2010
Finlay, Jacques C.; Doucett, Richard R.; McNeely, Camille
Tracing energy flow in stream food webs using stable isotopes of hydrogen Journal Article
In: Freshwater Biology, vol. 55, no. 5, pp. 941–951, 2010.
Abstract | Links | BibTeX | Tags: energy flow, food webs, stable isotopes, subsidies, trophic interactions
@article{Finlay2010,
title = {Tracing energy flow in stream food webs using stable isotopes of hydrogen},
author = {Jacques C. Finlay and Richard R. Doucett and Camille McNeely},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Finlay_2010_FreshBio.pdf},
doi = {10.1111/j.1365-2427.2009.02327.x},
year = {2010},
date = {2010-05-01},
journal = {Freshwater Biology},
volume = {55},
number = {5},
pages = {941–951},
abstract = {1. Use of the natural ratios of carbon and nitrogen stable isotopes as tracers of trophic interactions has some clear advantages over alternative methods for food web analyses, yet is limited to situations where organic materials of interest have adequate isotopic separation between potential sources. This constrains the use of natural abundance stable isotope approaches to a subset of ecosystems with biogeochemical conditions favourable to source separation.
2. Recent studies suggest that stable hydrogen isotopes (δD) could provide a robust tracer to distinguish contributions of aquatic and terrestrial production in food webs, but variation in δD of consumers and their organic food sources are poorly known. To explore the utility of the stable hydrogen isotope approach, we examined variation in δD in stream food webs in a forested catchment where variation in δ13C has been described previously.
3. Although algal δD varied by taxa and, to a small degree, between sites, we found consistent and clear separation (by an average of 67‰) from terrestrial carbon sources. Environmental conditions known to affect algal δ13C, such as water velocity and stream productivity did not greatly influence algal δD, and there was no evidence of seasonal variation. In contrast, algal δ13C was strongly affected by environmental factors both within and across sites, was seasonally variable at all sites, and partially overlapped with terrestrial δ13C in all streams with catchment areas larger than 10 km2.
4. While knowledge of isotopic exchange with water and trophic fractionation of δD for aquatic consumers is limited, consistent source separation in streams suggests that δD may provide a complementary food web tracer to δ13C in aquatic food webs. Lack of significant seasonal or spatial variation in δD is a distinct advantage over δ13C for applications in many aquatic ecosystems.},
keywords = {energy flow, food webs, stable isotopes, subsidies, trophic interactions},
pubstate = {published},
tppubtype = {article}
}
1. Use of the natural ratios of carbon and nitrogen stable isotopes as tracers of trophic interactions has some clear advantages over alternative methods for food web analyses, yet is limited to situations where organic materials of interest have adequate isotopic separation between potential sources. This constrains the use of natural abundance stable isotope approaches to a subset of ecosystems with biogeochemical conditions favourable to source separation.
2. Recent studies suggest that stable hydrogen isotopes (δD) could provide a robust tracer to distinguish contributions of aquatic and terrestrial production in food webs, but variation in δD of consumers and their organic food sources are poorly known. To explore the utility of the stable hydrogen isotope approach, we examined variation in δD in stream food webs in a forested catchment where variation in δ13C has been described previously.
3. Although algal δD varied by taxa and, to a small degree, between sites, we found consistent and clear separation (by an average of 67‰) from terrestrial carbon sources. Environmental conditions known to affect algal δ13C, such as water velocity and stream productivity did not greatly influence algal δD, and there was no evidence of seasonal variation. In contrast, algal δ13C was strongly affected by environmental factors both within and across sites, was seasonally variable at all sites, and partially overlapped with terrestrial δ13C in all streams with catchment areas larger than 10 km2.
4. While knowledge of isotopic exchange with water and trophic fractionation of δD for aquatic consumers is limited, consistent source separation in streams suggests that δD may provide a complementary food web tracer to δ13C in aquatic food webs. Lack of significant seasonal or spatial variation in δD is a distinct advantage over δ13C for applications in many aquatic ecosystems.
