The Effects of Conductivity on Periphyton Productivity and Enzyme Activity from Lake Tahoe and Lake Tanganyika Cultures

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Despite similarly low dissolved nutrient concentrations and similar communities dominated by N-fixing cyanobacteria, epilithic periphyton productivity in Lake Tanganyika, East Africa is 5x that of Lake Tahoe, California. If organic phosphorus is a significant resource for attached algae, the contrasting salt concentrations in the two lakes may be critical to understanding how the cyanobacteria meet their P demands. We tested the effects of conductivity and phosphorous source (organic vs. inorganic) on periphyton productivity, biomass, and alkaline phosphatase activity (APA) in cultures from the two lakes. We controlled conductivity and pH using Seachem Cichlid Lake Salt and Lake Tanganyika Buffer respectively, and added either beta-glycerophosphate disodium salt (organic) or sodium phosphate (inorganic). Periphyton biomass was 2x higher in the high conductivity treatment relative to the low conductivity treatment, regardless of P source or lake of origin. APA was undetectable in the inorganic phosphorous treatments. In Lake Tanganyika cultures, APA was increased in high conductivity, but APA in Lake Tahoe cultures was not related to conductivity. The results of this study suggest periphyton function is affected by conductivity.


Presented at the Society for Freshwater Science Annual Meeting, Louisville, KY.