Numerical study of hydrodynamic effects on Manila clam population distribution and transport in the Southwest Laizhou Bay, China

Pelagic larvae of marine organisms are abundant on many continental shelves. Due to their importance as a biological resource and contribution to marine biodiversity, the dynamics of pelagic larvae have received wide attention. Numer-ical models are an efficient approach to assessing pelagic larval transport driven by various ocean dynamics. However, few studies have focused on the pelagic larval distribution of Manila clam populations and related dynamic factors in the southwestern Laizhou Bay (SLB) during late spring. A hydrodynamic model including realistic meteorologic and oceanic boundary conditions was coupled with a larval transport model to describe the pelagic larval distribution and transport processes. The hydrodynamic model was validated with observational and satellite-derived data. Effects of hydrodynamics and biological behavior on pelagic dynamics were further simulated with numerical experiments. During the early planktonic period, most clam larvae in the SLB were transported eastward or northeastward. Two po-tential larval settlement areas (LSAs) were recognized: the east side of the dike outside Guangli port and the Lao River estuary. The dominant controlling factor was southerly wind, and larvae's response to river plume or estuarine circu-lation played a secondary role. Larval transport depended on bottom subtidal currents when late-stage larvae settled near the bottom layer. The hydrodynamic and larval transport model established in this study can be applied to other bays and coastal waters. Understanding the clam larval distribution and transport dynamics in the SLB can pro-vide a reference for predicting LSAs and biological resource management in coastal aquaculture areas.

Automated summary

This study investigates the distribution and transport processes of Manila clam larvae in the southwestern Laizhou Bay using numerical models. It finds that the northeastward current is the main factor affecting larval transport, with southerly wind being the dominant controlling factor. The study provides insights for predicting suitable settlement areas for clam larvae and for the management of biological resources in coastal aquaculture areas.