科研之友
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摘要
Irrigation water withdrawals can alter hydrologic and thermal regimes, which are two primary drivers of biological patterns and processes in lotic ecosystems. Despite irrigated agriculture being the largest use of freshwater resources in the world, impacts to macroinvertebrate life histories remain largely unknown. We sought to determine how water withdrawals affect larval development, growth, and population biomass of Brachycentrus occidentalis. We sampled three river segments within the Umatilla River, OR representing reference conditions above all points of diversion, hydrologic alterations below a first diversion, and hydrologic and thermal alterations below a second diversion. The three river segments were sampled monthly from June to September during average and drought water years. During the average water year, B. occidentalis growth and developmental patterns were more strongly related to naturally occurring elevated winter degree day accumulations than the hydrologic and thermal effects of water withdrawals. In contrast, water withdrawals interacted with drought conditions in 2005 to increase the magnitude and duration of hydrologic and thermal alterations. During this time, lethal temperatures slowed B. occidentalis growth rates and significantly reduced the individual dry weights of fourth and fifth instars. Growth rate reductions likely resulted from an inability to meet increased metabolic demands, as opposed to faster developmental rates. We provide evidence that water withdrawals can decouple life histories from environmental optima where individual%26apos;s size and fecundity are maximized. Such effects are particularly detrimental to holometabolous insects, which can lack the plasticity of hemimetabolous insects to make tradeoffs among body size, generation times, and voltinism.
- 出版日期2012-1
