BENTHIC ECOLOGY OF THE COLORADO RIVE

GLEN CANYON NATIONAL RECREATION AREA, AR

AQUATIC INVERTEBRATE BIOGEOGRAPHY AND THE 

SHALLOW HYPORHEIC ANOXIA (SHA)

Larry Stevens and Biology Department Staff

Museum of Northern Arizona, Flagstaff

and

Craig Ellsworth, WAPA
The Museum of Northern Arizona

Easton Collections Center

>400,000 invert specimens, 50 yr

databasing of MNA and other

Colo. Plateau collections is on-going
PROJECT TASKS

(ONE‐YEAR DURATION, FUNDING BY WAPA)

TASK 1: COMPILE AND EVALUATE EXISTING INFORMATION ON CRE REGIONAL

AQUATIC MACROINVERTEBRATE DIVERSITY AND WATER QUALITY REQU

• Emphasis on EPT

• Historical presence in the CRE drainage

• Diversity• Water quality requirements

TASK 2: MAP THE DISTRIBUTION OF SHALLOW HYPORHEIC ANOXIA (SHA)

AND CONDUCT FIELD EXPERIMENTS ON ITS DEVELOPMENT AND IMPAC

• Task 2a: Map the distribution of SHA

• Task 2b: Determine SHA impacts on WQ and soil geochemistry

• Task 2c: Determine the effects of SHA on aquatic invertebrates• Task 2d: Determine the effects of flood disturbance on SHA and the b

• Task 2e: Effects of flow variation on SHA development

Develop a conceptual model of SHA development
TASK 1:

COMPILE DISTRIBUTION, HABITAT, AND WATER QUALITY REQUIREMEN

EPT AND OTHER AQUATIC MACROINVERTEBRATES IN THE CRE DRAI

Adult Apatania arizona [Trichoptera:Apataniidae (Limnephilidae)]:Smithsonian Institution ♂ paratype ‐ AZ:

Apache Co., ASNF; Little Colorado River

Sheep Crossing; 33.58 N, ‐109.31W, 2800

m elevation; collected on 14 Aug 1995 by

CM & OS Flint Jr., identified by OS Flint,

Jr.; adult total length (excluding

antennae) = 8 mm.

Adult Polycentropus gertsc(Trichoptera: PolycentropoSpecimen from Smithsonia

Institution – AZ: Apache CoColorado River near Greer 

ft (2530 m) elevation, colle

August 1995 by C. and O. FTotal body length = 9‐10.5 
Shallow Hyporheic Ano
SHALLOW HYPORHEIC ANOXIA PILOT STUDY

WHAT?: BLACK OOZE, REDUCED SEDIMENTS AT SHALLOW DEPTH BELOW THE CRE CHANNEL WHERE 1?: UBIQUITOUS? THROUGHOUT LOWER LAKE POWELL?

FROM GLEN CANYON DAM DOWNSTREAM TO LEES FERRY

APPARENTLY NOT (YET) DOWNSTREAM IN GRAND CANYON

WHERE 2?: DEPTH PROFILE ACROSS CHANNEL AND WITHIN BED TBD

HOW?: ELEVATED ORGANIC CARBON CONCENTRATIONS FROM DECOMPOSING BENTHIC MAC

BUT WHY IN LAKE POWELL AND WHY NOT BELOW LEES FERRY?

WHEN?: DIEL VARIATION

SEASONAL VARIATIONHISTORY OF DEVELOPMENT

OTHER ?: GRAIN SIZE EFFECTS OR RESPONSES?

HFE RESPONSES? FLOOD SCOUR EFFECTS?

FOODBASE IMPACTS – BUT NOT A SOURCE AND PATHWAY ANALYSIS

SO WHAT ?: DOES SHA MATTER?

WILL SHA PROGRESS DOWNSTREAM?
Shallow Hyporheic Anoxia 

Anoxia• Oxidation of organic matter by

bacteria

• Depletion of dissolved oxygen

• Release of toxic

chemicals/compounds (e.g.,

mercury)?

Production of hydrogen sulfide• Rotten egg smell• Dark black color in sediment

• Toxic to most biota

• Impacts on aquatic organisms?
Shallow Hyporheic Anoxia 

Influenced by biochemical oxygen demand

(BOD)• Type of bacteria and organic material

present

• pH• TemperatureCommon in:

• Ocean sediments• Eutrophic systems• But not reported in cold‐stenothermic

dam tailwaters
Schedule and Planning

Pilot Trip: Pending NPS permittingSHA distribution monitored seasonally

Transects: 3 on Lake Powell shores

6 from GC Dam to LF

3 ds from LF

Water and soil geochemistry sampling

Experimental manipulations of temp,

flow variation, DO at Hidden Slough

(‐6.5R)

Bioassays on common aquatic taxa,

in situ and laboratory studies
Shallow Hyporheic Anoxia:

Just a strange process,

Or a phenomenon that affects Colorado River

ecosystem development?