The M/V Wellwood and other Large Vessel Groundings: Coral Reef Damage and Recovery

Gittings, Stephen; Bright, Thomas; Hagman, Derek

The characteristics of reef community damage caused by three large vessel groundings in the Florida Keys were investigated between 1984 and 1991. Damage at each site included impact to living resources, framework alteration and fracturing, reef rock displacement, and sediment production. These were caused by vessel contact with the bottom, by propwash and cable dragging during attempts by operators and/or salvagers to refloat the ships, and by subsequent movement of destabilized substrates. None of the groundings were accompanied by significant cargo or fuel spills. Coral community recovery was followed for five years on Molasses Reef after the grounding of a 122 m freighter. Repetitive and random photographic methods, and diver counts were used to assess coral populations, cover, recruitment, and the fate of damaged coral colonies. Substantial population recovery occurred in the five years following the grounding, but colonies remained small. Hard coral recruitment was dominated by species that brood larvae. These species were also numerical dominants in undamaged communities nearby. Though, in time, complete recovery would occur naturally, transplantation could be used to increase the relative abundance of species found only rarely as recruits. These include primarily the large massive corals conspicuous in mature reef communities. Most are broadcast spawners, and have long planktonic stages, low recruitment rates, and low relative abundances in mature communities. Following large vessel groundings that cause extensive flattening of portions of the reef surface, transplantation could also serve to restore lost habitat complexity, and enhance the rate of development of associated invertebrate and reef fish assemblages.