This study estimates for the very first time plastic litter levels in sea cucumbers (Echinodermata, Holothuroidea) sampled in situ and their intakes from sediments in three different rocky bottom habitats (slides, cliff, banks) settled in Salina Island (Aeolian Archipelago). Macroplastic were never recorded while meso- and microplastics were identified in all sediment (81–438 items/kg d.w.) and animal samples (1.8–22 items/ind.). Plastic intakes by sea cucumbers resulted frequently associated to the size range included within 100–2000 μm. Over than 70% of ingested plastic litter is represented by the size fraction >500 μm. Sediment/animals ratios % are included 2.7 ± 2.0% in studied habitats with a selective intake of fragments occurring in slides. Furthermore, results support the occurrence of selective ingestion of plastic litter by holothurians in natural environments underlining the role of these species in microplastic transfer from abiotic towards biotic compartments of the marine trophic web.

Understanding which factors influence the invasion of alien seaweed has become a central concern in ecology. Increasing evidence suggests that the feeding preferences of native herbivores influence the success of alien seaweeds in the new community. We investigated food selection of a generalist native grazer Paracentrotus lividus, in the presence of two alien seaweeds (Caulerpa cylindracea and Caulerpa taxifolia var. distichophylla) and two native seaweeds (Dictyopteris membranacea and Cystoseira compressa). Sea urchins were fed with six experimental food items: C. cylindracea, C. taxifolia var. distichophylla, a mixture of C. cylindracea and C. taxifolia var. distichophylla, D. membranacea, C. compressa and a mixture of D. membranacea and C. compressa. P. lividus ingested all the combinations of food offered, though it preferentially consumed the alien mixture, C. cylindracea and D. membranacea. The alien C. taxifolia var. distichophylla was consumed significantly less than the other food items and, interestingly, it was ingested in a greater amount when mixed with C. cylindracea than when on its own. This finding suggests that C. taxifolia var. distichophylla may become vulnerable to sea urchin grazing when it grows intermingled with C. cylindracea, which does not gain immediate protection from the presence of the very low palatable congeneric seaweed. The present study highlights the potential role of native grazers to indirectly affect the interspecific competition between the two alien seaweeds in the Mediterranean Sea.

Marine debris accumulation was analyzed from three exposed beaches of the Canary Islands (Lambra, Famara and Las Canteras). Large microplastics (1–5mm), mesoplastics (5–25mm) and tar pollution were assessed twice a month for a year. There was great spatial and temporal variability in the Canary Island coastal pollution. Seasonal patterns differed at each location, marine debris concentration depended mainly of local-scale wind and wave conditions. The most polluted beach was Lambra, a remote beach infrequently visited. The types of debris found were mainly preproduction resin pellets, plastic fragments and tar, evidencing that pollution was not of local origin, but it cames from the open sea. The levels of pollution were similar to those of highly industrialized and contaminated regions. This study corroborates that the Canary Islands are an area of accumulation of microplastics and tar rafted from the North Atlantic Ocean by the southward flowing Canary Current.

This baseline assessment reports on the occurrence, distribution, and sources of emerging organic contaminants (EOCs) in tropical coastal sediments of anthropogenically impacted Klang River estuary, Malaysia. Bisphenol A was the highest concentration detected at 16.84 ng g−1 dry weight, followed by diclofenac (13.88 ng g−1 dry weight) and E1 (12.47 ng g−1 dry weight). Five compounds, namely, amoxicillin, progesterone, diazinon, bisphenol A, and E1, were found in all sampling stations assessed, and other compounds such as primidone, diclofenac, testosterone, E2, and EE2 were ubiquitously present in sediment samples, with percentage of detection range from 89.04% to 98.38%. Organic carbon content and pH were the important factors controlling the fate of targeted compounds in the tropical estuarine sediment. On the basis of the literature from other studies, the sources of EOCs are thought to be from wastewater treatment plants, domestic/medical waste discharge, livestock activities, industrial waste discharge, and agricultural activities.

Very intense internal tides take place in Indonesian seas. They dissipate and affect the vertical distribution of temperature and currents, which in turn influence the survival rates and transports of most planktonic organisms at the base of the whole marine ecosystem. This study uses the INDESO physical model to characterize the internal tides spatio-temporal patterns in the Indonesian Seas. The model reproduced internal tide dissipation in agreement with previous fine structure and microstructure observed in-situ in the sites of generation. The model also produced similar water mass transformation as the previous parameterization of Koch-Larrouy et al. (2007), and show good agreement with observations. The resulting cooling at the surface is 0.3°C, with maxima of 0.8°C at the location of internal tides energy, with stronger cooling in austral winter. The cycle of spring tides and neap tides modulates this impact by 0.1°C to 0.3°C. These results suggest that mixing due to internal tides might also upwell nutrients at the surface at a frequency similar to the tidal frequencies. Implications for biogeochemical modelling are important.

