The community structure of macrobenthic fauna in the Minjiang Estuary during autumn and its relationship with environmental factors

In October 2021, a survey was conducted at 12 subtidal stations and 3 intertidal stations in the Minjiang Estuary. The results indicated that: (1) 17 macrobenthic species were collected in the subtidal zone, with polychaetes (10 species) as the dominant group. The average density was 60.0 ind./m2 and the average biomass was 1.12 g/m2. Byblis sp., Heteromastusfiliformis, and Sigambrabassi were dominant species commonly found in both nearshore and offshore subtidal areas. (2) 22 macrobenthic species were collected in the intertidal zone, dominated by crustaceans (12 species). The average density was 59.5 ind./m2 and the average biomass was 17.49 g/m2. Ucaarcuata was a dominant species across the high, middle, and low tide zones. (3) The C2 station might be moderately disturbed, while the remaining stations appeared undisturbed. (4) In the subtidal zone, polychaetes were influenced by Hg and carbon content, while crustaceans were affected by Cd, Cr, and oil pollutants. Among water quality parameters, NO3−, TSS, and NO2−, and among sedimentary parameters, Zn, As, and Pb were identified as key factors influencing community metrics. The subtidal sediments were predominantly sandy, and macrobenthic organisms exhibited a trend toward smaller body sizes. In the intertidal zone, diversity was higher in the middle and high tide zones than in the low tide zone. The heterogeneity of sediment composition due to differences in grain size may be a primary factor affecting the distribution of macrobenthic fauna in this region.