Where does Cayman’s beautiful white sand originate?
Believe it or not, from a colourful parrotfish and green
From a distance, all sandy beaches look the same. But if
you take a closer look, you will find they are all very different. Every grain
of sand is unique in colour, texture, and shape, depending on what it is made
from and where it lives on the beach. Sand is created from either rocks or sea
animal remains, such as fragmented shells.
The floury soft coral sand found on the majority of
Cayman’s beaches comes, almost entirely, from the coral reef community. This
type of sand is biogenic – sands made of the skeletal remains of plants and
animals. This is the main reason why our sand is so much finer and softer than
the sand found on most continental beaches, which comes from terrestrial
sources such as weathering rocks.
Most of our sand is created by wave and current energy
acting on the coral reef as coral, calcareous green algae (algae with a hard
exoskeleton), the shells of various sea creatures and sea urchin spines are
gradually broken down into sand sized grains. Calcified green algae,
particularly the Halimeda spp., are especially important as a major contributor
of marine sediments.
The white sand is largely composed of the sun-bleached
and eroded calcium-carbonate remnants of calcareous green algae. This calcified
sand is deposited from natural expiration and consumption by some marine
animals, such as the sea urchin species Clypeaster rosaceus and parrotfish.
Reef grazing fish, such as parrotfish, produce a
significant amount of sand found on the beaches. Parrotfish get their names
from their parrot-like mouths and they have strong teeth that resemble a
parrot’s bill. These strong, sharp teeth allow parrotfish to scrape algae from
rocks and corals. Parrotfish also bite off pieces of coral, grinding up the
coral ‘skeleton’ to eat the tiny coral polyps or algae. But the parrotfish
can’t digest the ground-up skeleton therefore this passes through their
digestive systems to be excreted as ‘sand’! A single parrot fish can produce
tons of soft white sand during its lifetime.
Parrotfish are not shy and are regularly seen while
snorkelling or diving. Often you can hear the sound of their beaks scraping
against the coral before you even see them! You may even see them relieving
themselves of the indigestible portion of their meal in the form of sand that
will settle slowly to the bottom of the sea.
Protect Cayman wildlife! For more information, to share
your knowledge or if you would like to get involved with the many activities in
the National Trust’s Know Your Islands Program, please visit
www.nationaltrust.org.ky, or contact [email protected] or 949-0121.