The effects of environmental changes on contaminant fate in the ecosystem are poorly understood, even in the otherwise well-studied Baltic Sea. This area is considered one of the most polluted in the world and is currently undergoing rapid shifts related to climate change and eutrophication. In this study, we focus on the effects of an altered productivity base and changes in food web structure on contaminant concentrations in the commercially important Baltic herring, which is also a key-species in the ecosystem. In herring of known size and age, collected within the Swedish National Monitoring Program for Contaminants in Marine Biota during the past two to three decades, retrospective analyses of contaminant concentrations and stable isotopes of carbon and nitrogen including amino acid-specific isotope analyses were performed. Partial least squares regression (PLSR) models were applied to dioxins, PCBs, and mercury time series to examine how biological, ecological, and environmental factors (i.e., age, trophic diversity and position, temperature, salinity, proxies of cyanobacterial blooms and ultimate nutrient sources, abundance of relevant benthic fauna as well as biomass and size structure of the zooplankton community) contribute in explaining contaminant concentrations in herring, beyond atmospheric deposition (the main contaminant input in the Central Baltic basin). Our results emphasize that the contaminant burden in Baltic herring is significantly influenced by factors other than atmospheric deposition. Primarily, changes in herring’s trophic ecology, together with nitrogen-fixing cyanobacterial blooms (supporting both growth biodilution and bloom-induced dilution), were linked to dioxin, PCB, and mercury concentrations in fish. Our results support the need to consider all potential ecological synergies and linkages when managing a rapidly changing system such as the Baltic Sea, in order to minimize noxious blooms without compromising the positive impact on contaminant concentrations in fish.

Environmental stressors, such as contaminants and physical factors, rarely act in isolation, and studying their joint effects provides a more accurate reflection of real-world scenarios. To capture these interactions and disentangle the direct and indirect influences on algal responses, we applied partial least squares structural equation modeling (PLS-SEM), allowing us to reveal the hierarchical relationships among stressors and their cumulative impact on algal physiology. We examined combined effects of microplastics (MP; presence/absence), polycyclic aromatic hydrocarbons (PAHs; a mixture of acenaphthene, fluorene, phenanthrene, and fluoranthene at a total chemical activity in the sediment of 0 or 0.14), and sediment resuspension (turbidity: 0.8–3.9 NTU) on Ceramium tenuicorne, a coastal macroalga that is likely to encounter all these stressors in its natural habitats. Mechanical mixing at two intensities (low and high) was applied as an experimental treatment to induce resuspension. The analysis separated the effects of mechanical mixing and turbidity, given their nonlinear relationship, as stronger mechanical mixing did not consistently result in proportional turbidity increases. The algal physiological responses were evaluated using changes in pigment composition (Chl a, Chl c, and carotenoids), photosystem II (PSII) performance, total antioxidant capacity, and algal stoichiometry measured as elemental (%C, %N, %H, and C/N) ratios. We found that PAH exposure was the main suppressor of pigment concentrations and PSII performance, underscoring the mechanisms of its adverse effects on the photosynthetic machinery and nutrient assimilation. Moreover, stronger turbulence further decreased pigment concentrations, while sediment resuspension increased antioxidant capacity in algae, possibly due to physical damage from abrasion and scouring. We also found that MP addition significantly increased turbidity, thus aggravating the effects of the sediment resuspension. In conclusion, we provide a mechanistic explanation of how the combined exposure to MPs, PAHs, and sediment resuspension can impact pigment composition, photosynthesis, and stoichiometry of the algae, leading to decreased productivity.