2. Recent studies suggest that stable hydrogen isotopes (δD) could provide a robust tracer to distinguish contributions of aquatic and terrestrial production in food webs, but variation in δD of consumers and their organic food sources are poorly known. To explore the utility of the stable hydrogen isotope approach, we examined variation in δD in stream food webs in a forested catchment where variation in δ13C has been described previously.
3. Although algal δD varied by taxa and, to a small degree, between sites, we found consistent and clear separation (by an average of 67‰) from terrestrial carbon sources. Environmental conditions known to affect algal δ13C, such as water velocity and stream productivity did not greatly influence algal δD, and there was no evidence of seasonal variation. In contrast, algal δ13C was strongly affected by environmental factors both within and across sites, was seasonally variable at all sites, and partially overlapped with terrestrial δ13C in all streams with catchment areas larger than 10 km2.
4. While knowledge of isotopic exchange with water and trophic fractionation of δD for aquatic consumers is limited, consistent source separation in streams suggests that δD may provide a complementary food web tracer to δ13C in aquatic food webs. Lack of significant seasonal or spatial variation in δD is a distinct advantage over δ13C for applications in many aquatic ecosystems.
2001
Finlay, Jacques C.; Power, Mary E.
In: Technical Completion Report, vol. UCAL-WRC-W-906, 2001.
Abstract | Links | BibTeX | Tags: cannibalism, Carbon and nitrogen stable isotope ratios, energy flow, Oncorhynchus mykiss, river food webs, river-watershed exchange, spatial scale, steelhead trout, terrestrial detritus, trophic structure
@article{Power2001,
title = {Carbon isotope signatures and spatial scales of energy flow in food webs supporting salmonids in food webs supporting salmonids in Northern California rivers},
author = {Jacques C. Finlay and Mary E. Power},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/eScholarship-UC-item-79t2s4f8.pdf},
year = {2001},
date = {2001-05-01},
journal = {Technical Completion Report},
volume = {UCAL-WRC-W-906},
abstract = {Spatial scales of the food webs that support the growth of juvenile salmonids in California rivers are largely unknown, but such information is essential for management of flows, species, and other ecosystem factors influencing salmonid production. Our project objectives were:
1. to determine whether predictable variation in algal d13C with water velocity, and measurements of consumer d13C and d15N could be used to examine energy flow and trophic structure in food webs of the South Fork Eel River, and other salmon-bearing streams in Northern California, and
2. to provide this information as a basis for examining how changes in access to energy sources following river regulation or invasions of exotic species might influence the access of various web members, including salmonids, to these sources.},
keywords = {cannibalism, Carbon and nitrogen stable isotope ratios, energy flow, Oncorhynchus mykiss, river food webs, river-watershed exchange, spatial scale, steelhead trout, terrestrial detritus, trophic structure},
pubstate = {published},
tppubtype = {article}
}
Spatial scales of the food webs that support the growth of juvenile salmonids in California rivers are largely unknown, but such information is essential for management of flows, species, and other ecosystem factors influencing salmonid production. Our project objectives were:
1. to determine whether predictable variation in algal d13C with water velocity, and measurements of consumer d13C and d15N could be used to examine energy flow and trophic structure in food webs of the South Fork Eel River, and other salmon-bearing streams in Northern California, and
2. to provide this information as a basis for examining how changes in access to energy sources following river regulation or invasions of exotic species might influence the access of various web members, including salmonids, to these sources.
1. to determine whether predictable variation in algal d13C with water velocity, and measurements of consumer d13C and d15N could be used to examine energy flow and trophic structure in food webs of the South Fork Eel River, and other salmon-bearing streams in Northern California, and
2. to provide this information as a basis for examining how changes in access to energy sources following river regulation or invasions of exotic species might influence the access of various web members, including salmonids, to these sources.
Finlay, Jacques C.
Stable-carbon-isotope ratios of river biota: Implications for energy flow in lotic food webs Journal Article
In: Ecology, vol. 82, no. 4, pp. 1052-1064, 2001, ISSN: 0012-9658.
