Shifts in aquatic macroinvertebrate community structure in response to perenniality, southern Cape, South Africa

• Published in: Journal of freshwater ecology Vol. 29; no. 4; pp. 475 - 490
• Main Authors: Eady, Bruce R, Hill, Trevor R, Rivers-Moore, Nick A
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 02.10.2014; Taylor & Francis Ltd
• Subjects: aquatic ecosystems; aquatic invertebrates; autumn; Biotopes; Communities; Community structure; flow variability; Freshwater; Gravel; hydrograph; Hydrology; Macroinvertebrates; Mud; perennial and non-perennial flows; Rivers; species diversity; Species richness; Stream discharge; Stream flow; Streams; Taxa; vegetation; winter; Zoobenthos; South Africa
• ISSN: 2156-6941; 0270-5060; 2156-6941
• DOI: 10.1080/02705060.2014.910146

Stream flow and associated seasonal hydrologic variation is a critical driver affecting the structure of aquatic macroinvertebrate communities. Quarterly aquatic macroinvertebrate sampling was carried out for a single year along the longitudinal axes of two streams in the southern Cape of South Africa. Stones-in-current, marginal vegetation, gravel-sand-mud, and stones-out-of-current biotopes were sampled for aquatic macroinvertebrates. Associations between macroinvertebrate communities and hydrographs were analyzed to investigate whether a non-perennial stream with greater flow variability had a higher prevalence of common or opportunistic species than a perennial one with less variable flow. Macroinvertebrate species richness was greater in the perennial as opposed to the non-perennial stream, where, on a seasonal basis, species richness increased from winter to autumn. Temporal species turnover differed between sites and streams, where reduced flows transformed the more dominant aquatic biotopes from stones-in-current into standing pools. Findings are that aquatic macroinvertebrates respond to changing flow conditions and reduced mean daily flows resulted in the disappearance of flow-dependant taxa and the arrival of non-flow-dependant taxa.