BackgroundThe rising temperature of the world's oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin.Methodology/Principal FindingsSatellite-based tools provided warnings for coral reef managers and scientists, guiding both the timing and location of researchers' field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles.Conclusions/SignificanceThermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate.

No abstract

We describe Symbiodinium necroappetens sp. nov. found predominantly in diseased or thermally damaged tissues in some reef corals of the Greater Caribbean. Small, albeit fixed, differences in the ribosomal DNA (ITS2 and LSU) and cytochrome b (cob) indicate that S. necroappetens is evolutionarily separate, but closely related to S. microadriaticum (members of Clade A). However, haplotype sequences of the non-coding region of the psbA minicircle are highly divergent, signifying that the degree of genetic divergence between these sibling lineages is far greater than indicated by changes in rDNA. Small morphological differences also support the delineation of this species. The Kofoidian plate formula for S. necroappetens (x-plate, EAV, 4′, 5a, 8′′, 9-11s, 21c, 6′′′, 2′′′′, PE) is generally the same as described for S. microadriaticum, except for the number of cingulum plates (21 vs 22-24), but plate shapes and configurations differ. Nuclear and mitochondrial volumes calculated from ultrastructural serial sections (published previously) also distinguish it from S. microadriaticum and S. pilosum. There are significant physiological differences in the response of S. necroappetens to high pCO 2 and thermal stress when compared with S. microadriaticum, indicating that large functional differences exist even among closely related species. This species appears to be necrotrophic rather than mutualistic. Before it was recognized as a distinct entity, reports on its ecology contributed to the supposition that members of Clade A Symbiodinium were opportunistic. Available evidence indicates that S. necroappetens exists at low environmental background levels, but may 'proliferate' selectively in artificial growth media, or emerge opportunistically in bleached coral colonies during early recovery from severe stress, or in diseased necrotic tissues, especially in colonies of the Orbicella (formerly Monstastraea) annularis complex. However, S. necroappetens fails to persist at detectable levels as populations of the typical symbiont recover. The description of this species raises awareness of the broad functional and ecological diversity exhibited by members of this large dinoflagellate genus.

Thirteen reef areas of Colombian territories in the Southwestern Caribbean were surveyed during the last 10 years. Coral diseases have been recorded in all these areas since 1990 and some of them have increased progressively. Six types were differentiated in the region, of which black band disease (BBD), dark spots disease (DSD), white band disease (WBD) and white plague disease (WPD) are widespread and common. Yellow band disease (YBD) was observed only since April 1998 but has been found now in seven reef areas and eight coral species (most of them recorded here as new hosts). In total, 25 species of hard corals were observed with diseases in the region, of which Colpophyllia natans, Diploria labyrinthiformis, Montastraea annularis, M. Javeolata, M. Jranksi and Acropora spp. appear to be highly susceptible.

No abstract