Elkhorn coral

About: Elkhorn coral is a research topic. Over the lifetime, 109 publications have been published within this topic receiving 16771 citations. The topic is also known as: Acropora palmata.

Climate change, coral bleaching and the future of the world's coral reefs

Abstract: Sea temperatures in many tropical regions have increased by almost 1 degrees C over the past 100 years, and are currently increasing at similar to 1-2 degrees C per century. Coral bleaching occurs when the thermal tolerance of corals and their photosynthetic symbionts (zooxanthellae) is exceeded. Mass coral bleaching has occurred in association with episodes of elevated sea temperatures over the past 20 years and involves the loss of the zooxanthellae following chronic photoinhibition. Mass bleaching has resulted in significant losses of live coral in many parts of the world. This paper considers the biochemical, physiological and ecological perspectives of coral bleaching. It also uses the outputs of four runs from three models of global climate change which simulate changes in sea temperature and hence how the frequency and intensity of bleaching events will change over the next 100 years. The results suggest that the thermal tolerances of reef-building corals are likely to be exceeded every year within the next few decades. Events as severe as the 1998 event, the worst on record, are likely to become commonplace within 20 years. Most information suggests that the capacity for acclimation by corals has already been exceeded, and that adaptation will be too slow to avert a decline in the quality of the world's reefs. The rapidity of the changes that are predicted indicates a major problem for tropical marine ecosystems and suggests that unrestrained warming cannot occur without the loss and degradation of coral reefs on a global scale.

Catastrophes, phase shifts, and large-scale degradation of a Caribbean coral reef.

Abstract: Many coral reefs have been degraded over the past two to three decades through a combination of human and natural disturbances. In Jamaica, the effects of overfishing, hurricane damage, and disease have combined to destroy most corals, whose abundance has declined from more than 50 percent in the late 1970s to less than 5 percent today. A dramatic phase shift has occurred, producing a system dominated by fleshy macroalgae (more than 90 percent cover). Immediate implementation of management procedures is necessary to avoid further catastrophic damage.

Long-Term Region-Wide Declines in Caribbean Corals

Abstract: We report a massive region-wide decline of corals across the entire Caribbean basin, with the average hard coral cover on reefs being reduced by 80%, from about 50% to 10% cover, in three decades. Our meta-analysis shows that patterns of change in coral cover are variable across time periods but largely consistent across subregions, suggesting that local causes have operated with some degree of synchrony on a region-wide scale. Although the rate of coral loss has slowed in the past decade compared to the 1980s, significant declines are persisting. The ability of Caribbean coral reefs to cope with future local and global environmental change may be irretrievably compromised.

White-band disease and the changing face of Caribbean coral reefs

Abstract: In recent decades, the cover of fleshy macroalgae has increased and coral cover has decreased on most Caribbean reefs. Coral mortality precipitated this transition, and the accumulation of macroalgal biomass has been enhanced by decreased herbivory and increased nutrient input. Populations of Acropora palmata (elkhorn coral) and A. cervicornis (staghorn coral), two of the most important framework-building species, have died throughout the Caribbean, substantially reducing coral cover and providing substratum for algal growth. Hurricanes have devastated local populations of Acropora spp. over the past 20–25 years, but white-band disease, a putative bacterial syndrome specific to the genus Acropora, has been a more significant source of mortality over large areas of the Caribbean region.

Regulation of microbial populations by coral surface mucus and mucus-associated bacteria

Abstract: Caribbean populations of the elkhorn coral Acropora palmata have declined due to envi- ronmental stress, bleaching, and disease. Potential sources of coral mortality include invasive microbes that become trapped in the surface mucus and thrive under conditions of increased coral stress. In this study, mucus from healthy A. palmata inhibited growth of potentially invasive microbes by up to 10-fold. Among cultured bacteria from the mucus of A. palmata, 20% displayed antibiotic activity against one or more tester strains, including the pathogen implicated in white pox disease. A novel mucus- mediated selection for coral symbionts revealed a discrete subset of bacteria and selected for isolates that produce antibiotics. This result suggests that coral mucus plays a role in the structuring of beneficial coral-associated microbial communities and implies a microbial contribution to the antibacterial activity described for coral mucus. Interestingly, antibiotic activity was lost when mucus was collected during a summer bleaching event. Isolates from apparently healthy A. palmata tissue during this event lacked antibiotic-producing bacteria and were dominated by members of the genus Vibrio, including species implicated in temperature-dependent bleaching of corals worldwide. This indicates an environmental shift from beneficial bacteria, and variability in the protective qualities of coral mucus, which may lead to an overgrowth of opportunistic microbes when temperatures increase. Finally, coral mucus inhibited antibiotic activity and pigment production in a poten- tially invasive bacterium, illustrating that coral mucus may inactivate mechanisms used for bacterial niche establishment.