SUMMARYAn eighteen month study (January 1979 - June 1980) of the sediment, emergent and submerged plant-associated benthic macro-invertebrates of the western sector of the Touw River Flood-plain is reported for four study sites: Wilderness Lagoon, the Touw River and East and West Serpentine. Total invertebrate standing stocks on emergent vegetation were negligible. Those associated with submerged plant communities (essentially Potamogeton pectinatus L.), were generally very much greater than sediment-associated invertebrate standing stocks. The following mean biomasses were recorded for the study period: (a) sediments - Wilderness Lagoon, 19,25; Touw River, 13,06; West Serpentine, 4,37; East Serpentine, 4,68 g dry mass m⁻²; (b) - Potamogeton-associated fauna - Touw River, 128,9; West Serpentine, 91; East Serpentine, 35,78 g dry mass m⁻². Of the 37 taxa recorded for Wilderness Lagoon, 33 for Touw River and 31 each for West and East Serpentine sites, the most consistently dominant species were the amphipods, Melita zeylanica Stebbing, Corophium triaenonyx Stebbing, and Grandidierella lignorum Barnard, the tanaid, Apseudes digitalis Brown, and the bivalve mollusc, Musculus virgiliae Barnard. However, suspension feeding Musculus was by far the most important taxon.In addition to normal winter die-back of Potamogeton, submerged plant cutting activities in the Serpentine lead to an extended period of plant senescence, a prolonged recovery period at the West Serpentine station (between 4–5 months, compared with un-cut Touw River - approximately 2 months), almost complete failure of the plant at East Serpentine, and associated reductions or shifts in the invertebrate community standing stocks, composition and structure. Sediment-associated invertebrate standing stocks at both West and East Serpentine stations increased after Potamogeton harvesting, both immediately and in the long-term. However, these sediment fauna increases nowhere near compensated for the reductions of plant-associated faunal standing stocks due to cutting activities. The significance of these findings is discussed in terms of future management of the area, and comparisons with the situation in Swartvlei, where natural Potamogeton reduction occurred, and with other estuarine and coastal systems, are made.