scholarly journals Stable isotopic composition of top consumers in Arctic cryoconite holes: revealing different position in supraglacial trophic network

2020 ◽  
Author(s):  
Tereza Jaroměřská ◽  
Jakub Trubač ◽  
Krzysztof Zawierucha ◽  
Lenka Vondrovicová ◽  
Miloslav Devetter ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Hot Spots ◽  
High Arctic ◽  
Biological Processes ◽  
Trophic Relations ◽  
Glacier Surface ◽  
Δ13c Values ◽  
Isotopic Analyses ◽  
Stable Isotopic ◽  
Trophic Network

Abstract. Cryoconite holes are ecosystems on the glacier surface characterized by dynamic nature and truncated food webs. It is acknowledged that cryoconite holes play an important role being biodiversity hot-spots and factories for organic matter on glaciers. The most common cryoconite apex consumers are the cosmopolitan invertebrates – tardigrades and rotifers. Several studies have highlighted the relevance of cryoconite tardigrades and rotifers to cryoconite holes’ ecosystem functioning. However, due to the dominant occurrence of prokaryotes on glaciers, these consumers are usually out of the major scope of most studies aiming at biological processes on glaciers. The aim of this study is to present data about isotopic composition of tardigrades, rotifers and cryoconite from three High Arctic glaciers in Svalbard and discuss their potential trophic relations. We found that tardigrades have lower δ15N values than rotifers, which indicates different food requirements of both consumers. The δ13C values revealed similarities among the consumers from the same glaciers and differences between consumers and cryoconite among glaciers. The resulted δ13C values point to similar carbon requirement of consumers within a glacier but differences in carbon input between glaciers. The results comprise the first observation of cryoconite holes’ consumers through stable isotopic analyses using an improved method of cryoconite sample processing and pave the way for further studies of the supraglacial trophic network.

scholarly journals Stable isotopic composition of top consumers in Arctic cryoconite holes: revealing divergent roles in a supraglacial trophic network

2021 ◽  
Vol 18 (5) ◽  
pp. 1543-1557
Author(s):  
Tereza Novotná Jaroměřská ◽  
Jakub Trubač ◽  
Krzysztof Zawierucha ◽  
Lenka Vondrovicová ◽  
Miloslav Devetter ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Isotopic Ratio ◽  
Isotopic Fractionation ◽  
Mechanistic Explanation ◽  
High Arctic ◽  
Biologically Active ◽  
Glacier Surface ◽  
Stable Isotopic Composition ◽  
Stable Isotopic ◽  
Trophic Network

Abstract. Arctic cryoconite holes represent highly biologically active aquatic habitats on the glacier surface characterized by the dynamic nature of their formation and functioning. The most common cryoconite apex consumers are the cosmopolitan invertebrates – tardigrades and rotifers. Several studies have highlighted the potential relevance of tardigrades and rotifers to cryoconite holes' ecosystem functioning. However, due to the dominant occurrence of prokaryotes, these consumers are usually out of the major scope of most studies aimed at understanding biological processes on glaciers. The aim of this descriptive study is to present pioneering data on isotopic composition of tardigrades, rotifers and cryoconite from three High Arctic glaciers in Svalbard and discuss their role in a cryoconite hole trophic network. We found that tardigrades have lower δ15N values than rotifers, which indicates different food requirements or different isotopic fractionation of both consumers. The δ13C values revealed differences between consumers and organic matter in cryoconite among glaciers. However, the mechanistic explanation of these variations requires further investigation focused on the particular diet of cryoconite consumers and their isotopic ratio. Our study introduces the first observation of carbon and nitrogen stable isotopic composition of top consumers in cryoconite holes analysed by an improved method for cryoconite sample processing, paving the way for further studies of the supraglacial trophic network.

scholarly journals Is there any isotopic fractionation of nitrate associated with diffusion and advection?

2012 ◽  
Vol 9 (2) ◽  
pp. 158 ◽  
Author(s):  
Priscillia Semaoune ◽  
Mathieu Sebilo ◽  
Joëlle Templier ◽  
Sylvie Derenne
Keyword(s):  
Isotopic Composition ◽  
Aquatic Ecosystems ◽  
Nitrate Solution ◽  
Isotopic Fractionation ◽  
Transport Processes ◽  
Biological Processes ◽  
Physical Processes ◽  
Nitrogen Inputs ◽  
Stable Isotopic ◽  
Transport Diffusion

Environmental contextAnthropogenic nitrogen inputs have significant effects on terrestrial and aquatic ecosystems, the extent of which can be traced by using the natural stable isotopic composition of nitrate to integrate the sources of nitrogen and the biological processes of their production. In ecosystems, nitrates are transported by diffusion in water and advection of water masses, but these physical processes have not been characterised in terms of isotopic fractionation. We report experiments demonstrating that physical transport processes have a negligible effect on the isotopic composition of dissolved nitrate. AbstractWe experimentally investigated the effect of the physical process of transport (diffusion and advection) on the isotopic composition of nitrate (δ15N and δ18O). Strict diffusion of nitrate in water was studied using a modified Richter apparatus. The combination of diffusion and advection processes was followed by elution of nitrate solution onto silica gel column. No significant isotopic fractionation was observed.

