limited to the (predictable) oxidative stressors that are associated with such pollutants but also tissue weight, tissue calcium concentration, and tissue calcification within the gill tissue of Chlamys islandica.