Wednesday, June 8, 2016

What's that crackling sound?

Have you ever noticed that if you put your ears in the water near a coral reef, you can hear a crackling sound?  That sound is produced by the many species of parrotfish, sea urchins, and snapping shrimp!  

Parrotfish are one of the most abundant and colorful larger fish to be seen on the coral reef. 

Princess Parrotfish - Image by Laszlo Ilyes via Flickr

Stoplight Parrotfish - Image by Adona9 via Wikipedia

Queen Parrotfish - Image by Amada44 via Wikimedia Commons

Here in Secret Harbor and around the Virgin Islands you are likely to see numerous princess parrotfish, stoplight parrotfish, queen parrotfish, and various others.  Parrotfish are named for their bright colors and fused teeth that resemble a beak.  They predominantly use their pectoral fins to propel themselves through the water, moving them up and down like miniature wings.

Video by Amy Kelley  - Parrotfish eating

That crackling noise you hear is made by the parrotfish eating.  They scrape algae and coral polyps from the reef, often breaking off chunks of the coral's limestone skeleton.  Sound travels about four times faster and farther in water than it does in air.  That's why you can hear so many parrotfish munching on the reef at any given momentThey crunch and grind down the limestone, digesting the organic matter and getting rid of the indigestible bits.  

Video by Amy Kelley - Parrotfish pooping

If you watch them for a while, you will see them magically make sand when they poop out the crushed limestone debris.  Thanks to the parrotfish for keeping our beaches beautiful and full of sand!  

Check out this hilarious but informative video.    

Video by Sisbro Studios via YouTube

Here's a great article and video by Scientific American: Parrotfish Poop Makes Beautiful Beaches

  Video by Amy Kelley - Long spine sea urchin

Sea urchins also contribute to the crackling sound on the reef.  They mainly eat algae, scraping it off of coral and rocks using 5 teeth-like plates on the bottom of their bodies.  Listen to a symphony of sea urchins via ABC Australia and scientist Ann Jones.

Image by Steve Childs via Flickr: Gobi and shrimp
Snapping shrimp use a specialized claw to produce a loud snapping sound for defense, hunting, and communication purposes.  You can often find them hanging out with gobies and hiding inside of corkscrew anemones.

Video by Amy Kelley - Snapping shrimp

Aqua Action Dive Center rents and sells snorkel gear if you'd like to snorkel in Secret Harbor and observe this underwater symphony first-hand!  Or better yet, come try scuba diving with us so you can spend some time under the sea and get an even closer encounter with our colorful fish and creatures!

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