Red Sea corals under Artificial Light Pollution at Night (ALAN) undergo oxidative stress and photosynthetic impairment

Abstract

Coral reefs represent the most diverse marine ecosystem on the planet, yet they are undergoing an unprecedented decline due to a combination of increasing global and local stressors. Despite the wealth of research investigating these stressors, Artificial Light Pollution at Night (ALAN) or “ecological light pollution” represents an emerging threat that has received little attention in the context of coral reefs, despite the potential of disrupting the chronobiology, physiology, behavior, and other biological processes of coral reef organisms. Scleractinian corals, the framework builders of coral reefs, depend on lunar illumination cues to synchronize their biological rhythms such as behavior, reproduction and physiology. While, light pollution (POL) may mask and lead de‐synchronization of these biological rhythms process. To reveal if ALAN impacts coral physiology, we have studied two coral species, Acropora eurystoma and Pocillopora damicornis, from the Gulf of Eilat/Aqaba, Red Sea, which is undergoing urban development that has led to severe POL at night. Our two experimental design data revealed that corals exposed to ALAN face an oxidative stress condition, show lower photosynthesis performances measured by electron transport rate (ETR), as well as changes in chlorophyll and algae density parameters. Testing different lights such as Blue LED and White LED spectrum showed more extreme impact in comparison to Yellow LEDs on coral physiology. The finding of this work sheds light on the emerging threat of POL and the impacts on the biology and ecology of Scleractinian corals, and will help to formulate specific management implementations to mitigate its potentially harmful impacts.

The Prokaryotic Microbiome of Acropora digitifera is Stable under Short-Term Artificial Light Pollution

“…After the acclimatization period, coral colonies were subjected to nightly exposure to cold white LED (5329 K) with a major blue peak from 420–480 nm (“cold white” treatment) or to warm white LED (2719 K) with a major red peak from 580–620 nm (“warm white” treatment). Nighttime PAR in the tanks ranged from 0.5–0.75 µmol quanta m −2 s −1 , which approximates ALAN values in populated nearshore environments, as reported by other studies [ 32 , 33 , 34 ]. Controls were subjected to natural moonlight (ambient treatment) with an average PAR of 0.01 ± 0.0 µmol quanta m −2 s −1 .…”

“…Light pollution has been shown to affect the activity of phototrophic symbiotic dinoflagellates (Symbiodiniaceae) of corals [ 32 , 33 , 34 ]. As Symbiodiniaceae are closely associated with nitrogen-fixing bacteria (diazotrophs) [ 6 , 7 , 35 ], it is possible that ALAN exposure may also affect the abundance of these particular microorganisms.…”

“…This is likely linked to changes in the expression of genes related to cell cycle progression, cell proliferation, survival, and growth [ 31 ]. ALAN exposure has also been shown to have deleterious effects on coral-dinoflagellate symbiosis, resulting in severe oxidative stress, reduced symbiont cell density, lower chlorophyll concentration, and decreased maximum quantum yield of photosystem II [ 32 , 33 , 34 ]. Metabolic activity of the coral animal and its microalgal and prokaryotic symbionts are tightly intertwined [ 35 ].…”

Biologically important artificial light at night on the seafloor

“…2 School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey LL59 5AB, UK. 3 Physics Department, University of Strathclyde, 107 Rottenrow, Glasgow G4 0NG, Scotland. 4 Plymouth Marine Laboratory, Prospect Place, Devon, Plymouth PL1 3DH, UK.…”

“…The potential for artificial light at night (ALAN) to reshape the ecology of marine habitats is increasingly recognised, and an emergent focus of research [1][2][3][4] . Artificial light can be detected above 22% of the world's coasts nightly 5 , and will dramatically increase as coastal human populations more than double by year 2060 6 .…”