Impacts of artificial light at night in marine ecosystems-A review

Abstract

The globally widespread adoption of Artificial Light at Night (ALAN) began in the mid-20th century. Yet, it is only in the last decade that a renewed research focus has emerged into its impacts on ecological and biological processes in the marine environment that are guided by natural intensities, moon phase, natural light and dark cycles and daily light spectra alterations. The field has diversified rapidly from one restricted to impacts on a handful of vertebrates, to one in which impacts have been quantified across a broad array of marine and coastal habitats and species. Here, we review the current understanding of ALAN impacts in diverse marine ecosystems. The review presents the current state of knowledge across key marine and coastal ecosystems (sandy and rocky shores, coral reefs and pelagic) and taxa (birds and sea turtles), introducing how ALAN can mask seabird and sea turtle navigation, cause changes in animals predation patterns and failure of coral spawning synchronization, as well as inhibition of zooplankton Diel Vertical Migration. Mitigation measures are recommended, however, while strategies for mitigation were easily identified, barriers to implementation are poorly understood. Finally, we point out knowledge gaps that if addressed would aid in the prediction and mitigation of ALAN impacts in the marine realm.

Keywords: artificial light at night (ALAN); conservation guidelines; coral reefs; marine ecosystem; pelagic organisms; rocky intertidal shores; sandy beach; sea-turtles; seabirds.

FIGURE 1

The depth of biologically important artificial light at night (ALAN) (Zc): around the world's coastlines (a); in the Mediterranean and Northeast Atlantic (b); in the Black Sea, the Red Sea and the Persian Gulf (c); and in the Gulf of Thailand, Andaman Sea, South China Sea and the Java Sea (d). The legend inset details the depths (m) to which biologically important ALAN penetrates the sea. The data is derived from the relationship between The New World Atlas of Artificial Night Sky Brightness (Falchi et al., 2016) and sea surface irradiances (Davies et al., 2020), coupled with the monthly climatologies of globally inherent optical water properties and validated against in situ data collected from the Persian Gulf (Tamir et al., 2017). “Biologically important ALAN” is defined as the minimum irradiances of white light that elicit diel vertical migration in female Calanus copepods (Båtnes et al., 2013) [see Smyth et al.,  for further details]. Maps are representative of average ALAN penetration over a typical year. Full dataset is available to download from https://doi.pangaea.de/10.1594/PANGAEA.929749.

FIGURE 2

(a) Different marine environments not affected by Artificial Light Pollution at Night (ALAN), and (b) marine environments under the potential impacts of ALAN: (i) Sandy beaches effects on invertebrate species day‐night activity rhythms and biodiversity, effects in the on‐beach orientation of adults and hatchling turtles, and seabirds fledgling grounded by ALAN; (ii) Rocky intertidal shores – influence in metabolic activity/behavior of primary producers, sessile and mobile animals; (iii) Shallow water coral reefs – effects on gametogenesis and the synchronization of gamete release in prominent coral species, and negative impacts over fish reproduction, (iv) Pelagic environment – inhibition of vertically migrating zooplankton, and disorientation and mortality of seabirds.

FIGURE 3

Los Choros Sandy beach, coast of Coquimbo, North of Chile (Credit; Josué Navarrete).

FIGURE 4

Sea turtles hatching in Heron Island, Australia (Credit; Levy, O).

FIGURE 5

Intertidal rocky shore in an urban area, Italy (Credit; Elena Maggi).

FIGURE 6

Coral reef 10‐m depth, Eilat, Red Sea (Credit; Shachaf Ben Ezra).

FIGURE 7

Lights from a ship working in the dark (Credit; Mike Snyder).

FIGURE 8

Cory's shearwater Calonectris borealis fledgling grounded by artificial light in Tenerife, Canary Islands (Credit; Beneharo Rodríguez).

FIGURE 9

Ten golden rules for dark night conservation for marine habitats.