[Coral-List] Sponge overgrowth of corals justifies MPAs on Caribbean reefs. Seaweeds? Maybe not.

[Pawlik, Joseph]

Hello Colleagues,

I'm pleased to alert you to a new publication from our research group that you might find interesting.
We took advantage of decades of overfishing that have resulted in a Caribbean-wide manipulative experiment to compare fish and benthic surveys of 25 sites subjected to fish-trapping and netting with 44 less-fished sites (MPAs or remote reefs) from 12 countries across the Caribbean.
(1) Reefs that were overfished had 3X more sponge overgrowth of reef-building corals, and 2X more overall contact between sponges and corals, and >25% of coral colonies at overfished sites were adjacent to, or overgrown by, sponges. These sponges were predominantly those that are eaten by sponge-eating fishes. Coral mortality by smothering and allelopathy was particularly evident at overfished sites.
These data provide unambiguous justification for MPAs on Caribbean reefs.
They also provide a rare example of indirect effects of fishing on coral mortality at the community-level (10s of fish species, 100s of sponge species) across a broad geographic region.

(2) Surprisingly, the seaweed cover was higher on less-fished reefs.
This last result will be controversial, but others have recently reported similar findings for Caribbean reefs (see Aronson, Burkepile refs in paper), which may reflect the inability of fishes alone to control macroalgae, or nutrient enrichment by larger fish biomass.

Here's the paper:
https://dx.doi.org/10.7717/peerj.901
Loh, T.-L., McMurray, S.E., Henkel, T.P., Vicente, J. and Pawlik, J.R. 2015.. Indirect effects of overfishing on Caribbean reefs: sponges overgrow reef-building corals. PeerJ, 3: e901

This paper is published in PeerJ, a relatively new and innovative journal that allows reviewers the option of signing their reviews, and also publishes the original manuscript, reviews, and authors' responses -- I encourage you to review these documents for this paper as they contain additional background information.

For those of you unfamiliar with sponge abundance on Caribbean reefs, you can check out these video dives at the Pawlik Lab YouTube channel from around the Caribbean:

"Reefs of Roatan"                 https://youtu.be/1JzdYwO2YGo

"Close-up on Conch Reef"   https://youtu.be/qdjhm7ojGJk

"Sponge gardens of Saba"   https://youtu.be/pISij0Zqj90

"The reefs of Carrie Bow"   https://youtu.be/Uy79ajDDIGg





Cheers,
Joe

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Joseph R. Pawlik, Professor,
Dept. of Biology and Marine Biology
UNCW Center for Marine Science
5600 Marvin K Moss Lane
Wilmington, NC  28409
Office:(910)962-2377; Cell:(910)232-3579
Website: http://people.uncw.edu/pawlikj/index.html
PDFs: http://people.uncw.edu/pawlikj/pubs2.html
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