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.
2007
Rosling, A.; Suttle, K. B.; Johansson, E.; Hees, P. A. W. Van; Banfield, J. F.
Phosphorous availability influences the dissolution of apatite by soil fungi Journal Article
In: Geobiology, vol. 5, no. 3, pp. 265-280, 2007.
Abstract | Links | BibTeX | Tags: apatite, phosphorus, soil fungi
@article{Rosling2007,
title = {Phosphorous availability influences the dissolution of apatite by soil fungi},
author = {A. Rosling and K. B. Suttle and E. Johansson and P. A. W. Van Hees and J. F. Banfield},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Rosling_2007_Geobio.pdf},
doi = {10.1111/j.1472-4669.2007.00107.x},
year = {2007},
date = {2007-09-01},
journal = {Geobiology},
volume = {5},
number = {3},
pages = {265-280},
abstract = {Apatite (Ca10(PO4)6(OH,F,Cl)2) is the primary inorganic source of phosphorus in the biosphere. Soil fungi are known to increase plant-available phosphorus by promoting dissolution of various phosphate minerals. Yet no apatite dissolution studies exist using fungi as weathering agents, and regulation of fungal weathering activity in response to different levels of phosphorus availability is largely unknown.
Fungi were isolated from a grassland soil in northern California. Three pathways of tri-calcium phosphate (Ca3(PO4)2) (TCP) dissolution in liquid culture were identified among biogeochemically active fungi: (1) acidification (pH 3.3 ± 0.16), (2) moderate acidification (pH 4.9 ± 0.11) and (3) no acidification. Isolates representing pathway 1 and 2 were Zygomycetes in the order of Mucorales. All non-acidifying isolates in pathway 3 were Ascomycetes and cleared the media by altering TCP into hydroxyapatite (Ca10(PO4)6(OH)2) and sequestering it within mycelial spheres. One isolate representing each pathway was used in fluorapatite dissolution experiments either with the fungi present or under abiotic conditions using cell-free liquid media conditioned by fungal growth at different phosphorus and calcium availabilities.
Both Mucorales isolates acidify their substrate when growing in the presence of phosphorus. Mucorales exudates were mainly oxalic acid, and conditioned cell-free media with phosphorus induced fluorapatite dissolution at a rate of 10−0.9±0.14 and 10−1.2±0.22 µmol P m−2 s−1. The ascomycete isolate on the other hand, induced fluorapatite dissolution at a rate of 10−1.1±0.05 µmol P m−2 s−1 by lowering the pH of the media under phosphorus-limited conditions, without producing significant amounts of low molecular weight organic acids (LMWOAs). Oxalate strongly etches fluorapatite along channels parallel to [001], forming needle-like features, while exudates from the ascomycete-induced surface rounding. We conclude that while LMWOAs are well-studied weathering agents, these do not appear to be produced by fungi in response to phosphorus-limiting growth conditions.},
keywords = {apatite, phosphorus, soil fungi},
pubstate = {published},
tppubtype = {article}
}
Apatite (Ca10(PO4)6(OH,F,Cl)2) is the primary inorganic source of phosphorus in the biosphere. Soil fungi are known to increase plant-available phosphorus by promoting dissolution of various phosphate minerals. Yet no apatite dissolution studies exist using fungi as weathering agents, and regulation of fungal weathering activity in response to different levels of phosphorus availability is largely unknown.
Fungi were isolated from a grassland soil in northern California. Three pathways of tri-calcium phosphate (Ca3(PO4)2) (TCP) dissolution in liquid culture were identified among biogeochemically active fungi: (1) acidification (pH 3.3 ± 0.16), (2) moderate acidification (pH 4.9 ± 0.11) and (3) no acidification. Isolates representing pathway 1 and 2 were Zygomycetes in the order of Mucorales. All non-acidifying isolates in pathway 3 were Ascomycetes and cleared the media by altering TCP into hydroxyapatite (Ca10(PO4)6(OH)2) and sequestering it within mycelial spheres. One isolate representing each pathway was used in fluorapatite dissolution experiments either with the fungi present or under abiotic conditions using cell-free liquid media conditioned by fungal growth at different phosphorus and calcium availabilities.
Both Mucorales isolates acidify their substrate when growing in the presence of phosphorus. Mucorales exudates were mainly oxalic acid, and conditioned cell-free media with phosphorus induced fluorapatite dissolution at a rate of 10−0.9±0.14 and 10−1.2±0.22 µmol P m−2 s−1. The ascomycete isolate on the other hand, induced fluorapatite dissolution at a rate of 10−1.1±0.05 µmol P m−2 s−1 by lowering the pH of the media under phosphorus-limited conditions, without producing significant amounts of low molecular weight organic acids (LMWOAs). Oxalate strongly etches fluorapatite along channels parallel to [001], forming needle-like features, while exudates from the ascomycete-induced surface rounding. We conclude that while LMWOAs are well-studied weathering agents, these do not appear to be produced by fungi in response to phosphorus-limiting growth conditions.
Fungi were isolated from a grassland soil in northern California. Three pathways of tri-calcium phosphate (Ca3(PO4)2) (TCP) dissolution in liquid culture were identified among biogeochemically active fungi: (1) acidification (pH 3.3 ± 0.16), (2) moderate acidification (pH 4.9 ± 0.11) and (3) no acidification. Isolates representing pathway 1 and 2 were Zygomycetes in the order of Mucorales. All non-acidifying isolates in pathway 3 were Ascomycetes and cleared the media by altering TCP into hydroxyapatite (Ca10(PO4)6(OH)2) and sequestering it within mycelial spheres. One isolate representing each pathway was used in fluorapatite dissolution experiments either with the fungi present or under abiotic conditions using cell-free liquid media conditioned by fungal growth at different phosphorus and calcium availabilities.
Both Mucorales isolates acidify their substrate when growing in the presence of phosphorus. Mucorales exudates were mainly oxalic acid, and conditioned cell-free media with phosphorus induced fluorapatite dissolution at a rate of 10−0.9±0.14 and 10−1.2±0.22 µmol P m−2 s−1. The ascomycete isolate on the other hand, induced fluorapatite dissolution at a rate of 10−1.1±0.05 µmol P m−2 s−1 by lowering the pH of the media under phosphorus-limited conditions, without producing significant amounts of low molecular weight organic acids (LMWOAs). Oxalate strongly etches fluorapatite along channels parallel to [001], forming needle-like features, while exudates from the ascomycete-induced surface rounding. We conclude that while LMWOAs are well-studied weathering agents, these do not appear to be produced by fungi in response to phosphorus-limiting growth conditions.