Open Access
Knowl. Manag. Aquat. Ecosyst.
Number 418, 2017
Article Number 24
Number of page(s) 4
Published online 23 May 2017

© Y. Tang et al., Published by EDP Sciences 2017

Licence Creative Commons
This is an Open Access article distributed under the terms of the Creative Commons Attribution License CC-BY-ND (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. If you remix, transform, or build upon the material, you may not distribute the modified material.

As a constituent of organic carbon content of lakes, terrestrial dissolved organic carbon (t-DOC) has significant ecological effects on food webs by serving as a substrate for heterotrophic metabolism (Tranvik, 1998; Karlsson et al., 2003; Solomon et al., 2015). Despite evidence of terrestrial support for secondary production in lakes (Berggren et al., 2010a,b; Tanentzap et al., 2015), the transfer of t-DOC to higher trophic levels remains contentious (Ducklow et al., 1986; Brett et al., 2012; Kelly et al., 2016).

Previous studies have used mesocosms with artificial t-DOC additions to address whether t-DOC affects zooplankton. Most published studies report zooplankton density increases after t-DOC input (Faithful et al., 2011; Cooke et al., 2015; Geddes, 2015). However, Kelly et al. (2016) suggested that it is the increase t-DOC-associated phosphorus, rather than t-DOC itself that boosts phytoplankton growth and ultimately causes zooplankton density increases. Others have confirmed zooplankton assimilation of t-DOC based on the natural abundance of stable carbon isotopes (δ13C) as a tracer (Karlsson et al., 2007; Hitchcock et al., 2016). Yet sometimes question exists when differences in δ13C between terrestrial and aquatic primary producers are too small to distinguish by this technique.

Major concern of t-DOC transfer to zooplankton centers on food quality (Brett et al., 2012; Taipale et al., 2014). Bacteria grown on t-DOC lack some biochemicals essential for the growth and reproduction of consumers (e.g. highly-unsaturated fatty acids, HUFA), and have thus been deemed unsuitable as a sole food source (Martin-Creuzburg et al., 2011). However, mixed algae-bacteria diet can support the growth and reproduction of zooplankton (Wenzel et al., 2012). Besides, microbial food for zooplankton consists of additional heterotrophic microbes in addition to bacteria, e.g. fungi and bactivorous protists (Sherr and Sherr, 1994; Rösel et al., 2012). Their ability of HUFA synthesis was previously reported (Hauvermale et al., 2006; Chu et al., 2008). So, we hypothesized that heterotrophic microbes may play important roles in transferring t-DOC to zooplankton.

To test our hypothesis, we traced the fate of 13C enriched glucose added to 15 aquatic mesocosms during June to July, 2013. Similar-sized microbes like algae and bacteria being difficult separated for sampling could be distinguished by PLFA (phospholipid fatty acids), for which specific microbial groups produce signature PLFA profiles (Boschker and Middelburg, 2002). Moreover, microbial PLFA and whole-cell share similar isotopic signatures (De Kluijver et al., 2015). Hence carbon stable isotopic analysis of their signature PLFA can be used to study the source of carbon they assimilated (PLFA-based stable isotope probing, PLFA-SIP), and is applied in our experiment.

Each mesocosm contained 100 L surface water from the shore of Fuxian Lake in China (24°21′28″–24°38′00″N, 102°49′12″–102°57′26″E). Fuxian Lake with an area of 211 km2, is a deep oligotrophic lake with low phosphorus content, while with macrophyte in shores. After setting up, 3 mesocosms were sampled to provide reference values (T0). 30 mg 13C-glucose was then added to rest 12 mesocosms, and each three mesocosms were sampled on days 1, 3, 6 and 9 during the experiment (T1, T3, T6 and T9 respectively). Each mesocosm was sampled only once. Total nitrogen (TN), total phosphorus (TP) and Chlorophyll a (Chl a) concentrations of mesocosm water were measured as previously described (Zhang et al., 2016). DOM (dissolve organic matter) concentrations were analyzed using a TOC analyzer (Shimadzu TOC-L CPH CN200, Japan).

Both particulate organic matter (POM) and microbial samples were gathered by filtering 2–5 L water through Whatman (GF-F) glass-fiber filters (pore size 0.7 µm). Water after filtration was dried 48 °C to form DOM samples. Zooplankton was collected from the mesocosms using a 64 µm mesh-size net. The dominant species in all mesocosms, Bosmina sp., was picked out. POM and Bosmina samples were dried also at 48 °C and subjected to carbon isotopic analysis by carrying on an EA 1112 elemental analyzer coupled to an isotope ratio mass spectrometer (Thermo Finnigan Delta V) together with DOM samples. Phospholipid fatty acids of microbial samples were extracted according to Guckert et al. (1985). δ13C of single PLFA was detected by a GC-c-IRMS (Thermo Finnigan, Germany). Isotopic analysis was conducted in Key Laboratory of Global Change and Marine-Atmospheric Chemistry, State Oceanic Administration, China. Based on sample replicates, the analytical precision was 0.3‰ for δ13C.

