Evaluation of isotopic fractionation error on calculations of marine-derived nitrogen in terrestrial ecosystems

2005 ◽  
Vol 35 (7) ◽  
pp. 1604-1616 ◽  
Author(s):  
Arthur EL Morris ◽  
John M Stark ◽  
Barrie K Gilbert
Keyword(s):  
Isotope Fractionation ◽  
Pacific Salmon ◽  
Model Simulation ◽  
Isotopic Fractionation ◽  
Terrestrial Ecosystems ◽  
Riparian Ecosystems ◽  
Terrestrial Plants ◽  
N Losses ◽  
Riparian Plant ◽  
Spawning Sites

Pacific salmon (Oncorhynchus spp.) transport nitrogen (N) from oceans to inland ecosystems. Salmon δ15N is higher than δ15N expected in terrestrial plants, so linear two-source mixing models have commonly been used to quantify contributions of marine-derived N (MDN) to riparian ecosystems based on riparian plant δ15N. However, isotopic fractionation potentially contributes to error in MDN estimates by changing δ15N of salmon-derived N appearing in soil and plants. We used a simulation model to examine potential effects of fractionation on MDN estimates. We also measured changes in δ15N and δ13C as N and carbon (C) moved from bear feces into soil, and compared MDN estimates using three different estimates for the marine endmember of a linear mixing model. Simulation demonstrated that fractionation during soil N losses could lead to large overestimations of MDN when δ15N of salmon tissue is used as the marine endmember. δ15N of bear feces was significantly enriched (by 1.9‰) relative to salmon tissue, but did not change during movement of feces-derived N into soil. In contrast, δ13C decreased by 1.9‰ between salmon and bear feces and declined an additional 4.2‰ during movement into soil. We propose a new method for estimating the δ15N of the marine endmember that accounts for isotope fractionation occurring as marine N is cycled in soil. This method uses the proportional difference in soil 15N content between reference and spawning sites to calculate the marine endmember δ15N.

Challenges for Diadromous Fishes in a Dynamic Global Environment

2009 ◽  
Author(s):  
Jon M. Honea
Keyword(s):  
Life Histories ◽  
Pacific Salmon ◽  
North Pacific Ocean ◽  
Terrestrial Ecosystems ◽  
Freshwater Ecosystems ◽  
Riparian Ecosystems ◽  
Nutrient Sources ◽  
Temporal And Spatial Variability ◽  
Ecological Importance ◽  
Animal Communities

<em>Abstract</em>.-We review the current understanding of major pathways, mechanisms, and consequences of salmon-borne marine-derived nutrients (MDN) in estuarine, freshwater, and riparian ecosystems. Semelparous Pacific salmon <em>Oncorhynchus </em>spp. acquire most of their body mass while at sea before returning to spawn and die in natal streams. The annual spawning migrations transport substantial quantities of MDN from the fertile North Pacific Ocean to relatively nutrient-poor coastal freshwater and terrestrial ecosystems. People have been long aware of the importance of salmon-borne MDN for the productivity of freshwater ecosystems in western North America, and the rapidly increasing knowledge base supports this notion. Nevertheless, many details associated with nutrient pathways, cycling processes, and the ecosystem-scale consequences of MDN transfer remain to be elucidated. The collective data suggest that freshwater portions of the salmon production system, as well as the dynamics of local terrestrial plant and animal communities, are intimately linked to MDN in complex ways. At the same time, the ecological importance of MDN, relative to other major nutrient sources, is temporally and spatially dependent and influenced by the life histories and abundances of salmonid stocks. Although interactions among climate cycles, salmon, riparian vegetation, predators, and MDN flowpaths and feedbacks are complex, they also form a wonderfully integrated ecological system with a high degree of resilience and productivity. Understanding this complex system and its inherent temporal and spatial variability requires a holistic scientific perspective that values important interactions among the salmonid life cycle, the physical setting, and the numerous linkages to other ecosystem components.

scholarly journals More than redox, biological organic ligands control iron isotope fractionation in the riparian wetland

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Elaheh Lotfi-Kalahroodi ◽  
Anne-Catherine Pierson-Wickmann ◽  
Olivier Rouxel ◽  
Rémi Marsac ◽  
Martine Bouhnik-Le Coz ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Isotope Fractionation ◽  
Isotopic Fractionation ◽  
Isotopic Signature ◽  
Organic Ligands ◽  
Riparian Wetland ◽  
Fe Isotopes ◽  
Preferential Binding ◽  
Isotope Systematics

