Rivers potentially conduct important components as result of anthropogenic stressors for coral reefs. Molecular techniques are increasingly being used for monitoring biological and chemical monitoring of rivers and reefs. Here, we use PhyloChips™ to process surface water samples collected along two rivers and associated reefs in an environmental protection area in northeastern Brazil. Our results indicate that a significant part of Operational Taxonomic Units (OTUs) identified were able to survive the transition from freshwater to seawater, several of them belonging to genera implicated in human pathogenesis. The BBC:A ratio and functional prediction suggests that both study rivers are subject to fecal contamination and xenobiotics input and that the bacterial communities were more homogeneous in these environments. We suggest that protection actions adopted for reefs should be broadly extended to the surrounding environment, and that other bacterial group (besides cultivable coliforms) should be included in routine water quality monitoring.

The occurrence and spatial distribution of persistent organic pollutants (POPs) and personal care products (PCPs) were investigated in surface sediments of Todos os Santos Bay. Samples were Soxhlet-extracted and analyzed by gas chromatography coupled with tandem mass spectrometry. Quantification limits (QL) ranged from 0.0025 ng g⁻¹ for POPs to 0.25 ng g⁻¹ for PCPs. Of the POPs studied, only PCBs and DDTs were detectable, with concentrations ranging from <QL to 4.66 ng g⁻¹, with increased concentrations near urban and industrial areas. PCPs ranged from <QL to 27.5 ng g⁻¹ and presented a homogeneous spatial distribution, probably related to the continuous inputs of these compounds from diffuse sources. Mean contaminant inventories ranged from 0.33 ± 0.23 ng cm⁻² for DDTs to 8.3 ± 8.4 ng cm⁻² for fragrances. To the best of our knowledge, this is the first study on the occurrence of UV filters in sediments from Brazilian coastal environments.

Sedimentary nitrogen (SN) provenience and fate in surface and subsurface sediments collected from the Baltic Sea were assessed. SN and sedimentary organic carbon (SOC) concentrations, stable isotopic signatures (δ¹⁵NSN and δ¹³CSOC) and SOC/SN molar ratios, were determined in subsequent layers of twenty-four sediment cores dated with ²¹⁰Pb/¹³⁷Cs and fifty-seven surface sediments. Sedimentation rates in the range 66–736 g/m²yr⁻¹ (0.05–0.34 cm/year) were measured. Prolonged incubation of sediments in the laboratory led to a 17–37% decrease of SN in surface sediments, and no SN loss in sediments deposited before 1940. Decrease of δ¹⁵NSN on incubation (1‰ on average), and gradients of δ¹⁵NSN, between recent - surface (3.5‰) vs. 100 years old - subsurface (2.1‰) sediments were attributed to varying contributions of labile nitrogen to the SN pool. Annual deposition of SN to sediment surface and burial in subsurface sediments amounted, respectively, to 5 ± 2 g/m² and 3.5 ± 1 g/m².

Assessing the carrying capacity of ecosystems is crucial to the selection of suitable and sustainable locations for aquaculture farms. In Malpeque Bay (PEI, Canada), the potential expansion of mussel farms has driven a series of numerical modelling studies. We coupled sub-models for sea lettuce, wild and cultured oysters and wild softshell clams to an existing ecosystem model to better understand nutrient dynamics and the carrying capacity of Malpeque Bay. Simulations suggested that competition for nutrients between phytoplankton and sea lettuce and filtration by cultured bivalves predominantly mitigate eutrophication effects. The addition of sea lettuce reduced mussel growth by 2% on average and up to 9% near eutrophic estuaries favouring macroalgae growth. Projected new mussel farms reduced current mussel growth by 2% also, suggesting that the carrying capacity of the bay may not be reached yet. Both current and projected aquaculture activities seemed to have limited effects on natural bivalve growth.

There is public concern about the behaviour of spilled diluted bitumen (dilbit) in marine and estuarine waters. We provide a preliminary assessment of the results of laboratory experiments and models, in the context of environmental conditions in the coastal waters of British Columbia. Most dilbit spilled within this region would likely float at the surface and be transported to shore by winds and currents. Fresh dilbit is too light to sink in coastal waters. Highly weathered dilbit could sink where salinity is less than 14, typically only near river mouths and in the top 1–3 m of fjords after heavy rainfall. Subsurface plumes of weathered dilbit could re-emerge at the surface. Sinking oil-particle aggregates are unlikely to form in coastal waters. However, dilbit could be entrained below the surface by wave mixing during storms and to depths of 150 m by coherent mixing in the Haro Strait tidal convergence zone.