The concentration-weighted δ13C of branched fatty acids i15:0 and ai15:0 were used to symbolize bacterial δ13C (δ13Cbacteria) according to Boschker and Middelburg (2002). δ13C of phytoplankton (δ13Cphytoplankton) was calculated as concentration-weighted δ13C of polyunsaturated fatty acids 18:2ω6, 18:3ω6, 20:5ω3 and 22:6ω3 (including cyanobacteria and eukaryotic algae), as recommended by De Kluijver et al. (2015). However, since 18:2ω6 and 18:3ω6 are also found in fungi (Wurzbacher et al., 2010), fungi must be considered as potential contributors to the observed phytoplankton isotopic signatures. One-way ANOVA and repeated measures ANOVA were conducted to compare stable isotopic signatures in different mesocosms and between different organisms respectively in SPSS 18.0. Correlation analysis used Pearson Correlation also in SPSS. Key physiochemical information of mesocosms is given in Table 1. All stable isotopic signatures are shown in Figure 1.

13Cbacteria values started at averaged −23.1‰. Subsequently, a significant increase in δ13Cbacteria was observed on day 1 samples (P < 0.05), consistent with massive t-DOC support for bacterial production (Cole et al., 2006). In following days, however, δ13Cbacteria fell rapidly. Quickly use up of labile glucose and following more incorporation of depleted DOM into bacterial biomass is a potential factor in decline of 13Cbacteria values. Besides, a bias towards allochthonous carbon in bacterial respiration reported (Karlsson and Jonsson, 2007) probably contributes to this rapid decrease of δ13Cbacteria.

Particulate organic matter comprises a mixture of bacteria, phytoplankton, detrital aggregates and other material, with an initial average δ13CPOM of −14‰. δ13CPOM was closely correlated to δ13Cbacteria (r = 0.984, P < 0.001) and changes in δ13CPOM recorded in the mesocosms were consistent with δ13Cbacteria. In experiments designed to record microbial uptake of 3H-labeled glucose and acetate, Paerl (1974) concluded that radioactive isotopic signature could be passed to POM by bacterial uptake and their help in the formation of detrital aggregates.

δ13CDOM of −14.8‰ in T0 mesocosm was observed to increase by a relatively small amount on the first day and increased gradually in following days, indicating that 13C-glucose supplement was exhausted in the very first day. 13CDOM values that persist later in the experiment are likely due to excretion by bacteria and zooplankton.

δ13Cphytoplantkon was also affected by 13C-glucose addition, increasing from −26.3‰ on average to a maximum of 222.6‰. There are three plausible explanations for this observed increase. Firstly, the inclusion of heterotrophic fungi, which can be supported by extra organic carbon, e.g. t-DOC (Rösel et al., 2012). Second, the presence of mixotrophic and heterotrophic protists by grazing on bacteria or osmosis as well as osmotrophic algae, which are able to assimilate DOC and synthesize HUFA (Jones, 2000; Tittel et al., 2009). A third possibility is that dissolved inorganic carbon (DIC) could be derived from respiration of non-autochthonous carbon (Karlsson and Jonsson, 2007), possibly supporting the growth of autotrophic phytoplankton. Since all these fungi, mixotrophic and heterotrophic protists, as well as algae are available as potential food for zooplankton, they offer a variety of trophic transfer pathway for glucose-C into zooplankton.

A significant increase in δ13Czooplankton was also observed after glucose addition (P < 0.05), and δ13Czooplankton values remained significantly higher than those of phytoplankton thereafter (P < 0.05). These results confirmed the rapid assimilation of glucose-C by Bosmina. δ13Czooplankton was substantially higher than δ13CPOM after glucose addition (P < 0.05) indicating that Bosmina had utilized an isotopically heavier food source than the analyzed POM fraction. Only bacteria were isotopically heavier than POM, suggesting selective consumption of bacteria by Bosmina. Freese and Martin-Creuzburg (2013) found that Daphnia magna grew better with a mixed bacteria-algae diet than sole algae, possibly due to bacteria-derived nutrients, e.g. vitamins, which could also explain our results.

