Effects of Biomass, Light, and Grazing on Phosphorus Cycling in Stream Periphyton Communities

The influence of periphyton biomass, irradiance, and herbivory by snails on phosphorus turnover in stream periphyton communities was examined over a 15-d experimental period. A 2 × 2 × 2 factorial design was employed with each treatment combination replicated twice. Percent increase in periphyton biomass was greater under: low vs. high initial biomass; high vs. low light levels; and no-snail vs. snail-present conditions. Significant interactions among main effects revealed that the percent increase in biomass in the low initial biomass treatment was greater when snails were absent, whereas the effect of light was greater when snails were present. Phosphorus turnover from the mat was significantly greater under low than high initial biomass levels and snail-present vs. no-snail conditions. Grazing removed periphyton biomass from the substrates, resulting in increased P turnover because of physical and consumptive losses. In the absence of snails, initial biomass level had surprisingly little effect on P turnover. We suspect that biomass accrued rapidly in the absence of snails, thereby blurring the distinction between low and high biomass treatments by day 15. However, in the presence of snails, P turnover rate was significantly lower in communities with high initial biomass. Despite the fact that lower irradiance resulted in significantly lower metabolic rates of periphyton, irradiance had no significant effect on P turnover. These results suggest that internal cycling provides an important source of nutrients in periphyton communities with high biomass and that grazing promotes nutrient turnover in periphyton, regardless of biomass level.

[1]  H. L. Boston,et al.  Grazers and Nutrients Simultaneously Limit Lotic Primary Productivity , 1992 .

[2]  H. Utermöhl.  Zur Vervollkommnung der quantitativen Phytoplankton-Methodik , 1958 .

[3]  R. Wetzel,et al.  Distributions and fates of oxygen in periphyton communities , 1987 .

[4]  R. Wetzel,et al.  Boundary-layer and internal diffusion effects on phosphorus fluxes in lake periphyton1 , 1987 .

[5]  J. Elwood,et al.  Role of Nutrient Cycling and Herbivory in Regulating Periphyton Communities in Laboratory Streams , 1991 .

[6]  J. Sharp,et al.  Determination of total dissolved phosphorus and particulate phosphorus in natural waters1 , 1980 .

[7]  D. DeAngelis,et al.  Resistance of lotic ecosystems to a light elimination disturbance: a laboratory stream study , 1990 .

[8]  J. Lubchenco.  Littornia and Fucus: Effects of Herbivores, Substratum Heterogeneity, and Plant Escapes During Succession , 1983 .

[9]  Walter R. Hill,et al.  Photosynthesis–light relations of stream periphyton communities , 1991 .

[10]  A. Steinman,et al.  Productive Capacity of Periphyton as a Determinant of Plant‐Herbivore Interactions in Streams , 1989 .

[11]  F. Stuart Chapin,et al.  Resource Availability and Plant Antiherbivore Defense , 1985, Science.

[12]  N. Grimm,et al.  Temporal Variation in Enrichment Effects during Periphyton Succession in a Nitrogen-Limited Desert Stream Ecosystem , 1992, Journal of the North American Benthological Society.

[13]  Walter R. Hill,et al.  Functional Responses Associated with Growth Form in Stream Algae , 1992, Journal of the North American Benthological Society.

[14]  Patrick J. Mulholland,et al.  Top‐Down and Bottom‐Up Control of Stream Periphyton: Effects of Nutrients and Herbivores , 1993 .

[15]  S. Findlay,et al.  BACTERIAL-ALGAL RELATIONSHIPS IN STREAMS OF THE HUBBARD BROOK EXPERIMENTAL FOREST' , 1993 .

[16]  A. Steinman,et al.  Effects of Herbivore Type and Density on Taxonomic Structure and Physiognomy of Algal Assemblages in Laboratory Streams , 1987, Journal of the North American Benthological Society.

[17]  Mary K. Bolin,et al.  EVIDENCE OF DARK AVOIDANCE BY PHOTOTROPHIC PERIPHYTIC DIATOMS IN LOTIC SYSTEMS 1 , 1989 .

[18]  J. M. Noel,et al.  Marsh phosphorus concentrations, phosphorus content and species composition of Everglades periphyton communities , 1993 .

[19]  William G. Cochran,et al.  Experimental Designs, 2nd Edition , 1950 .

[20]  B. Paul,et al.  Nutrient cycling in the epilithon of running waters , 1989 .

[21]  R. Bilger,et al.  Effects of water velocity on phosphate uptake in coral reef-hat communities , 1992 .

[22]  V. Resh,et al.  Periphyton responses to invertebrate grazing and riparian canopy in three northern California coastal streams , 1989 .

[23]  L. Whitford,et al.  Effect of a Current on Respiration and Mineral Uptake In Spirogyra and Oedogonium , 1964 .

[24]  V. Resh,et al.  Stream Periphyton and Insect Herbivores: An Experimental Study of Grazing by a Caddisfly Population , 1983 .

[25]  M. Bothwell.  Growth Rate Responses of Lotic Periphytic Diatoms to Experimental Phosphorus Enrichment: The Influence of Temperature and Light , 1988 .

[26]  Walter R. Hill,et al.  Community development alters photosynthesis‐irradiance relations in stream periphyton , 1991 .

[27]  The effect of flow patterns on uptake of phosphorus by river periphyton , 1979 .

[28]  T. Bott,et al.  Diel fluctuations in bacterial activity on streambed substrata during vernal algal blooms: Effects of temperature, water chemistry, and habitat , 1989 .

[29]  R. Sterner.  The Ratio of Nitrogen to Phosphorus Resupplied by Herbivores: Zooplankton and the Algal Competitive Arena , 1990, The American Naturalist.

[30]  W. Hill.  Food Limitation and Interspecific Competition in Snail-Dominated Streams , 1992 .