There are few scenarios in this life where something pooping out the equivalent of five giant landmarks could be considered a good thing, but - hot damn - if sea cucumbers haven’t gone and found one. According to a new study published in the journal Coral Reefs, these mobile, squishy aerators collectively turn over approximately 70,000 tons (64,000 metric tonnes) of sand on a single coral reef annually. The ecological service all this excrement provides is known as bioturbation and it essentially involves airing out the upper layers of sediments as a means of releasing the organic material trapped within to the benthic (seafloor) community that rely on it.
This new research found that marine science has been overlooking the significance of sand-guzzling sea cucumbers (known as the holothurians) as a bioturbation tool. These alien-like lifeforms come in all shapes and sizes but are united in a shared purpose: to poop like no species has pooped before. Much like the popular 90s toy Water Wigglies, these animals are like a squishy hollow tube that takes in sand at one end, draws out things of nutritional interest, and excretes the rest from the other end.
“Despite being the larger and more conspicuous bioturbators on coral reefs, the value of holothurians (sea cucumbers) to reef ecosystems is less often attributed to their ecosystem services than their value for fisheries,” wrote the study authors. “This may be because they are considered to have an insignificant effect on reef health relative to other animals.”
But all is not so with these bountiful bioturbation tools, as revealed by remote sensing data taken from drone and satellite imagery across the Heron Island Reef in Queensland, Australia. The team used these images to estimate the population of cucumbers across the reef, which they found to be around the 3 million mark. Using this information, they could estimate the bioturbation rates of the area’s most abundant sea cucumber, Holothuria atra, by combining it with turn-over experiments with single H. atra and density measurements for the reef.
They found that just one H. atra was capable of turning over approximately 14 kilograms of bioturbated sediment per year. When this estimate was extrapolated to account for all the sea cucumbers on the reef they found the total sediment aerated by holothurians on Heron Reef to be around 70,000 tons per year, or “slightly more than the mass of five Eiffel Towers,” to quote the study abstract.
It’s perhaps unsurprising that the poop quota of sea cucumbers’ is so enormous, as these animals have proven they can even poop on the move. The value of these “walking colons” (to use Bill Bailey’s words) and their booties are certainly not lost on Pearlfish, who are known to occupy the back passages of sea cucumbers as a comfortable and secure hangout. You might sneer at such a concept, but - as the below footage demonstrates - Pearlfish aren’t one to pass up free real estate.
While an amusing stat on the defecation rates of sea cucumbers, the results of this study highlight the integral role carried out by holothurians, without which animals across the entire reef would suffer. As such, the researchers urge that steps must be taken to protect sea cucumbers from overharvesting as without an abundant and healthy population of these animals, reef ecosystems could find themselves in trouble.
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