No abstract

Two main hypotheses have been developed for describing the role and importance of the sea urchin Diadema antillarum on reefs of the Caribbean region in both space and time. The first and most crucial is whether D. antillarum was the most important “keystone” grazer on Caribbean reefs? The alternate to this hypothesis is that D. antillarum was merely a redundant species, playing a secondary role to herbivorious fishes which only came into dominance after herbivorous fishes had been removed by man through exploitive fishing practices. To resolve this debate, we pose the question: “What is the role of Diadema antillarum in altering the composition of the benthic community on Caribbean coral reefs in time and space?” The interpretation presented herein implies that D. antillarum was and is the most important shallow-water herbivore on Caribbean coral reefs. This is contrary to a prevailing model but in substantial agreement with the historical importance of the species. If correct, the continued and future recovery of this sea urchin may be the key ingredient to facilitating coral reef recovery throughout the region. In addition, on coral reefs where the natural recovery of Diadema has been delayed or is absent (e.g. the Florida Reef Tract); measures to actively restore these urchins may be the most efficient and cost-effective tool for conserving and enhancing the ecological function of reefs. This debate also emphasizes the requirement for implementing ecologically-based, not ideologically-based management of natural systems.

While diving and snorkeling in shallow water (1-3 m) on the leeward side of the exposed reef flat at Grecian Rocks within the Florida Keys National Marine Sanctuary in December 2006, we discovered numerous exposed colonies of Siderastrea siderea. These S. siderea colonies each measured approximately 40 cm in total height with the upper 10 cm still being alive. Each coral head is represented by three punctuated periods of coral growth (Fig. 1). These corals were found in areas dominated by mobile carbonate sand. Based on measured growth rates of shallow-water colonies of S. siderea (average~5.75 mm yr-1) from the region (WF Precht, unpublished data using annual growth band records from slabbed colonies), we calculated that the exposed portions of these corals are approximately 70-75 yr in age. Using the measured height of each individual section, we can reconstruct the history of these colonies in relationship to the passage of known significant hurricanes in the upper Florida Keys. The notch at the base of the lowermost section is coincident with the passage of the Great Florida Keys Hurricane of 1935, the second notch correlates with the passage of Hurricane Donna in 1960, and the third notch (at the base of the living coral) is contemporaneous with Hurricane Andrew in 1992. Each of the three storms moved from east to west over the Florida Keys. Each punctuated segment records coral growth during the intervening period between major storms. During the passage of Hurricane Wilma in October 2006, the bases of these colonies were excavated and exposed. Hurricane Wilma traversed the Florida reef tract in the opposite direction from these earlier storms, moving west to east; transporting great quantities of sediment out of the back reef and onto the fore reef. These colonies show the amazing resilience of S. siderea to sediment burial and help to explain the widespread occurrence of these corals on reefs throughout south Florida.

Two main hypotheses have been developed for describing the role and importance of the sea urchin Diadema antillarum on reefs of the Caribbean region in both space and time.The first and most crucial is whether D. antillarum was the most important "keystone" grazer on Caribbean reefs? The alternate to this hypothesis is that D. antillarum was merely a redundant species, playing a secondary role to herbivorious fishes which only came into dominance after herbivorous fishes had been removed by man through exploitive fishing practices. To resolve this debate, we pose the question: "What is the role of Diadema antillarum in altering the composition of the benthic community on Caribbean coral reefs in time and space?" The interpretation presented herein implies that D. antillarum was and is the most important shallow-water herbivore on Caribbean coral reefs. This is contrary to a prevailing model but in substantial agreement with the historical importance of the species. If correct, the continued and future recovery of this sea urchin may be the key ingredient to facilitating coral reef recovery throughout the region. In addition, on coral reefs where the natural recovery of Diadema has been delayed or is absent (e.g. the Florida Reef Tract); measures to actively restore these urchins may be the most efficient and cost-effective tool for conserving and enhancing the ecological function of reefs. This debate also emphasizes the requirement for implementing ecologically-based, not ideologically-based management of natural systems.PeerJ PrePrints | https://doi.org/10.7287/peerj.preprints.1565v2 | CC-BY 4.0 Open Access |

Two main hypotheses have been developed for describing the role and importance of the sea urchin Diadema antillarum on reefs of the Caribbean region in both space and time.The first and most crucial is whether D. antillarum was the most important "keystone" grazer on Caribbean reefs? The alternate to this hypothesis is that D. antillarum was merely a redundant species, playing a secondary role to herbivorious fishes which only came into dominance after herbivorous fishes had been removed by man through exploitive fishing practices. To resolve this debate, we pose the question: "What is the role of Diadema antillarum in altering the composition of the benthic community on Caribbean coral reefs in time and space?" The interpretation presented herein implies that D. antillarum was and is the most important shallow-water herbivore on Caribbean coral reefs. This is contrary to a prevailing model but in substantial agreement with the historical importance of the species. If correct, the continued and future recovery of this sea urchin may be the key ingredient to facilitating coral reef recovery throughout the region. In addition, on coral reefs where the natural recovery of Diadema has been delayed or is absent (e.g. the Florida Reef Tract); measures to actively restore these urchins may be the most efficient and cost-effective tool for conserving and enhancing the ecological function of reefs. This debate also emphasizes the requirement for implementing ecologically-based, not ideologically-based management of natural systems.PeerJ PrePrints | https://doi.org/10.7287/peerj.preprints.1565v2 | CC-BY 4.0 Open Access |