Desiccation and recolonization of phytobenthos in a regulated desert river: Colorado River at Lees Ferry, Arizona, USA

Abstract

We tested the recolonization of the phytobenthic community in the tailwaters of Glen Canyon Dam following longand short-term experimentally induced desiccation. The response of Cladophora glomerata, Oscillatoria spp., miscellaneous phytobenthos species and periphyton was studied over 18 weeks using three treatments: (1) undisturbed control cobbles from the submerged zone; (2) cobbles desiccated and replaced into the submerged zone; and (3) cobbles desiccated and replaced into the varial zone. Periphyton density and compositional response resulting from these treatments were also examined.Desiccation treatments were significantly different in biomass from controls throughout the study. The biomass of desiccated and replaced river cobbles averaged B30% of the controls for C. glomerata and periphyton during the 18-week recolonization period. In contrast, the biomass of the control Oscillatoria and miscellaneous phytobenthos species averaged only 3 and 50% of that in the desiccation treatments, respectively. Cladophora, the dominant alga, comprised 77% of the phytobenthic biomass. A significant positive relationship between discharge, Cladophora and periphyton biomass was present in all treatments, while there was a negative relationship with discharge for Oscillatoria and miscellaneous phytobenthos species.There was a significant inverse correlation, as well as a pattern of separate biomass dominance, between C. glomerata and Oscillatoria. Cladophora was the dominant phytobenthos species on cobbles below the baseflow and Oscillatoria was dominant on cobbles in the varial zone. In general, the Cladophora biomass decreased under intermittent drying conditions, while Oscillatoria declined under permanently wet conditions. Diatom composition was not significantly different between treatments; however, their density was lower on desiccated cobbles. Diatom density on desiccated cobbles in the submerged and varial zones averaged 69 and 42% of that of the controls, respectively.Recovery and maintenance of benthic resources are hindered by fluctuating flow regimes driven by electricity and irrigation requirements. Repeated desiccation of the phytobenthos has major effects on the bottom-up interactions in the Colorado River ecosystem.

The succession dynamics of a macroalgal community after a flood disturbance in a tropical stream from São Paulo State, southeastern Brazil

“…This theoretical justification can explain the local replacement of Stigeoclonium amoenum by other species with higher relative abundances. A similar pattern was described by Benenati et al (1998) in a study of the recolonization of phytobenthos in a regulated desert stream after an experimental drought period. The authors showed that After the disturbance, the macroalgal community was greatly modified.…”

How periphytic algae respond to short-term emersion in a subtropical floodplain in Brazil

“…Weakened parts of the algae filaments that are damaged due to desiccation are easily broken, causing loss of the damaged portions of the filaments and the viable parts (Usher & Blinn 1990). Benenati et al (1998) reported a pronounced decline of Cladophora filaments and its periphyton epiphytes as a consequence of the repeated episodes of exposure and desiccation. According to Lowe (1996) andDodds (1991), filamentous algae, such as oedogoniophyceans, continuously create new and complex areas through growth, increasing the area available for epiphytism.…”

“…Periphyton and other communities may respond in different manners to the onset, duration and cessation of a disturbance. Changes in hydrometric levels caused by dam operations should create periods of shortterm desiccation (10-15 hours), owing to a diel tide associated with daily electricity demand (Benenati et al 1998), and may strongly influence periphyton communities (Benenati et al 1998;Bergey et al 2010). …”

“…In general, the effects of desiccation on the processes and structures of communities are not fully understood (Lake 2000(Lake , 2003Boulton 2003). Studies performed with algal communities have attempted to evaluate these effects on recolonisation (Benenati et al 1998;Robson 2000;Ledger & Hildrew 2001;Mosisch 2001;Robson & Matthews 2004) and on community structure and composition under distinct exposures and durations (Peterson 1987;Gottlieb et al 2005;Bergey et al 2010).…”

Changes in the Species Composition of the Fish Community in a Reach of the Kootenai River, Idaho, after Construction of Libby Dam

“…Usually fish populations and communities change in conjunction with decreases in productivity Ney 1989, Pefiaz et al 1999). For example, changes in seasonal flow patterns, dewatering of varial zones, loss of flushing flows, and temperature changes are known to play roles in altering the fish species composition and life history characteristics (Benenati et al 1998, Bain et al 1988, Binn et al 1995, McKinney et al 2001). …”