2011
Finlay, J. C.; Hood, J. M.; Limm, M. P.; Power, M. E.; Schade, J. D.; Welter, J. R.
Light-mediated thresholds in stream-water nutrient composition in a river network Journal Article
In: Ecology, vol. 92, no. 1, pp. 140-150, 2011.
Abstract | Links | BibTeX | Tags: Angelo Coast Range Reserve, autotrophy, elemental stoichiometry, geomorphology, heterotrophy, N fixation, nitrogen, phosphorus, primary production, South Fork Eel Riverwatershed, stream network
@article{Finlay2011,
title = {Light-mediated thresholds in stream-water nutrient composition in a river network},
author = {J. C. Finlay and J. M. Hood and M. P. Limm and M. E. Power and J. D. Schade and J. R. Welter},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Finlay_2011_Ecology.pdf},
doi = {10.1890/09-2243.1},
year = {2011},
date = {2011-01-01},
journal = {Ecology},
volume = {92},
number = {1},
pages = {140-150},
abstract = {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 (∼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 ∼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.},
keywords = {Angelo Coast Range Reserve, autotrophy, elemental stoichiometry, geomorphology, heterotrophy, N fixation, nitrogen, phosphorus, primary production, South Fork Eel Riverwatershed, stream network},
pubstate = {published},
tppubtype = {article}
}
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 (∼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 ∼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.
2010
Schade, John D.; MacNeill, Keely; Thomas, Steve A.; McNeely, F. Camille; Welter, Jill R.; Hood, James; Goodrich, Maria; Power, Mary E.; Finlay, Jacques C.
The stoichiometry of nitrogen and phosphorus spiraling in heterotrophic and autotrophic streams Journal Article
In: Freshwater Biology, vol. 56, no. 3, pp. 424-436, 2010.
Abstract | Links | BibTeX | Tags: autotrophic streams, heterotrophic streams, nitrogen, phosphorus
@article{Schade2010,
title = {The stoichiometry of nitrogen and phosphorus spiraling in heterotrophic and autotrophic streams},
author = {John D. Schade and Keely MacNeill and Steve A. Thomas and F. Camille McNeely and Jill R. Welter and James Hood and Maria Goodrich and Mary E. Power and Jacques C. Finlay},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Schade_2010_FreshBio.pdf},
doi = {10.1111/j.1365-2427.2010.02509.x},
year = {2010},
date = {2010-10-18},
journal = {Freshwater Biology},
volume = {56},
number = {3},
pages = {424-436},
abstract = {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 (UN : UP) 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.},
keywords = {autotrophic streams, heterotrophic streams, nitrogen, phosphorus},
pubstate = {published},
tppubtype = {article}
}
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 (UN : UP) 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.
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 (UN : UP) 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.
2004
Tenuta, Mario; Ferris, Howard
Sensitivity of Nematode Life-History Groups to Ions and Osmotic Tensions of Nitrogenous Solutions Journal Article
In: Journal of Nematology, vol. 36, no. 1, pp. 85-94, 2004, ISSN: 0022-300X.
