Intensive use of lake water affects freshwater food webs

Many lakes are important sources of water for agriculture and other purposes, while also supporting diverse ecosystems. In a new study, a comparison is made between the food webs of two natural lakes that were dammed early in the 20th century. The neighboring lakes are nearly identical except that one (Lake Keechelus) experiences rapid drawdown of water beginning early summer while the other (Lake Kachess) remains fuller and fluctuates less in water height during summer, but is lowered to a lesser extent beginning early fall. This water management scheme helps balance water needs for irrigation and threatened salmon downstream. A comparison of the food webs in the two lakes reveals that the more intensively used lake has a less diverse food web (termed “trophic compression”). Thus water use, like other human disturbances such as warming, excessive nutrients, and invasive species, results in lake ecosystems that are less able to cope with external stress. The new paper by Adam Hansen, a SAFS alum, two SAFS post-bachelor researchers Jennifer Gardner and Kristin Connelly, Matt Polacek, and David Beauchamp, appears in the journal Ecosphere.

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