Influence of inorganic nitrogen cycling on the δ<sup>15</sup>N of Lake Ontario biota

Leggett, M F; Johannsson, Ora E.; Hesslein, Raymond H.; Dixon, D. George; Taylor, William D.; Servos, Mark R.

doi:10.1139/f00-085

Cited by 42 publications

(28 citation statements)

References 21 publications

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“…Individual zooplankton species exhibit large seasonal variation in ␦ 15 N (Graham 1997;Leggett et al 2000). How do we account for this large variation in our estimates of fish trophic position and trophic variation using ␦ 15 N?…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…Different zooplankton taxa have unique isotopic signatures (Meili et al 1996;Matthews and Mazumder 2003) and can exhibit distinct seasonal patterns of ␦ 15 N (Graham 1997;Leggett et al 2000;Grey et al 2001; Fig. 2).…”

Section: Specific Taxa or Bulk Size Fractions For ␦mentioning

confidence: 99%

“…Read together, these studies suggest that temporal variation in ␦ 15 N of a zooplankton taxon does not necessarily indicate trophic variation. Indeed, ␦ 15 N signatures of zooplankton are frequently influenced by changes in nitrogen cycling (Leggett et al 2000;O'Reilly et al 2002). A striking example is from Lake Tanganyika, where O'Reilly et al (2002) demonstrated how a change in the nitrogen source can rapidly change the stable isotope representation of a pelagic food web.…”

Section: Estimating the Trophic Position Of Planktivorous Fish Using mentioning

confidence: 99%

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Consequences of large temporal variability of zooplankton δ¹⁵ N for modeling fish trophic position and variation

Matthews

Mazumder

2005

Limnol. Oceanogr.

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We use a temporal integration model (TIM) to determine how estimates of trophic variation, using ␦ 15 N, depend on consumer growth dynamics and temporal isotopic variation (␦ 15 N) of food sources. Consumers are rarely in isotopic equilibrium with their food sources, so instantaneous comparisons between the ␦ 15 N of a consumer and its diet provide little information about trophic variation, even if the trophic positions of the diet are known. In this paper, we focus on the trophic link between zooplankton and planktivorous fish. We first review the extent of temporal variability of zooplankton ␦ 15 N, then examine the consequences of this variability for understanding the isotopic composition of planktivorous fish communities. We use time series of ␦ 15 N for Daphnia, calanoid copepods, and particulate organic matter (Ͼ200 m) to generate theoretical diets for a model juvenile sockeye over a typical growing season. We use a TIM to predict the isotopic trajectory of individual juveniles feeding on these diets and explore how variance in growth rate and isotopic enrichment (⌬ ␦N ) can affect estimates of trophic position and intrapopulation isotopic variability. In general, we found that using a seasonal average of Daphnia ␦ 15 N to estimate the trophic position of planktivorous fish is nearly equivalent to using a TIM. However, temporal variation in the ␦ 15 N of food sources, coupled with individual differences in the growth rate of consumers, can contribute to intrapopulation isotopic variation of consumers and lead to correlations between consumer size and ␦ 15 N.

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Section: Acknowledgmentsmentioning

confidence: 99%

Section: Specific Taxa or Bulk Size Fractions For ␦mentioning

confidence: 99%

Section: Estimating the Trophic Position Of Planktivorous Fish Using mentioning

confidence: 99%

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Consequences of large temporal variability of zooplankton δ¹⁵ N for modeling fish trophic position and variation

Matthews

Mazumder

2005

Limnol. Oceanogr.

