Red tide has always been an environmental issue with global concern. A Noctiluca scintillans red tide and a Mesodinium red tide occurred successively in Yantai nearshore, China, where is usually oligotrophic, in October 2019. Currents, phytoplankton community composition and nutrients were analyzed to access the driving factors of the red tides. The maximum N. scintillans and Mesodiniium abundance reached 124.92 ± 236.84 × 10³ cells/L and 1157.52 ± 1294.16 × 10³ cells/L respectively. The fast growth of N. scintillans was due to increasing abundance of phytoplankton. The currents were crucial to the assembly and dispersal of red tides. The red tides significantly redistributed the nutrients in the red tide patches and regulated the dominant species in phytoplankton community. Our study illuminates the influence of physical-biochemical coupling processes on red tides, and suggests that ocean dynamics such as currents and tidal factors deserve more attention when considering the ecosystem health problems of coastal zones.

Deposits of fluid mud on wave-dominated beaches are rare. Where they happen frequently and periodically, they can be associated with anthropic processes that bring fluid mud to the shoreface and surf zone. To determine the reason for the frequent deposition of fluid mud at Cassino Beach (Southern Brazil) in the 2014–2020 period, the La/Eu and Gd/Yb ratios in marine, beach, and adjacent Patos estuary sediments were investigated. Mud from the beach showed similar ratios of REE to dredged sediments from the harbor basin and navigation channel within the estuary. Industrial and port activity changes REE ratio in sediments of the navigation channel, and they are distinct from naturally deposited marine and estuarine sediments. We conclude that the mud deposition events at the beach are most likely associated with dredging processes in the estuary especially where overflow is the source of fluid mud on the beach shoreface.

The performance of three approaches for macrobenthic classification in distinguishing communities subjected to different environmental conditions was compared: i) the traditional species-based approach; ii) a tolerance-based approach according to ecological groups of the AMBI index; and iii) a character-based approach using biological traits. We used a hierarchical sampling design including three progressively smaller spatial scales, considering that the environmental degradation influence benthic communities at the larger spatial scale. Despite small-scale spatial variations, all approaches performed similarly, distinguishing eutrophic from non-eutrophic benthic communities as they varied significantly at the larger scale, corresponding to the scale at which human induced changes act. Our results suggest that all three methodological approaches could be used as operational criteria to assess estuarine environmental quality, and despite more meaningful, there is still a degree of subjectivity in functional approaches, associated to the lack of more detailed information on macrofaunal life-cycles and levels of tolerance to disturbance.

Microplastics (MPs) are present in fresh, brackish, or marine waters. Micro- and macroinvertebrates can mistake MPs or small microplastics (SMPs, <100 μm) to be food particles and easily ingest them according to the size of their mouthparts. SMPs may then block the passage of food through the intestinal tract (i.e. hepatopancreas), accumulate within the organism, and enter the food web. Pacific oysters (Crassostrea gigas) are allochthonous filter-feeding bivalve mollusks, which have been introduced in coastal seas around the world in both natural banks and farms. Considering their economic and ecological value, these bivalves have been chosen as a model to study the ingestion of SMPs. A novel method for the extraction and purification of SMPs in bivalves was developed. Quantification and simultaneous polymer identification of SMPs using Micro-FTIR (Fourier Transform Infrared Spectroscopy) were performed, with a limit of detection for the particle size of 5 μm.

We investigated the distribution of microplastics in the water column along a large remote estuarine system located between the Northern and Southern Patagonian Ice Fields in Chilean Patagonia, and connected with the Pacific Ocean through the Gulf of Penas. Microplastic particles were found in all samples, with abundances ranging from 0.1 to 7 particles/m³. Polymers identified were principally acrylics, PET, and cellophane. The average abundance of microplastics in surface waters was similar along the whole estuary (0.4 ± 0.3 particles/m³) with acrylics and epoxy resins being more abundant near Caleta Tortel, the only small village in the area. The observed higher abundance of microplastics in the deeper waters towards the Gulf of Penas points to intrusions of subsurface waters transporting plastic particles from the ocean into the channel system. This underlines the potential of ocean currents in transporting plastic pollution into pristine fjords and channels in Chilean Patagonia.

