Comparative analysis of co-occurrence patterns of macrobenthic communities in intertidal and offshore zones of the Yellow River Delta, China

Species co-occurrence is crucial for understanding ecological processes, species interactions, and predicting community responses, supporting biodiversity conservation and ecosystem health. In this study, we explored co-occurrence patterns of macrobenthos in the intertidal and offshore two different habitat types of the Yellow River Delta (YRD) based on both the matrix level and the species-pair level methods. Results showed the intertidal zone displayed lower species diversity, primarily featuring mollusks, crustaceans, and polychaetes, while the offshore zone consistently exhibited higher crustacean abundance, particularly shrimps and crabs, along with an increased fish species count across multiple months. Matrix-level results using a null model indicated that macrobenthic species with low mobility predominantly exhibited a random pattern across the intertidal zone; on the other hand, these species with high mobility showed a significant segregated pattern within offshore regions. The pairwise-level analysis showed that the species pairs of the macrobenthic communities were mainly randomly associated and fewer species pairs demonstrated both the significant aggregation/separation existing within the intertidal zone and its various subdivisions. Furthermore, species pairs displaying significant aggregation were more numerous than those showing separation among the overall pairs. These findings further support the notion that macrobenthic species within the intertidal zone tend to lack a distinct structure, likely due to the diminished impact of interspecific competition and also the increased impact of environment factors in this unique habitat of the YRD. This study improves understanding of species co-occurrence across different ecological types in estuarine wetlands, supporting biodiversity conservation and ecosystem management.