In semi-enclosed seas, eutrophication may affect both the coastal waters and the whole sea. We develop and test a modelling approach that can account for nutrient loads from land as well as for influences and feedbacks on water quality across the scales of a whole semi-enclosed sea and its coastal zones. We test its applicability in the example cases of the Baltic Sea and one of its local archipelagos, the Archipelago Sea. For the Baltic Sea scale, model validation shows good representation of surface water quality dynamics and a generally moderate model performance for deeper waters. For the Archipelago Sea, management scenario simulations show that successful sea measures may have the most important effects on coastal water quality. This highlights the need to consistently account for whole-sea water-quality dynamics and management effects, in addition to effects of land drivers, in modelling for characterisation and management of local water quality.

Ballast water discharges may cause negative impacts to aquatic ecosystems, human health and economic activities by the introduction of potentially harmful species. Fifty untreated ballast water tanks, ten in each port, were sampled in four Adriatic Italian ports and one Slovenian port. Salinity, temperature and fluorescence were measured on board. Faecal indicator bacteria (FIB), phyto- and zooplankton were qualitatively and quantitatively determined to identify the species assemblage arriving in ballast water. FIB exceeded the convention standard limits in 12% of the sampled tanks. Vibrio cholerae was not detected. The number of viable organisms in the size groups (minimum dimension) <50 and ≥10 μm and ≥50 μm resulted above the abundances required from the Ballast Water Management Convention in 55 and 86% of the samples, respectively. This is not surprising as unmanaged ballast waters were sampled. Some potentially toxic and non-indigenous species were observed in both phyto- and zooplankton assemblages.

Ports are subject to a variety of anthropogenic impacts, and there is mounting evidence of faecal contamination through several routes. Yet, little is known about pollution in ports by faecal indicator bacteria (FIB). FIB spatio-temporal dynamics were assessed in 12 ports of the Adriatic Sea, a semi-enclosed basin under strong anthropogenic pressure, and their relationships with environmental variables were explored to gain insight into pollution sources. FIB were abundant in ports, often more so than in adjacent areas; their abundance patterns were related to salinity, oxygen, and nutrient levels. In addition, a molecular method, quantitative (q)PCR, was used to quantify FIB. qPCR enabled faster FIB determination and water quality monitoring that culture-based methods. These data provide robust baseline evidence of faecal contamination in ports and can be used to improve the management of routine port activities (dredging and ballast water exchange), having potential to spread pathogens in the sea.

This study utilizes suspended particles and seafloor sediments collected from the northern Gulf of Mexico (GOM) continental margin to study the fate, transport, residence times and accumulation rates of particle-bound polycyclic aromatic hydrocarbons (PAHs). Total particulate-PAHs and particulate organic carbon (POC) varied between 0.9 and 7.0 ng/L, and 4–131 μg/L, respectively. Particulate-PAHs were positively correlated with POC, while both particulate-PAHs and POC were negatively correlated with salinity (P-value < 0.05). These results show that the river-derived particle influx and associated POC are important vectors for transport and fate of particulate-PAHs in the river-dominated northern GOM continental ecosystems. The composition of underlying seafloor sediment-PAHs were not correlated to the water column particulate-PAHs, which is attributed to re-mineralization, sediment resuspension/redistribution and different timescales of comparison. The 210Pb-derived residence time of particles and associated particulate-PAHs in water column varied between 2 and 39 days. Residence times of particulate-PAHs were significantly correlated with seafloor sediment-PAHs accumulation rates, shorter water column residence times leading to higher PAHs accumulation rates.

Microplastics are commonly found in marine ecosystems, but their distribution, prevalence, and impacts on resident fauna are still not well understood. Microplastics in coastal sediments expose invertebrate infauna to the risk of ingestion of plastic debris and associated toxicants. We assessed the prevalence of microplastics in beach sediments and ingested by Pacific mole crabs (Emerita analoga) at sandy beaches spanning >900 km of the California coast. Microplastics were present in sediments of every one of 51 beaches sampled. At a subset of 38 beaches Pacific mole crabs were collected and crabs at every beach had ingested microplastics. Across all beaches sampled, an average of 35% of Pacific mole crabs examined had microplastics in their guts. Our study demonstrates that microplastics are ubiquitous in sediments on California beaches and they are frequently consumed by a filter-feeding crustacean that is a common prey item in the diet of a wide variety of taxa, including fishes and birds.

