Seasonal variation of the δC and δN of particulate and dissolved carbon and nitrogen in Lake Lugano: Constraints on biogeochemical cycling in a eutrophic lake

Lehmann, Moritz F.; Bernasconi, Stefano M.; McKenzie, Judith A.; Barbieri, Alberto; Simona, Marco; Veronesi, Mauro

doi:10.4319/lo.2004.49.2.0415

Cited by 188 publications

(216 citation statements)

References 64 publications

(106 reference statements)

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“…Our findings, however, are significantly different from the results of other studies on the dynamics of the stable carbon isotope composition of POM in lacustrine ecosystems: Lehmann et al (2004a), for example, have demonstrated that in Lake Lugano the total annual POM flux did not directly reflect variations in phytoplankton primary production. Also the annual flux-weighted d 13 C POM values did not correlate with the amount of annual phytoplankton primary production, as is the case in Lake Holzmaar.…”

Section: Discussioncontrasting

confidence: 99%

Controls on the seasonal and interannual dynamics of organic matter stable carbon isotopes in mesotrophic Lake Holzmaar, Germany

et al. 2009

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We investigated the particulate organic matter (POM) flux and its stable carbon isotope composition in response to changes in phytoplankton primary production and abiotic environmental affects in mesotrophic Lake Holzmaar. POM fluxes were determined by sediment traps emptied biweekly from 1995 to 2004. Water chemical measurements and meteorological observations were done concurrently. POM fluxes within and directly below the lake's epilimnion were relatively low during winter (,0.5 g m 22 d 21 ) and increased to 1.0-1.5 g m 22 d 21 during summer months because of enlarged phytoplankton production. In contrast, in the lake's hypolimnion a much higher POM flux was observed during winter as result of resuspension of particulate material from the lake's bottom. C : N (weight, total organic carbon : total nitrogen) ratios of settling organic matter vary around 8 at all three depths, indicating a predominant phytoplankton origin of POM. The annual epilimnic POM flux correlates with the epilimnic phosphate concentration early in the seasonal cycle, indicating that the supply of phosphate is the major control on the amount of algal biomass. A recurrent annual oscillation of the stable carbon isotope composition of POM with low d 13 C values during winter and more positive values during summer is interpreted as the result of phytoplankton primary production. A close d 13 C POM -POM flux relationship was observed, testifying to the primary dependence of d 13 C POM on lacustrine primary production. Contrary to POM flux, the epilimnic d 13 C POM signal is transferred to the lakes bottom notwithstanding sediment resuspension and microbial alteration. Our results demonstrate that sedimentary stable carbon isotopes are a valuable proxy for lacustrine paleo-productivity in Lake Holzmaar.

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Section: Discussioncontrasting

confidence: 99%

Controls on the seasonal and interannual dynamics of organic matter stable carbon isotopes in mesotrophic Lake Holzmaar, Germany

et al. 2009

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“…Alternatively, these results suggest that the processes leading to depleted d 13 C DIC signatures in the hypolimnion were predominantly microbial degradation of DOC (producing d 13 C CO2 from À28.0‰ to À26.3‰, Table 5) and/or CH 4 oxidation (producing d 13 C CO2 from À63.0‰ to À47.5‰) [Jedrysek, 1995]. The relationships between [DIC] À1 and d 13 C DIC shown in Figure 5c for the wood harvested lakes (spring: r 2 = 0.34, p < 0.05) and in Figure 5d for the wood harvested reservoir (spring and summer: r 2 = 0.81, p < 0.0001 and r 2 = 0.50, p < 0.0001, respectively) suggest that the concentration and stable isotope composition of the DIC pool were mostly controlled by the combined influence of DOC degradation (causing low [DIC] À1 and d 13 C DIC depletion), photosynthesis and photo-oxidation (causing high [DIC] À1 and d 13 C DIC enrichment) in these systems [Lehmann et al, 2004;McCallister and del Giorgio, 2008;Vähätalo and Wetzel, 2008].…”

Section: Sources Of Ommentioning

confidence: 91%

“…[35] To identify the relationship between FPOM sources and their relationship to DIC Lehmann et al, 2004], d 13 C DIC was plotted against the d 13 C POC of the FPOM fraction (d 13 C POC , Figure 6). The spring d 13 C POC results presented in Figures 6a and 6b show that water bodies with a non-harvested watershed were dominated by algal OM.…”

