Marine fish communities in the Yangtze River Estuary and Adjacent East China Sea (YRE-ECS) are subject to complex environmental gradients; however, their multidimensional assembly mechanisms remain insufficiently resolved. Here, we integrated environmental DNA (eDNA) metabarcoding, co-occurrence network analysis, and environmental profiling to examine fish community structure across vertical layers, hydrographic zones, and seasons. Vertically, surface communities dominated by pelagic-associated Perciformes and Clupeiformes showed more variable assembly patterns, whereas bottom communities enriched in Gobiiformes and Pleuronectiformes were more strongly associated with temperature and dissolved oxygen. Horizontally, among three zones delineated by salinity and hydrographic characteristics, the Mixed Transitional Water (MTW) supported the most diverse and interactive assemblages and functioned as an ecological connector between estuarine (EHSW) and offshore (OWSW) waters. Seasonally, community structure shifted markedly: spring communities exhibited higher diversity and denser trophic networks supported by zooplankton-rich, phototrophic plankton (e.g., Arthropoda, Bacillariophyta), whereas autumn communities were simpler, dominated by Chlorophyta and microbial taxa, with fish assemblages showing increased modularity and reliance on fewer planktonic groups. This seasonal pattern suggests a transition from diversified energy pathways to more constrained trophic coupling. βNTI and Mantel analyses jointly revealed a stratified environment-response-feedback framework driving community differentiation through combined stochastic and deterministic mechanisms. These findings highlight the importance of integrated spatial-temporal monitoring and suggest that protecting transitional zones and spring food-web integrity is critical for ecosystem resilience in the YRE-ECS.

For nearly two decades, the Yellow Sea has experienced recurrent green tides, which are now considered the largest of their kind globally; the mechanism behind these outbreaks remains highly complex and not fully understood. This study investigates the pre-outbreak distribution, abundance, and species composition of suspended macroalgae in the Southern Yellow Sea (SYS) during 2023–2024, along with environmental parameters. The results indicate that suspended macroalgae were predominantly distributed in the nearshore waters, particularly along the shallow beaches of northern Jiangsu. Furthermore, their abundance in the surface water layer significantly exceeded that in the bottom water. A total of 1353 and 493 algal filament samples were collected in 2023 and 2024, respectively. Dominant species included Ulva prolifera, Ulva linza, Ulva flexuosa, and Blidingia sp. Nutrient levels positively correlated with filament abundance. As a primary means of rapid proliferation for U. prolifera, suspended macroalgae contribute significantly to the initial expansion of green tides. Furthermore, their abundance holds promise as a biological indicator for forecasting the scale and extent of impending blooms, thereby providing a critical foundation for elucidating the underlying outbreak mechanisms.

Mass–balance discrepancies exist between estimated land-based inputs and observed marine plastic inventories. While current global mass–balance models predominantly treat the open ocean as a passive terminal sink, they overlook the rapid expansion of offshore and deep-sea industrial frontiers. This review identifies offshore and deep-sea activities as active, in situ emission nodes of microplastics (MPs). Through a bibliometric analysis and numerical descriptions of studies, we document that direct offshore emissions are underrepresented in the current literature. By synthesizing these limited quantitative data, preliminary metrics indicate localized MP enrichment signals and elevated biological exposure near specific offshore infrastructures. Furthermore, plastics released directly into the marine environment bypass terrestrial weathering, undergoing distinct multiscale aging pathways governed by the complex interplay of wave-induced physical fragmentation bounded by critical size thresholds, UV-driven chemical photo-oxidation, and biological interactions. We conclude that refining global plastic budgets supports moving toward an integrated ocean-industrial framework. However, the synthesis remains constrained by data scarcity and high methodological heterogeneity across different environmental matrices. Future strategies must prioritize standardized in situ flux quantification and the incorporation of MP emission risks into offshore Environmental Impact Assessments.

The Yangtze River Estuary is a highly dynamic river–sea transition zone in which freshwater discharge, tidal exchange, saltwater intrusion, plume dispersion, turbidity, and shallow-water habitat mosaics jointly shape fish assemblages. To provide a synoptic autumn baseline for this estuarine–coastal system, we analysed bottom-trawl survey data collected at 89 stations during October–November 2024 across three spatially defined sectors: the Yangtze River Estuary moratorium zone (EMZ), offshore waters outside the estuary mouth (OFF), and the northern waters of Hangzhou Bay (HB). Species composition, dominant taxa, catch density, catch per unit effort (CPUE), station-level alpha diversity, abundance–biomass comparison (ABC) curves, and Bray–Curtis-based multivariate structure were compared among sectors. A total of 71 fish species belonging to 12 orders and 29 families were recorded. Perciformes was the most species-rich order, and Collichthys lucidus was the only dominant species shared by all three sectors. The EMZ showed the highest abundance density (24.49 × 10³ ind./km²), biomass density (216.03 kg/km²), and mean CPUE (7.9 kg/h), whereas OFF had lower density values and the most negative ABC pattern. Station-level alpha diversity differed significantly among sectors (Kruskal–Wallis, all P < 0.001), with the EMZ showing the lowest diversity and evenness. Cluster analysis, NMDS, and PERMANOVA revealed statistically significant multivariate separation both within and among sectors. These results indicate that autumn fish assemblages in the Yangtze River Estuary and adjacent waters are strongly structured by spatial heterogeneity along the estuarine–offshore gradient. The higher fish density observed within the EMZ should be interpreted as a spatial ecological pattern of the inner estuary rather than as direct evidence of management effectiveness. The consistently negative ABC curves across all sectors further suggest that the assemblages remain dominated by small-bodied fishes, highlighting the need to evaluate density, size structure, and community composition jointly. This study provides an updated autumn reference for future monitoring and ecosystem-based management in the Yangtze estuarine–coastal system.

Amoya chusanensis and Wuhanlinigobius polylepis are endemic goby species (Gobiidae, Perciformes) in Chinese waters, with A. chusanensis occurring in the East China Sea and W. polylepis distributed in waters off Shanghai and Hainan. We applied mitochondrial COI gene sequencing to larval specimens collected from the Yangtze River estuary in August 2017, confirming species identity for both endemic gobies. This study presents the first detailed morphological descriptions of their larvae, supported by high-resolution photographic documentation, and compares their ontogenetic development with related gobiid species. Comparative analysis revealed that the melanin pigmentation pattern along the ventral body margin—extending from the anus to the posterior terminus of the notochord—exhibits species-specific characteristics and serves as a diagnostic criterion for larval identification. These findings establish a novel approach for early developmental research on endemic Chinese fishes and provide scientific basis for conservation strategies targeting their nursery grounds.