This study presents baseline records of trace metals for two commercial shrimps from the inner continental shelf of southeast Brazil (~22°S). Organisms were sampled in 2004, 10 years before the beginning of large port activities in coastal waters. The concentrations of trace metals in muscle tissues (μg.g⁻¹ w.w.) of Xyphopenaues kroyeri and Artemesia longinaris are as follows: Al: 141.57 and 146.71, Fe: 83.17 and 91.68, Zn: 28.69 and 29.70, Cu: 7.19 and 3.94, Mn: 1.47 and 1.72, Pb: 1.14 and 0.60, V: 0.66 and 0.56, Ni: 0.38 and 0.34, Cr: 0.42 and 0.29, and Cd: 0.15 and 0.14, respectively. Significantly higher concentrations of Cu and Pb were recorded for X. kroyeri. In general, the concentrations are below the maximum permissible limits for metals in fishery/food products, as established by the Brazilian Agency for Sanitary Vigilance (ANVISA), except for Pb and Cr. These baseline records are relevant for future monitoring.

Samples for sediment and two species of native mangrove plants were collected from seven sampling sites for assessing the level of metal contamination. Results of the studied metals displayed the order of pollution as Fe > Ti > Zr > Rb > Zn > Sr > Pb > Y > Cu > Cr > As accordingly. Geoaccumulation index and contamination factor revealed that the sediment samples were unpolluted to moderately polluted by Zn, Fe, Ti, Rb, Y, and Zr. Ecological risk factor depicted a pollution-free condition in the study areas. PCA, CA, and correlation coefficient indicated that the source of the metals in the environment was anthropogenic. Bioconcentration factor values were found to be below 1 in both plant species. Conversely, transfer factor values for most heavy metals were found to be >1 in both plant species, which reflects the phytoremediation ability of plants.

The prediction models of MWQI in mangrove and estuarine zones were constructed. The 2011–2015 data employed in this study entailed 13 parameters from six monitoring stations in West Malaysia. Spatial discriminant analysis (SDA) had recommended seven significant parameters to develop the MWQI which were DO, TSS, O&G, PO4, Cd, Cr and Zn. These selected parameters were then used to develop prediction models for the MWQI using artificial neural network (ANN) and multiple linear regressions (MLR). The SDA-ANN model had higher R2 value for training (0.9044) and validation (0.7113) results than SDA-MLR model and was chosen as the best model in mangrove estuarine zone. The SDA-ANN model had also demonstrated lower RMSE (5.224) than the SDA-MLR (12.7755). In summary, this work suggested that ANN was an effective tool to compute the MWQ in mangrove estuarine zone and a powerful alternative prediction model as compared to the other modelling methods.

Increased sediment loads within algal turfs, can be highly detrimental to coral reef systems. However, significant knowledge gaps remain in relation to sediment dynamics, especially linking suspended sediments, sedimentation and turf-bound sediments. To examine these links, a series of different methods for quantifying suspended sediments, sedimentation and the accumulation of turf sediments were compared, simultaneously, on an inner-shelf reef. We revealed that the amount and composition of sediment quantified using different methods varied markedly, with commonly employed measures of sedimentation failing to accurately reflect patterns of sediment accumulation in turfs. Our results highlighted the propensity for turfs to trap and retain sediments, with turfs accumulating approximately 2.6 times more sediment than traps, and 6 times more sediment than SedPods, over a seven-day period. This study highlights the major, but often overlooked, role that algal turfs can play in sediment dynamics on coral reefs.

The European oyster Ostrea edulis is a keystone species that is internationally recognised as ‘threatened and declining’ in the NE Atlantic by OSPAR and several nations have consequently adopted strategies for its conservation and restoration. Understanding the settlement behaviour of O. edulis larvae is crucial to inform these strategies. We compared the efficiency of several treatments in triggering settlement. The most effective settlement occurred with the presence of conspecifics: 100% settled in <23 h. Marine stones with habitat-associated biofilms induced 81% settlement that started after a 45 h delay. Sterile shells and terrestrial stones did not induce more settlement than control treatments. These results indicate that O. edulis larvae are gregarious and finely-tuned to settle in response to cues which are indicative of their adult habitat requirements. The role of chemical cues in mediating settlement, and the importance of this to restoration, are discussed.