In summary, our mesocosm experiments confirm the rapid incorporation of glucose-C by Bosmina. The results provide evidence for a transfer of carbon by direct consumption of bacteria. Besides, fungi, mixotrophic and heterotrophic protists as well as algae offer further likely pathways whereby from glucose-C may be assimilated by zooplankton. To be noticed, t-DOC is a more recalcitrant carbon than labile glucose. However, Berggren et al. (2010a) and Attermeyer et al. (2014) reported t-DOC to include some low molecular weight substances labile to bacteria thus similar to glucose. Considering that labile part of t-DOC has an unproportionally large impact on aquatic secondary production compared its share of total t-DOC (Berggren et al., 2010b), this experiment hints at possible transfer pathways for DOC included t-DOC into zooplankton.


This study was financially supported by National Natural Science Foundation of China (Nos. 31370478, 31000219, 41471086 and U1033602).


  • Attermeyer K, Hornick T, Kayler ZE, et al. 2014. Enhanced bacterial decomposition with increasing addition of autochthonous to allochthonous carbon without any effect on bacterial community composition. Biogeosciences 11(6): 1479–1489. [CrossRef] (In the text)
  • Berggren M, Laudon H, Haei M, Strom L, Jansson M. 2010a. Efficient aquatic bacterial metabolism of dissolved low-molecular-weight compounds from terrestrial sources. ISME J 3: 408–416. [CrossRef] (In the text)
  • Berggren M, Ström L, Laudon H, et al. 2010b. Lake secondary production fueled by rapid transfer of low molecular weight organic carbon from terrestrial sources to aquatic consumers. Ecol Lett 13(7): 870–880. [CrossRef] (In the text)
  • Boschker HTS, Middelburg JJ. 2002. Stable isotopes and biomarkers in microbial ecology. FEMS Microbiol Ecol 40(2): 85–95. [CrossRef] (In the text)
  • Brett MT, Arhonditsis GB, Chandra S, Kainz MJ. 2012. Mass flux calculations show strong allochthonous support of freshwater zooplankton production is unlikely. PLOS ONE 7(6): e39508. [CrossRef] (In the text)
  • Chu F-LE, Lund ED, Podbesek JA. 2008. Quantitative significance of n-3 essential fatty acid contribution by heterotrophic protists in marine pelagic food webs. Mar Ecol Prog Ser 354: 85–95. [CrossRef] (In the text)
  • Cole JJ, Carpenter SR, Pace ML, et al. 2006. Differential support of lake food webs by three types of terrestrial organic carbon. Ecol Lett 9(5): 558–568. [CrossRef] (In the text)
  • Cooke SL, Fischer JM, Kessler K, et al. 2015. Direct and indirect effects of additions of chromophoric dissolved organic matter on zooplankton during large-scale mesocosm experiments in an oligotrophic lake. Freshw Biol 60(11): 2362–2378. [CrossRef] (In the text)
  • De Kluijver A, Ning J, Liu Z, Jeppesen E, Gulati RD, Middelburg JJ. 2015. Macrophytes and periphyton carbon subsidies to bacterioplankton and zooplankton in a shallow eutrophic lake in tropical China. Limnol Oceanogr 60: 375–385. [CrossRef] (In the text)
  • Ducklow HW, Purdie DA, Williams PJL, Davies JM. 1986. Bacterioplankton – a sink for carbon in a coastal marine plankton community. Science 232: 865–867. [CrossRef] [PubMed] (In the text)
  • Faithful CL, Huss M, Vrede T, Bergström AK. 2011. Bottom–up carbon subsidies and top–down predation pressure interact to affect aquatic food web structure. Oikos 120: 311–320. [CrossRef] (In the text)
  • Freese HM, Martin-Creuzburg D. 2013. Food quality of mixed bacteria-algae diets for Daphnia Magna. Hydrobiologia 715: 63–76. [CrossRef] (In the text)
  • Geddes P. 2015. Experimental evidence that subsidy quality affects the temporal variability of recipient zooplankton communities. Aquat Sci 77: 609–621. [CrossRef] (In the text)
  • Guckert JB, Antworth CP, Nichols PD, White DC. 1985. Phospholipid ester-linked fatty acid profiles as reproducible assays for changes in prokaryotic community structure of estuarine sediments. FEMS Microbiol Ecol 31: 147–158. [CrossRef] (In the text)
  • Hauvermale A, Kuner J, Rosenzweig B, Guerra D, Diltz S, Metz JG. 2006. Fatty acid production in Schizochytrium sp.: involvement of a polyunsaturated fatty acid synthase and a type 1 fatty acid synthase. Lipids 41: 739–747. [CrossRef] [PubMed] (In the text)
