MULTILEVEL EFFECTS OF SEVERE STORMS ON AN OFFSHORE TEMPERATE REEF SYSTEM - BENTHIC SEDIMENTS, MACROALGAE, AND IMPLICATIONS FOR FISHERIES

Episodic events have been shown to strongly affect structure and funct ion of marine benthic ecosystems. Severe storms can have profound effe cts on the distribution of marine sediments which could, in turn, infl uence the development of benthic communities. The rich and diverse epi benthic communities on the United States mid-Atlantic continental shel f owe their existence to the presence of a complex sequence of rocky o utcrops. An unusually strong storm struck this shelf system in March 1 993. Two of these carbonate platforms had been characterized by modera te sediment cover for at least the previous two years, but bottom wate r velocities generated by this storm removed considerable amounts of s ediment from these upper flat hardbottom habitats. Macroalgal cover on these platforms dramatically increased between 1992 and 1993 with the increased exposure of hard substrate for attachment. The edges of the outcrops (scarps and rubble ramps), which are usually free of sedimen t, maintained their dense algal cover. Settlement blocks placed in var ious sub-habitats showed little variation in algal cover among flat ha rdbottom and scarp areas during both years, indicating that available hard substrate habitat may be the primary limiting factor for algal gr owth on the North Carolina continental shelf. Since macroalgal meadows provide food and shelter for juvenile fish, the increase in critical habitat following these storms may have implications for recruitment o f economically important fish species. Thus, indirect effects of episo dic storms, i.e., redistribution of sand bodies leading to algal meado w development over large spatial scales, may have important consequenc es for benthic community development and persistence in temperate reef systems.