Marine debris, in particular plastic debris and debris related to fishing activities, have an impact on marine mammals and seabirds. In marine-coastal species such as otariids, we can detect the incidence of these interactions through land-based observations. In this study, we recorded and described interactions between marine debris and the otariids Arctocephalus australis and Otaria byronia in a natural protected area in Peru, according to age class categories. Between 2016 and 2020, we recorded 151 animals that were directly impacted and/or were observed interacting with marine debris. Residual collars from fishing gear, ropes, plastic bags and unidentified material were recorded. Direct interactions with debris at colonies (e.g., plastic bags) were also recorded, as well as animals evidenced interacting with hooks. The age class category and species with the highest number of individuals impacted by residual collars were adult female A. australis and subadult male O. byronia. Single-use plastics were the most commonly bitten/moved waste by animals in the reserve. In the case of hooks, these were mostly lodged in the mouths of otariids. Our results highlight the importance of continuing to promote segregation at source, as well as the correct disposal of waste, locally and globally, to mitigate impacts on marine fauna.

The Karnaphuli River is one of the prime and most important streams in the southeastern part of Bangladesh. The favorable water current and the geographic location have rendered the Karnaphuly River estuary a suitable habitat and a breeding ground for diverse fish species. Reversely, this estuary has been polluted by discharges from many point and non-point sources due to its location in the catchment area of a heavily industrialized area, Chattagram port city. However, published research concerning the status of toxic and trace elements in some commercially important benthic and pelagic coastal fish species in Karnaphuli River estuary was not found in the existing literature. Therefore, it's an important field of study on the assessment of toxic and trace elements concentration in the commercially important benthic and pelagic coastal fish species and their health taxation in the Karnaphuli River Estuary. Energy dispersive X-ray fluorescence (ED-XRF) was used to quantify trace metal concentration in edible parts of the fish species. This study revealed that the rank of the trace metals concentration was as follows (mg/kg): Zn (37.1) > Mn (16.12) > V (11.16) > Cu (9.49) > Rb (5.62) > Pb (2.98) > Cr (1.59) > Co (1.17). The F-test showed that a significant difference at 95 % confidence level in the distribution pattern of trace metals concentration among the examined fish species in the study area. The metal pollution index (MPI) in the muscle of fishes were found to be in the following order: L. bata > P. monodon > T. cirratus > M. bleekeri > O. pabda > H. nehereus > L. calcarifer > P. argenteus > P. paradiseus > T. toli, and the MPIs for most of the benthic fish species were higher compared to the pelagic fishes. On the other hand, the examined fish species were significantly bio-accumulative with the highest bio-accumulation factor value for benthic species. The multivariate analysis identified that the sources of the trace metals were associated with anthropogenic activities. For the human health risk assessment concern, estimated daily intake, target hazard quotient and cancer-causing risk were estimated. The results for non-cancer hazardous index values were found to be lower than unity. On the other hand, the total cancer risk data ranging from 1.24E−05 to 1.70E−05 were fallen within the range for the threshold values (1.0E−06 to 1.0E−04). However, considering the suggested values set by the environmental and regulatory agencies, it has been recommended that no significant non-carcinogenic and cancer-causing health risk for humans was seen due to the consumption of the studied fish species.

There is scarce information on the current importance of oyster beds as fishing grounds in the United Arab Emirates (UAE). This study aims to understand the socio-economic value of oyster bed fisheries through questionnaire-based surveys with fishers. Of 106 Emirati fishers interviewed, 67 % use oyster beds due to the proximity to shore, better catch quality, and species abundance. Oyster bed fisheries are recreational and commercial, with handline and fish traps the most common used gears. They provide food for local consumption and cash income. All respondents noticed a fish abundance and size decrease throughout the last decade. Fishers suggest establishing marine protected areas and updating fishing regulations to improve fishing stock status. During the Covid-19 pandemic, oyster fisheries increased, highlighting the value of these fishing grounds for food availability. These fisheries support the local economy and heritage, and urgently need management to ensure the protection of these often-overlooked habitats.

The dynamics of contaminants, such as mercury (Hg), in marine trophic webs is a critical topic in the scientific community due to the high concentrations encountered in organisms. In this study we attempted to provide information on total Hg accumulation patterns and possible pathways of trophic transfers assessed in combination with δ¹³C and δ¹⁵N to understand how this contaminant permeates three sub-Antarctic food webs: the Beagle Channel (BC), the Atlantic coast of Tierra del Fuego (AC-TDF) and Burdwood Bank (BB). We found a site-specific pattern of Hg transfer and biomagnification processes, while the oceanic BB showed major Hg transfer through the pelagic domain, coastal sectors (BC and AC-TDF) indicate a general biodilution process but with Hg concentrations incrementing with the benthivory grade. This represents a dissimilar Hg bioavailability for marine consumers that rely on different diet and forage in different habitats, and may become an issue of important conservation concern for these southern areas.