AbstractAlthough redox reactions are recognized to fractionate iron (Fe) isotopes, the dominant mechanisms controlling the Fe isotope fractionation and notably the role of organic matter (OM) are still debated. Here, we demonstrate how binding to organic ligands governs Fe isotope fractionation beyond that arising from redox reactions. The reductive biodissolution of soil Fe(III) enriched the solution in light Fe isotopes, whereas, with the extended reduction, the preferential binding of heavy Fe isotopes to large biological organic ligands enriched the solution in heavy Fe isotopes. Under oxic conditions, the aggregation/sedimentation of Fe(III) nano-oxides with OM resulted in an initial enrichment of the solution in light Fe isotopes. However, heavy Fe isotopes progressively dominate the solution composition in response to their binding with large biologically-derived organic ligands. Confronted with field data, these results demonstrate that Fe isotope systematics in wetlands are controlled by the OM flux, masking Fe isotope fractionation arising from redox reactions. This work sheds light on an overseen aspect of Fe isotopic fractionation and calls for a reevaluation of the parameters controlling the Fe isotopes fractionation to clarify the interpretation of the Fe isotopic signature.

Influence of wildfire severity on geomorphic features and riparian vegetation of forested streams of the Sierra Nevada, California, USA

2020 ◽  
Vol 29 (7) ◽  
pp. 611
Author(s):  
Breeanne K. Jackson ◽  
S. Mažeika P. Sullivan
Keyword(s):  
Sierra Nevada ◽  
Riparian Vegetation ◽  
Fire Severity ◽  
Riparian Ecosystems ◽  
High Severity ◽  
Sediment Size ◽  
Rim Fire ◽  
Geomorphic Features ◽  
Biodiversity And Ecosystem Function ◽  
Riparian Plant

Fires are a common feature of many landscapes, with numerous and complex ecological consequences. In stream ecosystems, fire can strongly influence fluvial geomorphic characteristics and riparian vegetation, which are structural components of stream–riparian ecosystems that contribute to biodiversity and ecosystem function. However, the effects of fire severity on stream–riparian ecosystems in California’s Sierra Nevada region (USA) are not well described, yet critical for effectively informing fire management and policy. At 12 stream reaches paired by fire severity (one high-severity burned, one low-severity burned), no significant differences were found in riparian plant community cover and composition or stream geomorphic characteristics 2–15 years following wildfire. In addition, minimal changes in riparian vegetation and stream geomorphic properties were observed in the first summer following the extensive and severe Rim Fire. However, an upstream-to-downstream influence of multiple fire occurrences was observed over the previous 81 years within each catchment on stream geomorphic metrics, including sediment size, embeddedness and channel geometry, at our study reaches. The inconsistent effects of wildfire on stream–riparian vegetation and geomorphic characteristics over space and time may be related to time since fire and precipitation.

An Electrophysiological Basis for Olfactory Discrimination in Homing Salmon: A Review

1970 ◽  
Vol 27 (3) ◽  
pp. 565-586 ◽  
Author(s):  
Toshiaki J. Hara
Keyword(s):  
Pacific Salmon ◽  
Electrical Response ◽  
High Amplitude ◽  
Polluted Water ◽  
Sensitive Period ◽  
Young Fish ◽  
Spawning Site ◽  
Short Period ◽  
Sign Stimulus ◽  
Spawning Sites

Past and current researches relating to olfactory acuity and discrimination in fishes, with special reference to homing salmon, are reviewed.When the nasal sac of spawning Pacific salmon is stimulated with water from the spawning site a high amplitude electroencephalographic response of characteristic pattern is recorded from the olfactory bulb. This electrical response is specific in the sense that it cannot be evoked by water from spawning sites of other groups of breeding salmon. Further, the salmon respond clearly to water taken from places along their migratory routes below the spawning sites. These findings suggest that olfaction is an important factor in guidance during the final phases of homeward migration of salmon. It is also possible that salmon retrace sequentially a trail of stimuli that is the reverse of that imprinted in the young fish on their seaward migration.Although the available data do not delineate the sensitive period, or the duration of the imprinting process, there is accumulating evidence that only a short period is necessary for imprinting, which may occur when the smolts are in their freshwater life.Recent study on the effect of antimetabolites (puromycin, actinomycin D, or cycloheximide) on olfactory bulbar discrimination in homing salmon suggests that long-term olfactory memory in these fish depends upon continued metabolism of RNA and continued protein synthesis. The possibility that the imprinting process in young fish may be affected by polluted water, which has recently become a serious problem in fisheries, is discussed. The need for electrophysiological as well as biochemical studies at a macromolecular level of the imprinting process is emphasized.Finally, the hypothesis is discussed that a home stream odour may act most effectively as a simple "sign stimulus," which, through the release of a positive rheotropic response, induces the fish to move upstream toward home. This is largely based on the recent experimental observations of the orientation mechanism in several species of teleost fishes.

