Sensitivity of a hypersaline crater lake to the seasonality of rainfall, evaporation, and guano supply
Por:
Kienel U., Plessen B., Schettler G., Weise S., Pinkerneil S., Bohnel, H, Englebrecht A.C., Haug G.H.
Publicada:
1 sep 2013
Resumen:
The hypersaline crater lake and its catchment on seabird island Isabel (Pacific, off Mexico) was studied to explore the influence of strong seasonal variations in rainfall/evaporation and guano contribution on its limnology. The hypersaline lake water (HSW, 78 ‰) is up to 2.2-times enriched in inert ions relative to mean seawater. Rainfall during summer dilutes the HSW to form a less saline rainwater body (RWB) above a chemolimnion between 2 and 4 m water depth. The RWB is inhabited first by diatoms and ostracods followed later on by cyanobacteria and ciliates. Evaporation of > 1.5 m depth of lake water over the dry season increases the salinity of the RWB until the water column becomes isohaline at HSW concentrations in the late dry season. Differences in the stable isotope composition of water and primary producers in RWB and HSW reflect this development. Introduction of seabird guano and the decrease of salinity fuel a high primary production in the RWB with higher d 13CDIC and d13Corg of particulate organic matter than in the HSW. The high N supply leads to high d15N NH4 values (+39 ‰ in the HSW) as the consequence of ammonia volatilization that is strongest during guano maturation and with evaporative salinity increase from the HSW. Precipitation of carbonate (calcite and aragonite) from the RWB and the HSW is hindered by the high concentration of guano-derived P. This inhibition may be overcome with evaporative supersaturation during particularly dry conditions. Carbonate may also precipitate during particularly wet conditions from the dilute RWB, where the P-concentration is reduced during an active phytoplankton production that raises the pH. Differences in the stable isotope signatures of carbon and oxygen in HSW and RWB (+5 ‰ d13CDIC and -3 ‰ d18OH2O) suggest the processes of carbonate precipitation can be distinguished based on the isotope signature of the carbonates deposited. Changes in the lake system are indicated when lower temperatures and higher rainfall in the 2006 wet season introduced more and less mature guano to the lake. The lower pH was accompanied by lower ammonia volatilization and carbonate precipitation as indicated by an increased concentration of NH4, Ca, Sr and DIC, while d2H, d15NNH4, and salinity were lower. According to our results, the observed sediment laminations should reflect the introduction of catchment material (including guano) with runoff, the RWB plankton production, and the carbonate precipitation in relation to its origin and seasonality. © 2013E. Schweizerbart'sche Verlagsbuchhandlung.
Filiaciones:
Kienel U.:
DFG Leibniz Center for Surface Processes and Climate Studies, Institut für Erd- und Umweltwissenschaften, Universität Potsdam, Karl-Liebknecht-Straße 24, 14476 Golm, Germany
Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ, Climate Dynamics and Landscape Evolution, Telegrafenberg, 14473 Potsdam, Germany
Plessen B.:
Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ, Climate Dynamics and Landscape Evolution, Telegrafenberg, 14473 Potsdam, Germany
Schettler G.:
Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ, Climate Dynamics and Landscape Evolution, Telegrafenberg, 14473 Potsdam, Germany
Weise S.:
UFZ - Helmholtz-Zentrum für Umweltforschung, Department Isotopenhydrologie, Theodor-Lieser-Straße 4, 06120 Halle, Germany
Pinkerneil S.:
Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ, Climate Dynamics and Landscape Evolution, Telegrafenberg, 14473 Potsdam, Germany
Bohnel, H:
Ctr Geociencias, Queretaro 76230, Mexico
Englebrecht A.C.:
Department of Earth and Planetary Science, 307 McCone Hall, University of California, Berkeley CA 94720, United States
Haug G.H.:
DFG Leibniz Center for Surface Processes and Climate Studies, Institut für Erd- und Umweltwissenschaften, Universität Potsdam, Karl-Liebknecht-Straße 24, 14476 Golm, Germany
Geologisches Institut, Department Erdwissenschaften, ETH Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland
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