Sewage is one of the biggest contributors to coastal pollution. The study was aimed to assess the impact of sewage on coastal water quality of Kanyakumari, the southernmost part of India. A bacteriological survey was made on distribution and abundance of fecal indicators and human pathogenic bacteria and seasonal influence on the bacterial load and antibiotic resistance of the isolates. Samples were collected from sewage discharge point along the eastern shore of Kanyakumari Coast from February 2019 to January 2020. Nine pollution indicator bacteria and pathogenic species such as Escherichia coli, Klebsiella spp., Enterococcus faecalis, Aeromonas spp., Proteus mirabilis, Salmonella typhi, Vibrio cholerae, Shigella spp. and Flavobacterium spp. were isolated from the samples. These isolates were tested against 10 antibiotics, using Kirby Bauer method. All the isolates were resistant to at least two antibiotics. The presence of antibiotic resistant bacteria has been used as bio-indicators of pollution. Hence it is clear that the domestic sewage entering the coast is untreated which might lead a serious impact on human and marine wildlife along coastlines.

Metal concentrations were concurrently quantified in seawater, phytoplankton, and zooplankton from a heavily impacted coast of southern Taiwan. Combined size and density fractionation were used to accurately quantify metal concentrations in phytoplankton. Cr, Co, Ni, Cu, As, and Pb were analyzed using an inductively coupled plasma mass spectrometer (ICP-MS). As expected, metals significantly increased with an order of seawater < phytoplankton < zooplankton (p < 0.05); but did not differ between estuarine, nearshore, and offshore sites (p > 0.05). Metals were higher along Kaohsiung Harbor and marine outfall diffusion sites, highlighting their major impacts on plankton metal contamination. Notably, phytoplankton (Cr BCF > 100; half of the sites) significantly accumulated more metals contrary to zooplankton (BAF < 10). Metal concentrations and bioaccumulation factors between phytoplankton and zooplankton showed significant negative correlations. This demonstrates a non-proportional distribution and bioaccumulation of metals in phytoplankton and zooplankton—corroborating laboratory findings on zooplankton ability to control metals, irrespective of significantly high bioaccumulation in phytoplankton.

Ecosystem based water quality models are important tools for prognostic site assessment and evaluation of ecosystem-performance of marine fish farms. We present the development and application of a comprehensive Fish Culture Zone Water Quality Model using continuous bi-weekly field data over a six-year period (2012–2017). The model simulates five interacting subsystems: phytoplankton, phosphorus and nitrogen cycles, and the dissolved oxygen (DO) and particulate organic carbon balance. The application of the model to two fish culture zones in Hong Kong shows the model captures the trends of nutrient and DO variation and the performance in quantitative prediction of algal biomass is challenging. The effect of errors in the specification of primary model inputs are evaluated using dimensionless sensitivity coefficients based on First Order Variance Analysis reveals the relative importance of fish stock (loading), physical size (volume), tidal flushing rate and boundary conditions in the prediction of key water quality variables.

Cadmium (Cd) is a highly toxic metal, regularly monitored uniformly for water quality across Europe, but scarcely for sediments. This study was designed to compare the kinetics of Cd remobilization and the amplitude of its transfers with different marine sediments. The results showed a highly reproducible transfer kinetics. Dissolved Cd was strongly and quickly removed from the dissolved phase (from 5 min up to 7 h). Then, the dissolved Cd concentration increased progressively to reach a maximal value after two weeks of mixing. The influence of the resuspension intensity representing light wind-induced resuspension up to dredging operations was observed after 2 weeks. The intensity of the sediment resuspension clearly impacted the amplitude of Cd remobilization, dissolved Cd ranging from a few ngL⁻¹ to few hundreds of ngL⁻¹, exceeding the maximal dissolved Cd concentration accepted by the European Union Water Framework Directive (WFD-2008/105 32/EC).

The evolution of the bottom water in Amvrakikos Gulf in Ionian Sea at western Greece for a 50-year timespan was assessed by benthic foraminifera assemblages. The degradation of the bottom water of Amvrakikos has been a catalyst for the surface water degradation. The east basin has shown permanent low environmental quality in bottom waters since 1980, while the west basin has been under seasonal hypoxic regime since 2000. The most adverse environmental conditions occurred in 1990–2000 and 2005–2010 coinciding with the recorded fish mortality events. The major cause of the environmental quality improvement of the bottom water is the intrusion of seawater. In western areas of the gulf, where the influence of the seawater is high, the decreased temperature improves the environmental conditions, while in the areas influenced by river discharges (east and northern), the environmental conditions are depended on multiple causes like organic matter input and surface salinity.