Our ocean filters – sea janitors under threat
An older blog for the Uto Ni Yalo.
22 July 2012 –
Our Ocean Filters – sea janitors under threat
From Lattitude 14o S, Longitude 163o E
Here’s a thought from the Uto ni Yalo as she makes her way to Espiritu Santo to re-stock her supplies before attempting the now very elusive crossing to New Caledonia. It will be the third attempt and if history is anything to go by, we will make it this time.
But here’s our food for thought for today. It is based on the Holothuria or to most, beche-de-mer or sea cucumbers. This blog will discuss very briefly the distribution of sea cucumbers before giving you an insight into its ecological importance and the threats they currently face.
Sea cucumbers live in all sea habitats, ranging from areas exposed at low tide to the bottom of the deepest part of the ocean. Some species live on wave-hammered reef crests and rocky shorelines. Many species live on hard bottoms, others burrow in sand or mud whereas some species swim miles above the sea floor.
They are also found in great numbers on the deep sea floor, where they often make up the majority of the animal diversity. In more shallow waters, sea cucumbers can form dense populations, where for some species they can sometimes reach densities of 1,000 individuals per square meter.
The body of some deep water holothurians is made of a tough gelatinous tissue with unique properties that makes them able to control their own buoyancy, making it possible for them to either live on the ocean floor or to float over it to move to new locations with a minimum of energy.
The greatest holothurian diversity occurs in the tropical Indo Pacific region. However there are a growing number of reports stating that sea cucumber populations are declining world-wide in tropical and subtropical countries with reports of overexploitation from collection areas in Australia, India, Thailand, Papua New Guinea, the Galapagos, Pacific and other locations.
Sea cucumbers are important components of the food chain. When feeding, once the food enters the sea cucumber’s mouth it travels to a simplistic stomach and through intestines where basic nutrients are absorbed, before the waste is displaced out of the anus. Often times the sea cucumber acts as a sea floor janitor, ingesting large amounts of sand, absorbing any organic matter before releasing the clean sand.
Sea cucumbers are also important in determining the presence or otherwise of other marine organisms. In the absence of fishing pressure, individual sea cucumbers process an immense amount of sediment each day. This process prevents the build-up of algal growth and may help control populations of pest and invasive species including certain bacteria.
In some areas, the local extinction of sea cucumbers has resulted in the hardening of the sea floor, eliminating habitat for other ocean floor organisms and plants.
Sea cucumbers are threatened by overexploitation to supply international markets with luxury food items, as well as a source of aquariams and specimens for biomedical research.
They are extremely vulnerable to over exploitation due to their late maturity, density-dependent reproduction, low survival of larvae and ease of collection by humans.
On the deep sea floor, as already mentioned, holothurians can comprise more than 90% of the ecosystem diversity, and since deep waters cover over 70% of the surface of the earth, holothurians are among the most dominant organisms on our planet.
It must be highlighted therefore, that their threatened status goes beyond their own existence. The more we kill and trade the sea cucumber off, the worse our marine environments will become. The sands on the beach wont as white as it should be. Algae will grow and Small fish wont be able to feed, and when small fish disappear, big fish disappear. Algae will smother and kill the coral.
Like all organisms on land and sea, we are all interdependent on each other, Bech de mer (Dri in Fijian) (holothurians) are no exception. Remove them to our own peril.
By Teddy Fong,
Uto Ni Yalo