How do marine animal larvae know where to settle on a coral reef?
It just may be that it sounds like home.
According to a new study from the Woods Hole Oceanographic Institution, based on research conducted along reef systems in waters off Maui, sound might play an important role in letting larvae know where it is safe to land.
Results of the study were published in the Aug. 23 edition of the online journal Scientific Reports.
A key question in the team’s investigation was how far sounds emanating from adult fish in the area could be detected by larvae.
Max Kaplan, a graduate student in the MIT/WHOI Joint Program in Oceanography, and adviser Aran Mooney, a WHOI associate scientist, recorded two different sound components: pressure waves and particle motion.
Most fish sense sound by way of particle motion, the physical vibration of water as a sound wave travels through it.
“Particle motion is really the relevant cue for marine animals,” Mooney said in a new release. “When we’re measuring pressure, we’re measuring the wrong thing — it only gives a ballpark sense of what marine species hear. We think studying particle motion is a big step to figuring out how larvae find their way to a reef.”
Using customized accelerometers, the researchers measure sound levels at dawn and midmorning, placing the sensors at various distances from zero to 1,500 meters from the reef.
The results were not what they expected. Particle motion was much lower than expected, making it unlikely that larvae could sense it even just a few meters from the reef.
Kaplan still thinks that sound might play a role in how larvae locate safe spaces to settle once they find a reef.
Noting the way in which some damselfish live their entire adult lives within a square meter, Kaplan said, “In cases like that, sensing sound on the order of meters would make a big difference. If you hear sounds of your species instead of predators, you might be more inclined to settle in a specific spot.”
The researchers said they intend to expand their efforts to get a better understanding of how sound travels within other types of reef systems.