Abstract | Links | BibTeX | Tags: c-p grouping, nematode faunal analysis, nitrogen, osmotic tension, sensitivity
@article{Tenuta2004,
title = {Sensitivity of Nematode Life-History Groups to Ions and Osmotic Tensions of Nitrogenous Solutions},
author = {Mario Tenuta and Howard Ferris},
editor = {Deborah A. Neher},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Sensitivity-of-Nematode-Life-History-Groups-to-Ions-and-osmotic-tensions-of-Nitrogenous-Solutions_Tenuta-and-Ferris.pdf},
issn = {0022-300X},
year = {2004},
date = {2004-03-01},
journal = {Journal of Nematology},
volume = {36},
number = {1},
pages = {85-94},
abstract = {Guild designation of nematodes of similar trophic function and life-history strategy provides a basis for Using nematode faunal analyses in all integrative assessment of soil food web condition. Omnivorous and predaceous nematodes, categorized at the upper end of a colollizer-persistcr (C-P) continuum of nematode functional guilds are generally not abundant in cropped soil. These nematodes are more sensitive to heavy metal concentrations than those in other c-p groups, but whether sensitivity to agrochemicals contributes to the observed low abundance of high c-p groups in cropped Soils is less Well Understood. An exposure assay in solution was itself to compare the sensitivity of nematodes representing various guilds obtained front field soils and front laboratory culture to several nitrogen sources. Nematodes in c-p groups 4 and 5 were more sensitive to nitrogen solutions titan nematodes representing lower c-p groups. There were both osmotic and specific ion effects-the latter most evident in exposure of nematodes to NaNO2 and (NH4)2SO(4). The RC50 (concentration resulting in nematode recovery of one half of that of distilled water) for (NH4)(2)SO1 was < 0.052 M-N for c-p groups 4 and 5 compared to much greater Values (0.34 to 0.81 M-N) for c-p groups 1 to 3. In non-ionic polyethylene glycol (PEG) solutions, osmotic tensions of 0.40 to 0.43 MPa reduced the recovery of exposed nematodes by half (RT50; water potential of solution resulting in nematode recovery of one half of that of distilled water) for c-p groups 4 and 5 compared to > 1.93 MPa for c-p groups 1 to 3. RT50 values for urea solutions, also non-ionic, were greater than for PEG. Caenorhabditis elegans N2 (c-p 1) and Meloidogyne javanica (c-p 3) reared oil solid medium and in hydroponic culture, respectively, were slightly more sensitive to specific ion and osmotic effects than nematodes of similar c-p groups obtained front soil. The greater sensitivity of c-p 4 and 5 nematodes to nitrogen solutions suggests that fertilizers may contribute to the low abundance of these nematodes in annual cropping systems. This study supports the use of nematode faunal analyses as indicators of chemical stress in soil.},
keywords = {c-p grouping, nematode faunal analysis, nitrogen, osmotic tension, sensitivity},
pubstate = {published},
tppubtype = {article}
}
Guild designation of nematodes of similar trophic function and life-history strategy provides a basis for Using nematode faunal analyses in all integrative assessment of soil food web condition. Omnivorous and predaceous nematodes, categorized at the upper end of a colollizer-persistcr (C-P) continuum of nematode functional guilds are generally not abundant in cropped soil. These nematodes are more sensitive to heavy metal concentrations than those in other c-p groups, but whether sensitivity to agrochemicals contributes to the observed low abundance of high c-p groups in cropped Soils is less Well Understood. An exposure assay in solution was itself to compare the sensitivity of nematodes representing various guilds obtained front field soils and front laboratory culture to several nitrogen sources. Nematodes in c-p groups 4 and 5 were more sensitive to nitrogen solutions titan nematodes representing lower c-p groups. There were both osmotic and specific ion effects-the latter most evident in exposure of nematodes to NaNO2 and (NH4)2SO(4). The RC50 (concentration resulting in nematode recovery of one half of that of distilled water) for (NH4)(2)SO1 was < 0.052 M-N for c-p groups 4 and 5 compared to much greater Values (0.34 to 0.81 M-N) for c-p groups 1 to 3. In non-ionic polyethylene glycol (PEG) solutions, osmotic tensions of 0.40 to 0.43 MPa reduced the recovery of exposed nematodes by half (RT50; water potential of solution resulting in nematode recovery of one half of that of distilled water) for c-p groups 4 and 5 compared to > 1.93 MPa for c-p groups 1 to 3. RT50 values for urea solutions, also non-ionic, were greater than for PEG. Caenorhabditis elegans N2 (c-p 1) and Meloidogyne javanica (c-p 3) reared oil solid medium and in hydroponic culture, respectively, were slightly more sensitive to specific ion and osmotic effects than nematodes of similar c-p groups obtained front soil. The greater sensitivity of c-p 4 and 5 nematodes to nitrogen solutions suggests that fertilizers may contribute to the low abundance of these nematodes in annual cropping systems. This study supports the use of nematode faunal analyses as indicators of chemical stress in soil.