Abstract | Links | BibTeX | Tags: algae, carbon limitation, energy flow, lotic food webs, stable-carbon-isotope ratios, terrestrial detritus, watershed area, δ13C
@article{Finlay2001,
title = {Stable-carbon-isotope ratios of river biota: Implications for energy flow in lotic food webs},
author = {Jacques C. Finlay},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/STABLE-CARBON-ISOTOPE-RATIOS-OF-RIVER-BIOTA-IMPLICATIONS-FOR-ENERGY-FLOW-IN-LOTIC-FOOD-WEBS_Finlay_2001.pdf},
doi = {10.1890/0012-9658(2001)082[1052:SCIROR]2.0.CO;2},
issn = {0012-9658},
year = {2001},
date = {2001-04-00},
journal = {Ecology},
volume = {82},
number = {4},
pages = {1052-1064},
abstract = {Stable-isotope ratios of carbon (13C/12C or δ13C) have been widely used to determine the energy base of stream food webs, but such use is controversial due to unexplained variability in algal δ13C. I used published δ13C data from temperate headwater streams through medium-sized rivers (0.2–4000 km2 watershed area) collected during summer baseflows and original data from streams in northern California to analyze energy pathways through river food webs. The analyses showed three important results. First, epilithic algal δ13C and watershed area are positively related, suggesting that effects of carbon limitation on algal carbon uptake result in 13C enrichment of algal δ13C in larger, more productive rivers. Second, epilithic algae and terrestrial detritus δ13C values are often distinct in small shaded streams but overlap in some larger unshaded streams and rivers. Measurements of δ13C values may be most useful in distinguishing algal and terrestrial energy sources in unproductive streams with supersaturated dissolved CO2 concentrations, and some productive rivers where CO2 concentrations are low relative to photosynthetic rates. Finally, consumer δ13C values are more strongly related to algal δ13C than terrestrial δ13C. The relative contribution of terrestrial and algal carbon sources often varied by functional feeding group within and between sites. However, with the exception of shredders and scrapers, which respectively relied on terrestrial and algal carbon sources, patterns of consumer δ13C clearly show a transition from terrestrial to algal carbon sources for many lotic food webs in streams with ≥10 km2 watershed area. The observed transition to algal carbon sources is likely related to increasing primary production rates as forest canopy cover declines in larger streams, although decreasing retention or quality of terrestrial carbon may also play a role. Improved analyses of algal δ13C and δ15N combined with quantitative study of organic matter dynamics and food web structure should allow the relative importance of these factors to be distinguished in future food web studies.},
keywords = {algae, carbon limitation, energy flow, lotic food webs, stable-carbon-isotope ratios, terrestrial detritus, watershed area, δ13C},
pubstate = {published},
tppubtype = {article}
}
Stable-isotope ratios of carbon (13C/12C or δ13C) have been widely used to determine the energy base of stream food webs, but such use is controversial due to unexplained variability in algal δ13C. I used published δ13C data from temperate headwater streams through medium-sized rivers (0.2–4000 km2 watershed area) collected during summer baseflows and original data from streams in northern California to analyze energy pathways through river food webs. The analyses showed three important results. First, epilithic algal δ13C and watershed area are positively related, suggesting that effects of carbon limitation on algal carbon uptake result in 13C enrichment of algal δ13C in larger, more productive rivers. Second, epilithic algae and terrestrial detritus δ13C values are often distinct in small shaded streams but overlap in some larger unshaded streams and rivers. Measurements of δ13C values may be most useful in distinguishing algal and terrestrial energy sources in unproductive streams with supersaturated dissolved CO2 concentrations, and some productive rivers where CO2 concentrations are low relative to photosynthetic rates. Finally, consumer δ13C values are more strongly related to algal δ13C than terrestrial δ13C. The relative contribution of terrestrial and algal carbon sources often varied by functional feeding group within and between sites. However, with the exception of shredders and scrapers, which respectively relied on terrestrial and algal carbon sources, patterns of consumer δ13C clearly show a transition from terrestrial to algal carbon sources for many lotic food webs in streams with ≥10 km2 watershed area. The observed transition to algal carbon sources is likely related to increasing primary production rates as forest canopy cover declines in larger streams, although decreasing retention or quality of terrestrial carbon may also play a role. Improved analyses of algal δ13C and δ15N combined with quantitative study of organic matter dynamics and food web structure should allow the relative importance of these factors to be distinguished in future food web studies.