Sea cucumber 'poo' crucial in protecting coral reefs | Pacific Beat

Sea cucumber 'poo' crucial in protecting coral reefs

Sea cucumber 'poo' crucial in protecting coral reefs

Updated 6 February 2012, 15:31 AEDT

Scientists have found that the humble sea cucumber can play an important role in protecting coral reefs from the impacts of climate change.

The research by a team from the University of Sydney has upset some Pacific nations where sea cucumbers or bêche de mer is being over fished, sometimes to the point of local extinction.

Presenter:Geraldine Coutts

Speaker:Professor Maria Byrne, Universtiy of Sydney

BYRNE: Sea cucumbers eat an enormous amount of sand, it's almost like the worms in your garden, they process sand through their body using all the nutrients that they need from them, but in the process they agitate the sediment and what we found what was really quite extraordinary what they release is of higher PH than what they take in. So they're actually increasing alkalinity, increasing the PH of the water immediately around the corals, and that's good for the corals and will work to protect the corals from ocean acidification, which is what is happening with climate change.

COUTTS: Well if that process is withdrawn through the over-harvesting of bêche de mer or sea cucumber, what is the impact of that?

BYRNE: Well that's the whole point really is now, we really need to know the ecological impact of the removal of these animals from reefs. And this has been going on for hundreds of years, so we need to know more about their role in the environment but what it points out is that in order for reefs to be healthy all the parts of the ecosystem are needed. So these vacuum cleaners that vacuum up the sediment are really an important part of the ecosystem, and for sustainable fishing there needs to be a balance with how many of these animals that you leave behind to allow them to reproduce and replace themselves and to fulfill these ecological roles, and over-fishing is just taking them, because they're easily fished, they don't run very fast, it's like a mining exercise, once you take them they don't necessarily come back very quickly.

COUTTS: Are they prolific breeders, can they be replaced easily?

BYRNE: No, this is the real problem, it's called gnarly effect, boys got to find girl because they spawn into the environment. So unless the eggs and the sperm are within proximity with each other there can be no babies. So this is a real problem with a lot of fisheries for invertebrates, if you take enough of the maters away there can be no reproduction.

COUTTS: Well what's the status of the population at the moment? Is it critical?

BYRNE: Right through the Pacific world these animals have been taken off to the point where they no longer exist, so there's local extinction of some of the very, very high value species. There's been a terrific interest in aquaculture but that's a little ways off too. So the island nations that have lost their sea cucumbers off their coral reefs I would be concerned.

COUTTS: Can they be reintroduced if there's a supply elsewhere, can they be introduced into a location or are they location specific?

BYRNE: A lot of them are location specific, now you do have to worry about moving brood stock around of different genetics, but aquaculture might be one way but the aquaculture is used for market and has only be successful for really only one way species. So it's actually rather grim I have to say.

COUTTS: Well how many species are there?

BYRNE: Well there's hundreds but there's about 40 that are commercially fished and of course the ones that are commercially fished are the biggest ones and they're probably the ones that do the greatest positive ecological role on the reef.

COUTTS: Are you suggesting then Professor that it's too late even if they stop fishing them or put a clamp down on fishing?

BYRNE: Well ok put it this way, before World War 2 when they were still being fished for China there was whole parts of the Indo Pacific where the sea cucumbers were fished out and weren't there. Then the Chinese market closed down for about 50 years and during that 50 years there was a replacement, slowly but surely a replacement. Then because these are fish for China the market has come back on again and now the same situation's happened. So it could be another 50 to 100 years before they're back.

COUTTS: Well we know that our scientists are smart people and geneticists in particular, are they able to reproduce on the bench and then introduce them or synthetically synthesise in any way?

BYRNE: No that sort of magic even though you see them in science fiction movies, that sort of solution is very far away. I think the most important solution is to try and keep our reefs as healthy as we can and be aware that every part of the ecosystem, and in particular now the sea cucumbers, are playing a crucial role for the health of that particular reef system.

COUTTS: Well without the fertiliser or the PH that the sea cucumber produces, what happens to the coral, is there a substitute, can it be substituted in any way to protect the coral reefs?

BYRNE: No not very easily because the interesting thing about the sea cucumbers because they also release ammonia, which in big amounts is toxic, but it's like a slow release fertiliser which assists the coral to grow, and when they live in and around corals it's the slow release of this higher PH, it'd be their faeces really, the poo coming out their end, and that sort of local effect is very difficult to manage artificially.

COUTTS: So we are going to lose some species then?

BYRNE: Well we've already lost the species, but from certain areas what's really important to recognise is that it's not just the losing the species that's of concern, but it's the ecological role of losing these to reef systems, particularly at a time now when they're facing the challenge of climate change and ocean acidification.

COUTTS: What are you recommending Professor?

BYRNE: Well I'm recommending there's reefs throughout the system that are still in reasonable condition. We know the Great Barrier Reef for instance has received lots of protection and so I think peoples that have reefs that are in good shape should try and maintain those reefs and maintain their sea cucumber populations, as well as all the other invertebrates that also must be doing important things, and use that as a mean perhaps to re-populate down the track other places locally.

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