Aquaculture-induced boundary circulation and its impact on coastal frontal circulation

Cheng Tang,Yuqing He,Jiliang Xuan,Hui Liu,Feng Zhou,Jianfang Chen,Liangju Yu,Xiangyang Zheng

doi:10.1088/2515-7620/ab22cd

Abstract

With the development of coastal suspended aquaculture industry, aquaculture facilities have extended into the open sea to depths of up to 30 m. This practice will likely affect the natural ocean circulation in such areas. For a case study in the high-density aquaculture region of the coastal Yellow Sea, an aquaculture-induced boundary circulation (ABC) is identified and its effects on the background frontal circulation and cross-shore nutrient supply are examined. The ABC is composed of a southward along-boundary current and a counterclockwise cross-boundary cell. The southward along-boundary current (∼5 cm s−1) along with the natural frontal current (∼5 cm s−1) forms a strong coastal current (∼10 cm s−1) along 20–30 m isobaths. The counterclockwise cross-boundary cell exhibits the opposite direction to the natural clockwise cross-frontal cell in the frontal area, which reduces the cross-shore nutrient supply by nearly 25%. Our results suggest that aquaculture boundaries and densities should be considered when planning high-density aquaculture activities.

Highlights

Over recent years, aquaculture has developed into offshore area or open seas (Watson-Capps and Mann 2005, Radiarta et al 2008, Byron et al 2011, Wu et al 2014) where natural ocean circulation has rarely been affected by human activity
Frontal circulation in natural conditions The tides and wind experiment (TWE) results show that the frontal circulation structure mainly has two components: an along-frontal current (figure 4(a)) and a clockwise cross-frontal cell (figure 5(a), vectors), which is in agreement with the previous studies (Van Heijst 1986, Dong et al 2004)
Both the along-frontal current and the clockwise crossfrontal cell are located in the frontal zone between the 10–50 m isobaths

Summary

Introduction

Aquaculture has developed into offshore area or open seas (Watson-Capps and Mann 2005, Radiarta et al 2008, Byron et al 2011, Wu et al 2014) where natural ocean circulation has rarely been affected by human activity. For a case study in the high-density aquaculture region of the coastal Yellow Sea, the aquaculture is developing, expanding, and intensifying in numerous coastal regions (figure 1(a), red dots). In order to meet the increasing demand for aquatic food products, high-density aquaculture facilities have been expanded into the open sea to depths of up to 30 m, broadening the range of aquaculture activities, which were previously restricted to intertidal mudflats or bays. The impact of suspended aquaculture on coastal circulation and nutrient supply following the expansion of high-density aquaculture facilities into open seas remains unclear

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Discussion

Conclusion