Algae and Aquatic Macrophytes

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Cladophora, a filamentous green algae

Algae and Aquatic Macrophytes below Glen Canyon Dam The aquatic flora within the project area is currently dominated by various species of algae, macrophytes, and bryophytes including filamentous green algae (mainly Ulothrix zonata and Spirogyra spp.), the stonewort Chara contraria, the aquatic moss Fontinalis spp., and the macrophyte Potamogeton pectinatus. Cladophora occurs along the entire course of the river within the project area, although its abundance decreases downstream (Blinn and Cole 1991; Shannon et al. 1994; Shaver et al. 1997; Stevens, Shannon et al. 1997) due to higher suspended sediment loads contributed by major perennial tributaries (especially the Paria River and Little Colorado River) (Blinn et al. 1995). Cladophora is colonized by a variety of diatom species (Dodds and Gudder 1992) that are an important component of the food base in the tailwaters of Glen Canyon Dam (Blinn et al. 1992). The cyanobacteria Oscillatoria is co-dominant with Cladophora in Marble Canyon and dominates farther downstream in the Grand Canyon due to its tolerance of exposure to air and lower light levels compared to Cladophora (Blinn et al. 1992; Stevens, Shannon et al. 1997). Submerged macrophytes in the mainstem, backwaters, and off channel ponds in the project area include non-native species such as horned pondweed (Zannichellia palustris), Canadian waterweed (Elodea canadensis), Brazilian waterweed (Egeria densa), pondweed (Potamogeton spp.), aquatic moss (Fontinalis spp.), and muskgrass (Chara spp. [green alga]) (Carothers and Minckley 1981; Valdez and Speas 2007). Curly pondweed (Potamogeton crispus), which is known to be present within the Grand Canyon portion of the project area is believed to pose a medium level of threat to the aquatic ecosystem because it competes with native aquatic plants and can cause fish die-offs when algal blooms begin to die off; curly pondweed can also clog some waterways and inhibit recreational activities (Expanded Non-Native Aquatic Species Management Plan EA).

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Updates Cladophora, a filamentous green algae (Ulothrix zonata and Spirogyra sp.) Oscillatoria a filamentous blue-green algae Stonewort or Muskgrass (Chara sp.) Aquatic moss (Fontinalis sp.) Sago pondweed (Potamogeton_pectinatus) Horned pondweed (Zannichellia palustris) Canadian waterweed (Elodea canadensis) Brazilian waterweed (Egeria densa) Brazilian vs Canadian waterweed (Egeria densa vs Elodea canadensis) Curly pondweed (Potamogeton crispus)

Links and Information Aquatic Foodbase GCMRC Aquatic Food Base Lab Measuring Primary Production in the Lees Ferry Reach Papers and Presentations 2012 Hall et al. 2012. Air-water oxygen exchange in a large whitewater river. Limnology and Oceanography: Fluids and Environments 2: 1-11. 1991 Algal and Invertebrate Biota in the Colorado River: Comparison of Pre- and Post-Dam Conditions 1990 Blin and Cole, 1990, Algal and Invertebrate Biota in the Colorado River: Comparison of Pre- and Post-Dam Conditions 1988 The utilization of Cladophora glomerata and epiphytic diatoms as a food resource by rainbow trout in the Colorado River below Glen Canyon Dam, Arizona 1981 A survey of the aquatic flora and fauna of the Grand Canyon Other Stuff Primary production from algae represents the base of food webs in many rivers, and dissolved oxygen is a by-product of primary production. By developing detailed dissolved oxygen budgets for a river reach, which account for rates of air-water gas exchange, it is possible to estimate rates of primary production for entire reaches of river. GCMRCs Sediment Transport Group is continuously measuring dissolved oxygen concentration at 5 locations downstream of Glen Canyon Dam. In collaboration with Robert Hall and Robert Payne, the Aquatic Ecology Group is developing models for continuously estimating rates of primary production of the Colorado River in Glen, Marble, and Grand Canyon. [1] Cladophora is a structural host for Gammarus and chironomids below Glen Canyon Dam (Shannon et al., 1994; Stevens et al., 1997), and diatom epiphytes on the alga provide a food resource for these invertebrates (Blinn et al., 1992; Stevens et al., 1997). [2]