Rare earth elements (REEs) are increasingly recognised as emerging contaminants, yet their transfer from sediment and water to biota remains poorly understood in coastal marine systems characterised by shallow-water hydrothermal vents. These vents release REEs at concentrations approaching those of anthropogenically impacted sites, providing a natural laboratory to investigate their transfer to marine biota. REE distribution and sediment-to-biota transfer were characterised along the pH gradient of the shallow CO2-vent system of Levante Bay (Vulcano Island, southern Tyrrhenian, Italy), combining sediment analyses with those of three co-occurring, functionally distinct organisms representing complementary exposure pathways: the seagrass Cymodocea nodosa, the sea anemone Anemonia viridis, and the benthic goby Gobius incognitus. REE concentrations decreased overall along the sequence: sediment > C. nodosa > G. incognitus > A. viridis. Biota-Sediment Accumulation Factor (BSAF) values were below unity in all matrices at both areas, indicating limited transfer despite hydrothermal enrichment. Post-Archean Australian Shale (PAAS) normalised REE patterns, diagnostic anomalies and multivariate ordination revealed three distinct biotic signatures in species sharing the same hydrothermally enriched environment: a sediment-like, light REE-enriched profile in A. viridis; a relatively heavy REE-enriched, biologically fractionated profile in C. nodosa; and a low, dispersive profile in G. incognitus. The latter was the only matrix showing higher BSAF at both low-pH sites, possibly reflecting the dietary pathway. Differences in REE accumulation among matrices exceeded those between the two pH conditions. These results indicate that co-occurring species exhibit distinct REE signatures and that the choice of bioindicator embeds a specific exposure pathway.
Walleye pollock and Pacific cod are cold-water semi-demersal species with similar life histories; however, their long-term catch trends have diverged since the late 1980s along their southern distribution limits in Korea and Japan. This study examined how warming-driven water-column changes differentially affect these species with contrasting spawning strategies (pelagic eggs: pollock; demersal eggs: cod). Using data from 1982 to 2023, spawning-season water-column structure, early life-stage thermal habitat suitability index (HSI), and habitat suitable depth (HSD; HSI ≥ 0.6) were compared with catches across three regional groups (A: Korean East/Japan Sea coast; B: Japanese East/Japan Sea coast; C: Japanese Pacific coast), and lead–lag relationships were assessed by cross-correlation function (CCF) analysis of detrended time series. Surface temperatures increased in all groups under Kuroshio-origin warm currents (A: East Korea Warm Current; B: Tsushima Warm Current; C: Kuroshio Extension), whereas bottom thermal conditions differed depending on regional cold-water masses. Pollock catches declined sharply in all groups after the late 1980s without recovery, even where surface HSI remained suitable. In Group A, pollock HSI declined or remained low in sub-regions, whereas suitable cod habitat persisted and catches increased. In parts of Groups B and C, cod catches declined after the early 2010s; HSD deepened in Group B and was negatively associated with catch five years later in B-1 (r = −0.72, p < 0.001), whereas HSD–catch relationships varied among Group C sub-regions. Contrasting spawning strategies therefore expose early life stages to different water-column layers, whereas catch responses depend on regional oceanographic conditions.
Body size is a fundamental ecological trait that integrates growth condition, size structure, and population response to environmental change. Using fishery-independent surveys conducted in the Yellow Sea and adjacent waters during 2000–2025, we quantified seasonal, interannual, and decadal variation in mantle length and body weight of the Japanese flying squid (Todarodes pacificus), and evaluated the roles of sea surface temperature (SST) and latitude. Mantle-length distributions differed significantly among seasons and among decadal groups (Holm-adjusted pairwise Kolmogorov–Smirnov tests), with a shift in the observed mantle-length distribution toward smaller individuals in the most recent period, particularly in summer and autumn. A linear model based on mean mantle length indicated a positive SST correlation and a significant SST × decade interaction, implying decade-specific SST–size relationships. Bayesian hierarchical models revealed the allometric exponent (b) was highest in the earliest decade and lower thereafter, indicating temporal variation in weight-at-length. Model comparison using leave-one-out cross-validation indicated that SST contributed to predictive performance of body-weight variation, while spatial predictions highlighted geographic heterogeneity, with higher predicted body weight concentrated in the southeastern part of the study area. Together, these results demonstrate that size metrics from long-term surveys provide sensitive indicators of changes in body-size and weight-at-length patterns of short-lived cephalopods, and underscore the importance of accounting for non-stationary environment-size relationships.
Benthic organisms can act as bioindicators of microplastic pollution in aquatic environments by enabling a time-integrated assessment of the ambient particles suspended in the water column. We employ a geostatistical approach using data of microplastics concentrations found in tissue of the barnacles and benthic fauna collected by Xu et al. (2020a, 2020b) to estimate the spatial extent of marine microplastics pollution in Hong Kong. This paper therefore uses data from two previously published studies and no new samples were collected or new experiments conducted. Regional pollution maps are generated which demonstrate the highest marine microplastics levels occur in the northeast bays and regions adjacent to the Pearl River Delta, indicating terrestrial pollution as a source. We conclude that some classes of benthic fauna and in particular barnacles and gastropods, may provide a pragmatic tool to assist with pollution assessments that are based on contamination levels measured in the environment, which are typically transient.
Anthropogenic noise is a well-recognized stressor in the marine environment. Seismic airguns, used to locate oil and gas deposits in the seabed, are among the loudest sources of anthropogenic noise in the North Sea. Their low-frequency sounds overlap with the hearing and vocalisations range of many teleost fishes. Cod (Gadus morhua) produce sounds both during courtship and male-male aggression, and seismic surveys may therefore interfere spawning behaviour. In large spawning pens, we exposed spawning groups of wild caught cod to three hours of daily seismic shooting at varying distances to mimic what fish would be exposed to during a real seismic survey. We examined both short-term (minutes before and after individual air gun shots)) and long-term responses (hours to days, before, during and after the full exposure period) on spawning behaviour. Short-term effects included startle responses, reduction in courtship behaviours, and increased activity in female fish, but no significant effect on vocalisation. The only long-term effect was a significant reduction of flaunting behaviour, while all other reproductive behaviours were resumed quickly after exposure. In conclusion, our study shows that seismic shooting, at levels up to ~165 dB re 1μPa2s (similar to levels found about 5–35 km from a conventional survey) may affect cod courtship behaviour at each onset, within a time frame of minutes from the first close by shot, but not over subsequent hours or days.
