Dataset Listing

Boulder Creek - Diatoms - Didymosphenia Geminata (2008-2010)

Variables:  Didymo Rating Index (DRI), ash-free-dry-mass(AFDM), chlorophyll concentration and didymo cell densities.

Date Range:  (2008-05-02 to 2010-09-30)

Dataset Creators/Authors:  James Cullis


Field Area:   Boulder Creek Watershed

  • Description

    In the recent years, particularly since the 2002 drought, the presence of Didymosphenia Geminata have significantly increased in Colorado mountain streams. Didymosphenia geminata is a nuisance algal species also known as "didymo" or "rock snot". Didymo can coat streambeds as a thick brown algal mat, with mats as thick as 1-2cm. Click here to get more details and microscopic views of D. geminata.

    A study was conducted along Boulder Creek from 2008-2010 to investigate factors affecting the removal of D. geminta. Samples of D. geminata were collected at various points Boulder Creek(see map) between June 2008 and September 2010. Metrics for measuring didymo growth includes Didymo Rating Index (DRI), ash-free-dry-mass(AFDM), chlorophyll concentration and didymo cell densities. Didymo Rating Index(DRI) is a qualitative way to gauge didymo growth. It ranges from 0, representing no obvious signs of didymo growth, to a maximum of 10, representing 100% coverage and mats greater than 5 cm thick. The maximum DRI for Boulder Creek was a 6 or 7 (100% coverage with a mat thickness of 1 to 2cm).

    Results of the study show the importance of taking into account site specific geomorphologic controls such as the potential for bed disturbance in addition to simple hydrologic controls such as variations in discharge. The results also show the importance of considering different controls for individual processes such distinguishing between the drivers of increased cell division or increased mat production in understanding the dynamics of complex ecological systems such as that presented by D. geminata.
  • Keywords

    Didymosphenia Geminata, diatom, Boulder Creek

  • Citation for This Dataset

    Cullis, James. Removal of benthic algae in swift-flowing streams: the significance of spatial and temporal variation in shear stress and bed disturbance. Thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirement for the degree of Doctor of Philosophy Department of Civil, Environmental and Architectural Engineering

    Citation for This Webpage

    James Cullis (2010). "CZO Dataset: Boulder Creek - Diatoms (2008-2010) - Didymosphenia Geminata." Retrieved 20 Sep 2017, from

  • Publications

    Primary Publications


    Hydrodynamic shear removal of the nuisance stalk-forming diatom Didymosphenia geminata. Cullis, J., Crimaldi J., and McKnight, M. (2013): Limnology and Oceanography: Fluids and Environments


    Hydrologic Control of the Nuisance Diatom, Didymosphenia germinata . Cullis J. (2010): Colorado Water 2 (3) 4-6


    Hydrodynamic control of benthic mats of Didymosphenia geminata at the reach scale. Cullis, J., McKnight, M. and Spaulding, S. (2015): Canadian Journal of Fisheries and Aquatic Sciences


Boulder Creek - Didymo rating density, ash-free-dry-mass(AFDM), chlorophyll concentration

(xlsx)   Data Level 0

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Overview Maps
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  • Overview Maps

    Map Showing locations of Samplings of Didymosphenia Geminata

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