caa a22 4500 469098198 CHVBK 20180323133037.0 cr unu---uuuuu 170328e19920801xx s 000 0 eng 10.1007/BF00317779 doi (NATIONALLICENCE)springer-10.1007/BF00317779 Steinman Alan Environmental Sciences Division, Oak Ridge National Laboratory, Bldg. 1504, P.O. Box 2008, 37831-6351, Oak Ridge, TN, USA aut Does an increase in irradiance influence periphyton in a heavily-grazed woodland stream? [Elektronische Daten] [Alan Steinman] Summary: Irradiance level and grazer density were manipulated in a factorial design to examine the relative effects of biotic and abiotic factors on periphyton biomass, productivity, and taxonomic structure in a heavily grazed, woodland stream. Irradiance levels were increased from 0.26 to 12.42 mol quanta/m2/d by placing metal halide lamps over the stream. The major grazer in this system was the prosobranch snail Elimia clavaeformis. Its densities were reduced from ca. 750 individuals/m2 to near zero by raising platforms off the stream bottom. Experimental treatments were maintained for 48 days. Biomass-specific carbon fixation rates increased significantly in response to higher light levels, indicating that periphyton communities were light-limited at this time of year. However, positive effects of irradiance on areal-specific carbon fixation and biomass were detected only when grazer density was reduced. Basal cells of the chlorophyte Stigeoclonium dominated communities exposed either to low light or high grazing pressure. When light was increased and grazer density reduced, large or upright diatoms became more abundant. Results from this study indicated that limitation of periphyton photosynthesis could be mitigated by increasing the levels of an abiotic resource (light) to this system, but that periphyton biomass was controlled by biotic interactions. Springer-Verlag, 1992 Herbivory nationallicence Light limitation nationallicence Periphyton nationallicence Snails nationallicence Streams nationallicence Oecologia Springer-Verlag 91/2(1992-08-01), 163-170 0029-8549 91:2<163 1992 91 442 https://doi.org/10.1007/BF00317779 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00317779 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Steinman Alan Environmental Sciences Division, Oak Ridge National Laboratory, Bldg. 1504, P.O. Box 2008, 37831-6351, Oak Ridge, TN, USA aut NATIONALLICENCE 773 0- Oecologia Springer-Verlag 91/2(1992-08-01), 163-170 0029-8549 91:2<163 1992 91 442 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer