Sponges recycle food for reefs

It is known as Darwin’s paradox: Coral reefs are rife with animal and plant life, yet exist in clear, nutrient-free waters. Where is the food coming from? The answer is sponges, researchers say.

Sponges take organic matter that is cast off by coral and algae and recycle it into food that is consumed by larger organisms like snails and crabs, according to a new study in the journal Science. The result is a “sponge loop” that allows the reefs to thrive in otherwise inhospitable waters.

“The largest source of energy and nutrients produced on the reef consist of things you cannot see,” said the lead author, Jasper M. de Goeij, a marine biologist at the University of Amsterdam. “And no one else but sponges can make use of that source.”

His team discovered the process while observing four common species of coral reef sponges in aquariums. They absorbed carbon and nitrogen from the water and converted 11 percent to 24 percent of it into choanocytes, the filtering cells that line a sponge’s interior walls. The sponges quickly shed those choanocytes, which were then eaten by larger organisms. The researchers confirmed that the sponges behaved similarly in a natural ocean environment.

De Goeij said his team was the first to discover that sponges also recycle dissolved organic matter. The findings could aid in efforts to conserve endangered coral reefs.

– New York Times

Earwax chronicles the life of a whale

Just as rings in a tree’s trunk can tell the story of that tree’s life and the environmental conditions it faced, so can plugs of earwax chronicle the life of a whale.

In a recent Science Friday podcast, researchers Sascha Usenko and Stephen Trumble of Baylor University explained how the robust, waxy plugs can provide a record of a blue whale’s health and illuminate such factors as pesticide exposure, stress and hormone levels, and sexual maturity.

Whales’ blubber has been used to analyze pesticide exposure, but fat can indicate only whether the animal was exposed to certain contaminants. The earwax reveals when the exposure occurred.

“What we’re able to do is to essentially go back in time,” the researchers said. “When we actually cut the ear plug in half, we can actually see the light and dark lamina, or the layers in there. … The farther we go toward the center, the farther back in time we go.”

– Washington Post