Nitrogen mineralization is a critical biogeochemical process that transfers organic nitrogen into inorganic forms using heterotrophic microorganisms. However, few studies have focused on this potential nutrient supplier. In this study, the composition of sediment organic nitrogen (SON) was studied, and nitrogen mineralization flux entering the water column was quantified. The results indicate that acid-hydrolyzable nitrogen (AHN) accounts for more than 40% of the SON, especially in the riverine input and marine aquaculture areas, which had significantly higher concentrations than the bay mouth area. Similar results were found for the ammonium nitrogen (AN), amino-sugar nitrogen (ASN), the total hydrolyzable amino acid (THAA), and unidentified hydrolyzable nitrogen (HUN). The mineralization rate in the marine aquaculture area was as high as 9.03 ± 1.33 mg·kg⁻¹·d⁻¹, while those of the riverine input (4.77 ± 1.55 mg·kg⁻¹·d⁻¹) and bay mouth (5.12 ± 1.42 mg·kg⁻¹·d⁻¹) areas were lower. The SON fractions, including the AHN, AN, ASN, and AAN, could obviously affect the mineralization of the SON. However, the extracellular enzymes, including proteinase and urease, are the predominant factors controlling the SON mineralization process. Anthropogenic activities, including riverine input and marine aquaculture, exert significant influences on the fractions and mineralization of the SON, and thus, they may increase the amount of dissolved inorganic nitrogen in the bottom of the water column in Daya Bay.

The metal detoxification mechanism is essential for the accumulation activity of some polychaetes. In order to investigate the detoxification function of metalloprotein II in polychaete Perinereis aibuhitensis, a recombinant fusion protein of MP II was successfully expressed in vitro and an anti-MP II polyclonal antibody was got. The tissue distribution of MP II in P. aibuhitensis and the protein expression under Cd, Pb and Zn exposure were detected by ELISA with this antibody. The results showed that MP II was higher in the intestine of P. aibuhitensis, followed by the body wall and parapodium. Cd, Zn and Pb exposure can induced MP II expression, but the change trend of MP II under various heavy metal exposure was different. The amount of MP II induced in P. aibuhitensis increased with the rises of Cd concentration, but there is no significant relationship between Zn and Pb concentration and MP II level.

In this study, transport and possible accumulation of microplastic marine litter in enclosed coastal waters are modeled numerically. The model is applied to the Fethiye Inner Bay, located in Fethiye-Göcek Specially Protected Area. In modeling studies, three dimensional coastal hydrodynamics, transport and water quality numerical model HYDROTAM-3D was used. The current climate was prepared by modeling long-term circulation patterns due to wind, wave and density stratifications. Following the hydrodynamic studies, the advection and diffusion of 3 mm size polystyrene particles by the coastal currents in the surface waters of Fethiye Inner Bay were simulated. The coastal regions where the microplastic pollution will be concentrated and transported were determined by the modeling scenarios. It has been found that microplastic accumulation is expected in the southwest and east coastal waters of the Fethiye Inner Bay. The results of the model will contribute to the databases for sustainable protection of the marine environments.

For much of the 20th century, the Mersey in North West England was one of the worst polluted estuaries in Europe. Water from a range of polluting industries plus domestic sewage was discharged into the Mersey Catchment and Estuary. Recovery came through a concerted clean-up campaign and tightening environmental regulations, partly driven by European Commission Directives, coupled with de-industrialisation from the 1970s onward. Recovery of oxygen levels in the Estuary led to the return of a productive ecosystem. This led to conservation designations, but also concerns about transfer of pollutants to higher trophic levels in fish, birds and humans. As part of urban renewal, ecosystems in disused dock basins were restored using mussel biofiltration and artificial de-stratification, facilitating commercial redevelopment and creation of a tourist destination. The degradation and recovery of the Mersey from peak-pollution in the mid-20th century is put in the context of wider environmental change and briefly compared to other systems to develop a hysteresis model of degradation and recovery, often to novel ecosystems.

Micro-plastics (MPs) are an environmental threat that has been gaining importance lately with an increasing number of studies demonstrating that they are a larger threat than previously thought. Scientists around the world have used a wide number of methods in their studies and they have adapted changes in response to the specific nature of the research undertaken. This article provides an account of the historical development of the MP menace, development of methods and tools used in MP research and also describes the challenges that are faced to further advancement to take place. The article is categorized into various sections that include history, sources, isolation, extraction, and characterization of MPs. Among the thermal characterization techniques, direct pyrolysis mass spectrometry and secondary ion mass spectrometry, which are widely used to characterize the plastics, but not utilised so far in this field are also highlighted for future direction.