Periphyton plays an important role in stream ecology, and can be sensitive to macroinvertebrate grazers, near-bed current velocity, and bedload abrasion. We manipulated conditions to examine influences on periphytic accrual in the St. Anthony Falls Laboratory Outdoor StreamLab in Minneapolis, MN, USA. Macroinvertebrate grazers were excluded from 27 of 65 clay tiles using electric pulses. We examined periphytic biomass accrual as a function of grazer presence, sampling run, and near-bed current velocity using ANCOVA. We found significant temporal differences between sampling runs but no significant effect of grazer presence. Along with a strong association between bedload transport rates and mean periphytic biomass, our results suggest that grazers are relatively unimportant in stream systems with high levels of physical disturbance from floods and associated sand bedload. However, the interaction between grazer presence and velocity was marginally significant. Regression analyses showed no relation between velocity and periphyton in the absence of grazers but a negative relation when grazers were present, suggesting that mechanical dislodgement of periphyton by grazers may increase with velocity. We conclude that grazers can have subtle effects on periphyton, particularly in streams with high bedload transport rates.
Periphyton Chlorophyll aNear-bed current velocity Bedload transport rate Experimental stream
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Kathryn Kramarczuk provided technical assistance and an ongoing presence at the Outdoor StreamLab which made this work possible. Mallory Immerfall, Jordan Theissen, and Brandon Trimbell also assisted with experimental setup and maintenance. Miki Hondzo gave advice on the experimental design. This work was supported by the National Science Foundation through a CAREER grant (DEB-0642512) to T.W. and by the STC program via the National Center for Earth-surface Dynamics under agreement number EAR-0120914.
Biggs, B. J. F., 1996. Patterns in benthic algae of streams. In Stevenson, J. R., M. I. Bothwell & R. L. Lowe (eds), Algal ecology: freshwater benthic ecosystems. Academic Press, Inc, San Diego, CA: 31–56.Google Scholar
Biggs, B. J. F. & R. A. Smith, 2002. Taxonomic richness of stream benthic algae: effects of flood disturbance and nutrients. Limnology and Oceanography 47: 1175–1186.CrossRefGoogle Scholar
Biggs, B. J. F., D. G. Goring & V. I. Nikora, 1998. Subsidy and stress responses of stream periphyton to gradients in water velocity as a function of community growth form. Journal of Phycology 34: 598–607.CrossRefGoogle Scholar
Brown, G. G., R. H. Norris, W. A. Maher & K. Thomas, 2000. Use of electricity to inhibit macroinvertebrate grazing of epilithon in experimental treatments in flowing waters. Journal of the North American Benthological Society 19: 176–185.CrossRefGoogle Scholar
Cattaneo, A. & B. Mousseau, 1995. Empirical analysis of the removal rate of periphyton by grazers. Oecologia 103: 249–254.CrossRefGoogle Scholar
Dzialowski, A. R. & V. H. Smith, 2008. Nutrient dependent effects of consumer identity and diversity on freshwater ecosystem function. Freshwater Biology 53: 148–158.Google Scholar
Feminella, J. W. & C. P. Hawkins, 1995. Interactions between stream herbivores and periphyton: a quantitative analysis of past experiments. Journal of the North American Benthological Society 14: 465–509.CrossRefGoogle Scholar
Gordon, N. D., T. A. McMahon, B. L. Finlayson, C. J. Gippel & R. J. Nathan, 2004. Stream hydrology: an introduction for ecologists. Wiley, New York.Google Scholar
Hayes, J. W., J. D. Stark & K. A. Shearer, 2000. Development and test of a whole-lifetime foraging and bioenergetic growth model for drift-feeding brown trout. Transactions of the American Fisheries Society 129: 315–332.CrossRefGoogle Scholar
Hondzo, M. & H. Wang, 2002. Effects of turbulence on growth and metabolism of periphyton in a laboratory flume. Water Resources Research 38: 63–68.CrossRefGoogle Scholar
Lamberti, G. A., 1996. The role of periphyton in benthic food webs. In Stevenson, J. R., M. I. Bothwell & R. L. Lowe (eds), Algal ecology: freshwater benthic ecosystems. Academic Press, Inc, San Diego, CA: 533–572.Google Scholar
Liess, A. & H. Hillebrand, 2004. Invited review: direct and indirect effects in herbivore periphyton interactions. Archiv Für Hydrobiologie 159: 433–453.CrossRefGoogle Scholar
Murdock, J., D. Roelke & F. Gelwick, 2004. Interactions between flow, periphyton, and nutrients in a heavily impacted urban stream: implications for stream restoration effectiveness. Ecological Engineering 22: 197–207.CrossRefGoogle Scholar
Opsahl, R., T. Wellnitz & N. L. Poff, 2003. Interactions of current velocity and herbivory in regulating stream algae: an in situ electrical exclusion. Hydrobiologia 499: 135–145.CrossRefGoogle Scholar
Poff, N. L., T. Wellnitz & J. B. Monroe, 2003. Redundancy among three herbivorous insects across an experimental current velocity gradient. Oecologia 134: 262–269.PubMedGoogle Scholar
Schofield, K. A., C. M. Pringle & J. L. Meyer, 2004. Effects of increased bedload on algal- and detrital-based stream food webs: experimental manipulation of sediment and macroconsumers. Limnology and Oceanography 49: 900–909.CrossRefGoogle Scholar
Scrimgeour, G. J., J. M. Culp, M. L. Bothwell, F. J. Wrona & M. H. McKee, 1991. Mechanisms of algal patch depletion: importance of consumptive and non-consumptive losses in mayfly-diatom systems. Oecologia 85: 343–348.CrossRefGoogle Scholar
Wellnitz, T. & N. L. Poff, 2006. Herbivory, current velocity and algal regrowth: how does periphyton grow when the grazers have gone? Freshwater Biology 51: 2114–2123.CrossRefGoogle Scholar
Wellnitz, T. & R. B. Rader, 2003. Mechanisms influencing community composition and succession in mountain stream periphyton: interactions between scouring history, grazing, and irradiance. Journal of the North American Benthological Society 22: 528–541.CrossRefGoogle Scholar