| Title | 20th century human pressures drive reductions in deepwater oxygen leading to losses of benthic methane-based food webs |
| Abstract | Freshwater lakes play a key role in the global carbon cycle as sinks (organic carbon sequestration) and sources (greenhouse gas emissions). Understanding the carbon cycle response to environmental changes is becoming a crucial challenge in the context of global warming and the preponderance of human pressures. We reconstructed the long-term (1500 years) evolution of trophic functioning of the benthic food web, based on methanotrophic ancient DNA and chironomid isotope analyses). In addition, human land use is also reconstructed in three different lakes (eastern France, Jura Mountains). Our findings confirm that the benthic food web can be highly dependent on methane-derived carbon (up to 50% of the chironomid biomass) and reveal that the activation of this process can correspond to a natural functioning or be a consequence of anthropic perturbation. The studied lakes also showed a similar temporal evolution over the last century with the disappearance of the profundal aquatic insects (Chironomidae, Diptera), considered as keystone for the whole lake food web (e.g., coupling benthic-pelagic), inducing a potential collapse in the transfer of methane to top consumers. This functional state, also called the dead zone expansion, was caused by the change in human land-use occurring at the beginning of the 20th century. The strong modification of agro-pastoral practices (e.g., fertilization practices, intensive grazing, and sewage effluent) modified the influx of nutrients (by diffuse and/or point-source inputs) and induced a significant increase in the trophic status and organic matter sedimentation to reach unprecedented values. Further studies should be planned to assess dead zone expansion and, according to the regime shift theory, to provide environmental tipping points for sustainable resource management. |
| Source | Quaternary science reviews 137, pp. 209–220 |
| Keywords | Anthropogenic impactBenthic food webBiogenic methaneDead zonesGlobal changePaleolimnologyTrophic functioning |
| Journal | Quaternary science reviews |
| Editor | Pergamon Press., New York, Regno Unito |
| Year | 2016 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.quascirev.2016.02.019 |
| Authors | Belle S.; Millet L.; Verneaux V.; Lami A.; David E.; Murgia L.; Parent C.; Musazzi S.; Gauthier E.; Bichet V.; Magny M. |
| Text | 386391 2016 10.1016/j.quascirev.2016.02.019 Scopus 2 s2.0 84958960352 Anthropogenic impact Benthic food web Biogenic methane Dead zones Global change Paleolimnology Trophic functioning 20th century human pressures drive reductions in deepwater oxygen leading to losses of benthic methane based food webs Belle S.; Millet L.; Verneaux V.; Lami A.; David E.; Murgia L.; Parent C.; Musazzi S.; Gauthier E.; Bichet V.; Magny M. UMR CNRS 6249, Laboratoire de Chrono Environnement, Universite Bourgogne Franche Comte, Besançon, , , France; UMR CNRS 6249, Laboratoire de Chrono Environnement, Universite Bourgogne Franche Comte, Besançon, , , France; CNR, Istituto per lo Studio degli Ecosistemi, Verbania Pallanza, , Italy; UMR INRA 42, Centre Alpin de Recherche sur les Reseaux Trophiques des Ecosystemes Limniques, Chambery, , France Freshwater lakes play a key role in the global carbon cycle as sinks organic carbon sequestration and sources greenhouse gas emissions . Understanding the carbon cycle response to environmental changes is becoming a crucial challenge in the context of global warming and the preponderance of human pressures. We reconstructed the long term 1500 years evolution of trophic functioning of the benthic food web, based on methanotrophic ancient DNA and chironomid isotope analyses . In addition, human land use is also reconstructed in three different lakes eastern France, Jura Mountains . Our findings confirm that the benthic food web can be highly dependent on methane derived carbon up to 50% of the chironomid biomass and reveal that the activation of this process can correspond to a natural functioning or be a consequence of anthropic perturbation. The studied lakes also showed a similar temporal evolution over the last century with the disappearance of the profundal aquatic insects Chironomidae, Diptera , considered as keystone for the whole lake food web e.g., coupling benthic pelagic , inducing a potential collapse in the transfer of methane to top consumers. This functional state, also called the dead zone expansion, was caused by the change in human land use occurring at the beginning of the 20th century. The strong modification of agro pastoral practices e.g., fertilization practices, intensive grazing, and sewage effluent modified the influx of nutrients by diffuse and/or point source inputs and induced a significant increase in the trophic status and organic matter sedimentation to reach unprecedented values. Further studies should be planned to assess dead zone expansion and, according to the regime shift theory, to provide environmental tipping points for sustainable resource management. 137 Published version http //www.scopus.com/inward/record.url eid=2 s2.0 84958960352 partnerID=q2rCbXpz Articolo 2016_A0_065.pdf Articolo in rivista Pergamon Press. 0277 3791 Quaternary science reviews Quaternary science reviews Quat. sci. rev. Quaternary science reviews. simona.musazzi MUSAZZI SIMONA andrea.lami LAMI ANDREA |
