Four cruises in the Bohai Sea and northern Yellow Sea off Yantai, China, in April and August of 2020, collected data on the species composition and community structure characteristics of macrobenthos in these sea areas. Temporal and spatial changes in the dominant macrobenthic species between April and August were also analyzed. The M-AMBI and environmental data were used to assess the benthic ecological quality of the coastal waters off Yantai. The results revealed differences in macrobenthic community structure and ecological quality status between the two sea areas. The main findings are as follows: A total of 7 phyla and 153 macrobenthic species were collected; 113 and 101 species were recorded in the Bohai Sea and northern Yellow Sea areas, respectively, and estimated abundance was 301 ind. m^-2 and 598 ind. m^-2 (p < 0.01), and biomass was 10.20 g m^-2 and 14.65 g m^-2, respectively. The dominant species comprised small-sized polychaetes and bivalves. The main dominant species were Glycinde bonhourei, Micronephthys oligobranchia, Sternaspis chinensis, and Moerella hilaris. The number of species differed significantly between seasons (p < 0.05). A comparison of the dominant species and community structure of the macrobenthos between seasons showed that more obvious replacement occurred in the Bohai Sea. There were major differences in community structure of the macrobenthos between the two areas. Macrobenthos abundance was positively correlated with depth, dissolved oxygen, and sand substrate, and negatively correlated with bottom-water temperature, pH, and fine silt or clay substrate. In April, sites with low ecological value were at the ports of Laizhou and Longkou and Yangma Island, with the water quality likely affected by intensive bivalve aquaculture, port activities, and river discharge; in August, low-ecological-value sites were the middle of Laizhou Bay, Longkou Port, west of Daheishan Island, and coastal water between the cities of Yantai and Weihai. Overall, the sea areas off Yantai were generally deemed to be in a “good” state of ecological quality.

Fisheries and bottom seawater data were collected in July in 2022 and 2023 from 15 sampling stations in the Huanghe River estuary and adjacent seas in China. The patterns of functional alpha and beta diversity of fish communities in this area and their relationships with environmental factors were studied using trait-based analysis. Five functional classifications, which included 16 functional traits, four functional alpha diversity indices (functional richness, functional evenness, functional divergence, and community-weighted mean), three functional beta diversity indices (functional beta diversity and its turnover and nestedness components), and 14 bottom environmental factors were considered. The dominant traits of fish communities were the following: benthivorous feeding habits, small and front-facing mouths, high trophic level, demersal, anguilliform, low growth coefficient, medium resilience, low vulnerability, and adapted to warm temperate conditions. The dominant migration traits and types of fish eggs varied by year, and fish abundance was the main factor affecting the dominant traits of the communities. The results of multiple regression on distance matrices and variance partitioning analysis indicated that ammonia nitrogen content, total phosphorus content, and pH were the main environmental factors that affected fish functional diversity. The N/P ratio had a bottom-up control effect on fish functional diversity. Our findings also revealed that high pH gradients and distant geographical distances can inhibit trait turnover in fish communities.

The coastal waters of the northern Shandong Peninsula have abundant fishery resources, which serve as a critical transitional fishing ground for economic fish migrating into the Bohai Sea for spawning and departing for overwintering habitats. However, anthropogenic pressures such as garbage dumping have led to severe degradation of local fishery resources and concomitant adverse effects on zooplankton communities. To assess these impacts, we analyzed the spatiotemporal distribution, community structure, dominant species, and diversity indices of zooplankton based on sampling data collected in spring from 2015 to 2018 in this region. A total of 24 zooplankton species and 11 larval classes were identified, with the highest species richness observed in 2016. Calanus sinicus and Centropages abdominalis were the primary dominant species, with C. sinicus consistently predominant across all four years. Notably, the dominant species exhibited marked annual variability. The abundance and biomass of zooplankton in the surveyed area exhibited significant annual variations, both showing a trend of first decreasing and then increasing. Peak abundance occurred in 2015 (594.36 ind/m³), while the lowest was recorded in 2017 (118.73 ind/m³). Spatially, abundance and biomass were heterogeneous, with coastal waters exhibiting higher concentrations than offshore areas. The overall low level of community diversity and its significant annual variations indicated that the zooplankton community structure in the surveyed sea area was unstable and showed a trend of degenerative succession. The community structure of zooplankton and larger-bodied dominant species showed stronger correlations with phytoplankton dynamics, whereas smaller-bodied species were more influenced by water temperature.

Fisheries and bottom seawater data were collected in July in 2022 and 2023 from 15 sampling stations in the Huanghe River Estuary and adjacent seas in China. The patterns of functional alpha- and beta-diversity of fish communities in this area and their relationship with environmental factors were studied using trait-based analysis. Five functional classifications, which included 16 functional traits, four functional alpha-diversity indices (functional richness, functional evenness, functional divergence, and community-weighted mean), three functional beta-diversity indices (functional beta-diversity and its turnover and nestedness components), and 14 bottom environmental factors were considered. The dominant traits of fish communities were: benthivorous feeding habits, small and front-facing mouths, high trophic level, demersal, anguilliform, low growth coefficient, medium resilience, low vulnerability, and adapted to warm temperate conditions. The dominant migration traits and types of fish eggs varied by year, and fish abundance was the main factor affecting the dominant traits of the communities. The results of multiple regression on distance matrices and variance partitioning analysis indicated that ammonia nitrogen content, total phosphorus content, and pH were the main environmental factors that affected fish functional diversity. The N/P ratio had an upward control effect on fish functional diversity. Our findings also revealed that high pH gradients and distant geographical distances can inhibit trait turnover in fish communities.