7799

• UCREFRP Catalog Number: 7799
• Author: Modde, T. and D. Irving.
• Title: Conceptual Management Plan for Habitat Enhancement In Old Charley Wash.
• USFW Year: 1994.
• USFW - Doc Type: \
• Copyright Material: NO

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CONCEPTUAL ECOLOGICAL MODEL OF THE VALUE OF LOW WATER VELOCITY HABITATS IN THE
UPPER COLORADO RIVER BASIN TO THE ENDANGERED FISHES

Generally, the input of terrestrial organic matter provides the basis for energy in headwater streams (Vannote

et al. 1980). Large rivers, such as those of the upper basin, depend upon fine particulate organic matter

from upstream reaches for basic productivity (Vannote et al. 1980; Sedell and Richey 1989). Although

detailed ecological studies of the various habitats in the upper basin have not been made, inferences can

be drawn from the published literature.

A. Relation of Nutrients. Sunlight Penetration. and Warm Water Temoeratures to Phytoplankton Production.

Phytoplankton productivity provides the basis for development of a food web. Phytoplankton production

and standing crops increase in concert with increases in annual input of nutrients regardless of latitude.

Carbon, nitrogen, and phosphorus are key elements for phytoplankton production. Phosphorus is perhaps

most limiting in north temperate and subarctic climates (Schindler 1978). Nitrogen is the most abundant

element in the atmosphere and is generally not limiting. Also. abundant carbon dioxide in the atmosphere

provides the necessary carbon. Therefore, phytoplankton production and standing crop in north temperate

freshwaters is generally proportional to the phosphorus input. Particulate phosphorus, either chemically

desorbed or actively mobilized by microbiota, is not readily available in rivers with a high sediment load

because most of the phosphorus is bound to the sediments (Ellis and Stanford 1988). Watts and Lamarra

(1983) determined that between 21 % and 49% of the total phosphorus in Colorado River water at the bridge

upstream from Moab, Utah in September and October 1978 was bioavailable with most of the extractable

element in the form of calcium-bound phosphorus. Therefore, Watts and Lamarra (1983) concluded that

algae production was not nutrient limited in this reach of the Colorado River but that primary production was

inversely related to the turbidity of the riverine environment.