scholarly journals Experimental assessment of environmental influences on the stable isotopic composition of <i>Daphnia pulicaria</i> and their ephippia

2015 ◽  
Vol 12 (3) ◽  
pp. 2573-2606
Author(s):  
J. Schilder ◽  
C. Tellenbach ◽  
M. Möst ◽  
P. Spaak ◽  
M. van Hardenbroek ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Water Temperature ◽  
Carbon Isotopic Composition ◽  
Daphnia Pulicaria ◽  
Underlying Assumption ◽  
Δ13c Values ◽  
Stable Isotopic Composition ◽  
Significant Difference ◽  
Stable Isotopic ◽  
A Minor

Abstract. The stable isotopic composition of fossil resting eggs (ephippia) of Daphnia spp. is being used to reconstruct past environmental conditions in lake ecosystems. However, the underlying assumption that the stable isotopic composition of the ephippia reflects the stable isotopic composition of the parent Daphnia, of their diet and of the environmental water have yet to be confirmed in a controlled experimental setting. We performed experiments with Daphnia pulicaria cultures, which included a control treatment conducted at 12 °C in filtered lake water and with a diet of fresh algae, and three treatments in which we manipulated the stable carbon isotopic composition (δ13C value) of the algae, stable oxygen isotopic composition (δ18O value) of the water, and the water temperature, respectively. The stable nitrogen isotopic composition (δ15N value) of the algae was similar for all treatments. At 12 °C, differences in algal δ13C values and in δ18O values of water are reflected in those of Daphnia. The differences between ephippia and Daphnia stable isotope ratios were similar in the different treatments (δ13C: + 0.2 ± 0.4‰ (SD); δ15N: -1.6 ± 0.4‰; δ18O: -0.9 ± 0.4‰) indicating that changes in dietary δ13C and δ18O values of water are passed on to these fossilizing structures. A higher water temperature (20 °C) resulted in lower δ13C values in Daphnia and ephippia than in the other treatments with the same food source and in a minor change in the difference between δ13C values of ephippia and Daphnia (to -1.3 ± 0.3‰). This may have been due to microbial processes or increased algal respiration rates in the experimental containers, which may not affect Daphnia in natural environments. There was no significant difference in the offset between δ18O and δ15N values of ephippia and Daphnia between the 12 °C and 20 °C treatments, but the δ18O values of Daphnia and ephippia were on average 1.2‰ lower at 20 °C compared with 12 °C. We conclude that the stable isotopic composition of Daphnia ephippia provides information on that of the parent Daphnia and of the food and water they were exposed to, with small offsets between Daphnia and ephippia relative to variations in Daphnia stable isotopic composition reported from downcore studies. However, our experiments also indicate that temperature may have a minor influence on the δ13C, δ15N and δ18O values of Daphnia body tissue and ephippia. This aspect deserves attention in further controlled experiments.

scholarly journals The stable isotopic composition of <i>Daphnia</i> ephippia reflects changes in δ<sup>13</sup>C and δ<sup>18</sup>O values of food and water

2015 ◽  
Vol 12 (12) ◽  
pp. 3819-3830 ◽  
Author(s):  
J. Schilder ◽  
C. Tellenbach ◽  
M. Möst ◽  
P. Spaak ◽  
M. van Hardenbroek ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Water Temperature ◽  
Carbon Isotopic Composition ◽  
Control Treatment ◽  
Underlying Assumption ◽  
Δ13c Values ◽  
Stable Isotopic Composition ◽  
Significant Difference ◽  
Stable Isotopic ◽  
A Minor

