ECOLOGIA ARTICULO 1 - Journal of the Marine Biological...

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Revisiting the population status of the sea urchin Diadema antillarum in northern Puerto Rico alex e. mercado-molina 1,2 , alfredo montan ~ez-acun ~a 1,2 , ruber rodri ’guez-barreras 1 , roberto colo ’n-miranda 1,2 , geraldine di ’az-ortega 1,2 , neidibel marti ’nez-gonza ’lez 1,2 , sandra schleier-herna ’ndez 2 and alberto m. sabat 1 1 University of Puerto Rico-Rı´o Piedras Campus, P.O. Box 70377, San Juan, Puerto Rico 00936-8377, 2 Sociedad Ambiente Marino, PO Box 22158, San Juan, Puerto Rico 00931-2158 The mass mortality suffered by the sea urchin Diadema antillarum between 1983–1984 is considered one of the major causes of coral reef degradation in the Caribbean. Its near disappearance resulted in a disproportionate growth of macroalgae that has led to a ‘phase shift’ from coral-to-algal dominated reefs. The close relationship between this echinoid and the functioning of coral reef ecosystems makes it imperative to better understand the potential for recovery of its populations. From 2009 to 2011, we assessed the density and size structure of D. antillarum in various reefs where previous population data were avail- able. Results indicate a modest increase in density in all localities with respect to the last time they were surveyed in 2003/2004. Nevertheless, density values are still lower than values reported for the island prior to the die-off. Overall density did not surpass 1.49 ind. per m 2 2 , and did not change considerably during the studied period. Lack of population growth coincided with a lack of juveniles; suggesting that population growth at the studied sites may be limited by the number of individuals recruiting into the juvenile stage. Keywords: Caribbean, coral reefs, Diadema antillarum , population recovery, Puerto Rico Submitted 19 July 2014; accepted 14 November 2014 I N T R O D U C T I O N In the early 1980s an unknown pathogen caused a massive mortality in the sea urchin Diadema antillarum that reduced its populations between 93–100% throughout the Caribbean (Bak et al. , 1984 ; Lessios et al. , 1984 ). Before the die-off, this echinoid was one of the major macroalgae consu- mers in coral reefs ecosystems, as Diadema africanum in sub- littoral ecosystems of the Canary Islands (Cabanillas-Tera ´n et al . 2014 ); what supports the importance of the genus Diadema as a keystone species (Edmunds & Carpenter 2001 ). The absence of this important herbivore has resulted in fleshy macroalgae out-competing coral for space and limiting coral recruitment (Edmunds & Carpenter, 2001 ; Carpenter & Edmunds, 2006 ; Myhre & Acevedo-Gutie ´rrez, 2007 ). Accordingly, the collapse of D. antillarum is considered one of the major causes of the drastic decline in coral cover in the Caribbean (Carpenter & Edmunds, 2006 ). Recent studies suggest that a recovery process is occurring across the Caribbean (Carpenter & Edmunds, 2006 ). In Puerto Rico the current state of recovery, however, is uncertain as very few population studies have been conducted after the die-off (i.e. Weil et al. , 2005 ; Ruiz-Ramos et al. , 2011 ; Soto-Santiago and Irizarry-Soto, 2013 ; Rodrı´guez-Barreras et al ., 2014 ). Moreover, no study has assessed changes in
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