Abstract
The impacts of artificial light at night (ALAN) on marine ecosystems have emerged as a focus for ecological light pollution research in recent years, yet the global prevalence of ALAN in underwater marine ecosystems is unknown. We have derived a global atlas of ALAN throughout the marine water column that will accelerate our understanding of its sources and environmental impacts. At a depth of 1 m, 1.9 million km2 of the world’s coastal seas are exposed to biologically important ALAN, which equates to around 3.1% of the global exclusive economic zones. This area decreases to 1.6 million km2 (2.7%) at a depth of 10 m, and to 840,000 km2 (1.4%) at 20 m. The most heavily exposed regions are those that experience intensive offshore development in addition to coastal urbanization. The atlas highlights that ALAN as a global change issue is not exclusive to land but is also widespread in the world’s underwater habitats at irradiances that elicit biological responses in marine organisms.
Highlights
The 21st century will see dramatic increases in coastal urbanization (Neumann et al, 2015) and offshore infrastructure
To understand the biological importance of the modelled underwater artificial light at night (ALAN) field, we calculated the critical depth (Zc) to which biologically important ALAN penetrates throughout the global ocean estuarine, coastal and nearshore regions, across the area defined by the Exclusive Economic Zone (EEZ) of individual countries
Greater impacts of ALAN are anticipated at depth in EEZs with clearer waters
Summary
The 21st century will see dramatic increases in coastal urbanization (Neumann et al, 2015) and offshore infrastructure. Satellite-derived images of the world’s night-time lights have been successfully coupled with atmospheric light dispersion models to produce new insights into the prevalence and growth of ALAN skyglow on land (Falchi et al, 2016a; Kyba et al, 2017). Much of this light will enter the world’s seas and oceans, which until now has been difficult to quantify. The resulting broadband irradiances were integrated to produce absolute irradiances of ALAN underwater with depth This approach allowed insight for the first time into the spatial extent of in-water marine light pollution and its temporal variability on a global scale. Such datasets are extremely rare due in part to the technical difficulty of measuring multi-spectral irradiances to the level of μW m–2 nm–1 with an associated high signal to noise ratio (SNR)
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