Having access to energy is recognised as a crucial factor in increasing the standards of living for people around the world. Artificial lighting allows communities to go about activities safely at night (Rondolat, 2015) and extends the hours that children can spend learning and studying. However, as urbanisation increased, it gave rise to the issue of light pollution. Light pollution is ‘the inappropriate or excessive use of artificial light’, often caused by unnecessary, overly bright, poorly focused or inefficient outdoor lighting (International Dark-Sky Association, n.d.). Coastal urban areas and offshore infrastructure contribute to light pollution in the marine environment, which can have effects on the behaviours of marine organisms. Artificial light affects the nesting behaviour of turtles and may cause hatchlings to be disoriented (Silva et al., 2017, Truscott et al., 2017). Light pollution also disrupts the behaviour and development of fish and zooplankton (Pulgar et al., 2019; Berge et al., 2020; Nguyen et al., 2020).
A recent study mapped out the prevalence of artificial light at night (ALAN) in marine habitats over a range of depths. Smyth et al. (2021) used global satellite data on artificial night sky brightness and in-water inherent optical properties to model the spatial extent of biologically important underwater light pollution. The findings showed that 1.9 million km2 of the ocean, making up approximately 3.1% of the world’s exclusive economic zones (EEZs), has been affected by ALAN. This is likely to affect the economic value of these EEZs, as ALAN can significantly impact the marine ecosystem and lead to a decline in fishery stocks. This issue may also be exacerbated by other threats to the ecosystems in EEZs, such as overfishing and shipping.
Smyth et al. (2021) also found that clarity of water was an important factor influencing the depth of penetration of ALAN. Coastal waters were generally more opaque, due to runoff from land, upwellings and tidal mixing. This was perhaps why the Persian Gulf and the North Sea were the most light-polluted regions identified (figure below). Their extensive offshore developments, such as wind farms and oil rigs, are likely situated in waters with higher clarity, allowing for light penetration to greater depths.
ALAN sky brightness (top) and critical depth (bottom) of the Persian Gulf (left) and the North Sea (right) (adapted from Smyth et al., 2021)
Another point mentioned in the study was that light-emitting diodes (LED) can penetrate deeper than older low-pressure sodium (LPS) lighting, as LED peaks strongly at shorter wavelengths in the blue end of the light spectrum. As more people switch to LED lighting for its energy efficiency properties, there will likely be negative implications for the marine environment. This signals that marine light pollution is likely to be a growing issue and greater urgency is needed to tackle the problem.
References
Berge, J., Geoffroy, M., Daase, M., Cottier, F., Priou, P., Cohen, J.H., Johnsen, G., McKee, D., Kostakis, I., Renaud, P.E., Vogedes, D., Anderson, P. Last, K.S. & Gauthier, S. (2020). Artificial light during the polar night disrupts Arctic fish and zooplankton behaviour down to 200 m depth. Communications Biology, 3: 102.
International Dark-Sky Association (n.d.). Light pollution. Retrieved from https://www.darksky.org/light-pollution/ on 5 April 2022.
Nguyen, T.T., Le, M., Doan, N.X., Pham, H.Q., Vu, M.T.T. & Dinh, K.V. (2020). Artificial light pollution increases the sensitivity of tropical zooplankton to extreme warming. Environmental Technology & Innovation, 20: 101179.
Pulgar, J., Zeballos, D., Vargas, J., Aldana, M., Manriquez, P.H., Manriquez, K., Quijón, P.A., Widdicombe, S., Anguita, C., Quintanilla, D. & Duarte, C. (2019). Endogenous cycles, activity patterns and energy expenditure of an intertidal fish is modified by artificial light pollution at night (ALAN). Environmental Pollution, 244: 361-366.
Rondolat, E. (2015). How can we switch off lighting poverty?. World Economic Forum. Retrieved from https://www.weforum.org/agenda/2015/01/how-can-we-switch-off-lighting-poverty/#:~:text=Light%20makes%20it%20safer%20for,these%20are%20dangerous%20and%20unhealthy on 5 April 2022.
Silva, E., Marco, A., Graça, J.S., Pérez, H., Abella, E., Patino-Martinez, J., Martins, S. & Almeida, C. (2017). Light pollution affects nesting behavior of loggerhead turtles and predation risk of nests and hatchlings. Journal of Photochemistry and Photobiology B: Biology, 173: 240-249.
Smyth, T.J., Wright, A.E., McKee, D., Tidau, S., Tamir, R., Dubinsky, Z., Iluz, D. & Davies, T.W. (2021). A global atlas of artificial light at night under the sea. Elementa: Science of the Anthropocene, 9(1): 00049.
Truscott, Z., Booth, D.T. & Limpus, C.J. (2017). The effect of on-shore light pollution on sea-turtle hatchlings commencing their off-shore swim. Wildlife Research, 44(2): 127-134.