Drift responses of Gammarus (Amphipoda) to experimental flow fluctuation in a mountain stream

---

Haoran Wang, Yongcan Chen, Zhaowei Liu, Kang Yu

Tuesday 30 june 2015

11:30 - 11:45h at Amazon (level 1)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology

Parallel session: 5G. Environment – Ecosystem

---

Flow regime is widely recognized as a significant habitat factor to aquatic species. Flow fluctuation below a daily-regulated hydropower plants (hydro-peaking flow) can exert impacts to benthic invertebrates, including the change of community structure and the drift rates. A series of experiments were conducted in a mountain stream to assess Gammarus sp. drift responses to flow fluctuation. T-cock weirs and pipes were used to manipulate the flow in experimental channels. Two flow patterns were introduced, including natural flow and pulse flow from 0.0002 to 0.00615 cuber metre per second. Drift samples were collected during experiments using drift net located in pools; riffles and glides. Drift densities were calculated. The experiment indicated that: (1) Gammarus sp. was the dominant species of drift macroinvertebrates in Yaojikan steam, which accounted more than 50% of all collected individuals during two experiments; (2) Macroinvertebrates drift differed during flow disturbance, more drift individuals were collected and drift density presented a periodical fluctuation with flow fluctuation. (3) Gammarus sp. drifts varied differently among different habitat types under fluctuating flow regime. Fewer drift Gammarus sp. were collected from pools and more drift individuals were sampled form riffles and glide. The results indicated that Gammarus sp. drifts were determined by the flow regime and habitat type and interactions between them. Flow regime varied with time to disturbance and can definitely be an essential factor affecting drift of Gammarus sp. In addition to temporal consideration, the spatial distribution of habitats is also affect drift to a large extent.