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| | ! style="width=33%; background:#cedff2;" | [[File:EPT.jpg|center|500px]] [https://www.wcc.nrcs.usda.gov/ftpref/wntsc/strmRest/wshedCondition/EPTIndex.pdf EPT as Biologic Indicators of Stream Condition] <br> | | ! style="width=33%; background:#cedff2;" | [[File:EPT.jpg|center|500px]] [https://www.wcc.nrcs.usda.gov/ftpref/wntsc/strmRest/wshedCondition/EPTIndex.pdf EPT as Biologic Indicators of Stream Condition] <br> |
| | ! style="width=33%; background:#cedff2;" | [[File:Chara.jpg|center|200px]] [[Algae and Aquatic Macrophytes]] <br> | | ! style="width=33%; background:#cedff2;" | [[File:Chara.jpg|center|200px]] [[Algae and Aquatic Macrophytes]] <br> |
| − | ! style="width=55%; background:#cedff2;" | [[File:Macroinvertebrates.jpg|center|400px]] [http://extension.usu.edu/waterquality/macrokey/ Aquatic Macroinvertebrates] <br> | + | ! style="width=55%; background:#cedff2;" | [[File:Macroinvertebrates.jpg|center|400px]] [http://gcdamp.com/index.php?title=Aquatic_Macroinvertebrates Aquatic Macroinvertebrates] <br> |
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| | [[File:2017AR HFEsFoodbase2.jpg|thumb|center|500px| https://www.usbr.gov/uc/rm/amp/twg/mtgs/17jan26/AR19_Kennedy.pdf ]] | | [[File:2017AR HFEsFoodbase2.jpg|thumb|center|500px| https://www.usbr.gov/uc/rm/amp/twg/mtgs/17jan26/AR19_Kennedy.pdf ]] |
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| − | ! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;"> Aquatic macroinvertebrates found below Glen Canyon Dam </h2>
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| − | [[File:GammarusLacustris.JPG|thumb|center|500px|Gammarus lacustris: an introduced non-native freshwater shrimp (amphipod)]]
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| − | [[File:Midge.jpg|thumb|center|500px|Midge (larvae)]]
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| − | [[File:Insect_leaf.png|thumb|center|500px|Midge (adult)]]
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| − | [[File:Blackfly.jpg|thumb|center|500px|Blackfly (larvae)]]
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The Aquatic Food Base below Glen Canyon Dam
The most abundant aquatic macroinvertebrates within the Glen Canyon reach include Gammarus lacustris (an introduced non-native amphipod), midges (order Diptera, family Chironomidae), snails (Physella sp. and Fossaria obrussa), segmented worms (especially Lumbricidae and Lumbriculidae) and other aquatic worms (Naididae and Tubificidae), fingernail clams in the family Sphaeriidae (Pisidium variable and P. walkeri), and the planarian Dugesia spp. (Blinn et al. 1992; Stevens, Shannon et al. 1997). Prior to 1995, snails were infrequently observed, but have since increased in abundance due to invasion by the non-native New Zealand mudsnail (Potamopyrgus antipodarum) (Valdez and Speas 2007; Cross et al. 2010). The mainstem Colorado River in Glen and Grand Canyons supports very few species or individuals of native mayflies, stoneflies, or caddisflies because of a combination of stressors, including altered temperature regimes and a pronounced varial zone (Stevens, Shannon, et al. 1997; Kennedy et al. 2016). Some tributaries of the Colorado River, along with backwaters and off-channel ponds, have higher diversity and densities of mayflies, stoneflies, and caddisflies compared to the mainstem. (2018 Expanded Non-Native Aquatic Species Management Plan EA)
The aquatic food base will sustainably support viable populations of desired species at all trophic levels. Assure that an adequate, diverse, productive aquatic foodbase exists for fish and other aquatic and terrestrial species that depend on those food resources.
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Links and Information
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Foodbase Projects
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Oviposition and Egg Desiccation Studies
Foodwebs and Bioenergetics Studies
Measuring Primary Production in the Lees Ferry Reach
The BugFlow Experiment
Citizen Science Insect Monitoring
Hyporheic Anoxia in the Lees Ferry Reach
Downstream Recovery of the Foodbase Community in Several Colorado River Tailwaters
Drift and Food Availability Studies
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Papers and Presentations
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2019
2018
2017
2016
2015
2014
2013
2012
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1998
- Stevens, L. E., J. P. Shannon, and D. W. Blinn. 1998. Colorado river benthic ecology in Grand Canyon, Arizona, USA: dam, tributary and geomorphological influences. Regulated Rivers.
- Blinn et al. 1998. Algal ecology in the tailwater stream communities: The Colorado River below Glen Canyon Dam, Arizona. J, Phycol. M, 734-740 (1998)
- Stevens et al. 1998. Chironomidae (Diptera) of the Colorado River, Grand Canyon, Arizona, USA, II: factors influencing distribution. Great Basin Naturalist: Vol. 58: No. 2, Article 2
1997
- Stevens, L. E., J. P. Shannon, and D. W. Blinn. 1997. Colorado River benthic ecology in Grand Canyon, Arizona, USA: dam, tributary and geomorphological influences. Regulated Rivers: Research and Management 13:129–149.
- Shaver et al. Effects of suspended sediment and desiccation on the benthic tailwater community in the Colorado River, USA. Hydrobiologia 357: 63–72, 1997.
- Stevens et al. 1997. Colorado River benthic ecology in Grand Canyon, Arizona, USA: Dam, tributary, and gomorphological influences. Regulated Rivers: Research and Management, Vol. 13, 129–149 (1997)
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Other Stuff
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The interaction of fish, foodbase, and temperature
Fish occupying warmer water have higher metabolic demands than individuals in cooler water, and if these demands increase concurrently with a seasonal decline in prey availability, then growth rates may be reduced. [1]
- Black Flies and Midges fuel fish production below Glen Canyon Dam.
- Black Flies and Midges respond positively to spring HFE's.
- Mud Snails were introduced below Glen Canyon Dam around 1995.
Notably, several species of cold-tolerant nonnative invertebrates were intentionally introduced into the Colorado River after Glen Canyon Dam was closed in 1963. Altogether 10,000 immature mayflies were secured from a commercial source in Minnesota and released at three sites in the Lees Ferry reach. Also, 10,000 snails, 5,000 leeches, and thousands of insects representing at least 10 families were transported from the San Juan River in New Mexico to the river near Lees Ferry. In addition, 50,000 “scuds” (Gammarus lacustris) were introduced into Bright Angel Creek in 1932 and at Lees Ferry and below the dam in 1968, in addition to 2,000 crayfish taken from the LCR near Springerville, AZ (Blinn and Cole 1991). Gammarus lacustris has thrived in the cold, clear reaches below the dam, but the fate of the other introduced species is unknown.
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