Time series of temperature, salinity and nutrients in the Strait of Gibraltar (SoG) were researched to analyze which factors explain the invasive success of Rugulopteryx okamurare, which has colonized wide coastal areas at the Spanish and Moroccan coasts since 2016. Temperature and salinity were higher in the SoG compared to its native habitat, implying that the alga is active during the whole seasonal cycle and grows optimally at the high salinities occurring in the SoG. Nitrate removal experiments indicate that the alga is able to linearly increase its N uptake rates following boost in nitrate concentration. Furthermore, R. okamurae N content ranged from 1.4% to 4.5% suggesting that this species has high N storage capacity potentially usable when the external N concentration decreases. These physiological characteristics would explain sharp growth of the alga in the SoG where high N concentrations are registered occasionally.

This study describes the occurrence of anthropogenic microfibres (AMFs) found in sediment trap samples collected at 25 m water depth in an Antarctic fjord (Potter Cove, King George/25 de Mayo Island) from 2012 to 2015. During visual sorting of samples, AMFs were detected and described, and a subset was confirmed, via FTIR (Fourier transform infrared) spectroscopy, as semi-synthetic cellulosic and polyacrylonitrile polymers. Estimated flux of AMF varied from 115 to 152,750 microfibres m⁻² throughout the studied period, with sizes ranging from 10 to 450 μm in length. Maximum AMFs fluxes occurred in summer months. Sediment traps allowed detecting temporal patterns of small (μm) AMFs, usually undersampled with nets or sieves, providing a new insight into microplastic pollution in Antarctica and its relation to environmental conditions.

Modern gillnets are usually made of nylon with high breaking strength, suitable elasticity and durability making them an efficient fishing gear. Lost, abandoned, or discarded gillnets at sea cause plastic pollution and can continue capturing marine animals over long periods of time. Biodegradable materials are being developed to replace nylon in gillnets. However, biodegradable gillnets have shown reduced catch efficiency compared to the nylon gillnets which challenges their acceptance by the fishing sector. This study investigated catch efficiency and modes of capture between biodegradable and nylon gillnets in commercial cod (Gadus morhua) fishery. On average, new biodegradable gillnets caught 25% fewer cod compared to new nylon gillnets. The main capture modes were by the gills and by the body in used and new biodegradable gillnets, respectively. Differences in catch efficiency are related to specific modes of capture that may be related to differences in material properties.

The redox speciation of iron was determined during the iron fertilization LOHAFEX and for the first time, the chemiluminescence assay of filtered and unfiltered samples was systematically compared. We hypothesize that higher chemiluminescence in unfiltered samples was caused by Fe(II) adsorbed onto biological particles. Dissolved and particulate Fe(II) increased in the mixed layer steadily 6-fold during the first two weeks and decreased back to initial levels by the end of LOHAFEX. Both Fe(II) forms did not show diel cycles downplaying the role of photoreduction. The chemiluminescence of unfiltered samples across the patch boundaries showed strong gradients, correlated significantly to biomass and the photosynthetic efficiency and were higher at night, indicative of a biological control. At 150 m deep, a secondary maximum of dissolved Fe(II) was associated with maxima of nitrite and ammonium despite high oxygen concentrations. We hypothesize that during LOHAFEX, iron redox speciation was mostly regulated by trophic interactions.

Interactions of microplastics and persistent organic pollutants (POPs) associated with Atlantic salmon farming were studied to assess the potential role of microplastics in relation to the environmental impact of aquaculture. HDPE, PP, PET and PVC microplastics placed for 3 months near fish farms sorbed POPs from aquafeeds. PET and PVC sorbed significantly higher levels of dioxins and PCBs compared to HDPE, while the levels sorbed to PP were intermediate and did not differ statistically from PET, PVC or HDPE. In addition, the composition of dioxins accumulated in caged blue mussels did not reflect the patterns observed on the microplastics, probably due to polymer-specific affinity of POPs. In conclusion, the results of this study show that microplastics occurring near fish farms can sorb aquafeed-associated POPs and, therefore, microplastics could potentially be vectors of such chemicals in the marine environment and increase the environmental impact of fish farming.

