Energy Balance and Significance of Microorganisms in a Kelp Bed Community

Abstract

Primary production by phytoplankton in a Benguela upwelling region off the west coast of the Cape Peninsula, South Africa, is almost equal to that within beds of the kelps Ecklonia maxima and Laminaria pallida . Total primary production of kelps, understorey algae and phytoplankton within an idealised kelp bed of 10 m average depth is 62,190 kJ m super(-2)yr super(-1), as compared to 54,037 kJ m super(-2)yr super(-1) for the phytoplankton community in deeper water nearby. Bacteria which utilise dissolved and particulate components of fragmented macrophytes and faeces may produce up to 6,403 kJ m super(-2)yr super(-1), which is small energetically but belies their importance in protein enrichment of food and in nutrient cycling. The kelp community appears to depend primarily on rapid bacterial mineralisation of fragmented kelp and faeces to recycle the minerals necessary to sustain primary production, supplemented by bouts of upwelling