Which are the European seas with the greatest risk of underwater light pollution

The European Union omitted limits for marine artificial light in its 2008 ecosystem protection directive. (Illustrative image Infobae) Every night, light from cities, ports, and oil platforms filters beneath the sea surface and reaches the depths where organisms that depend on darkness to feed, reproduce, and migrate live. This light intrusion already affects much of the planet's coastlines, but until now there was no standardized way to measure how much damage it can cause in Europe's seas. An international team proposed the first framework to assess it, and the data are compelling: in the western Mediterranean, 73% of the maritime strip up to 10 kilometers from the coast receives levels of artificial light classified as high risk, while the Adriatic and the Baltic also rank among the areas with the greatest exposure to marine light pollution. The problem is not new, but the tool to measure it is. The European Union approved a directive in 2008 to protect its marine ecosystems that considered the introduction of energy into the ocean as a possible threat. However, all regulatory efforts focused on underwater noise, and nighttime light was left out of any threshold or measurement protocol. The research, published in the journal Ocean & Coastal Management, proposes to fill that gap with a classification system that combines three variables: how much light cities and coastal infrastructure emit, how transparent the water is in each zone, and whether the exposed environment corresponds to the water column or the seabed. 73% of the coastal strip of the western Mediterranean registers levels of light pollution classified as high risk. (Illustrative image Infobae) This advance comes at a precise moment: the Marine Strategy Framework Directive is under review and the authors are seeking to have light pollution integrated into the next version of that regulation. The framework does not yet prescribe what specific level equates to a sea in good condition—a decision that will require political agreements and consultations with various sectors—but it offers, for the first time, a methodological basis with which governments can identify risk zones and design mitigation strategies. The Adriatic concentrates the highest risk in water column ecosystems To estimate the reach of artificial light under the sea, the researchers combined the lighting levels of coastal zones with water clarity, a factor that determines the depth to which that radiation penetrates. They used as a reference a precautionary threshold of 0.1 microwatts per square meter: the minimum intensity of white light at which copepods of the genus Calanus, small crustaceans considered among the most light-sensitive marine organisms documented to date, modify their behavior, as detailed in the study. Based on that reference, the analysis distinguishes two types of environments. Pelagic environments, that is, those that develop in the water column between the surface and the depths, receive the light impact first. Benthic environments, associated with the seabed, are exposed to radiation already attenuated by its passage through the water, although in shallow areas the intensity can still be considerable. Artificial nighttime light alters the daily vertical migration of marine species and the reproductive synchronization of corals. (Illustrative image Infobae) The results reveal a defined pattern: seas surrounded by land on several of their flanks accumulate the greatest exposure. In the Adriatic Sea, 56% of the coastal strip of up to 10 kilometers was classified as high risk for pelagic ecosystems. In the western Mediterranean, that percentage rose to 73%. At the opposite end, the open waters of Macaronesia, a region comprising the Canary Islands, the Azores, Madeira, and Cape Verde, along with the Barents Sea and the Iceland Sea, recorded the lowest values. The waters near the United Kingdom presented overall medium to low risks, although the work warns that the oil and gas fields of the North Sea, with all the infrastructure surrounding them, raise light pollution in an environment that, being open ocean, would naturally have lower exposure. Many marine species regulate vital behaviors based on variations in solar and lunar light. Among these processes are the daily vertical migration, a massive movement of organisms to different depths that constitutes the largest movement of biomass on the planet, and the synchronized reproduction of corals. The study points out that artificial nighttime emissions can disrupt these cycles and also compromise larval settlement. The AquaPLAN project and the GOALANN network seek to have the European Union incorporate light pollution into its revised marine regulations. (Illustrative image Infobae) The accelerated adoption of LED lighting deepened that interference. This type of lighting went from 2% of the global market in 2012 to 48% in 2019, with a projection of 87% for 2030, according to the data collected in the work. Its characteristic emission in blue wavelengths penetrates deeper into the water than that of previous technologies and, at the same time, coincides with the natural light signals that numerous species use to orient themselves. In other words, the light that propagates most beneath the surface is the one most likely to alter the behavior of organisms. "For many years, our research has repeatedly shown that light pollution significantly affects many important coastal species," said Thomas Davies, associate professor of Marine Conservation at the University of Plymouth, according to the press release. Davies added that the accumulated evidence on risk and harm "urgently needs to be translated into concrete actions" and that the argument that there are not enough data to legislate "no longer holds." The researchers propose shielding light fixtures and creating darkness reserves on Mediterranean tourist islands and coasts. (Illustrative image Infobae) Much of the seas with the greatest exposure coincides with Mediterranean coasts that receive millions of visitors each year. The University of Plymouth statement notes that the authorities of those regions could introduce changes to their lighting infrastructure, such as shielding light fixtures, reducing intensity, partial shutdowns during the night, and modifying the wavelengths emitted to limit how much light penetrates the water. The authors also propose the creation of dark spaces on and around islands, an alternative that would offer visitors an experience different from that of coasts bathed in artificial lighting. "We have substantial evidence that artificial light at night can affect marine organisms and ecological processes," said Elena Maggi, professor of Ecology at the University of Pisa and coordinator of the AquaPLAN project, according to the press release. The challenge, the expert indicated, is to turn that knowledge into tools that make it possible to identify where ecosystems are at greatest risk and to find sustainable ways for human activities and coastal environments to coexist.