Friday, April 24, 2009

Resilience in Acropora Corals

Great news - local management of water quality and other factors may significantly contribute to the survivability of coral reefs that have been negatively impacted by climate change.

A massive bleaching event took place on the Great Barrier Reef approximately three years ago and devastated a huge number of inshore reefs, but the Acropora corals made an unprecedented comeback – in only a year’s time!

According to Guillermo Diaz-Pulido, three critical factors contributed to this unprecedented turn around, “first was exceptionally high re-growth of fragments of surviving coral tissue. The second was an unusual seasonal dieback in the seaweeds, and the third was the presence of a highly competitive coral species, which was able to outgrow the seaweed. But this also all happened in the context of a well-protected marine area and moderately good water quality.”

Sophie Dove of the Centre for Marine Studies and Australian Research Council Centre of Excellence for Coral Reef Studies points-out that, “The exceptional aspect was that corals recovered by rapidly regrowing from surviving tissue. Recovery of corals is usually thought to depend on sexual reproduction and the settlement and growth of new corals arriving from other reefs. This study demonstrates that for fast-growing coral species asexual reproduction is a vital component of reef resilience.”

Coral recovery following algal overgrowth
(Images from Artcle)

Branches of Acropora corals died after bleaching and were subsequently colonized by a variety of benthic algae. Remnant coral tissue at the base of the coral colonies regrew upward and deposited new skeleton along the old dead coral branch, overgrowing

A) algal turfs (arrows). B) fleshy seaweed Lobophora variegata.

C) crustose coralline algae. D) Coral tissue has all but completely overgrown the colonizing algae.

E) Thin section of coral showing benthic algae sandwiched between old coral skeleton and a thin layer of new skeleton. Examination using a compound microscope showed that coral tissue overgrew a range of algal types.

Ove Hoegh-Guldberg of CoECRS and The University of Queensland suggests, “...that managing local stresses that affect reefs such as overfishing and declining water quality can have a big influence on the trajectory of reefs under rapid global change.”

Read the Article from PLoS One - HERE

Diaz-Pulido, G., McCook, L., Dove, S., Berkelmans, R., Roff, G., Kline, D., Weeks, S., Evans, R., Williamson, D., & Hoegh-Guldberg, O. (2009). Doom and Boom on a Resilient Reef: Climate Change, Algal Overgrowth and Coral Recovery PLoS ONE, 4 (4) DOI: 10.1371/journal.pone.0005239

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