A new study from the Woods Hole Oceanographic Institution (WHOI) will help researchers understand the ways that marine animal larvae use sound as a cue to settle on coral reefs. The study, published on August 23rd in the online journal Scientific Reports, has determined that sounds created by adult fish and invertebrates may not travel far enough for larvae —which hatch in open ocean—to hear them, meaning that the larvae might rely on other means to home in on a reef system.
“To keep a reef healthy, you need a constant supply of new larvae to repopulate animals that die off,” said Max Kaplan, the lead author of the paper and a graduate student in the MIT/WHOI Joint Program in Oceanography. “How larvae find reefs has been a big question, though. We think sound may play a role in attracting them, but exactly how far away they can sense those sounds has not yet been accurately measured.”
To address that problem, Kaplan and his PhD adviser, WHOI Associate Scientist Aran Mooney, a co-author on the paper, traveled to the Hawaiian island of Maui to make painstaking acoustic measurements of a healthy reef system. The pair focused their efforts on recording two different components of sound—pressure waves (the element of sound that pushes on a human eardrum), and particle motion (the physical vibration of the water column as a sound wave travels through it). The latter, Kaplan explained, is how the majority of fish and marine species detect sound, yet no previous studies have focused on recording it.
“Think of it like being at a loud concert—if you’re standing next to a huge speaker, you effectively feel the sound as it vibrates your skin,” Kaplan said. “Fish and invertebrates sense sound in a similar way.” Species like squid, octopus, and shrimp, for example, can detect vibrations through nerves embedded in their flesh. Similarly, adult fish sense them through the motion of tiny bone-like structures called otoliths inside their skulls.
- See more at: http://www.whoi.edu/news-release/soundscapes-of-coral-maui#sthash.DMfalOwi.dpuf
Image: A researcher monitors coral reefs in the waters around Virgin Islands National Park
Credits: National Park Service