Aquaculture practices at sea are far from impact neutral and remain an important source of marine plastic pollution. With projected rapid continual growth in the sector, if left unmanaged, aquaculture pollution can have detrimental environmental and social implications. Using the DPSIR framework, the paper examines current practices and pathways of plastic pollution from marine aquaculture in the NE-Atlantic, drawing on findings from literature, stakeholder consultations and beach litter assessments. Pathways for aquaculture-related litter identified include rough weather, farmer behavior, inadequate access to recycling facilities, low price of consumable plastics and high cost of recycling. Beach litter analyses conducted as part of the study exposed serious issues of under quantification, resulting from difficulties in source identification and a lack of detailed categorization in official monitoring systems. The paper makes recommendations to improve litter quantification and waste management, including the use of local knowledge and experts to identify sources of marine litter.

The Black Sea receives increasing amounts of microplastics from rivers. In this study, we explore options to reduce future river export of microplastics to the Black Sea. We develop five scenarios with different reduction options and implement them to a Model to Assess River Inputs of pollutaNts to seA (MARINA-Global) for 107 sub-basins. Today, European rivers draining into the Black Sea export over half of the total microplastics. In 2050, Asian rivers draining into the sea will be responsible for 34–46% of microplastic pollution. Implemented advanced treatment will reduce point-source pollution. Reduced consumption or more collection of plastics will reduce 40% of microplastics in the sea by 2050. In the optimistic future, sea pollution is 84% lower than today when the abovementioned reduction options are combined. Reduction options affect the share of pollution sources. Our insights could support environmental policies for a zero pollution future of the Black Sea.

Changes in species composition and relative abundance caused by pollution might have an impact on the community dynamics and ecosystem functioning. Macrobenthos are widely used as indicators of marine environmental health due to their sensitive to disturbance. The present study aims to evaluate spatial and temporal variability of functional diversity of macrobenthos of the Montevideo and Canelones coastal zone along a pre-established pollution gradient, based on Biological Traits Analysis, and functional diversity indices. Body-size”, “Feeding-mode”, “Habitat”, and “Indicator-role” were useful proxies to detect changes in environmental conditions in organically enriched habitats. FRic, FEve and FDis detected temporal variations but only FRic registered spatial variations. Differences among surveys would mainly reflect environmental variability caused by the 2009–2010 El Niño-Southern Oscillation event. Finally, negative correlations between FEve and FDis with AMBI suggest both indices as useful proxies of benthic environmental health, with potential to be used in monitoring and quality assessment programs.

Coccolithophore calcite production (CP) was investigated for the first time in the Bay of Bengal. Against expectation, calcite production was not fueled by the nutrient-enriched cold eddy because of the reduced light penetration. CP rate was observed to be higher at the anticyclonic eddy possibly benefited from rare species production. The adjoining river-induced shallow mixed-layer depth and eddy activity co-influenced CP rate. On average, the integrated CP rates were 0.04, 0.15, and 0.07 mmol C m⁻² h⁻¹ for the cyclonic eddy, anticyclonic eddy, and outer area, respectively. In the upper photic waters, CP rates showed a strong correlation with primary productivity (PP). However, a decoupling of CP and PP was observed in the lower photic zone due to differential light and nitrogen preferences in calcification and carbon fixation. Our findings could help to understand the biogenic response of eddy and inorganic-organic carbon association in the pelagic biogeochemical cycles.

Ecological restoration is an important tool to reverse habitat loss and recover ecosystem services. Here, for two years, we examine the dynamic of Posidonia oceanica following the restoration of a 1149 m² meadow damaged by the Concordia shipwreck. To evaluate the suitability of a recently employed seagrass restoration protocol, we assessed the patches' survival and development by high-spatial resolution photomosaics over the whole transplanted surface. To estimate recovery trajectories, we quantified the cuttings' survival, shoot density, and Daily Leaf Production within fixed monitoring squares. The outcomes confirmed that our protocol could be efficiently applied at larger scales, showing diminutions in cuttings' survival and shoot density over the first year (up to −20%), followed by stability in the number of living cuttings and increases of leaf bundles (up to +5%/year). Our insights demonstrate that the recovery of P. oceanica can be speeded up and underline the need for case-specific transplantation strategies.