Sponges feel the heat from climate change

Fron an article by Jessica Marshall on Discovery News:

Aug. 28, 2008 -- In the oceans, it's not just corals that feel the heat from climate change.

New research finds that marine sponges suffer at the same elevated water temperatures that cause corals to bleach, suggesting that coral reef ecosystems may experience broad effects in a warming ocean.

Coral bleaching is a well-known phenomenon predicted to occur in warming oceans. It happens when the single-celled algae living within the corals disappear, leaving only the white coral skeleton behind.

Because of the symbiotic relationship between the algae and the coral -- the algae provides up to 90 percent of the coral's food -- the corals die when the algae leave.

But Nicole Webster of the Australian Institute of Marine Science in Townsville noted that corals are not the only marine creatures that rely on a symbiotic relationship with microorganisms to survive.

Microorganisms can make up as much as 40 to 60 percent of the weight of some sea sponges. Meanwhile, clams, nematode worms and even starfish can have bacteria or other microbes living on or in them, although not enough research has been done in many cases to know whether the relationship is truly a "you-scratch-my-back-I'll-scratch-yours" symbiotic association.