Dislodged sponges can be successfully reattached to coral reefs

As part of a reef restoration study, researchers removed 20 specimens of the Caribbean giant barrel sponge from the Conch Reef off of Key Largo, Florida and then re-attached them using sponge holders consisting of polyvinyl chloride piping. The sponge holders were anchored in concrete blocks set on a plastic mesh base. Some sponges were reattached at a depth of 15 meters and some further down at 30 metres.

Venus Flower Basket sponge. A deep sea glass species.

The results of the study now show that sponges are capable of reattaching themselves to reefs if we help them by keeping them properly secured during the recuperation period. After being held stationary by sponge holders for as little as 6 months the sponges had reattached themselves to the Conch Reef. Of the 20 specimens reattached in 2004 and 2005, 62.5 percent survived at least 2.3-3 years and 90 percent of the sponges attached in deep water locations survived. During the study period, the area endured no less than four hurricanes.

This is very good news for anyone interested in reef restoration, since the new technique can be used to rescue sponges that have been dislodged from reefs by human activities or storms. Each year, a large number of sponges are extricated from reefs by human activities such as vessel groundings and the cutting movements of chains and ropes moving along with debris in strong currents. Severe storms can also rip sponges from the reef, which wouldn’t be a problem if it weren’t for the fact that so many sponges are also being removed by human activities. When combined, storms and human activities risk decimating sponge populations. Old sponges can be hundreds or even thousands of years old and their diameter can exceed 1 meter (over 3 feet). Sponges of such an impressive size and age can naturally not be rapidly replaced by new sponges if they die.

Sponges can survive for quite a while after being dislodged but is difficult for them to reattach themselves to reefs without any help since they tend to be swept away by currents and end up between reef spurs on sand or rubble, where they slowly erode and eventually die.

“The worldwide decline of coral reef ecosystems has prompted many local restoration efforts, which typically focus on reattachment of reef-building corals,” says Professor Joseph Pawlik of the University of North Carolina-Wilmington, co-author of the study. “Despite their dominance on coral reefs, large sponges are generally excluded from restoration efforts because of a lack of suitable methods for sponge reattachment.”

The results of the study, which were published in Restoration Ecology, show that we can help the sponges to survive by using the new technique. Earlier attempts were less successful since they relied on cement or epoxy; two types of adhesives that do not bind well to sponge tissue.