Guidelines for ecotoxicity testing with Daphnia magna specify particular feeding protocols during the exposure, yet standardization for preexposure feeding remains ambiguous despite its recognized significance in affecting organismal metabolic capacity and tolerance. This ambiguity may contribute to disparate responses and heightened uncertainty in determining the effect concentrations of test chemicals, particularly those inducing metabolic effects through narcosis. Here, we address this gap through a three-step doseresponse experiment with neonates of D. magna subjected to two alternative feeding regimes in the preexposure phase: starved and moderately fed during the first 24 hr after birth. Following this treatment, the daphnids were exposed to narcosis-inducing substances (polycyclic aromatic hydrocarbons; PAHs) for 72 hr before being transferred to clean media with algal food ad libitum for a 48 hr recovery phase. Daphnid survivorship, individual protein content, and body size at the end of each experiment phase-pre-exposure, postexposure and postrecovery-were compared between the treatments. Significant treatment effects were observed, including lower and less variable protein content in the starved daphnids entering the PAH exposure phase, yet higher survivorship and greater recovery potential in these daphnids compared with the fed individuals. Our findings underscore the importance of early-life food access and advocate for mandatory reporting of pre-exposure feeding regimes, particularly when testing substances acting via nonpolar narcosis.

Guidelines for ecotoxicity testing with Daphnia magna specify particular feeding protocols during the exposure, yet standardization for preexposure feeding remains ambiguous despite its recognized significance in affecting organismal metabolic capacity and tolerance. This ambiguity may contribute to disparate responses and heightened uncertainty in determining the effect concentrations of test chemicals, particularly those inducing metabolic effects through narcosis. Here, we address this gap through a three-step dose-response experiment with neonates of D. magna subjected to two alternative feeding regimes in the preexposure phase: starved and moderately fed during the first 24 hr after birth. Following this treatment, the daphnids were exposed to narcosis-inducing substances (polycyclic aromatic hydrocarbons; PAHs) for 72 hr before being transferred to clean media with algal food ad libitum for a 48 hr recovery phase. Daphnid survivorship, individual protein content, and body size at the end of each experiment phase—pre-exposure, postexposure and postrecovery—were compared between the treatments. Significant treatment effects were observed, including lower and less variable protein content in the starved daphnids entering the PAH exposure phase, yet higher survivorship and greater recovery potential in these daphnids compared with the fed individuals. Our findings underscore the importance of early-life food access and advocate for mandatory reporting of pre-exposure feeding regimes, particularly when testing substances acting via nonpolar narcosis.

Sediments can act as reservoirs for hydrophobic contaminants, such as polycyclic aromatic hydrocarbons (PAHs), but can also release these pollutants into the water, posing risks to aquatic life. Conventional risk assessments typically focus on total sediment concentrations, even though the bioavailable fraction provides a more accurate measure of ecological risk. This study aimed to explore how sediment resuspension and contaminant hydrophobicity influence contaminant release into the water. We conducted an experiment where the release of four PAHs (acenaphthene, fluorene, phenanthrene, and fluoranthene) from an artificial sediment was studied at different resuspension treatments. Polyethylene passive samplers were used to sample PAHs released from sediment and water turbidity was used as a proxy for sediment resuspension. We identified a turbidity threshold at 2.7 NTU, below which PAH release was primarily driven by diffusion from sediment pore water, whereas at higher turbidity, resuspension and desorption processes played a more dominant role. Hydrophobicity was a critical factor for contaminant release: contaminants with a log K_OW below 4.3 were more likely to be released at low turbidity, whereas those with a log K_OW above 4.5 were released more at higher turbidity. Taken together, the results show that the release of contaminants from sediment into the water column is influenced by contaminant hydrophobicity and turbidity.

