Multiple-scale controls on physical and chemical habitat conditions and their influence on biotic assemblages in Zambian rivers.

Little is known about the ecological status of rivers in Zambia, although there are concerns over the impact of flow regulation and land cover change on stream ecosystems. A river biomonitoring protocol is being developed to assess the ecological integrity of Zambian rivers. To develop the protocol, 143 sites distributed across 86 rivers were surveyed during 2010 and 2011. These sites were selected using a stream typology based upon the WWF Freshwater Ecoregions of the World (FEOW) classification. Site surveys involved assessment of biotic community characteristics (utilising macrophytes, macroinvertebrates and diatoms). Physical habitat data collected at each site included information on hydraulic and sedimentary characteristics as well as information on channel morphology and wider catchment features. Samples to assess water chemistry were also collected at each site. Preliminary data suggest that established Ecoregions reflect hydro-climatic variability across Zambian catchments. Much of the variability in plant, invertebrate and diatom assemblages between sites reflects local water quality and physical habitat characteristics. Overall, Zambian rivers appear to have relatively undisturbed assemblages: exceptions are found in urban locations and areas with large scale mining activity. The merits of using Ecoregions as a basis for stratifying sites to use in national ecological assessments is discussed and the relative influence of environmental conditions at different scales on-site biological assemblages.