Artificial lighting, an indispensable element of modern civilization, has long been identified as a factor posing certain threats to terrestrial life. However, recent studies have delved into the realm of marine life, examining how these vibrant life forms hidden beneath the ocean’s surface are being affected by artificial light pollution. The key concern revolves around Artificial Light at Night (ALAN), its source, implications and potential remedies to prevent its detrimental effects.
Artificial Lighting in the Marine Environment
Artificial lighting, primarily generated from sources like candles, electricity, and fire, is gradually being recognized for its negative impacts on underwater habitats. Research suggests that even extremely low levels and certain wavelengths of artificial light, especially blue and green light, can adversely affect marine life.
The excessive or improper use of this artificial light results in light pollution, disrupting the natural patterns of wildlife and amplifying the levels of carbon dioxide (CO2) in the atmosphere. Scientists have discovered biologically significant amounts of artificial light pollution across 1.9 million km2 of the ocean, about 3% of the world’s Exclusive Economic Zones (EEZs). In some cases, the impact extends to depths of over 40 metres in areas with clear water.
Sources of Marine Light Pollution
Artificial light in the marine environment primarily comes from coastal development structures like buildings, streetlights, ports, piers and docks. Additionally, vessels such as fishing and merchant marine vessels, harbours, and offshore infrastructures like oil rigs contribute to this issue. Common types of artificial lights include LED, fluorescent, metal halide, and plasma lamps.
White LEDs are particularly harmful as they produce broad-spectrum light sensed by numerous organisms and have a peak at short wavelengths (blue and green light). Consequently, the earth is being artificially brightened at the rate of 2.2% annually, causing substantial impacts on terrestrial ecology.
Effect on Marine Ecosystem
The introduction of artificial lighting has disrupted the natural cycles of marine organisms. These life forms, having evolved over millions of years to adapt to natural light, are now facing stark threats from the escalating anthropogenic light pollution. Artificial light hampers their hormonal cycles, inter-species behaviour, and reproduction cycles.
For instance, female sea turtles prefer a quiet, dark spot to lay their eggs, avoiding any kind of light. However, artificial light may deter them from coming ashore at all, leading their hatchlings towards inland lights instead of moonlight on the water, causing dehydration or starvation.
Furthermore, the growing usage of LED lighting has significantly altered the nature of artificial light, exacerbating the impacts on marine life.
Combatting the Threat
To mitigate the negative effects of ALAN, several courses of action have been proposed. Encouraging land-based ‘Lights Out’ efforts can help darken skies, aiding migrating birds attracted to light at night and benefiting marine systems near coastal cities.
Increasing the usage of red light in coastal areas as much as possible and erecting barriers to shield the coastline from artificial light is another potential solution. As red light possesses the longest wavelength in the visible spectrum, its penetration into the water is limited, thereby providing a safer lighting option for marine habitats. By implementing these tactics, we may be able to lessen the harm inflicted upon our marine ecosystems by artificial light pollution.