Linking 3D Perinereis burrows with physicochemical factors on a tidal flat (Pearl River Delta (PRD), China)

Resumo

This study employed a comprehensive approach involving field sampling, grain-size analysis, physicochemical measurements, CT scanning and three-dimensional reconstruction in order to investigate the intertidal flats of the Pearl River Delta (PRD). As Perinereis is an important group of bioindicators in relation to environmental factors, sedimentological and ichnological analyses were conducted at 6 out of 63 stations. These analyses aimed to clarify the composition and distribution characteristics of Perinereis traces, reveal their response relationships with physicochemical factors including sediment grain size, salinity, turbidity and total organic carbon (TOC) content, and further illustrate their environmental significance. The results showed that: (1) Perinereis traces are predominantly composed of grazing and dwelling burrows. These burrows display diverse morphologies, including simple cylindrical, Y-shaped, U-shaped and complex branching networks. Some branches exhibit swellings at junctions. (2) Salinity has a significant influence on the burrow diameter of Perinereis, exhibiting a positive correlation in the low to moderate salinity range (0.28–3.97 PSU). Perinereis growth plateaus when salinity exceeds a threshold of approximately 18 PSU, indicating a physiological tolerance limit. (3) Burrow diameter and sediment bioturbation exhibit no significant correlations with sediment grain size, salinity, turbidity or total organic carbon content. This may be attributed to infaunal interactions (e.g. associations with Macrophthalmus japonicus) and the combined influence of multiple environmental factors. This study improves our understanding of the biology and ichnology of modern Perinereis traces. It provides a quantitative basis for interpreting the interactions between infauna and their environment in intertidal flat ecosystems.