EFFECTS OF MACROPHYTE HARVESTING ON INVERTEBRATES ASSOCIATED WITH POTAMOGETON PECTINATUS L. IN THE MARINA DA GAMA, ZANDVLEI, WESTERN CAPE

SUMMARY

A four-month study of the effects of submerged aquatic plant harvesting on invertebrate communities associated with Potamogeton pectinatus L. at Marina Da Gama, Zandvlei, is described. Fifteen taxa were recorded. Five taxa formed 78,8-99,4% of the invertebrate biomass at all three sites: Ficopomatus enigmaticus (Fauvel) > Chironomidae larvae > Ischnura senegalensis (Rambur) > Tomichia ventricosa (Rve) > Ostracoda. Total invertebrate standing stocks were higher at an unharvested site (4,63-12,65 g dry mass m⁻²) than at a ‘controlled-height’ harvested site (1,36-4,43 g dry mass m⁻²) and a regularly harvested site (1,94-7,06 g dry mass m⁻²). Since both investigated harvesting procedures were deleterious to benthic standing stocks, it was concluded that any harvesting programme must include the conservation of undisturbed areas.