Hydrologic alteration affects aquatic plant assemblages in an arid-land river

Southwestern Naturalist
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Abstract

We evaluated the effects of long-term flow alteration on primary-producer assemblages. In 1962, Flaming Gorge Dam was constructed on the Green River. The Yampa River has remained an unregulated hydrologically variable river that joins the Green River 100 km downstream from Flaming Gorge Dam. In the 1960s before dam construction only sparse occurrences of two macroalgae, Cladophora and Chara, and no submerged vascular plants were recorded in the Green and Yampa rivers. In 2009–2010, aquatic plants were abundant and widespread in the Green River from the dam downstream to the confluence with the Yampa River. The assemblage consisted of six vascular species, Elodea canadensisMyriophyllum sibiricumNasturtium officinale,Potamogeton crispusPotamogeton pectinatus, and Ranunculus aquatilis, the macroalgae Chara and Cladophora, and the bryophyte, Amblystegium riparium. In the Green River downstream from the Yampa River, and in the Yampa River, only sparse patches of Chara and Cladophora growing in the splash zone on boulders were collected. We attribute the observed changes in the Green River to an increase in water transparency and a reduction in suspended and bed-load sediment and high flow disturbances. The lack of hydrophyte colonization downstream from the confluence with the Yampa River has implications for understanding tributary amelioration of dam effects and for designing more natural flow-regime schedules downstream from large dams.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Hydrologic alteration affects aquatic plant assemblages in an arid-land river
Series title Southwestern Naturalist
DOI 10.1894/JEM-04.1
Volume 59
Issue 4
Year Published 2014
Language English
Publisher Southwestern Association of Naturalists
Contributing office(s) Great Lakes Science Center
Description 9 p.
First page 480
Last page 488
Online Only (Y/N) N
Additional Online Files (Y/N) N