Phase shift, resulting from coral reef degradation, has been frequently recorded on reefs in optimal conditions, while marginal reefs were considered more resistant due to few records. Noting the lack of marginal reef phase shift studies, we quantitatively assessed their geographic extent in the Southwest Atlantic. Using metadata and a calculated phase shift index, we identified phase shifts from corals to both zoanthid and macroalgal dominance. Positive correlations existed between phase shift and local human impacts for zoanthids: proximity to human populations >100,000 inhabitants, urbanized surfaces and dredged ports and a negative relationship to the endurance of SST >1 °C above normal. Macroalgal shifts positively correlated to ports and urbanized surfaces, higher latitudes and shore proximity, indicating a possible link to nutrient runoff. The high frequency of these phase shifts suggests greater degradation than reported for Caribbean reefs, suggesting that marginal reefs do not have higher natural resistance to human impacts.

Seven hundred and nine surface sediment samples, along with deeper sediment samples, were collected from Hebei Province along the coastal section of the Bohai Sea, China, and analyzed for grain size, concentrations of organic carbon (Corg) and heavy metals (Cu, Pb, Zn, Cr, Cd, As, and Hg). Results indicated that the average concentrations in the sediments were 16.1 mg/kg (Cu), 19.4 mg/kg (Pb), 50 mg/kg (Zn), 48.8 mg/kg (Cr), 0.1 mg/kg (Cd), 8.4 mg/kg (As), and 20.3 μg/kg (Hg). These concentrations generally met the China Marine Sediment Quality criteria. However, both pollution assessments indicated moderate to strong Cd and Hg contamination in the study area. The potential ecological risk index suggested that the combined ecological risk of the seven studied metals may be low, but that 24.5% of the sites, where sediments were finer and higher in Corg concentration, had high ecological risk in Hg and Cd pollution.

Eight touristic beaches along the north coast of Santa Catarina Island, Brazil were assessed to determine litter influence on scenic quality. The application of the Coastal Scenic Evaluation System (CSES) categorized these beaches into four of the five available classes. Six of the investigated beaches belong to Class III (n = 3) and V (n = 3), while two beaches correspond to Class II and Class IV. Class I beaches were not found. A total amount of 4291 litter items weighing 29 kg were collected with average abundances of 0.29 items m2. Beach user's habits as well bad management practices along the adjoining river basins play an essential role on litter source, and are directly responsible for the decline of scenic quality of Santa Catarina Island Beaches. In fact, litter has a direct relation with the low scenic scores determined in the surveyed beaches.

We investigated at the single cell level during 16months (June 2012 to September 2013) the temporal distribution of picophytoplankton (picoeukaryotes, Synechococcus and Prochlorococcus) communities in two contrasted ecosystems: the Bay of Bizerte characterised by an oligotrophic regime typical of the Mediterranean Sea and the Bizerte Lagoon that exhibits a mesotrophic/eutrophic state. We aimed at depicting seasonal variations and quantifying the relationships between the environmental factors and the structure and abundance of picophytoplankton communities. Results showed that picophytoplankton groups were able to grow under a wide range of environmental conditions varying seasonally, although their abundances and contributions to the total chlorophyll biomass significantly varied and showed importance in the Bay of Bizerte. Synechococcus was the most abundant group reaching 225∗103cells·cm−3 in the Bay and 278∗103cells·cm−3 in the lagoon. This group was present all over the year in both ecosystems. Structural equation model results pointed out a different configuration regarding the picophytoplankton environmental drivers. The complexity of the configuration, i.e. number of significant links within the system, decreased under enhanced eutrophication conditions. The less exposure to anthropogenic stress, i.e. in the Bay of Bizerte, highlight a larger role of nutrient and hydrological conditions on the seasonal variations of picophytoplankton, whereas a negative effect of eutrophication on picophytoplankton communities was unveiled in the Bizerte Lagoon. We stress that such influence may be exacerbated under expected scenarios of Mediterranean warming conditions and nutrient release in coastal ecosystems.

The compartment model POSEIDON-R with an embedded food web model was used to assess 137Cs distributions in the Baltic and Black seas and off the Pacific coast of Japan during 1945–2020 due to the weapon testing and accidents at the Chernobyl and Fukushima Dai-ichi nuclear power plants. The results of simulations conducted with generic parameters agreed well with measurements of 137Cs concentrations in the water, bottom sediments, and in fish. In the Black and Baltic seas, salinity variations affected the transfer of 137Cs through the food web. The contamination of pelagic fish followed the water contamination with some delay, whereas demersal fish depuration was found to be related to decreasing 137Cs concentrations in the upper sediment layer. On the Pacific shelf off Japan, intensive currents and eddies caused the simulated depuration rates in fish to be one-two orders of magnitude larger than those in the semi-enclosed Black and Baltic seas.