We report the ratios of minor (K/Ca, Na/Ca, P/Ca, S/Ca) and trace elements (Al/Ca, Ba/Ca, Fe/Ca, Mn/Ca and Zn/Ca) in skeletons of five Arctic echinoderm species representing three classes: Asteroidea, Ophiuroidea, Crinoidea. We found that skeletons of Arctic echinoderms show a unique, species-specific trace element composition that may suggest that incorporation of elements into the skeleton is biologically controlled by the organism. On the other hand, the concentration of some minor elements in skeletal parts exhibit patterns that are consistent with elemental concentrations in seawater, indicating that formation of echinoderm skeletons is environmentally controlled. Seawater is the main source of ions and compounds needed for skeletal formation and maintaining similar concentrations most likely reduces the biological cost related to selective uptake of ions. Additionally, Al, Ba, Fe, Mg and Mn showed station specific variation in elemental concentration which again suggests that accumulation of metals can be shaped by environmental concentrations.

There are limited litter and microplastic (MP) studies in the Philippines despite the fact that is has one of the longest shorelines that is possibly threatened by waste disposal. This study was carried out to determine the litter and MP in surface sand samples in a highly urbanized coastal environment of Cagayan de Oro in Macajalar Bay, Philippines. The flotation and stereomicroscope identification methods were employed to study MP, while litters were counted to extrapolate the clean coast index (CCI). Overall, MP fibers were found ubiquitously with site-specific abundance. Particularly, the residential site adjacent to the river mouth had the highest litter and MP fiber counts. The built environment like the seaport showed fragmented forms of MP. Likewise, CCI analysis showed an extremely dirty beachfront (CCI = 85) which mainly caused by plastic litters. Overall, the highly urbanized coastal environment may accumulate a distinct form of plastics. This study is preliminary and may underestimate plastic analysis owing to the limited sampling.

The study aimed to explore ontogenetic dietary changes and microplastic ingestion in Chelon richardsonii associated with diatom Anaulus australis accumulations in a warm temperate South African surf zone. This species is commercially important and forms an important trophic link in southern African coastal waters. Postflexion larvae, juveniles and adults are dominant in surf zones and were used for comparison. Index of Relative Importance (%IRI) results showed an ontogenetic dietary shift, with postflexion larvae ingesting mostly copepods (%IRI = 52.0) and microplastic fibres (%IRI = 30.7); while older developmental stages fed predominantly on diatoms (%IRI ranging from 53.9 to 65.6) and sand (%IRI ranging from 34.2 to 46.0). Microplastic fibres were found in 40% of fish sampled, microplastic fragments in 5%, and both types were recorded across all developmental stages assessed. This study provides the first record of microplastics in C. richardsonii, adding to growing microplastic research in fishes.

Heavy metal pollution arising from agricultural and industrial activities poses a significant threat to the aquatic environment, especially the increasing levels of chromium (Cr) that is exacerbating marine pollution. Given the economic importance of the Pacific white shrimp Litopenaeus vannamei (L. vannamei), understanding the impact of marine Cr pollution is deemed to be significant. In this study, we used the transcriptome sequencing (RNA-seq) technique to characterize the molecular mechanism of Cr exposure in L. vannamei. Gene ontology enrichment analysis showed substrate-specific and ion transport-related functions were mainly influenced by Cr exposure. We further identified genes involved in protein digestion and absorption (PEPT1, BAT1, MDU1), chemical carcinogenesis (GST and UGTs), ABC transporters (ABCC2), apoptosis (CAPN1, CASP10, PARP), implying the potentially Cr disintoxication mechanisms in L. vannamei. Genes within pancreatic secretion (ALT, LDH), lysosome (CTSL and HEXB), and peroxisome (ACOX1, ECI2, NUDT12) pathways implied the potentially Cr toxicity mechanisms in L. vannamei.

A combination of idealised modelling and satellite imagery has been used to assess the dispersal of estuarine plume water and suspended material throughout the ecologically significant marine area off the west coast of the central North Island, New Zealand. The idealised modelling was used to elucidate the relative importance of oceanographic and meteorological conditions in controlling the horizontal structure of the estuary plumes, and then compared to plumes visible in satellite imagery and environmental monitoring data. Under low to average river flows the plumes can be categorised as either non-rotational or rotational. Rotational plumes are directed southwards under light (<5 m/s SW or <10 m/s E) winds and northwards under stronger (>5 m/s SW) winds. Non-rotational plumes remain close to the estuary mouth. The type, orientation and extent of the plumes have implications for estuarine flushing and for the dispersal of land-derived contaminants into the marine environment.

