Response of epiphytic diatom communities from the tailwaters of glen Canyon Dam, Arizona, to elevated water temperature

Abstract

The composition of epiphytic diatom communities from the cold tailwaters (12°C) of Glen Canyon Dam, Arizona, was analysed after a 2 wk incubation period at 12"C, 18°C and 21°C. There was a significant change in diatom composition between 12°C and 18"C, while no significant changes occurred between 18°C and 21°C. This suggests that a temperature threshold exists between 12°C and 18°C for the diatom flora in the tailwaters of Glen Canyon Dam. At the two higher water temperatures, smaller and closely adnate taxa became more important numerically than larger, upright, cold water stenotherms. The potential importance of this compositional shift in epiphytic diatoms on macroinvertebrate grazers has management implications regarding different release programs from reservoirs.

Effects of atmospheric exposure on chlorophyll a, biomass and productivity of the epilithon of a tailwater river

“…Stable isotope analyses (13C, "N) revealed that assimilated C and N in Gammarus collected at 14 Mile Bar originated from diatoms rather than from Oscillatoria, terrestrial detritus, or seston exported from Lake Powell (T. Angradi, unpublished data). Intact Cladophora has a high surface area which supports a dense assemblage of diatoms (Blinn et al, 1989). The most important ecosystem level function of attached Cladophora may be as a habitat for other organisms (Dodds and Gudder, 1992), and reach-wide disruption of this structural function due to exposure could precipitate higher trophic level effects within the Glen Canyon ecosystem.…”

Algal Ecology in Tailwater Stream Communities: The Colorado River Below Glen Canyon Dam, Arizona

“…The plan proposes to release warm subsurface water (18-21Њ C) from Lake Powell into the Colorado River. In a study with circulation chambers, Blinn et al (1989) reported a significant change in the composition and physiognomy of the diatom epiphyte community on Cladophora at Lees Ferry between 12Њ and 18Њ C, with no significant change between 18Њ and 21Њ C. At the two higher temperatures, smaller and more closely attached taxa such as C. pediculus and Achnanthes spp. replaced D. vulgare and R. curvata in treatments at 12Њ C. Changes in community physiognomy of this nature may have major ramifications on the grazer community in the Colorado River, as previously discussed (Colletti et al 1987, Steinman et al 1987).…”

Colorado river benthic ecology in Grand Canyon, Arizona, USA: dam, tributary and geomorphological influences

“…Diatoms comprised > 95% of the algae in chironomid larvae guts at each location, and Cladophora fragments comprised < 1% of the total gut contents. The diatom genera most frequently encountered in chironomid guts were Achnanthes, Cocconeis, Cymbella, Diatoma and Rhoicosphenia, all of which are common epiphytes associated with Cladophora in this system (Czarnecki and Blinn, 1978;Blinn et al, 1989;Hardwick et al, 1992). Chironomid larvae …”

“…Warmer summer river temperatures may increase benthic invertebrate, and possibly macrophyte, diversity and production. However, warmer temperatures may also alter competitive hierarchies and the distribution of Cladophora, Oscillatoria, epiphytes and other macrophytes, thereby affecting the invertebrate food base and non-native fish populations in unpredictable ways (Blinn et al, 1989).…”