Author Topic: bleached sponges??  (Read 4763 times)

zoomer4

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bleached sponges??
« on: July 31, 2008, 00:51:53 UTC »
on a few of my dives lately in the Keys I've seen barrel sponges that have lost all of their color, they're white. I think they are dead. Is this a normal part of their life cycle? I doubt it, but I'm wondering if anyone can tell me what's going on. thanks.

DocV

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Re: bleached sponges??
« Reply #1 on: July 31, 2008, 10:42:41 UTC »
Hi Zoomer4,

Sponges, and corals, too, do not have intrinsic color.  They are naturally white or light grey.

However, their tissues are colonized by symbiotic microorganisms which do provide coloration. In corals these are an algae, specifically zooxanthellae. In sponges, including barrel sponges, they are a bacteria, specifically cyanobacteria.

Bleaching results when these microorganisms are lost due to pollution, abnormally high water temps (such as are caused by an El Nino), direct physical injury (such as results from divers grabbing them) and similar trauma.

While bleaching is becoming distressingly common, and may be accompanied by a reduction in size and increased susceptibility to predation by creatures like parrotfishes, it is only rarely fatal to the entire sponge.

Helpful?

Regards,

DocVikingo

zoomer4

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Re: bleached sponges??
« Reply #2 on: July 31, 2008, 20:07:19 UTC »
Thanks DocV
That is helpful. I have only seen a few bleached sponges and they are in amongst healthy ones. The entire sponge was affected. I don't recall noticing any trauma to them, but I will be more observant next time.
thanks again

 

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