| Abstract: | The vertical distribution of algal biomass in the bed sediment and the seasonal development of benthic algae on stones and
fine-grained sediments were studied in a small unshaded stream. In addition, field experiments were conducted on the role
of irradiance and phosphorus in regulating algal biomass.
We found that algal biomass was high at a sediment depth of ten centimetres. Comparison of studies on algal biomass where
different depths of the sediment are used should therefore be made with caution. Substrata-dependent differences in algal
biomass development were substantial. While algal biomass development on stones was controlled by macroinvertebrate grazing,
that on the fine-grained sediment followed the dynamics of incident irradiance, but was attenuated by sediment rebedding.
Because of the high grazing pressure on algal biomass on stony substrata, no significant response to phosphorus enrichment
was attained. In contrast, algal biomass development on fine-grained sediments was phosphorus-limited. Heavy shading of the
fine-grained sediments did not significantly affect algal biomass development, thus suggesting that phosphorus limitation
prevents algae from fully utilizing the light resource in this stream.
This revised version was published online in July 2006 with corrections to the Cover Date. |
