Does rock chemistry affect periphyton accrual in streams? |
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Authors: | Elizabeth A Bergey |
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Institution: | (1) Oklahoma Biological Survey and Department of Zoology, University of Oklahoma, Norman, OK 73019, USA |
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Abstract: | Stones of different rock types often accrue different amounts of periphytic algae. Although algal biomass may be positively
related to stone roughness, the confounding role of rock chemistry is unclear. This independent effect of rock chemistry on
benthic algae was tested using the nutrient-diffusing technique, by incorporating powdered stone, rather than nutrients, into
the agar matrix. Rocks tested were sandstone, obsidian, schist, greywacke, pumice, gypsum, limestone, serpentine, and phosphorite.
Petri-dishes containing powdered rock and agar, and covered with a permeable cellulose filter, were incubated in eight pools
in a granitic stream. Algal biomass did not differ among any of the nine rock types and plain agar control, whereas biomass
differed among the concurrently placed nutrient diffusing substrates (the stream was phosphorus-limited). Algal composition
was more related to an upstream-downstream gradient (for filamentous algae) and pool-specific effects (deposition of fine
sediment for diatoms) than rock chemistry. This minimal effect of rock chemistry may be caused by the low dissolution rate
of stones.
Handling editor: J. Padisak |
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Keywords: | Benthic algae Epilithic algae Substrate texture Nutrient diffusing substrates Bedrock |
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