  • Hitchcock, JN, Mitrovic SM, Hadwen WL, et al. 2016. Terrestrial dissolved organic carbon subsidizes estuarine zooplankton: an in situ mesocosm study. Limnol Oceanogr 61(1): 254–267. [CrossRef] (In the text)
  • Jones RI. 2000. Mixotrophy in planktonic protists: an overview. Freshw Biol 45(2): 219–226. [CrossRef] (In the text)
  • Karlsson J, Jonsson A. 2007. Respiration of allochthonous organic carbon in unproductive forest lakes determined by the keeling plot method. Limnol Oceanogr 52(2): 603–608. [CrossRef] (In the text)
  • Karlsson J, Jonsson A, Meili M, Jansson M. 2003. Control of zooplankton dependence on allochthonous organic carbon in humic and clear-water lakes in northern Sweden. Limnol Oceanogr 48: 269–276. [CrossRef] (In the text)
  • Karlsson J, Lymer D, Vrede K, Jansson M. 2007. Differences in efficiency of carbon transfer from dissolved organic carbon to two zooplankton groups: an enclosure experiment in an oligotrophic lake. Aquat Sci 69(1): 108–114. [CrossRef] (In the text)
  • Kelly P, Craig N, Solomon CT, Weidel BC, Zwart JA, Jones S. 2016. Experimental whole-lake increase of dissolved organic carbon concentration produces unexpected increase in crustacean zooplankton density. Global Change Biol 22(8): 2766–2775. [CrossRef] (In the text)
  • Martin-Creuzburg D, Beck B, Freese HM. 2011. Food quality of heterotrophic bacteria for Daphnia magna: evidence for a limitation by sterols. FEMS Microbiol Ecol 76: 592–601. [CrossRef] [PubMed] (In the text)
  • Paerl HW. 1974. Bacterial uptake of dissolved organic matter in relation to detrital aggregation in marine and freshwater systems. Limnol Oceanogr 19(6): 966–972. [CrossRef] (In the text)
  • Rösel S, Rychla A, Wurzbacher C, Grossart H-P. 2012. Effects of pollen leaching and microbial degradation on organic carbon and nutrient availability in lake water. Aquat Sci 74: 87–99. [CrossRef] (In the text)
  • Sherr EB, Sherr BF. 1994. Bacterivory and herbivory: key roles of phagotrophic protists in pelagic food webs. Microb Ecol 28(2): 223–235. [CrossRef] [PubMed] (In the text)
  • Solomon CT, Jones SE, Weidel BC, et al. 2015. Ecosystem of changing inputs of terrestrial dissolved organic matter to lakes: current knowledge and future changes. Ecosystems 18: 376–389. [CrossRef] (In the text)
  • Taipale SJ, Brett MT, Hahn MW, et al. 2014. Differing Daphnia magna assimilation efficiencies for terrestrial, bacterial, and algal carbon and fatty acids. Ecology 95(2): 563–576. [CrossRef] [PubMed] (In the text)
  • Tanentzap AJ, Szkokan-Emilson EJ, Kielstra BW, Arts MT, Yan ND, Gunn JM. 2015. Forests fuel fish growth in freshwater deltas. Nat Commun 5: 4077. (In the text)
  • Tittel J, Wiehle I, Wannicke N, Kampe H, Poerschmann J, Meier J. 2009. Utilisation of terrestrial carbon by osmotrophic algae. Aquat Sci 71(1): 46–54. [CrossRef] (In the text)
  • Tranvik LJ. 1998. Degradation of dissolved organic matter in humic waters by bacteria. In: Hessen DO, Tranvik LJ, eds. Aquatic humic substances. New York: Springer-Verlag, pp. 259–283. [CrossRef] (In the text)
  • Wenzel A, Bergström A-K, Jansson M, Vrede T. 2012. Survival, growth and reproduction of Daphnia galeata feeding on single and mixed Pseudomonas and Rhodomonas diets. Freshw Biol 57: 835–846. [CrossRef] (In the text)
  • Wurzbacher CM, Bärlocher F, Grossart H-P. 2010. Fungi in lake ecosystems. Aquat Microb Ecol 59:125–149. [CrossRef] (In the text)
  • Zhang X, Tang Y, Jeppesen E, Liu Z. 2016. Biomanipulation-induced reduction of sediment phosphorus in a tropical shallow lake. Hydrobiologia, doi:10.1007/s10750-016-3079-x. (In the text)

Cite this article as: Tang Y, Su Y, Sun H, Liu Z, Dumont HJ, Hu J, Zhang Y, Yu J. 2017. Carbon transfer from dissolved organic carbon to the cladoceran Bosmina: a mesocosm study. Knowl. Manag. Aquat. Ecosyst., 418, 24.

All Tables

Table 1

Physiochemical information of experimental groups. Note: Values given in average and – indicates not detected.

All Figures

thumbnail Fig. 1

Carbon stable isotope signatures of bacteria (indicated by PLFA), POM, DOM, phytoplankton (indicated by PLFA) and Bosmina in mesocosms after 0 d, 1 d, 3 d, 6 d, 9 d incubation with 13C-glucose (mean ± SD).

In the text

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.