Estuarine Health and Function Phase I - Spatial and Temporal Variations in Macrozoobenthic Communiteis in Kwazulu-Natal Temporarily Open/Closed Estuaries

Estuaries are complex ecosystems that, for many reasons are among the most rapidly deteriorating environments worldwide. According to past water quality assessments, a quarter of all temporarily open/closed estuarine systems (TOCEs) in KwaZulu-Natal are in a ‘poor’ to ‘very poor’ condition. With recent, unprecedented increases in coastal development it is probable that more estuaries will fall into these categories. Macrozoobenthos comprises various benthic invertebrates living in, and at the sediment-water interface. They are preferable biological indicators because of their sensitivity to changes in habitat quality and are thus used in anthropogenic impact studies on estuaries. This study aims to address aspects of ‘change’ inherent in the macrozoobenthic communities of 32 subtropical estuaries. ‘Change’ as measured in temporal and spatial community differences using various community metrics, namely species composition, abundance, diversity and feeding guild structure. Standard and widely published quantitative sampling techniques were undertaken, with simultaneous measurements of ambient physico-chemical conditions, including sediment characteristics. Long-term decadal-type changes in community structure are being investigated using historical data (1998/9) compared with currently sampled data. The recolonisation of two urban and two peri-urban estuaries by macrozoobenthos after episodic flood disturbance is being examined, to describe short-term community changes in the recovery process. Biogeographic trends in macrozoobenthic communities across KwaZulu-Natal TOCEs and using feeding guilds structures as proxies of key estuarine environmental characteristics will also be determined using this extensive dataset. It is predicted that distinct macrozoobenthic assemblages will better explain differences amongst TOCEs and also contribute to better management