Sensitivity of global gross primary production to elevated CO2

2021 ◽  
Author(s):  
Wenjia Cai ◽  
Iain Colin Prentice
Keyword(s):  
Field Experiments ◽  
Carbon Sink ◽  
Gross Primary Production ◽  
Light Response ◽  
Terrestrial Ecosystems ◽  
Percentage Increase ◽  
Terrestrial Plants ◽  
Fertilization Effect ◽  
Vegetation Models ◽  
The Impact

&lt;p&gt;Terrestrial ecosystems have accounted for more than half of the global carbon sink during the past decades and offset 25%-30% of current anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; emissions. The projected increase in CO&lt;sub&gt;2&lt;/sub&gt; concentration will depend on the magnitude of terrestrial plants&amp;#8217; feedback to CO&lt;sub&gt;2&lt;/sub&gt;: i.e. the sensitivity of plant carbon uptake in response to elevated CO&lt;sub&gt;2&lt;/sub&gt;, and the strength of the CO&lt;sub&gt;2&lt;/sub&gt; fertilization effect (CFE) in a changing (and warming) environment. Projecting vegetation responses to future increases in CO&lt;sub&gt;2&lt;/sub&gt; concentration under climate change is a major uncertainty, as ecosystem models, field experiments and satellite-based models show large disagreements. In this study, using a recently developed, parameter-sparse model (the &amp;#8216;P model&amp;#8217;), we assess the sensitivity of GPP to increasing CO&lt;sub&gt;2&lt;/sub&gt; under idealized conditions, in comparison with other vegetation models and field experiments. We investigate the impact of two central parameters, the ratio of J&lt;sub&gt;max &lt;/sub&gt;to V&lt;sub&gt;cmax&lt;/sub&gt; (at a common temperature) and the curvature of the light response curve, on the sensitivity of GPP to CO&lt;sub&gt;2&lt;/sub&gt;. We also quantified the spatial-temporal trend of CFE using the &amp;#946; factor, defined as the percentage increase in GPP in response to a 100-ppm increase in atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentration over a defined period. We show how modelled &amp;#946; has changed over the satellite era, and infer the possible effect of climatic variables on changes of CFE from spatial patterns of the modelled trend in &amp;#946;.&lt;/p&gt;

Pacific Salmon: Ecology and Management of Western Alaska’s Populations

2009 ◽  
Keyword(s):  
Food Source ◽  
Driving Forces ◽  
Pacific Salmon ◽  
Late Summer ◽  
Terrestrial Ecosystems ◽  
Food Resources ◽  
Growth And Survival ◽  
Terrestrial Invertebrates ◽  
Riverine Ecosystems ◽  
Aquatic Food

<em>Abstract.</em>—Much is known about the importance of the physical characteristics of salmonid habitat in Alaska and the Pacific Northwest, with far less known about the food sources and trophic processes within these habitats, and the role they play in regulating salmonid productivity. Freshwater food webs supporting salmonids in Alaska rely heavily on nutrient, detritus, and prey subsidies from both marine and terrestrial ecosystems. Adult salmon provide a massive input of marine biomass to riverine ecosystems each year when they spawn, die, and decompose, and are a critical food source for young salmon in late summer and fall; riparian forests provide terrestrial invertebrates to streams, which at times comprise over half of the food ingested by stream-resident salmonids; up-slope, fishless headwater streams are a year-round source of invertebrates and detritus for fish downstream. The quantity of these food resources vary widely depending on source, season, and spatial position within a watershed. Terrestrial invertebrate inputs from riparian habitats are generally the most abundant food source in summer. Juvenile salmonids in streams consume roughly equal amounts of freshwater and terrestrially-derived invertebrates during most of the growing season, but ingest substantial amounts of marine resources (salmon eggs and decomposing salmon tissue) when these food items are present. Quantity, quality, and timing of food resources all appear to be important driving forces in aquatic food web dynamics, community nutrition, and salmonid growth and survival in riverine ecosystems.

VARIATION IN PACIFIC SALMON REPRODUCTIVE BEHAVIOUR ASSOCIATED WITH SPECIES, SEX AND LEVELS OF COMPETITION

Behaviour ◽  
1999 ◽  
Vol 136 (2) ◽  
pp. 179-204 ◽  
Author(s):  
Thomas Quinn
Keyword(s):  
Pacific Salmon ◽  
Local Area ◽  
Reproductive Behaviour ◽  
Male Aggression ◽  
Male And Female ◽  
Sexual Display ◽  
Resource Space ◽  
Intensity Of Competition ◽  
Satellite Males ◽  
Spawning Sites

AbstractMale and female Pacific salmon compete for different resources; females for suitable spawning sites and males for access to ripe females. Aggression should thus be primarily intra-sexual rather than inter-sexual. When different species are sympatric, males should primarily attack conspecifics whereas females should attack all females, regardless of species because they all compete for the same resource-space. The level of aggression should be a function of density, being relatively low at low densities and peaking at either intermediate or high densities. These predictions were supported in most respects by data collected on the behaviour of adult sockeye (Oncorhynchus nerka), chum (O. keta) and pink (O. gorbuscha) salmon in a large, relatively homogeneous spawning channel. Males almost exclusively attacked other males, especially conspecifics. Females were more likely to attack female heterospecifics than males but still tended to attack conspecifics most often, and also directed many attacks at males. Male aggression and digging, apparently a form of intra-sexual display, were related to density of male conspecifics in the local area, and the intensity of competition from satellite males courting the female.