Abstract. The stable isotopic composition of fossil resting eggs (ephippia) of Daphnia spp. is being used to reconstruct past environmental conditions in lake ecosystems. However, the underlying assumption that the stable isotopic composition of the ephippia reflects the stable isotopic composition of the parent Daphnia, of their diet and of the environmental water have yet to be confirmed in a controlled experimental setting. We performed experiments with Daphnia pulicaria cultures, which included a control treatment conducted at 12 °C in filtered lake water and with a diet of fresh algae and three treatments in which we manipulated the stable carbon isotopic composition (δ13C value) of the algae, stable oxygen isotopic composition (δ18O value) of the water and the water temperature, respectively. The stable nitrogen isotopic composition (δ15N value) of the algae was similar for all treatments. At 12 °C, differences in algal δ13C values and in δ18O values of water were reflected in those of Daphnia. The differences between ephippia and Daphnia stable isotope ratios were similar in the different treatments (δ13C: +0.2 ± 0.4 ‰ (standard deviation); δ15N: −1.6 ± 0.4 ‰; δ18O: −0.9 ± 0.4 ‰), indicating that changes in dietary δ13C values and in δ18O values of water are passed on to these fossilizing structures. A higher water temperature (20 °C) resulted in lower δ13C values in Daphnia and ephippia than in the other treatments with the same food source and in a minor change in the difference between δ13C values of ephippia and Daphnia (to −1.3 ± 0.3 ‰). This may have been due to microbial processes or increased algal respiration rates in the experimental containers, which may not affect Daphnia in natural environments. There was no significant difference in the offset between δ18O and δ15N values of ephippia and Daphnia between the 12 and 20 °C treatments, but the δ18O values of Daphnia and ephippia were on average 1.2 ‰ lower at 20 °C than at 12 °C. We conclude that the stable isotopic composition of Daphnia ephippia provides information on that of the parent Daphnia and of the food and water they were exposed to, with small offsets between Daphnia and ephippia relative to variations in Daphnia stable isotopic composition reported from downcore studies. However, our experiments also indicate that temperature may have a minor influence on the δ13C, δ15N and δ18O values of Daphnia body tissue and ephippia. This aspect deserves attention in further controlled experiments.

Seasonal trends in the stable isotopic composition of snow and meltwater runoff in a subarctic catchment at Okstindan, Norway

2004 ◽  
Vol 35 (2) ◽  
pp. 119-137 ◽  
Author(s):  
S.D. Gurney ◽  
D.S.L. Lawrence
Keyword(s):  
Isotopic Composition ◽  
Mean Value ◽  
Mean Values ◽  
Stable Isotopic Composition ◽  
Meltwater Runoff ◽  
Stable Isotopic ◽  
The Mean ◽  
The Difference ◽  
Δ18o And Δd

Seasonal variations in the stable isotopic composition of snow and meltwater were investigated in a sub-arctic, mountainous, but non-glacial, catchment at Okstindan in northern Norway based on analyses of δ18O and δD. Samples were collected during four field periods (August 1998; April 1999; June 1999 and August 1999) at three sites lying on an altitudinal transect (740–970 m a.s.l.). Snowpack data display an increase in the mean values of δ18O (increasing from a mean value of −13.51 to −11.49‰ between April and August), as well as a decrease in variability through the melt period. Comparison with a regional meteoric water line indicates that the slope of the δ18O–δD line for the snowpacks decreases over the same period, dropping from 7.49 to approximately 6.2.This change points to the role of evaporation in snowpack ablation and is confirmed by the vertical profile of deuterium excess. Snowpack seepage data, although limited, also suggest reduced values of δD, as might be associated with local evaporation during meltwater generation. In general, meltwaters were depleted in δ18O relative to the source snowpack at the peak of the melt (June), but later in the year (August) the difference between the two was not statistically significant. The diurnal pattern of isotopic composition indicates that the most depleted meltwaters coincide with the peak in temperature and, hence, meltwater production.

Stable isotopes in planktonic and benthic foraminifera from Arctic Ocean surface sediments

1988 ◽  
Vol 25 (5) ◽  
pp. 701-709 ◽  
Author(s):  
A. E. Aksu ◽  
G. Vilks
Keyword(s):  
Surface Water ◽  
Arctic Ocean ◽  
Sea Water ◽  
Ocean Surface ◽  
The Arctic ◽  
Size Fractions ◽  
Isotopic Compositions ◽  
Isotopic Analyses ◽  
Stable Isotopic ◽  
Surface Water Salinity

Oxygen and carbon isotopic analyses have been performed on the tests of Planulina wuellerstorfi and three size fractions of sinistral Neogloboquadrina pachyderma recovered from 33 Arctic Ocean surface-sediment samples. Stable isotopic compositions of N. pachyderma are found to be dependent on the test size: larger specimens show considerable enrichment in both δ18O and δ18C. The difference between the isotopic compositions of the 63–125 and 125–250 μm size fractions in N. pachyderma can be explained by biogenic fractionation effects during foraminiferal test growth. Larger (250–500 μm) N. pachyderma displayed accretions of secondary calcite, i.e., the outermost shell contained significant amounts of inorganically precipitated magnesium calcite. Thus, larger foraminifera may not be suited for down-core stable isotopic studies. There is a difference of ~2‰ between δ18O values of surface samples from the eastern and western Arctic Ocean, reflecting large differences between surface-water salinity in these regions. Therefore, oxygen isotopic data may have limited use as a chronostratigraphic tool in down-core studies in the Arctic Ocean, but we can use them to infer past variations in surface-water salinities. Planulina wuellerstorfi also showed depletions of both δ18O and δ18C in its calcite tests relative to calcite precipitated in isotopic equilibrium with ambient sea water; these depletions ranged from −0.8 to −0.9‰ in δ18Oand −1.2 to −0.9‰ in δ18C. This taxon is found to deposit its shell very close to the δ18C of ΣCO2 of bottom waters.

Sign in / Sign up

Export Citation Format

Share Document