Summary 



In September 2003, periphyton samples were collected from three sites on lower Careless 

 Creek above and below the Deadman's Basin irrigation return to assess whether this segment is 

 water-quality hmited and in need of TMDLs. The samples were collected following MDEQ 

 standard operating procedures, processed and analyzed using standard methods for periphyton, 

 and evaluated following modified USEPA rapid bioassessment protocols for wadeable streams. 



Because Careless Creek begins in a mountain ecoregion and ends in a prairie ecoregion, 

 and because water delivered to Careless Creek originates in a mountain ecoregion, diatom 

 metrics generated from the three samples were compared to criteria for both mountain and plains 

 streams. This segment of Careless Creek is classified as a prairie (C-3) stream. 



Compared to criteria for mountain streams, diatom metrics suggest moderate 

 impairment from sedimentation at the site above the Deadman's Basin return, and moderate 

 impairment from organic loading at this site and the site near the mouth of Careless Creek. 

 Minor impairment from sedimentation was noted at both sites below the return and minor 

 impairment from organic loading was registered at the site immediately below the return. Based 

 on criteria for prairie streams, there was no impairment from sedimentation and only minor 

 impairment from organic loading at the three sites. 



Composition of the periphyton community indicates a substantial change in ecological 

 conditions from above to below the discharge from Deadman's Basin Reservoir. Upstream of 

 the discharge the algae indicate a warm, slowly flowing stream with a muddy bottom and 

 brackish waters. Downstream of the discharge, the algae indicate cooler, fresher waters and 

 faster current velocities. Taxonomic composition at the two downstream sites was very similar. 

 The major algal taxa here suggest moderate loads of organic compounds, fresh to brackish-fresh 

 water, somewhat depressed levels of dissolved oxygen, and elevated concentrations of inorganic 

 nutrients. 



