Flood effects on invertebrates, sediments and particulate organic matter in the hyporheic zone of a gravel-bed stream

• Published in: Freshwater biology 2005-05, Vol.50 (5), p.839-853
• Main Authors: OLSEN, DEAN A., TOWNSEND, COLIN R.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Copepoda; disturbance; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; Hydora; hyporheos; interstitial; Invertebrata; Isopoda; Leptophlebiidae; Nematoda; patchiness; streams; Synecology
• ISSN: 0046-5070; 1365-2427
• DOI: 10.1111/j.1365-2427.2005.01365.x

Summary 1. We investigated the effects of a flood on the fauna and physical habitat of the hyporheic zone of the Kye Burn, a fourth order gravel‐bed stream in New Zealand. 2. Freeze core hyporheic samples (to 50 cm depth) and benthic samples (to 10 cm) were taken, along with measurements of vertical hydrological gradient, before, 2 days after and 1 month after the flood (estimated return period: 1.5 years, estimated Qmax = 10.4 m3 s−1). 3. The composition of the hyporheos differed over the three sampling occasions with fewer taxa collected immediately postflood than preflood. The equitability of the community was higher on both postflood occasions, consistent with the reduced densities of two abundant taxa (Leptophlebiidae and Copepoda). 4. Total invertebrate abundance was lower on the postflood occasions than preflood in both benthic (0–10 cm) and hyporheic (10–50 cm) sediments. Several taxa, including asellotan isopods and amphipods, recovered within 1 month of the event. Hyporheic densities of larval Hydora and nematodes did not differ among the three sampling occasions, but the water mite Pseudotryssaturus was more abundant 1 month after the flood than preflood. There was no evidence of vertical movements (to 50 cm) by any taxa in response to the flood. 5. The proportion of fine sediments (