Abstract
The growth in human population along coastal areas is exposing marine environments to increasing anthropogenic light sources. Despite the potential effects of this modern phenomenon, very few studies have examined its implications for corals. Here, we present a long-term study of coral early life stages under light pollution conditions at night. Coral larvae were collected from Stylophora pistillata colonies, and then settled and grown under experimental conditions of two different common city lighting methods (fluorescent or LED). Effects of the artificial lighting on the coral settlement success, survivorship, growth rate, photosynthetic efficiency, and calcification rate were examined over a period of one year. The control exhibited ~30% higher settlement success compared to the two light treatments, while under the light treatments corals showed higher survivorship, growth, and calcification rates. In addition, an indication of damage to the photosynthetic system was found in the light-polluted corals, which was reflected in their photosynthesis efficiency parameters: i.e., lower maximum light utilization coefficient (α), lower maximum potential photosynthetic rate (Pmax), and lower photosynthetic maximal quantum yield (Fv/Fm). Our findings provide evidence of the potential adverse effects of artificial lighting methods on the natural environment of coral reefs. We conclude that the use of the LED lighting method has high interference potential for the early life stages of corals.
Highlights
Coral reefs, which are highly sensitive and complex ecosystems, are continuously exposed to a variety of both direct anthropogenic disturbances: e.g., sewage, nutrient enrichment, and diving activities [1]; and indirect ones: e.g., water thermal stress and acidification [2,3]
Using Light Emitting Diode (LED) lighting as the light source, Boch et al [11] demonstrated that the major driver of spawning on a given night of the lunar cycle appears to be that of a critical threshold, determined by lunar photoperiod cues and possibly wavelength-dependent
There was no significant difference between the two illumination treatments, ‘Yellow’ and ‘LED’
Summary
Coral reefs, which are highly sensitive and complex ecosystems, are continuously exposed to a variety of both direct anthropogenic disturbances: e.g., sewage, nutrient enrichment, and diving activities [1]; and indirect ones: e.g., water thermal stress and acidification [2,3]. Using LED lighting as the light source, Boch et al [11] demonstrated that the major driver of spawning on a given night of the lunar cycle appears to be that of a critical threshold, determined by lunar photoperiod cues and possibly wavelength-dependent. Those mechanisms were found to be synchronized in accordance with the detection of moonlight by blue-light-sensing photoreceptor cryptochromes, which absorb mainly blue light [12]. This may in turn cause a negative cascading effect on larval dispersal and recruitment in coral reefs [14]
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