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“… A schematic illustration of the measured δ 15 N ranges of particulate organic matter (PON),

{NH}_{4}^{+}

and

{NO}_{3}^{-}

, and predicted values of excess N 2 formed in denitrification, based of the studies on Lake Lugano,25 Jyväsjärvi 22 and Ontario 26 surface waters.…”

mentioning

confidence: 99%

Stable isotope profiles of nitrogen gas indicate denitrification in oxygen‐stratified humic lakes

Tiirola

Rissanen

Sarpakunnas

et al. 2011

Rapid Comm Mass Spectrometry

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Mid-summer N(2) profiles were analyzed from nine oxygen-stratified, humic-acid-rich lakes using a continuous flow isotope ratio mass spectrometer and a Gasbench II device. Sample preparation steps were performed under water to avoid air contamination. The instrument precision for the δ(15)N measurement was high (0.03‰), but for the whole sampling and analysis procedure the mean deviation between replicate samples was 0.13‰ for the δ(15)N measurements and 5.5% for the N(2) gas concentration analysis. The results show that the Gasbench peripheral was suitable for measurement of the (15)N natural abundance of dissolved nitrogen gas, with denitrification indicated by the oversaturation and slightly (<1‰) depleted δ(15)N values of the dissolved N(2) gas in the suboxic zones of some of the study lakes. Calculated values for the denitrified (excess) N(2) varied between -5.3 and 0.7‰. The denitrification potential was determined using the (15)N tracer method, with results showing nitrate-inducible denitrification and no signs of anaerobic ammonium oxidation (anammox).

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“…Uncertainties-An additional process that may contribute to the asymptotic trend that we observed is uptake fractionation of inorganic N (Leggett et al 2000). Marine and lab studies have demonstrated that d 15 N of phytoplankton will asymptote as the availability of surface water NO { 3 increases (Altabet and Francois 1994;Sigman et al 1999;Altabet 2006).…”

Section: Discussionmentioning

confidence: 92%

Untitled

2012

Limnology & Oceanography

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Runoff from human-dominated watersheds has greatly altered nitrogen (N) and phosphorus (P) cycling in lakes. Nutrients from human sources are distinct from those from undisturbed ecosystems in several ways including lower N : P ratios, which can drive ecosystems to N-limited conditions, and enriched stable N isotope ratios. In this study, we used these distinct characteristics to estimate shifts in N sources to 27 lakes across a human density gradient in western Washington. We compared an N stable isotope two-source mixing model with a mixing model that coupled N stable isotopes to N : P stoichiometry and included N fixation. We found that a two-source mixing model (human and watershed sources) did not explain observed variation in d 15 N of particulate organic matter (POM) and primary consumers (R 2 5 0.60) as well as a model that included a third N source (N fixation; R 2 5 0.72). When fixed N was facultatively added to the ecosystem below a critical N : P ratio, the more complex mixing model captured the observed patterns in POM and primary-consumer d 15 N among lakes extremely well. In lakes with P concentrations . 20 mg L 21 (N : P mass ratio , 15.3), N fixation became an increasingly important component of the N cycle, accounting for . 50% of lake N budgets. This model provides a novel way to estimate the contribution of nonpoint N sources and N fixation to lakes in watersheds subject to human nutrient inputs.

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Influence of inorganic nitrogen cycling on the δ¹⁵N of Lake Ontario biota

Cited by 42 publications

References 21 publications

Consequences of large temporal variability of zooplankton δ¹⁵ N for modeling fish trophic position and variation

Consequences of large temporal variability of zooplankton δ¹⁵ N for modeling fish trophic position and variation

Stable isotope profiles of nitrogen gas indicate denitrification in oxygen‐stratified humic lakes

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Influence of inorganic nitrogen cycling on the δ15N of Lake Ontario biota

Cited by 42 publications

References 21 publications

Consequences of large temporal variability of zooplankton δ15 N for modeling fish trophic position and variation

Consequences of large temporal variability of zooplankton δ15 N for modeling fish trophic position and variation

Stable isotope profiles of nitrogen gas indicate denitrification in oxygen‐stratified humic lakes

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Influence of inorganic nitrogen cycling on the δ¹⁵N of Lake Ontario biota

Consequences of large temporal variability of zooplankton δ¹⁵ N for modeling fish trophic position and variation

Consequences of large temporal variability of zooplankton δ¹⁵ N for modeling fish trophic position and variation