Lake Pavin History, geology, biogeochemistry, and sedimentology of a deep meromictic maar lake

© Springer International Publishing Switzerland 2016 185
T. Sime-Ngando et al. (eds.), Lake Pavin, DOI 10.1007/978-3-319-39961-4_11

Carbon Cycle in a Meromictic Crater

Lake: Lake Pavin, France

Didier Jézéquel, G. Michard, E. Viollier, P. Agrinier,

P. Albéric, F. Lopes, G. Abril, and L. Bergonzini

Abstract

Lake Pavin is a meromictic maar lake located in the French Massif Central. Its maximum

depth is 92 m and its mean diameter is 750 m (0.445 km^2 ). Waters below about 60 m are

never mixed with overlying waters and are permanently anoxic. DIC (Dissolved Inorganic

Carbon) and CH 4 concentrations in the deep monimolimnion are 14 and 4 mmol/L respec-

tively. DIC has two origins: biogenic and volcanic.

Data on C species,^13 C and^14 C isotopes as well as auxiliary data were used to build a

carbon mass balance in the lake. Main features of the carbon cycle are:

1. Between 70 and 92 m depth, DIC and methane fluxes coming from the sediment are
   estimated to 1.5 and 10 .kmold−^1 respectively.


2. At about 65–70 m depth, a PM^14 C (percent of modern carbon) minimum suggests the
   inflow of a mineral water which brought DICk=± 26 .. 02 mold−^1.


3. As suggested by a minimum of δ^13 C of DIC and very low CH 4 concentration at ca.
   60 m depth, methane is almost quantitatively transformed mainly into DIC at the
   redoxcline. The methane escape toward the atmosphere is very low and negligible in
   the carbon mass balance.


4. The δ^13 C DIC, DIC vs. O 2 plots and some thermal and dissolved oxygen anomalies
   suggest a fresh water inflow at about 53 m depth; the corresponding input of DIC is
   estimated to 16 ..± 02 kmold−^1.


5. Between 20 and 50 m depth, mineralization of organic matter produced in the photic
   zone occurs partially. From a δ^13 C versus 1/DIC plot, a production of DIC of
   03 ..± 02 kmold−^1 can be derived.


6. The maximum of photosynthesis is located within the metalimnion (10–15 m depth).
   A mean value for the corresponding DIC uptake of 35 ..± 05 kmold−^1 is assumed.
   During seasonal stratification of the mixolimnion (about April to December), water

D. Jézéquel (*) • G. Michard • E. Viollier • P. Agrinier
IPGP (Institut de Physique du Globe de Paris), Sorbonne Paris
Cité, Univ. Paris Diderot, UMR 7154 CNRS,
1 rue Jussieu, 75005 Paris, France
e-mail: [email protected]

P. Albéric
ISTO (Institut des Sciences de la Terre d’Orléans), Observatoire
des Sciences de l’Univers en région Centre, UMR 7327
(CNRS- Université d’Orléans-BRGM),
1A rue de la Férollerie, 45071 Orléans Cedex 2, France

F. Lopes
ECP (Ecole Centrale Paris), Grande Voie des Vignes,
92295 Châtenay-Malabry Cedex, France

11

G. Abril

EPOC (Laboratoire Environnements et Paléoenvironnements

Océaniques et Continentaux), UMR 5805, Université de Bordeaux,

Allée Geoffroy Saint-Hilaire, 33615 Pessac, France

L. Bergonzini

GEOPS (Géosciences Paris Sud), Université Paris-Saclay,

Univ. Paris-Sud, UMR 8148 CNRS, rue du belvédère, Bât 504,

91405 Orsay Cedex, France

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