Day 94: Oops, snagged a reef sponge? Just put it back.

Large barrel sponge. Credit: John Burke

Out of the University of North Carolina at Wilmington — which happens to be my undergraduate alma mater — comes good news for coral reef restoration.

Study authors Steven McMurray and Joseph Pawlik report that sponges knocked off their reefs by human activities or storms can actually be re-attached with excellent success.

“The worldwide decline of coral reef ecosystems has prompted many local restoration efforts, which typically focus on reattachment of reef-building corals,” said Pawlik, a marine biologist at the university.

“Despite their dominance on coral reefs, large sponges are generally excluded from restoration efforts because of a lack of suitable methods for sponge reattachment.”

Credit: Joseph Pawlik lab, UNCW

Pawlik and his lab group have been studying giant barrel sponges for more than a decade. Two species of the sponges live deep in tropical waters on both sides of the globe.

In an essay on his website that reads as part research description and part tribute to the large (up to six feet) sponges, Pawlik describes them as “very complicated animals with very simple body plans.”

He continues:

They use millions of tiny flagellated cells both to move water through channels in their bodies and to capture bacteria-sized food particles.  They may build an internal skeleton of tiny glass needles or protein fibers, both of which help to prevent their bodies from being torn apart by currents.  Unlike any other animals, they don’t separate the inside of their bodies from the outside  – their tissue is an aggregation of cells, and among the sponge cells are often a diverse array of microorganisms, including photosynthetic blue-green bacteria, which give some of them a brownish coloration.

The largest of the sponges can be up to 2,000 years old, and researchers have dubbed them “the redwoods of the reef.”

But the seemingly robust sponges face numerous threats, including the same bleaching that can occur in corals from both human-caused and natural changes to their environments. 

More importantly with respect to this study, the great sponges are at risk from becoming damaged or dislodged by severe storms, vessel groundings and the cutting movements of chains or ropes moved along with debris by strong currents. After these events, detached large sponges are commonly found, still alive and intact, between reef spurs on sand or rubble where — unable to re-attach on their own — they slowly erode in the currents.

In an underwater experiment off the Florida coast at Key Largo, McMurray and Pawlik transplanted sponges and tethered them to their new substrates using piping anchored in concrete blocks.

Though the test area endured four hurricanes during the study period, 62.5 percent of sponges survived at least two to three years, and 90 percent of the sponges attached in deep water locations survived. The sponges reattached to the reef after being held stationary by sponge holders for as little as six months. 

The paper appeared in the March 2009 issue of the journal Restoration Ecology.

Source: A Eurekalert press release and the study, accessed through Joseph Pawlik’s website.