Macrophytes are essential primary producers in coastal ecosystems, significantly shaping food webs and providing critical ecosystem services. However, their habitats are increasingly becoming hotspots for plastic pollution due to their efficiency in trapping plastic particles from terrestrial runoff. This review explores the complex interactions between plastic litter and macrophyte systems, focusing on four main areas: (1) physical interference and habitat alterations due to particle retention by macrophytes; (2) chemical contamination and ecotoxicity; (3) nutrient dynamics affecting productivity; and (4) impacts on microbial communities associated with environmental compartments and plant microbiomes. Plastic debris can physically obstruct light and gas exchange, alter sediment properties, and leach toxic chemicals, adversely affecting macrophyte physiology and growth. These impacts can cascade through the ecosystem, disrupting habitat structure, food webs, and biogeochemical processes, ultimately threatening biodiversity and ecosystem stability. We highlight the necessity for a unified research approach to deepen our understanding of these interactions and advocate for leveraging macrophytes in bioremediation efforts and as indicators of plastic pollution in environmental management strategies. Understanding these often-overlooked interactions is crucial for assessing the environmental impact of plastic pollution and for the development of effective conservation and remediation policies.

Det samordnade recipientkontroll-programmet vid Oxelösundskusten omfattar vattenkemiska analyser (näringsämnen, klorofyll, siktdjup, salthalt), bottenfauna, samt provtagning av sediment, fisk och blåmussla för metaller och PAH:er. Den här rapporten redovisar bottenfauna insamlad 2024 samt två pilotförsök för att undersöka miljöeffekter av förorenat sediment som genomförts under 2023–2024. Övriga parametrar i det samordnade recipientkontroll-programmet presenteras i Walve och Raymond (2024).

Bottenfaunan visar god status för området när det utvärderas med det bentiska kvalitetsindexet BQI. Undersökningar har genomförts fem gånger seden 2006 och vid dessa tillfällen nådde området upp till god status vid alla undersökningar. Däremot visar en undersökning från 1982 att området då endast nådde upp till måttlig status och att faunan var generellt utarmad. Idag är mångfalden och individtätheten betydligt bättre.

Trots att bottenfaunan visar på god status hittas höga halter av metaller och PAH:er i sedimentet. Två pilotförsök har därför genomförts under 2023–2024 för att undersöka miljöeffekter av förorenat sediment. I båda försöken har sediment samlats in i en gradientstudie, där två stationer uppvisar förhöjda miljögifter i sediment och två stationer utgör referens-områden (Dragviksfjärden och Askö).

I det första försöket tillsattes 15 gravida vitmärlor Monoporeia affinis till sedimentproppar från de fyra stationerna. Efter 7 veckors exponering studerades överlevnaden, antal gravida honor, fekunditet per hona, missbildade embryon och döda/outvecklade embryon. Den mest förorenade stationen SS1 närmast SSAB:s verksamhet uppvisade lägre överlevnad, även om skillnaden inte var statistiskt säkerställd, men framför allt färre rekryteringar av nya individer.

I det andra försöket tillsattes 5 uppodlade märlkräftor Hyalella azteca till provburkar med sediment från samma fyra gradientstationer som vitmärlorna exponerades för. Efter 7 dagar analyserades biomarkörer som RNA/DNA-kvot för indirekt tillväxt, ORAC för oxidativ status samt AChE för neuro-toxicitet. På den mest förorenade stationen SS1 förekom hög andel avvikande RNA/DNA-kvoter och AChE-aktivitet samt måttlig ORAC-status. Den referensstation, Askö, där vitmärlorna till reproduktionsförsöket samlades in, visade också på biomarkör-effekter vilket antyder att vitmärlorna redan var påverkade av föroreningar när de samlades in till försöket. 

Undersökningen har beställts av SSAB Oxelösund och utförts av det Marinekologiska laboratoriet (MEL) vid institutionen för ekologi, miljö och botanik på Stockholms universitet (SU) med biomarköranalyser utförda vid institutionen för miljövetenskap vid SU .

