CORAL REEFS “RING,” ACCORDING TO NEW RESEARCH. You may not hear it above your bubbles or the cacophony of surges or the clacking of snapping shrimp that contribute to the sounds we hear underwater.
But, if listened to properly, the reefs may be able to tell us about their health.
IT’S THE BUBBLES
More specifically, algae on the reef produces ringing sounds as it goes about its business of photosynthesizing H2O molecules into simple-sugar nutrients for growth. A happy side effect of the process is that it produces oxygen (and nitrogen) as a by-product.
Actually, it’s bubbles of the gasses taking on spherical shapes as they separate from algal surfaces that produce ringing sounds in the 2 to 20 kilohertz range.
LISTENING TO REEFS RING COULD TELL US A LOT
The intensity of the ringing varies with the amount of algae present, according to the study by scientists at the U.S. Naval Research Laboratory and other U.S. Navy agencies.
“Many such bubbles create a large, distributed sound source over the sea floor,” they write in “Photosynthesis by marine algae produces sound, contributing to the daytime soundscape on coral reefs,” published in the science journal PLOS ONE.
The way that reefs ring, and other noise in the reef soundscape, can provide a lot of biological information, they note. In effect, they suggest that it could be possible to study the health of a reef by listening to it.
ALGAL COVER A KEY FACTOR IN REEF HEALTH
Photosynthesizing algae, of course, is one of the foundations of the oceanic food chain. But too much of it can be bad news for a coral reef. Algae growth that takes off can smother the corals that makes the reef possible, so finding ways to monitor it are important.
Major elements in increased algal growth are man-made – pollution through fertilizer runoff and overfishing that removes algae-eating fish that keep algae in check. Climate change is and will also be a significant factor.
In studying the way that reefs ring, the researchers monitored algae at 17 reef sites in the Pacific stretching from the Hawaiian Islands to Kure Atoll, west of Midway Island. They also grew and studied the invasive Hawaiian algae species, Salicornia gracilaria, in laboratory tanks.
PRINCIPAL SOURCES: “Photosynthesis by marine algae produces sound, contributing to the daytime soundscape on coral reefs,”PLOS ONE; “Image of the Day: “Ringing” Coral Reefs,” The Scientist.