Macrobenthos is widely used as an indicator of ecological health in marine monitoring and assessment. The present study aimed to characterize the interrelationships between the distribution of the macrobenthos community and environmental factors near Xiaoqing Estuary, Laizhou Bay. Responses of species richness to environmental factors were studied using the generalized additive model (GAM) and the Margalef diversity index (d_M) as indicators of species diversity instead of individual indicator species. Six factors were selected in the optimal model by stepwise regression: sediment factors (organic matter, phosphate, nitrate nitrogen, and ammonium nitrogen) and water factors (salinity, and ammonium nitrogen). The response curves generated by the GAM showed a unimodal relationship among taxa diversity, salinity in water, and sediment organic matter. d_M was positively correlated with ammonium nitrogen in water and was negatively correlated with phosphate in the sediment. The model optimized by forward stepwise optimization explained 92.6% of the Margalef diversity index with a small residual (2.67). The model showed good performance, with the measured d_M strongly correlated with the predicted d_M (Pearson R² = 0.845, p < 0.05). The current study examined the combined influence of multiple eco-factors on macrobenthos, and the Margalef diversity index of macrobenthos was predicted by the GAM model in a salinity-stressed estuary.

In order to examine the seasonal variations in the morphological characteristics and diet of Mactra veneriformis in the Northern Yellow River Delta’s intertidal zone and provide a scientific basis for its resource conservation and population restoration, tested clams were collected in four consecutive seasons from summer of 2022 to spring of 2023. Morphological traits were measured, and the DNA of the stomach contents was analyzed using high-throughput sequencing. The tidal differences and seasonal variations in the northern habitat of the Yellow River Estuary significantly affect the morphological characteristics and growth of M. veneriformis. Among the four seasons, significant differences in the morphological characteristics of M. veneriformis were observed between the middle-tide and low-tide zones (p < 0.05). In both middle-tide and low-tide zones, the morphological characteristics and body wet weight of M. veneriformis in winter were significantly higher than those in other seasons (p < 0.05). Moreover, the morphological characteristics of M. veneriformis were extremely significantly influenced by the interaction between tide and season (two-way interaction, p < 0.001). In all seasons, M. veneriformis in the middle- and low-tide zones exhibited positive allometric growth. While there was no significant difference in the stomach content between the spring and summer samples in the same tidal zone (p > 0.05), there was a significant difference between the middle- and low-tide samples in winter (p < 0.05). This suggests that seasonal variations, rather than tidal differences, had a larger impact on the diet of M. veneriformis in the northern Yellow River estuary and that feeding differences may be related to changes in environmental factors, such as temperature. The findings of this study provide initial insights into the feeding ecology of M. veneriformis and offer a scientific foundation for the conservation and management of its resources.

Natural recruitment of Manila clam (Ruditapes philippinarum) often persists in degraded estuaries, yet the environmental thresholds enabling this resilience remain quantitatively undefined. We employed binomial generalized additive model (GAM) coupled with field surveys (n = 168) in the Xiaoqing River estuary (Laizhou Bay, China) to identify critical limits for adult occurrence, which served as a field-based proxy for recruitment potential. Sediment median grain size (D₅₀), salinity (Sal) and dissolved inorganic nitrogen (DIN) were identified as the key factors, collectively explaining 79.30% of the deviance (AUC = 0.98). The probability of occurrence decreased sharply beyond two distinct thresholds: D₅₀ > 95 μm and salinity < 17.50‰. While DIN had a positive effect, it did not offset the strong negative associations with coarse sediment or low salinity. These field-validated thresholds provide quantifiable criteria to guide habitat suitability mapping, activation of early-warning systems against salinity-driven mortality, and site prioritization for ecological restoration in the Xiaoqing River estuary. Our findings offer a framework for developing management strategies to support clam resilience under environmental stress.

Marine ranching is a crucial component of the “blue granary” strategy. Evaluating the long-term conservation effectiveness of artificial reef areas in marine ranches helps to assess the current conservation status, identify issues during the conservation process, and develop targeted solutions. Based on survey data from the national marine ranching in the western waters of Furong Island in 2019 and 2022, we used Ecopath with Ecosim version 6.7 to construct Ecopath models for the two periods. By comparing factors such as trophic structure, system attributes, and energy flows, we evaluated the potential ecological effects associated with sustained conservation and management activities. The results indicated that the trophic level structures of the ecosystem food web between 2019 and 2022 were similar. The trophic levels of most functional groups in 2022 were slightly higher than those in 2019, and the biomass increased significantly. The biodiversity slightly increased, with the Shannon index rising from 1.544 to 1.570, and the trophic levels of most functional groups increased. The overall ecosystem scale expanded by 29.37%, while total primary production/total respiration (TPP/TR), total primary production/total biomass (TPP/TB), and the ascendancy (A) value decreased, and Finn’s cycling index (FCI), mean path length (MPL), and transfer efficiency (TE) increased. Collectively, these changes suggest a tendency toward greater ecosystem maturity, although not all ecosystem indicators exhibited consistent responses. In the energy transfer process, the proportion of energy flowing into each trophic level improved. The detrital food chain dominated the system’s energy supply, though its proportion of total flow decreased from 61% to 57% over the years, while the energy contribution from primary producers increased, and the total transfer efficiency of both pathways improved. Analysis of mixed trophic impacts and keystone species revealed changes in keystone species. Overall, the observed changes from 2019 to 2022 were consistent with potential ecological improvements under sustained conservation and management. These findings will contribute to the further refinement of fisheries resource conservation methods and support decision-making for marine ecosystem restoration.