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Title: Top-down and bottom-up control of stream periphyton: Effects of nutrients and herbivores

Abstract

Two experiments determineD the relative effects of herbivory and nutrients on an algal community in in a stream having effectively two trophic levels: primary producers and herbivorous snails. The first study (1989), in streamside channels, tested the effects of three factors: (1) stream water nitrogen (N), (2) phosphorus (P), and (3) snail grazing, on periphyton biomass, productivity, and community composition. The second study (1990), conducted in situ, tested the effects of snail grazing and nutrients (N + P). In the 1989 study, nutrients had positive effects, and herbivores had negative effects, on algal biomass and primary productivity. Likewise, both nutrients and snail grazing exerted effects (+ and [minus], respectively) on biomass measured in the 1990 study. Grazed communities, dominated by chlorophytes and cyanophytes, were overgrown by diatoms when herbivores were removed. Algal species , reduced the most by herbivores, were increased most by nutrient addition, and vice versa, suggesting a trade-off between resistance to herbivory and nutrient-saturated growth rates. The greatest changes in periphyton structure or function were observed when both N and P were added and simultaneously, grazers were removed, in contrast to lesser effects when nutrients were added under grazed conditions or grazers were removed at low nutrientmore » levels, indicating dual control by both factors. Nutrient addition also positively affected snail growth in both experiments, indicating tight coupling between herbivore and algal growth (top-down effects) and that bottom-up factors that directly affected plant growth could also indirectly affect consumers belonging to higher trophic levels. Indices showed that the relative strength of top-down and bottom-up factors varied among biomass and productivity parameters and that top-down and bottom-up effects, alone, were less important than their combined effects. 67 refs., 8 figs., 7 tabs.« less

Authors:
 [1]; ;  [2]
  1. Vanderbilt Univ., Nashville, TN (United States)
  2. Oak Ridge National Lab., TN (United States)
Publication Date:
OSTI Identifier:
6389501
DOE Contract Number:  
AC05-84OR21400
Resource Type:
Journal Article
Journal Name:
Ecology; (United States)
Additional Journal Information:
Journal Volume: 74:4; Journal ID: ISSN 0012-9658
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; ALGAE; PLANT GROWTH; NUTRIENTS; BIOLOGICAL EFFECTS; SNAILS; STREAMS; DIATOMS; GRAZING; NITROGEN; PHOSPHORUS; PRODUCTIVITY; WATER; ANIMALS; AQUATIC ORGANISMS; CHROMOPHYCOTA; ELEMENTS; FEEDING; GROWTH; HYDROGEN COMPOUNDS; INVERTEBRATES; MOLLUSCS; NONMETALS; OXYGEN COMPOUNDS; PLANTS; SURFACE WATERS; 550000* - Biomedical Sciences, Basic Studies; 560300 - Chemicals Metabolism & Toxicology

Citation Formats

Rosemond, A D, Mulholland, P J, and Elwood, J W. Top-down and bottom-up control of stream periphyton: Effects of nutrients and herbivores. United States: N. p., 1993. Web. doi:10.2307/1940495.
Rosemond, A D, Mulholland, P J, & Elwood, J W. Top-down and bottom-up control of stream periphyton: Effects of nutrients and herbivores. United States. doi:10.2307/1940495.
Rosemond, A D, Mulholland, P J, and Elwood, J W. Tue . "Top-down and bottom-up control of stream periphyton: Effects of nutrients and herbivores". United States. doi:10.2307/1940495.
@article{osti_6389501,
title = {Top-down and bottom-up control of stream periphyton: Effects of nutrients and herbivores},
author = {Rosemond, A D and Mulholland, P J and Elwood, J W},
abstractNote = {Two experiments determineD the relative effects of herbivory and nutrients on an algal community in in a stream having effectively two trophic levels: primary producers and herbivorous snails. The first study (1989), in streamside channels, tested the effects of three factors: (1) stream water nitrogen (N), (2) phosphorus (P), and (3) snail grazing, on periphyton biomass, productivity, and community composition. The second study (1990), conducted in situ, tested the effects of snail grazing and nutrients (N + P). In the 1989 study, nutrients had positive effects, and herbivores had negative effects, on algal biomass and primary productivity. Likewise, both nutrients and snail grazing exerted effects (+ and [minus], respectively) on biomass measured in the 1990 study. Grazed communities, dominated by chlorophytes and cyanophytes, were overgrown by diatoms when herbivores were removed. Algal species , reduced the most by herbivores, were increased most by nutrient addition, and vice versa, suggesting a trade-off between resistance to herbivory and nutrient-saturated growth rates. The greatest changes in periphyton structure or function were observed when both N and P were added and simultaneously, grazers were removed, in contrast to lesser effects when nutrients were added under grazed conditions or grazers were removed at low nutrient levels, indicating dual control by both factors. Nutrient addition also positively affected snail growth in both experiments, indicating tight coupling between herbivore and algal growth (top-down effects) and that bottom-up factors that directly affected plant growth could also indirectly affect consumers belonging to higher trophic levels. Indices showed that the relative strength of top-down and bottom-up factors varied among biomass and productivity parameters and that top-down and bottom-up effects, alone, were less important than their combined effects. 67 refs., 8 figs., 7 tabs.},
doi = {10.2307/1940495},
journal = {Ecology; (United States)},
issn = {0012-9658},
number = ,
volume = 74:4,
place = {United States},
year = {1993},
month = {6}
}