effects of added nutrients on dry mass, afdm, chlorophyll a and biovolume of periphyton algae in artificial streams

we studied the role of nutrients on various aspects of the periphyton community in artificialstreams. dry mass, ash-free dry mass, chlorophyll a and biovolume of the periphyton community weremeasured under 3 different nutrient regimes, including one from natural streams as a control and twowhich were enriched with n and n+p. results of this experiment indicate that the standing crop of theperiphyton community in the artificial streams increased with increasing the amount of the nutrient.also, we showed that diatom diversity was affected by increasing the nutrients concentrations. theperiphyton dry mass following 23 days of experiment was 0.96, 1.4 and 3.52 mg/cm2 for control, n andn+p artificial streams, respectively. ash-free dry mass (afdm) of the periphyton community forcontrol, n and n+p treatment were 0.2, 0.98 and 1.04 mg/cm2, respectively. the experiment alsodepicted that the periphyton chlorophyll a increased with increasing the nutrient content in the artificialstreams (for control, n and n+p enriched artificial streams, the chlorophyll a content was 2.11, 2.20 and6.36 mg/m2respectively). the total diatom biovolume as a measure of standing crop in the periphytoncommunity was 6x106, 8x106 and 48x106 μm3/cm2 for control, n and n+p enriched artificial streams,respectively. results of this experiment demonstrated that adding nutrient increases the relativeabundance of navicula, achnanthes, nitzschia and cocconies in artificial streams.