Spatial Variation in Caddisfly Grazing Regimes Within a Northern California Watershed

McNeely, Camille; Power, Mary E.

doi:10.1890/06-0796.1

Cited by 28 publications

(22 citation statements)

References 66 publications

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“…Little rain falls between June and October, when sample collection occurred. Epilithic algae were present at all sites as a thin, heavily grazed layer consisting primarily of diatoms (McNeely and Power 2007). Effects of heterogeneity in land cover appear to be minimal, in part due to low human population density (,2 persons/km 2 ) facilitating examination of in-stream processes.…”

Section: Site Characteristicsmentioning

confidence: 90%

Light-mediated thresholds in stream-water nutrient composition in a river network

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Hood

Limm

et al. 2011

Ecology

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The elemental composition of solutes transported by rivers reflects combined influences of surrounding watersheds and transformations within stream networks, yet comparatively little is known about downstream changes in effects of watershed loading vs. in-channel processes. In the forested watershed of a river under a mediterranean hydrologic regime, we examined the influence of longitudinal changes in environmental conditions on water-column nutrient composition during summer base flow across a network of sites ranging from strongly heterotrophic headwater streams to larger, more autotrophic sites downstream. Small streams (0.1-10 km2 watershed area) had longitudinally similar nutrient concentration and composition with low (approximately 2) dissolved nitrogen (N) to phosphorus (P) ratios. Abrupt deviations from this pattern were observed in larger streams with watershed areas > 100 km2 where insolation and algal abundance and production rapidly increased. Downstream, phosphorus and silica concentrations decreased by > 50% compared to headwater streams, and dissolved organic carbon and nitrogen increased by approximately 3-6 times. Decreasing dissolved P and increasing dissolved N raised stream-water N:P to 46 at the most downstream sites, suggesting a transition from N limitation in headwaters to potential P limitation in larger channels. We hypothesize that these changes were mediated by increasing algal photosynthesis and N fixation by benthic algal assemblages, which, in response to increasing light availability, strongly altered stream-water nutrient concentration and stoichiometry in larger streams and rivers.

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Section: Site Characteristicsmentioning

confidence: 90%

Light-mediated thresholds in stream-water nutrient composition in a river network

Finlay

Hood

Limm

et al. 2011

Ecology

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“…The riparian community includes bay (Umbellularia californica), madrone (Arbutus menziesii), Douglas fir (Pseudotsuga menziesii), alder (Alnus rhombifolia), and maple (Acer macrophyllum). A thin, heavily grazed layer of diatoms dominates epilithic communities during the summer months (McNeely and Power 2007).…”

Section: Study Sitesmentioning

confidence: 99%

Selective feeding determines patterns of nutrient release by stream invertebrates

et al. 2014

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One common stoichiometric approach to predicting patterns of nutrient release (excretion + egestion) by animals in aquatic ecosystems is to base predictions on elemental mass-balance constrained by homeostatic maintenance. An easily measured resource composite (i.e., seston, epilithon, or leaf litter) often is used to represent ingested stoichiometry, but whether such a composite is a good indicator of food actually ingested is a relatively unexplored assumption. We examined the application of a stoichiometric model to the diets of 4 generalist stream invertebrates. We fed 3 trichopteran and 1 amphipod taxa rations consisting of cultured algae, stream epilithon, and several species of conditioned leaf litter. The rations ranged widely in C ∶ N from 10 to 69 (molar) and in C ∶ P from 165 to 3500. After a 2-d feeding period, we measured NH 4 + and PO 4 3− excretion, and C, N, and P egestion rates. The relationships observed between the stoichiometries of release and ration were unexpected. Total N ∶ P release rates conformed to stoichiometric predictions for only 1 taxon. Excretion and egestion rates and ratios were generally similar across diets and rarely varied with ration stoichiometry. These patterns were the result of smaller-than-expected responses to leaf-litter rations, which were the most imbalanced relative to body stoichiometry. Analysis of the C ∶ N stoichiometry of foregut material for 2 taxa showed selective ingestion of an N-rich fraction of leaf litter, in 1 case reducing an apparent 8.4 ∶ 1 C ∶ N imbalance between diet and body composition to 1.5 ∶ 1. Our results show that selective feeding can reduce potential stoichiometric imbalances, altering patterns of nutrient release relative to expectations based on bulk-diet stoichiometry. Assuming that stream invertebrates consume materials stoichiometrically similar to a resource composite can obscure understanding of stoichiometric imbalances and the role of invertebrates in nutrient cycles.

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“…Fox Creek is slightly larger, with a drainage area of 2.57 km 2 . Light, although still relatively low, is high enough in Fox Creek to support sufficient autotrophic production for high grazer biomass, and algal biomass and production are kept low mainly by grazing pressure (McNeely & Power, 2007). Jack O’Hearts Creek is a medium‐size stream with a drainage area of approximately 10.6 km 2 and has higher gross primary production rates and P : R (Table 2).…”

Section: Site Descriptionmentioning

confidence: 99%

The stoichiometry of nitrogen and phosphorus spiralling in heterotrophic and autotrophic streams

et al. 2010

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1. Nutrient spiralling provides a conceptual framework and a whole-system approach to investigate ecosystem responses to environmental changes. We use spiralling metrics to examine how the coupling of nitrogen and phosphorus uptake varies between streams dominated by either heterotrophic (i.e. bacteria-dominated) or autotrophic (algal-dominated) microbial communities. 2. Algae generally exhibit greater capacity to store nutrients than bacteria because of differences in cellular structures. These differences led us to hypothesise that the uptake of N and P in heterotrophic ecosystems should have reduced stoichiometric variation in response to changes in supply N : P compared to autotrophic ecosystems when assimilation dominates nutrient uptake. 3. To test this hypothesis, we used an array of serial nutrient additions in several streams in the South Fork Eel River watershed in Northern California. In one set of experiments, N and P were added alone and simultaneously in separate experiments to two small, heterotrophic streams to assess uptake rates and interactions between nutrient cycles. In a second set of experiments, N and P were added simultaneously at a range of N : P in one heterotrophic and one autotrophic stream to assess differences in uptake responses to changes in supply N : P. 4. Results of these experiments suggest two important conclusions. First, increased N supply significantly shortened P uptake lengths, while P addition had little impact on N uptake in both streams, indicating that uptake of non-limiting nutrients is tightly coupled to the availability of the limiting element. Second, changes in P uptake and uptake ratios (U N : U P ) with increased supply N : P supported our hypothesis that heterotrophic streams are more homeostatic in their responses to changes in nutrient supply than autotrophic streams, suggesting that physiological controls on nutrient use scale up to influence ecosystem-scale patterns in nutrient cycling.

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Spatial Variation in Caddisfly Grazing Regimes Within a Northern California Watershed

Cited by 28 publications

References 66 publications

Light-mediated thresholds in stream-water nutrient composition in a river network

Light-mediated thresholds in stream-water nutrient composition in a river network

Selective feeding determines patterns of nutrient release by stream invertebrates

The stoichiometry of nitrogen and phosphorus spiralling in heterotrophic and autotrophic streams

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