Spatial patterns, potential origins, and ecotoxicological risk of alkylated (APAH) –and parent –(PPAH) polycyclic aromatic hydrocarbons (PAHs) were studied in mangrove surface sediments along the northern coasts of the Persian Gulf, Iran. The mean total concentrations (ngg⁻¹dw) ∑₃₂PAH, ∑PPAHs and ∑APAHs in sediments were 3482 (1689–61228), 2642 (1109–4849), and 840 (478–1273), respectively. The spatial variability was similar among these PAH groups, with the highest levels occurring in Nayband National Marine Park (NNMP). Physicochemical environmental factors, such as sediment grain size, and total organic carbon (TOC) contents, are significant factors of PAH distribution. These findings suggest that PAH pollution level is moderate-to-high, supporting the current view that mangrove ecosystems are under intensive anthropogenic impacts, such as petrochemical, oil and gas loads, port activities, and urbanization. Non-parametric multidimensional scaling (NPMDS) ordination demonstrated that NNMP mangrove is the critical site exhibiting high loading of PAH pollutants. Here, for the first time in this region, Soil quality guidelines (SQGs), Toxic equivalency quotient (TEQ), Mutagenic equivalency quotient (MEQ), and composition indices comprising Mean maximum permissible concentration quotient (m-MPC-Q), and Mean effect range median quotient (m-ERM-Q) methods were used to have a comprehensive risk assessment for PAH compounds and confirmed medium-to-high ecological risks of PAHs in the study area, particularly in the western part of the Gulf, highlighting the industrial impacts on the environment.

Persistent organic pollutants (POPs) pose a risk in aquatic environments. In sediment, this risk is frequently evaluated using total or organic carbon-normalized concentrations. However, complex physicochemical sediment characteristics affect POP bioavailability in sediment, making its prediction a challenging task. This task can be addressed using chemical activity, which describes a compound's environmentally effective concentration and can generally be approximated by the degree of saturation for each POP in its matrix. We present a proof of concept to load artificial sediments with POPs to reach a target chemical activity. This approach is envisioned to make laboratory ecotoxicological bioassays more reproducible and reduce the impact of sediment characteristics on the risk assessment. The approach uses a constantly replenished, saturated, aqueous POP solution to equilibrate the organic carbon fraction (e.g., peat) of an artificial sediment, which can be further adjusted to target chemical activities by mixing with clean peat. We demonstrate the applicability of this approach using four polycyclic aromatic hydrocarbons (acenaphthene, fluorene, phenanthrene, and fluoranthene). Within 5 to 17 weeks, the peat slurry reached a chemical equilibrium with the saturated loading solution. We used two different peat batches (subsamples from the same source) to evaluate the approach. Variations in loading kinetics and eventual equilibrium concentrations were evident between the batches, which highlights the impact of even minor disparities in organic carbon properties within two samples of peat originating from the same source. This finding underlines the importance of moving away from sediment risk assessments based on total concentrations. The value of the chemical activity-based loading approach lies in its ability to anticipate similar environmental impacts, even with varying contaminant concentrations. 

Understanding how key-species respond to anthropogenic stress such as chemical pollution is critical for predicting ecosystem changes. Little is however known about the intra-specific variability in the physiological and biochemical traits involved in contaminant exposure responses. Here, we explored this idea by exposing the Baltic amphipod Monoporeia affinis from two sites, one moderately polluted and one more pristine, to a sediment spiked with PAHs and PCBs. We evaluated the amphipods responses related to feeding, growth, a stress biomarker (acetylcholinesterase [AChE] inhibition) and stable isotope (delta C-13 and delta N-15) composition including isotope niche analyses. More adverse responses were expected in animals from the low-pollution site than those from the high-pollution site due to tolerance development in the latter. Amphipods from both populations showed a similar to 30% AChE inhibition when exposed to the contaminant spiked sediment. However, both controls and exposed amphipods from the high-pollution site had higher survival, nutrient uptake and condition status than the amphipods from the low-pollution site, which did not feed on the added diatoms as indicated by their isotope values. We found no signs of population-specific responses in physiological adjustments to contaminants with regard to classic ecotoxicological biomarkers such as AChE inhibition and growth status. Instead, isotope niche analyses proved useful in assessing contaminant stress responses at the population level.