Reserve effects and natural variation in coral reef communities

Published source details Harborne A.R., Mumby P.J., Kappel C.V., Dahlgren C.P., Micheli F., Holmes K.E., Sanchirico J.N., Broad K., Elliott I.A. & Brumbaugh D.R. (2008) Reserve effects and natural variation in coral reef communities. Journal of Applied Ecology, 45, 1010-1018.
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Summary

Increasing numbers of ‘no-take’ marine reserves are being established, their objectives including conservation of fisheries and biodiversity. Despite promotion of conservation benefits, actual data documenting beneficial effects are scarce. To identify reserve benefits, reserve effects must be separated from confounding variables. This study was undertaken in The Bahamas (a relatively lightly fished area of the Caribbean) in a large no take coral reserve and several ‘unprotected’ sites at varying distances from it.

In October 2004, benthic (video quadrats) and fish communities (underwater visual censuses) were sampled in the well-protected Exuma Cays Land and Sea Park coral reef reserve (442 km²). Changes inside and outside the reserve were compared with those at equivalent spatial scales in other Bahaman reefs lacking reserve status. Two habitats were sampled:

i) Montastraea reef - 3 sites around the reserve centre, 3 unprotected sites 5.8-18.1 km to the north and 3 unprotected sites 70 km to the south;

ii) Gorgonian plain - 9 sites around the reserve centre; 6 unprotected sites (><1-10 km distant) both south and north of the reserve.

Reserve-level differences in benthic or fish communities not apparent in the unprotected study reefs were considered 'robust' effects; 'misleading' effects were those where equivalent differences were also apparent in unprotected reefs.

To assess natural variation, reefs around five islands (Andros, San Salvador, South Caicos, Bimini and Abaco) were surveyed between July 2002-November 2003.

Reserve Montastraea reef sites had 15% more fish species than unprotected sites (average 48.7 vs. 42.3). This was the sole significant ‘robust’ reserve effect on species diversity observed; the greater diversity was mostly due to more large-bodied groupers (Serranidae: four Mycteroperca spp. and Epinephelus striatus), damselfish (Pomacentridae: six Stegastes spp. and Microspathodon chrysurus), and butterflyfish (Chaetodontidae: five species) inside the reserve.

Increases in fish biomass and differences in community structure inside the reserve were limited to large-bodied groupers on Montastraea reefs (average large serranid biomass 4,751g/200 m² inside vs. 1,029g for unprotected sites).

On reserve Montastraea reefs, increased grazing pressure by parrotfish (Scaridae) lowered seaweed cover, causing some changes in benthic community structure compared to the unprotected sites.

Note: The compilation and addition of this summary was funded by the Journal of Applied Ecology (BES). If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://www3.interscience.wiley.com/cgi-bin/fulltext/120120658/PDFSTART