Initial results of a long-term coral reef monitoring program: Impact of Hurricane Hugo at Buck Island Reef National Monument, St. Croix U.S. Virgin Islands

Abstract

Fixed position linear transects were established in early 1989 at Buck Island Reef National Monument, St. Croix, U.S. Virgin Islands. On September 17–18 of that year Hurricane Hugo, the most severe cyclone to impact the area in over 60 years, passed directly over the island bringing hurricane-force winds for over 12 h and maximum estimated wind speeds of 70 m · s −1 (160 mph). Despite the severity of the storm, damage to coral reefs was extremely localised and concentrated mainly on reefs open to its southeasterly direction of approach. The southeast reef front at Buck Island was razed to substrate level between the surface and 7 m depth and the reef crest behind it was smothered in a 1 m deep berm of broken coral rubble. At a site on the north backreef, however, only a slight loss of coral cover was detected which was more than compensated for during 1990–1991. At a south reef site which was in 8–10 m depth, just outside the region of severe damage, coral cover was reduced by 40–46% on three out of four transects. Shifts in community structure were detected by multi-dimensional scaling of Bray-Curtis similarity measures and by k-dominance curves, but not by the Shannon diversity statistic (H′). Coral cover had returned to approximate pre-hurricane levels by June 1991, but community composition remained distinct. One of the four transects at this south site was apparently not significantly damaged during the hurricane. Such spatial variability may affect recovery rates, since pockets of relatively undisturbed benthos may provide seed populations for recruitment into adjacent, more severely damaged areas. Hurricane Hugo did not appear to cause an immediate increase in species diversity by differential mortality of the dominant species in the community. This result is consistent with previous studies of the impact of less severe storms on St. Croix, but contrary to several reports of hurricane impact in other areas.