Why magnesium isotope fractionation is absent from basaltic melts under thermal gradients in natural settings

2019 ◽  
Vol 157 (7) ◽  
pp. 1144-1148
Author(s):  
Yingkui Xu ◽  
Dan Zhu ◽  
Xiongyao Li ◽  
Jianzhong Liu
Keyword(s):  
Isotope Fractionation ◽  
Isotope Effects ◽  
Isotopic Fractionation ◽  
Chemical Diffusion ◽  
Kinetic Isotope Effects ◽  
Thermal Gradients ◽  
Magnesium Isotopes ◽  
Magnesium Isotope ◽  
Natural Systems ◽  
Kinetic Isotope

AbstractLaboratory experiments have shown that thermal gradients in silicate melts can lead to isotopic fractionation; this is known as the Richter effect. However, it is perplexing that the Richter effect has not been documented in natural samples as thermal gradients commonly exist within natural igneous systems. To resolve this discrepancy, theoretical analysis and calculations were undertaken. We found that the Richter effect, commonly seen in experiments with wholly molten silicates, cannot be applied to natural systems because natural igneous samples are more likely to be formed out of partially molten magma and the presence of minerals adds complexity to the behaviour of the isotope. In this study, we consider two related diffusion-rate kinetic isotope effects that originate from chemical diffusion, which are absent from experiments with wholly molten samples. We performed detailed calculations for magnesium isotopes, and the results indicated that the Richter effect for magnesium isotopes is buffered by kinetic isotope effects and the total value of magnesium isotope fractionation can be zero or even undetectable. Our study provides a new understanding of isotopic behaviour during the processes of cooling and solidification in natural magmatic systems.

Perspectives on the age and distribution of large wood in riparian carbon pools

2002 ◽  
Vol 59 (3) ◽  
pp. 578-585 ◽  
Author(s):  
Richard P Guyette ◽  
William G Cole ◽  
Daniel C Dey ◽  
Rose-Marie Muzika
Keyword(s):  
Woody Debris ◽  
Age Distribution ◽  
Terrestrial Ecosystems ◽  
Large Wood ◽  
Riparian Ecosystems ◽  
Riparian Areas ◽  
Exponential Distributions ◽  
Drainage Patterns ◽  
Order Of Magnitude ◽  
Negative Exponential

Most knowledge of carbon budgets is derived from the productivity and sequestration of carbon in terrestrial and marine ecosystems. Less is known of carbon stored in riparian areas associated with lakes and rivers. Case studies of the age distribution of carbon in aquatic large wood (Clw) from two different landscapes with different drainage patterns were established using tree-ring and 14C dating. Cumulative negative exponential distributions of the age of Clw ranged over periods from 1000 to 9485 years. Large woody debris had mean residence times of 261 years in small oligotrophic lakes and 350–800 years in a stream reach. Large wood can reside for an order of magnitude longer in freshwater–riparian ecosystems than in comparable above-ground terrestrial ecosystems. Although riparian areas make up only a small fraction of most landscapes, they may account for a relatively larger proportion of aged Clw than is stored above ground in terrestrial ecosystems.

Sulfur isotope fractionation by Proteus vulgaris and Salmonella heidelberg during the reduction of thiosulfate

1980 ◽  
Vol 26 (10) ◽  
pp. 1173-1177 ◽  
Author(s):  
R. G. L. McCready ◽  
V. A. Grinenko ◽  
H. R. Krouse
Keyword(s):  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Isotope Composition ◽  
Isotopic Fractionation ◽  
Proteus Vulgaris ◽  
Sulfane Sulfur ◽  
Sulfur Isotope Fractionation ◽  
Fractionation Pattern ◽  
High Concentrations ◽  
Salmonella Heidelberg

Proteus vulgaris metabolized thiosulfate to H2S. The amount evolved and its sulfur isotope composition identified it solely with sulfane sulfur. In contrast. Salmonella heidelberg sequentially reduced the sulfane sulfur of S2O32− with slight enrichment of the evolved sulfide in 32S and then reduced the sulfonate sulfur of S2O32− with large isotopic selectivities and an inverse isotopic fractionation pattern. The inverse isotope fractionation pattern for the H2S derived from the sulfonate sulfur was almost identical to that observed during the reduction of high concentrations of sulfite by S. heidelberg.

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