The 'song' of the coral reefs changes with the moon: depending on the night light, in fact, the biological activity of fish and invertebrates that live among the corals changes.
This is demonstrated by a study conducted in Hawaii by researchers from the Naval Undersea Warfare Center of the United States Navy.
The results, published in the journal Plos One, provide valuable indications for exploiting sounds in monitoring the health of these ecosystems increasingly threatened by climate change.
The advantage of acoustic monitoring lies in the fact that the organisms that populate the coral reef emit sounds continuously, even during the night when the darkness prevents conducting visual inspections.
To best interpret the data collected, however, we need to know whether this choral 'song' undergoes physiological variations during the night.
To find out, US researchers conducted surveys at several sites in Hawaii.
The findings demonstrate that diverse communities of coral reef organisms react rapidly to nocturnal variations in ambient light: their sounds change significantly between moonrise and moonset.
In particular, it was found that under moonlight the sounds of fish consisting of trains of high-frequency impulses (0.5-1.5 kHz) increase, while the sounds of invertebrates (2-20 kHz) and high-frequency vocalizations decrease. low fish frequency (0.1-0.3 kHz).
This finding suggests that the rising and setting of the moon triggers periodic changes in the interactions that occur on the coral reef.
In the future, acoustic monitoring of these ecosystems could be improved by comparing sounds recorded during moonlight and dark hours, in order to derive indicators that can early reveal any alterations in the relative abundance of the different species present.
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