The fauna and flora of a kelp bed canopy

Abstract

The fauna and flora of the canopy of a kelp bed off Oudekraal, on the Cape Peninsula, Is surveyed. Four species of epiphytic algae occur In the kelp canopy, three restricted to Ecklonia maxima and the fourth to Laminaria pallida. Epiphyte biomass is equivalent to 4-9% of host standing crop amongst E. maxima, but less than 1% in stands of L. pallida. Wherever E. maxima is common, epiphyte standing crop considerably exceeds that of benthic understorey algae. The canopy fauna comprises at least 27 species and is composed largely of small Crustacea, molluscs and polychaetes. Since these organisms are mainly associated with the epiphytic algae they are most abundant amongst E. maxima in the shallower regions of the kelp bed. In such areas the biomass of the canopy fauna may exceed that of the relatively impoverished benthos, but further offshore the canopy fauna is insignificant in relation to a rich benthic community. Indications are that canopy organisms are an important source of food for the fish of the kelp bed system.