The dynamics of plastic debris were assessed in the Seine River, especially in the estuary, using plastic bottles equipped with GPS-trackers. In one year, 50 trajectories were recorded, covering a wide range of hydrometeorological conditions. Results show a succession of stranding/remobilization episodes in combination with alternating upstream and downstream transport in the estuary. In the end, 100% of the tracked bottles stranded somewhere, for hours or weeks, from one to several times at different sites. The overall picture shows that different physical phenomena interact with various time scales ranging from hours/days (high/low tides) to weeks/months (spring/neap tides and highest tides) and years (seasonal river flow). Thus, the fate of plastic debris is highly unpredictable, but the consequence of those interactions is that the transfer of debris is chaotic and not straightforward, and its residence time is much longer than the transit time of water.

We investigated the impact of microplastics (MPs) on marine fish by estimating the uptake and retention by mummichogs (Fundulus heteroclitus) and red seabreams (Pagrus major) of MPs similar in size (≥0.25 mm) and composition (polyethylene) to MPs detected in fish intestines. Results revealed a correlation between MP concentrations in aquarium water and the content of MPs in the gastrointestinal tracts of exposed fish. More than 95% were excreted from both species within 25 h; this retention time is similar to the processing time of food items. The rate of excretion showed little dependence on MP size, but there was some dependence on fish species and MP shape. These results suggest that MPs similar to those we studied have little direct adverse impact on these two marine fish species.

In order to maintain the hydraulic outflow in land reclaimed canalizations, the competent agencies provide to mechanically mow the Giant Reed (Arundo donax, L. 1753) along the aquatic ecosystem banks. Nevertheless, the reeds mowed can be transported away from the waters following storm surges and can be deposited in large quantities along the sandy beaches. We carried out a stratified study in a Mediterranean sandy beach to test the hypothesis that Giant Reed wrack may act as a sink and barrier for plastic beach litter. We observed a large amount of plastic litter entrapped in the Arundo donax wrack (density of 0.868 items/m²), with a higher density when compared to both the inner and the shoreline belts. Density of litter is significantly higher considering the categories of meso- and micro-plastics. Organic macrophyte wrack is useful for dunal macrodetritivorous invertebrates and generally for fauna communities, which use this litter as refuge and trophic pabulum. Significant accumulations of organic wrack can mitigate coastal erosion; nevertheless, for its structural characteristics, Arundo wrack can also act as a barrier for litter towards the inner vegetated dunes, so entrapping a large amount of anthropogenic litter. In this regard, Arundo wrack can represent a sink habitat, first attracting (due to large availability of detritus with a relative high rate of decomposition) and then, entrapping many organisms in anthropogenic litter. We suggest that, once mechanically mowed, the land reclaimed agencies should periodically remove from the channel banks the Arundo donax reeds, impeding the accumulation of incoherent vegetated matter along the aquatic ecosystem banks.

It has been proven that there is an extensive bulk of plastic debris in marine ecosystems. The present study analyzed solid waste generation, its management and final disposal methods in Caspian Sea coastal countries, and the amount of plastic waste entering the Caspian Sea. The results showed that, on average, more than 90% of waste in the Caspian Sea coastal countries is mismanaged. According to our estimates, 425 kilotons (Kt) of plastic waste was generated by Caspian Sea coastal countries in 2016, of which, with high probability, 58–155 Kt find their way to the Caspian Sea. It is estimated that without improved waste management infrastructures, the amount of plastic waste entering the Caspian Sea will increase to 68–182 Kt by 2030, an increase of about 15%. Accordingly, the related cumulative environmental and health problems could be more severe. All countries located in the coastal areas of the Caspian Sea should revise their solid waste and plastic waste management programs to protect that sensitive marine ecosystem.

Seagrasses provide a wide range of services including food provision, water purification and coastal protection. Pacific small island developing states (PSIDS) have limited natural resources, challenging economies and a need for marine science research. Seagrasses occur in eleven PSIDS and nations are likely to benefit in different ways depending on habitat health, habitat cover and location, and species presence. Globally seagrass habitats are declining as a result of anthropogenic impacts including climate change and in PSIDS pressure on already stressed coastal ecosystems, will likely threaten seagrass survival particularly close to expanding urban settlements. Improved coastal and urban planning at local, national and regional scales is needed to reduce human impacts on vulnerable coastal areas. Research is required to generate knowledge-based solutions to support effective coastal management and protection of the existing seagrass habitats, including strenghened documentation the socio-economic and environmental services they provide. For PSIDS, protection of seagrass service benefits requires six priority actions: seagrass habitat mapping, regulation of coastal and upstream development, identification of specific threats at vulnerable locations, a critique of cost-effective restoration options, research devoted to seagrass studies and more explicit policy development.