The global decline of reef corals has been driven largely by several marine heatwaves. This has greatly reduced coral cover but has reduced coral diversity also. While there is a lack of data in most locations to detect coral species losses, reefs of the Chagos Archipelago, central Indian Ocean, have long term monitoring data extending back to the late 1970s. Severe declines in cover have occurred since the 1970s, with regional extinctions of some species and key species assemblages. There is a severe decline in coral settlement, along with a substantial loss of habitat quality which has reduced the habitat available for settlement. This is a clear precursor to positive feedback. Regional species extinctions here occur mainly when total coral cover is <10% of pre-warming levels. Climate models predict more frequent and more severe marine heatwaves, and even if this ecosystem recovers it will contain fewer species.

This study investigates the mean concentration and characteristics of macroplastics (>2.5 cm), mesoplastics (5 mm - 2.5 cm) and microplastics (<5 mm) on eight sandy beaches along the shoreline of Tuticorin, Tamil Nadu. Prevalence of plastic litters varies among the study sites depending on the intensity of fishing and other human activities. Mean concentrations of macroplastics (1.38 ± 78 to 6.16 ± 94 items/m²), mesoplastics (2 ± 0.8 to 17 ± 0.11 items/m²) and microplastics (25 ± 1.58 to 83 ± 49 items/m²) were estimated in respect of the polymers composing them namely PE, PP, PET, NY, PS and PVC, of which PE is the most predominant polymer. At Sites 1, 2, 3, 5 and 8 there is correlation between the intensity of fishing activity and the concentrations of macro- (p = 0.02) and microplastics (p = 0.03). Sites 4, 6 and 7 there is correlation established between the degree of recreational activity and the concentrations of meso- (p = 0.02) and microplastics (p = 0.01).

Iron is recognized as an efficient method to alleviate sulfide stress. This study tested the response of Zostera marina plants to different levels of sedimentary sulfides (100.0–818.7 μmol L⁻¹) and iron inputs (590.0–825.3 μg L⁻¹) in a field experiment performed over an eighty-day period. We measured plant responses in terms of shoot density and plant morphology and productivity. The relationship between the propagation effort (PE, in %) and sulfide content (S, in μmol L⁻¹) was expressed as: PE = −14.01 × ln (S) + 86.86 (R² = 0.99, p < .01), which indicates that the toxic limit of the pore-water sulfide concentration for the survival of eelgrass is 493 μmol L⁻¹. The addition of iron can reduce the toxicity of sulfides to eelgrass beds, resulting in an increase in plant density and productivity, and can even reverse the decline of eelgrass beds exposed to high sulfide concentrations.

This review represents a comprehensive analysis on pollutants in elasmobranchs including meta-analysis on the most studied pollutants: mercury, cadmium, PCBs and DDTs, in muscle and liver tissue. Elasmobranchs are particularly vulnerable to pollutant exposure which may pose a risk to the organism as well as humans that consume elasmobranch products. The highest concentrations of pollutants were found in sharks occupying top trophic levels (Carcharhiniformes and Lamniformes). A human health risk assessment identified that children and adults consuming shark once a week are exposed to over three times more mercury than is recommended by the US EPA. This poses a risk to local fishing communities and international consumers of shark-based products, as well as those subject to the widespread mislabelling of elasmobranch products. Wider screening studies are recommended to determine the risk to elasmobranchs from emerging pollutants and more robust studies are recommended to assess the risks to human health.

Understanding the faunal community structure in the estuary would be crucial in assessing the health of the ecosystem. The poor visibility in the estuarine area due to the outflow from the Pearl River hinders the conventional visual census in assessing the megafaunal biodiversity. In this study, the fish and crustacean biodiversity of Hong Kong's western waters, i.e. the outer maritime estuary of the PRD, were studied through the metabarcoding of environmental DNA (eDNA). eDNA from the seawater and sediment samples was extracted from five sites in the region. After testing the performance of two genetic markers, amplicons of the cytochrome oxidase I, amplified by polymerase chain reaction, were subjected to Illumina high-throughput sequencing (MiSeq) analysis. A total of 22 fish species from 17 families and 34 crustacean species from 27 families were identified by blasting the sequences against the NCBI GenBank database, demonstrating segregation between samples from different sites. This study provides insight on the detail distribution of fish assembly in PRD, when compared with a previous eDNA study in the inner brackish PRD.