Review of Artificial Downwelling for Mitigating Hypoxia in Coastal Waters

Yiwen Pan,Ying Chen,Shuo Liu,Lige Zhao,Wei Fan,Canbo Xiao,Yong Cai

doi:10.3390/w12102846

Yiwen Pan, Ying Chen + Show 5 more

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https://doi.org/10.3390/w12102846

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Journal: Water	Publication Date: Oct 13, 2020
Citations: 8	License type: CC BY 4.0

Affiliation: Zhejiang Ocean University, Zhejiang University

Abstract

Hypoxia is becoming a serious problem in coastal waters in many parts of the world. Artificial downwelling, which is one of the geoengineering-based adaptation options, was suggested as an effective means of mitigating hypoxia in coastal waters. Artificial downwelling powered by green energy, such as solar, wind, wave, or tidal energy, can develop a compensatory downward flow on a kilometer scale, which favors below-pycnocline ventilation and thus mitigates hypoxia in bottom water. In this paper, we review and assess the technical, numerical, and experimental aspects of artificial downwelling all over the world, as well as its potential environmental effects. Some basic principles are presented, and assessment and advice are provided for each category. Some suggestions for further field-based research on artificial downwelling, especially for long-term field research, are also given.

Highlights

Due to global warming and coastal eutrophication, the coastal waters that are usually associated closely with intensive human activities are facing hypoxia, or low dissolved oxygen concentrations, representing a significant threat to the health and economy of coastal ecosystems [1,2,3,4]
Coastal hypoxia can be caused by natural processes, such as stratification and hydromorphology [2,12,13], the dramatic increase in the number of world coastal waters developing hypoxia is linked to anthropogenic factors, such as eutrophication and global climate change resulting from human activities [14]
A prototype device of ocean artificial downwelling named a density current generator (DCG), i.e., an electrical pump powered by solar energy and fossil fuel, was proposed by the University of Tokyo and was developed and moored in the Hazama Inlet of Gokasyo Bay, Japan [32,33], where the red tide was insignificant since the installation of the apparatus in 1997 [27]

Summary

Introduction

Due to global warming and coastal eutrophication, the coastal waters that are usually associated closely with intensive human activities are facing hypoxia, or low dissolved oxygen concentrations, representing a significant threat to the health and economy of coastal ecosystems [1,2,3,4]. Individuals of immobile species, such as oysters, mussels, and sea cucumber, have no capacity for escaping low-oxygen areas and are especially vulnerable to hypoxia [5,6,7]. These organisms can become stressed and may die in low-oxygen conditions. It is reported nowadays that major fishery areas—the Baltic, Kattegat, North Adriatic, Black Sea, Gulf of Mexico, and the East China Sea—are suffering ecological degradation and loss of biomass as a result of coastal hypoxia [3,7,16,17]

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