This is how light pollution reaches the bottom of the sea

Microscopic crustaceans provide a measure of the damage caused by artificial light as it penetrates below the surface of seas and oceans.

The light pollution produced by artificial light also extends to the seas and oceans. Coastal areas are increasingly developing and artificial light that passes through the water surface at night can have negative impacts on the marine environment. This artificial light is called ALAN, which means artificial light at night (artificial night light).

The effects of light pollution on the night sky, astronomy and terrestrial ecosystems had already been well studied, but until now researchers did not know the extent of ALAN in the oceans.

The UK Environmental Research Council (NERC) funded a study to create a map of the most affected areas of the ocean by light pollution. The result shows that up to 1.9 million square kilometers of the world’s coastal waters are exposed to biologically significant levels of ALAN.

The biological impacts of artificial light at sea

Artificial light can even penetrate 100 meters deep below the surface, altering the migration and feeding rates of marine organisms, especially zooplankton, affecting the entire ecosystem. The researchers combined several techniques, such as computer modeling, satellite technology and observations. on site on the River Tamar, southwest of Great Britain. Thus, they were able to construct an image of the coastal areas of the ocean exposed to ALAN at night.

ALAN impact and critical water depth in the Persian Gulf and North Sea. Source: Elementa: Science of the Anthropocene

To measure artificial light from the oceans, the study used the light sensitivity of copepods, a microscopic crustacean, as a measure to find the depth of light penetration. It is important to know how light levels affect marine organisms, as well as other impacts of man-made pollution on these creatures.


a copepod

The main author of the research, thomas daviessaid the extent of man-made light pollution on Earth has been known for many years. Some people may think that this light does not penetrate the oceans, but it does, and in sufficient quantities to cause biological impacts. This atlas is the first to quantify the extent of ALAN in the oceans. The severity of the problem in certain regions, including the Mediterranean, the Persian Gulf and the South China Sea, is very alarming.

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Many marine species are used to the changes in light that occur throughout the day, the seasons and the lunar cycle naturally. However, artificial coastal light can be scattered deep into the sea and is quite different from moonlight and sun light.

Two million square kilometers of ocean exposed to ALAN

The new global undersea ALAN atlas indicates that at a depth of one meter, 1.9 million square kilometers of coastal ocean are exposed to biologically significant ALAN, ie approximately 3.1% of the global exclusive economic zones (EEZs). ). At a depth of ten meters, 1.6 million square kilometers are exposed, 2.7%, and at a depth of 20 meters, 840 thousand square kilometers, 1.4%.

Researchers from the University of Plymouth, the Plymouth Marine Laboratory, the University of Strathclyde, the Arctic University of Norway, the Bar-Ilan University, the Eilat Interuniversity Institute of Marine Sciences and the Beit Berl Academic College participated in the article.

Another author, Tim Smyth, explained that the creation of this atlas shows us how pervasive the problem of artificial light is in our coastal seas at night. Much research is still needed to understand the specific effects on marine organisms, the exact spectral nature of this light pollution and how it changes with the seasons or tides, for example. But recognizing its global presence in this way is a big step towards understanding ALAN and its consequences for the oceans.


A global atlas of artificial light at night under the sea.

Main photo: NASA

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