Fengqing Li

Impacts of cascade run-of-river dams on benthic diatoms in the Xiangxi River, China

The ecological effects of small run-of-river dams on aquatic ecosystems are poorly understood, especially on downstream benthic algal communities. We examined impacts of such dams on the benthic diatom community at a regional scale in the Xiangxi River, China. A total of 90 sites were visited, which were divided into five habitats (H1–H5) according to impact extent of each dam. Using partial least squares (PLS) modeling, we developed two predictive models (diatom species richness and total diatom density) based on environmental variables of an unregulated habitat (H1). These models were then used to predict species richness and total densities at impacted habitats (H2–H5) and residuals, i.e. the differences between observed and predicted values, were used to evaluate impact strength of flow regulation. Significant impacts of flow regulation on diatom species richness were detected at three impacted habitats (H3–H5), where observed species richness were significantly higher—70.6, 63.9 and 46.6%, respectively—than predicted values. Then, possible mechanisms for observed impacts were discussed. Further research is necessary to address the potential negative impacts of cascade run-of-river dams on other aquatic organisms in different seasons, and to explore more appropriate mechanisms for such impacts, which may lead to sustainable management strategies and help to determine the optimal ecological water requirement for the Xiangxi River.

Macroinvertebrate relationships with water temperature and water flow in subtropical monsoon streams of Central China: implications for climate change

Effects of global climate change on freshwaters are still poorly known, particularly in systems where they interact with other environmental variables. Using data from a subtropical monsoon stream in Central China, we assessed the relationships between a macroinvertebrate community and variations in temperature and water flow. We then used these data to assess potential changes under different climate change scenarios. Winter macroinvertebrate abundance and richness decreased with increasing water temperature during the last six years. However, effects of climate on biotic metrics in summer were less clear. Partially constrained ordination revealed that variations in community composition could not be explained clearly by individual climatic variables, but total dissolved solids and total nitrogen were more important. Over the period 1978-2008, average annual air temperature in the study area increased by 0.6 degrees C, whereas total annual water flow declined. Projections suggest that further winter warming of 1 degrees C could decrease the macroinvertebrate abundance and richness by 11.1 % and 6.0 %, respectively. One unit increase in the smoothed sea surface temperature (SSST) during winter could increase the abundance and richness by 38.2 % and 21.1 %, respectively. With further global change effects likely in future, our data highlight the importance of the conservation of mountainous streams in the upper Yangtze River.

Spatial distribution of benthic macroinvertebrates in the Erhai basin of southwestern China

The macroinvertebrate communities and relationships with environmental variables were characterized in the Erhai basin by sampling at 44 sites. Among the 76 taxa observed, Baetis sp., Tubificidae, Simulium sp., Eukiefferiella sp., Gammarus sp. and Parakiefferiella sp. were the dominant taxa. Canonical correspondence analysis indicated that seven environmental variables, namely altitude, Ca2+, chemical oxygen demand, NO3–N, total phosphorus, streambed width, and a qualitative habitat evaluation index (QHEI), were significantly related to the distribution of benthic macroinvertebrates. Two-way indicator species analysis divided total sampling sites into four groups. Weighted-averaging regression and cross-calibration produced strong models for predicting NO3–N, altitude, and QHEI, which enabled the selection of the following benthic taxa as potentially sensitive indicators of certain levels of NO3–N, altitude, and QHEI: Aracina, Atrichops morimotoi, Ceratopsyche sp., Guttilelopia sp., and Nemoura sp. for NO3–N; Heptagenia sp. and Parakiefferiella sp. for altitude; and Aracina for QHEI.