Open AccessHydrodynamic shear removal of the nuisance stalk‐forming diatom Didymosphenia geminata
Author(s) -
Cullis James D. S.,
Crimaldi John P,
McKnight Diane M.
Publication year - 2013
Publication title -
limnology and oceanography: fluids and environments
Language(s) - English
Resource type - Journals
ISSN - 2157-3689
DOI - 10.1215/21573689-2414386
Subject(s) - nuisance , diatom , algae , shear stress , streams , substrate (aquarium) , environmental science , ecology , stream bed , ecosystem , habitat , benthic zone , biology , materials science , computer network , computer science , composite material
Lay Abstract Variability of flow is important in maintaining diversity of stream ecosystems. One reason for this is that periodic high flows result in the removal of algae growing on the stream bed (i.e., the substrate), leaving a patchwork of different species and habitat conditions. This is particularly true for nuisance algae such as Didymosphenia geminata that can grow quickly to blanket the stream bed restricting the available space for other organisms to live and feed. These nuisance species are thought, however, to be well adapted to the normal variability or regulation of flow, particularly in high‐gradient mountain streams. It is hypothesized that algal removal during these high‐flow events is limited and that effective removal requires much higher flows that result in the physical disturbance of the substrate and the mechanical scouring of the algae growing on the stream bed. We set out to examine this hypothesis by placing rocks attached with D. geminata colonies into a laboratory flow chamber. We then subjected the samples to increasing flows and determined the amount of material removed as the flow rate increased. We then investigated the relationship between the increasing applied shear stress (the force per unit area across the stream bed) and the amount of organic material removed. Our results showed that the removal due to elevated shear stress alone was low, up to the maximal levels of that which could be achieved in the flow chamber. A comparison with the estimated shear stress in the stream from where the samples were taken showed that removal was likely to be low up to a flow equal to the average annual maximum flow in the river and coinciding with the onset of widespread physical disturbance of the substrate. The results of this study have significance for understanding the ecosystem dynamics of streams and the potential use of flushing flows from reservoirs as a management tool for the mitigation of blooms of nuisance algal species such as D. geminata .