Chemical characteristics and aquatic macroinvertebrate diversity, abundance, and biomass in thermal backwaters and hyporheic zones of Tomichi Creek, Gunnison County.
Brigid Heckel, Patrick Magee, and Anne Ryter.
The Tomichi Creek floodplain, in the Gunnison Basin, Colorado, is characterized by a unique wetland complex
which includes thermal backwaters arising from hydrologic ground vents. Macroinvertebrates play key roles in wetland
and stream ecosystems as a source of food for consumer organisms and by facilitating organic matter decay. In
this study, I compared the aquatic macroinvertebrate assemblages n the funning waters and thermal backwaters of
lower Tomichi Creek, with special emphasis on habitats that have different chemical and physical properties. In
comparing the main channel of Tomichi Creek and its thermal backwaters, I found that 1) the main channel of the
creek housed higher numbers of aquatic macroinvertebrates, 2) the species richness was higher in the main channel
of Tomichi Creek, 3) taxa heterogeneity was higher in the thermal backwaters, and 4) biomass was variable between
the main channel of Tomichi Creek and its thermal backwaters. In comparing the hyporheic zones of the main channel
of Tomichi Creek and of the thermal backwaters, I found that 1) higher numbers of macroinvertebrates were collected
in the thermal hyporheic zones, 2) diversity was variable between hyporheic sites, and 3) biomass was variable
between hyporheic sites. In comparing benthic invertebrates in running waters to their associated hyporheic zones,
I found that 1) higher numbers of invertebrates were collected in benthic habitats, 2) diversity was higher in
the benthos, and 3) biomass was variable between the benthic and hyporheic zones of the creek. In comparing water
chemistry between the main channel of Tomichi Creek and its thermal backwaters, I found that 1) pH and dissolved
oxygen were higher in the main channel and 2) temperature was higher in the thermal backwaters. This research
is important as a step in determining functions of relatively unexplored aquatic habitats (i.e. thermal wetlands
and hyporheic zones) and will be useful to the Colorado Wetlands Partnership in identifying strategies for wetland
conservation.