Crown of Thorns

Not sure if this is the right place to post this, but I stumbled upon hundreds of crown-of-thorns starfish on a dive site in Lembeh recently. They were devouring coral like a plague of underwater locusts.

If anyone is visiting the area again soon, would be great if you can check to see if they're still there.

http://www.tonywublog.com/20070521/crown-of-thorns.html

Cheers,

Tony

Not sure if this is the right place to post this, but I stumbled upon hundreds of crown-of-thorns starfish on a dive site in Lembeh recently. They were devouring coral like a plague of underwater locusts.

 

If anyone is visiting the area again soon, would be great if you can check to see if they're still there.

 

http://www.tonywublog.com/20070521/crown-of-thorns.html

 

Cheers,

 

Tony

Last year I observed a huge invasion of crown of thorns on a dive site in Philippines. I was diving it on my first day there. Could count hundreds of COT eating nearly every hard coral in sight, except for one or two species like brain coral. The next week, all of the COT were already gone. And so was just about all of the hard corals. One year later, the dive site is still good, but different, with more soft coral and some recovery of some of the hard corals.

I hope that this site is OK.

some time ago someone (i think Seagrant) posted a good summary of how to properly go about getting rid of COTs. This involved a lot more than picking them up in baskets as they have a tendency to spawn when disturbed.

Can't find that post though... it was a good one and i learned some things i didn't know.

Mike - Searched WP and couldn't find anything more than injection of copper sulphate, a method I stumbled upon elsewhere on the net too. Other than that, I haven't come across any other references on how to dispose of them properly.

docrobina - I'm hoping they've dimished in number. I'm asking as many people as possible to check for me. I don't want the COT to decimate the reef, and I'm also just interested in knowing what happens, since there seems to be so little available information on outbreaks of these animals.

Despite the propensity for us to blame COT outbreaks on people, I haven't come across any clear studies demonstrating or suggesting this is true (still looking though). There are many potential reasons cited for COT outbreaks, but as with many other things, we just don't seem to really know.

The oft-cited potential human-induced causes for outbreaks include deforestation and runoff from land. The trees around Batu Angus look healthy, and there don't seem to be any farms or other causes of runoff nearby. The visibility was also clear. Global warming is often cited as a possible cause too. The water temperature was 28 Celsius, not out of the norm. Air temperature was nothing unusual, at least while I was there.

So I couldn't see any immediately obvious potential cause, but of course, that's probably just due to my own ignorance and/ or insufficient observational skills.

Wow Tony. That is too bad. The reefs in our part of the world are but rubbish since the bleaching and crown of thorns have done their work. I have heard that nitrates runoff from frarming have a role in this as well but i may be twisting topics.

-shawn

another reason for more COTs but certainly not on the # Tony is talking about is the sale of big shells. One of the main natural predators of the COT is the Tritons Trumpet. Unfortunately loads of people like to take those home as a lovely tropical souvenier....which of course sends the message to local folks to go out and capture more of them to make some money...

Simple message, don't buy shells!!!! Its one of my biggest pet peeves in this job, watching people pick up shells grrrr

Agree with you Mike re: the shells. They can be pretty and shiny when polished up for tourists, but collection of shells must take its toll, whether in the context of COT predators or just general health of reefs. Don't see any upside for the marine environment.

Shawn - I'm hoping this is just a temporary thing. The phenomenon appears to be something that can flare up and disappear relatively rapidly, allowing corals to recover within a reasonable timeframe. Given the location, I can't see nitrate runoff playing a major role, but who knows?

Just got a comment on my blog that suggests there might be some kind of similar event taking place on the Bunaken side of the area too. Difficult to know without more reports/ observation, but if there are outbreaks on both sides of the peninsula...

For now, I'm keeping my fingers crossed and hoping for the best.

It is not know the exact reasons for these outbreaks however anthropogenic causes are believed to be a major factor

This could occur in a few different ways but one is believed to be the increased amount of agricultural run-off causes algal blooms. This algae forms a major part of the corals diet, also a major part of the diet is the eggs of starfish including that of COT. Thus more starfish eggs survive and drift…. Hence ‘the outbreak came from nowhere’

It also may occur due to over fishing removing / reducing predators of the starfish. These include shrimps that feed on their larvae and more obviously fish species that actually feed on the adult starfish for example the Hump head Wrasse.

Lets hope that it is just a small scale outbreak and that the coral will recover, it's funny sometimes small scale disturbances can actually increase diversity.

Jon

docrobina - I'm hoping they've dimished in number. I'm asking as many people as possible to check for me. I don't want the COT to decimate the reef, and I'm also just interested in knowing what happens, since there seems to be so little available information on outbreaks of these animals.

 

 

So I couldn't see any immediately obvious potential cause, but of course, that's probably just due to my own ignorance and/ or insufficient observational skills.

The good news is that when I went there this year, (Anilao), there were no abnormal numbers of COTs, and when I asked my guide what happened to the COTs, as in did they go to another site.... he said nope did n't see them again. Who knows what causes them to do this swarming like behavior?

The site was very productive, and we found loads of great critters in the sand as expected. I unfortunately waited until the last day diving to go there, as I was reluctant to go from the prior year's COTs, but I should have had faith, and the site was just fine.

Hopefully it will just pass in Indo as well...

Robin

Hey Tony,

I'll be in Lembeh next week for almost a complete month of loverly, unadulterated, exquisite muck and macro filming. Which dive site are you referring to and I'll make a point to check it out. Mind you I have also been doing some macro here recently and some of the textures of COT's under the right light are stunning.

Another take on it is that these 'outbreaks and population explosions' could also be a natural phenomena of the species at hand, with or without the presence of Triton Trumpets, or other predators. As underwater imagery chasers we are also have our own ideas of what is good, bad and indifferent to the well being of our reef systems etc. Take away the mankind induced problems (pollution, construction, recuperation's of lands etc) and this could well be a natural fluctuation of this species population.

Just another possible idea, we know so little about the Ocean and its workings its anyone's guess really.

Cheers,

Mark.

Hey Mark,

Batu Angus. Can't miss it while you're there. I'll describe it to you when I see you in Singapore next week. Will be good to have you on the ground there to see how this thing is progressing, or not.

Cheers,

Tony