Abstract

Green tides have occurred in Jinmeng Bay (JMB) since 2015. Wind field is a very important physical factor controlling the migration of green algae. Based on MIKE 21, a particle tracking model was established to simulate the movement of green algae driven by wind and tide. The results reveal that: (1) the current was reciprocating flow along the coastline and it was very weak in JMB; (2) the wind direction had an important effect on the wind-driven residual current and the trajectory of particles; (3) the greater the wind speed is, the greater the drift distance and range is.

INTRODUCTION

Jinmeng Bay (JMB) is one of the famous bathing beaches in the Bohai Bay, China. Two artificial islands (Lotus Island and Conch Island) have been built since 2011, which resulted in a lower capacity of water exchange (Wang et al., 2020). In 2015, a novel green tide occurred in the coastal areas of Qinhuangdao City, making it the second coastal area in China influenced by macroalgae blooms (Han et al., 2020).

Typical green-tides are characterized by choking of waterways in the immediate area of the bloom and subsequent local wind and tide driven local deposition on the shore, and this can be destructive to marine environment and cause economic losses of coastal zones (Liu et al., 2009; Jin et al., 2018). Except for main hydrodynamic factors such as tidal current and wave, wind field is also a very important physical factor controlling the migration of green algae. Qiao et al. (2011) emphasized that the drift path of floating algae near Qingdao was mainly controlled by the wind-induced onshore surface current. Li et al. (2014) illustrated that the effect of wind drag on green macroalgae cannot be ignored. Bao et al. (2015) found that wind became the dominant forcing of floating green algae in the Subei Shoal in the western Yellow Sea. Chen et al. (2018) reported the drifting velocity of green tide had a close correlation with wind speed and the drifting direction of green tide was also in good accordance with local tide cycle.

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