Disturbance and recovery of a deep-water Caribbean seagrass bed

The seagrass community in a deep-water (20 m) submarine canyon on St. Croix, US Virgin Islands showed strong seasonal changes in abundances (50 to 90 % of yearly maxima) of major plant species in response to predictable winter conditions of low light and storms. Major species were the seagrass Halophila decipiens and the green macroalga Halimeda incrassata. Virtual elimination of the seagrass occurred following particularly severe storms; the alga was more resistant. Seagrass and alga regained their pre-disturbance biomass or abundance within 6 to 8 mo after major storms. Addition of nutrients to the sediments had no effect on the growth or recolonization rate of the alga. The rates of recolonization of the alga and seagrass were controlled by light availability in winter. Dynamics of disturbance and recovery in this deep-water seagrass bed are very different from other Caribbean seagrass communities in shallow waters, which are more resistant to storms of similar magnitude but once disturbed take many years for recovery. The deep-water seagrass bed is an example of a tropical community that is structured by seasonal abiotic disturbances and physiological extremes, as are many temperate marine communities.