Section: Sources Of Ommentioning

confidence: 99%

Assessing carbon dynamics in natural and perturbed boreal aquatic systems

et al. 2012

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[1] Most natural freshwater lakes are net greenhouse gas (GHG) emitters. Compared to natural systems, human perturbations such as watershed wood harvesting and long-term reservoir impoundment lead to profound alterations of biogeochemical processes involved in the aquatic cycle of carbon (C). We exploited these anthropogenic alterations to describe the C dynamics in five lakes and two reservoirs from the boreal forest through the analysis of dissolved carbon dioxide (CO 2 ), methane (CH 4 ), oxygen (O 2 ), and organic carbon (DOC), as well as total nitrogen and phosphorus. Dissolved and particulate organic matter, forest soil/litter and leachates, as well as dissolved inorganic carbon were analyzed for elemental and stable isotopic compositions (atomic C:N ratios, d 13 C org , d 13 C inorg and d 15 N tot ). We found links between the export of terrestrial organic matter (OM) to these systems and the dissolved CO 2 and O 2 concentrations in the water column, as well as CO 2 fluxes to the atmosphere. All systems were GHG emitters, with greater emissions measured for systems with larger inputs of terrestrial OM. The differences in CO 2 concentrations and fluxes appear controlled by bacterial activity in the water column and the sediment. Although we clearly observed differences in the aquatic C cycle between natural and perturbed systems, more work on a larger number of water bodies and encompassing all four seasons should be undertaken to better understand the controls, rates, and spatial as well as temporal variability of GHG emissions, and to make quantitatively meaningful comparisons of GHG emissions (and other key variables) from natural and perturbed systems.

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“…The stable nitrogen isotope ratio (d 15 N) of particulate organic matter (POM) has been used as an indicator for the source, availability and the cycling processes of nitrogen in lakes (Gu et al, 1996;Teranes and Bernasconi, 2000;Lehmann et al, 2004;Gu et al, 2006). Previous studies have revealed that d 15 N POM varies over time in individual lakes (Gu et al, 1994(Gu et al, , 2006Lehmann et al, 2004;Syva¨ranta et al, 2008;Hadas et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies have revealed that d 15 N POM varies over time in individual lakes (Gu et al, 1994(Gu et al, , 2006Lehmann et al, 2004;Syva¨ranta et al, 2008;Hadas et al, 2009). Several studies have compared d 15 N POM among lakes.…”

Section: Introductionmentioning

confidence: 99%

Patterns and controls of nitrogen stable isotopes of particulate organic matter in subtropical lakes

Schelske

2010

Ann. Limnol. - Int. J. Lim.

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-Nitrogen stable isotope composition (d 15 N) of particulate organic matter (POM) has been used to infer dominant nitrogen cycling processes in lakes. However, very few studies have compared the isotope variations in lakes along trophic state and other biogeochemical gradients. Here we report an analysis of d 15 N POM and selected environmental variables from 96 subtropical lakes to assess the patterns and controls of isotope variations. Results indicate that d 15 N POM values varied from x 2.8 to 13.2‰ and were not significantly correlated with total phosphorus (TP), total nitrogen (TN) and chlorophyll a (Chl a). The 15 N depletion in POM was found across the entire trophic gradient and likely reflected contributions from planktonic nitrogen fixation. The 15 N enrichment was attributed to high primary production and the contributions of anthropogenic wastes in eutrophic lakes, and the presence of microzooplankton in the water samples of the oligotrophic lakes. The d 15 N POM was negatively correlated with water color and positively correlated with pH. Because water color is indicative of light availability which affects phytoplankton growth and pH is significantly correlated with Chl a concentration in the study lakes, the close relationship between water color, pH and d 15 N POM therefore suggests primary productivity-driven isotope fractionation. Results from this study did not reveal the importance of trophic state, nitrogen concentration and surface area to the variations of d 15 N POM and points to the complex interactions of nitrogen cycling processes in lakes with diverse biogeochemical features.

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Seasonal variation of the δC and δN of particulate and dissolved carbon and nitrogen in Lake Lugano: Constraints on biogeochemical cycling in a eutrophic lake

Cited by 188 publications

References 64 publications

Controls on the seasonal and interannual dynamics of organic matter stable carbon isotopes in mesotrophic Lake Holzmaar, Germany

Controls on the seasonal and interannual dynamics of organic matter stable carbon isotopes in mesotrophic Lake Holzmaar, Germany

Assessing carbon dynamics in natural and perturbed boreal aquatic systems

Patterns and controls of nitrogen stable isotopes of particulate organic matter in subtropical lakes

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