Sedimentation Patterns of Photosynthetic Bacteria Based on Pigment Markers in Meromictic Lake La Cruz (Spain): Paleolimnological Implications |
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Authors: | Lidia Romero Antonio Camacho Eduardo Vicente Maria R Miracle |
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Institution: | (1) Department of Microbiology and Ecology and Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, E-46100 Burjassot, Spain |
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Abstract: | Sedimentation fluxes of photosynthetic pigments and their derivatives, focused on the anoxygenic bacteria populations, were
determined in meromictic Lake La Cruz over a three-year period using sediment traps. Bacterial settling occurs in pulses in
response to lake dynamics. Two main annual events affect particle settling in Lake La Cruz: (1) Following an event of massive
calcium precipitation in summer that caused water whiting, a maximum flux of chlorophyll a and derivatives towards the sediment was registered. Although whiting is accompanied by massive phytoplankton biomass sinking,
it was not followed by concomitant photosynthetic bacterial sinking. (2) In contrast, the disruption of the chemocline and
the contact of bacterial populations with oxygenated waters during autumn overturn provoked a destruction of the sulfur bacterial
plate, causing mass mortality, registered in the settling material as photosynthetic pigments and their derivatives from phototrophic
bacteria. Among the bacteriochlorophyll a oxidation products, bacterioviridin (bvir) was detected in high relative abundance in the settled material collected by sediment
traps. The much increased flux of bvir after thermal overturn, associated with mass mortality of the purple sulfur bacterium,
Amoebobacter purpureus, confirms the suitability of this molecule as a useful paleoindicator of the degree of oxygen exposure experienced by the
purple sulfur bacteria population. |
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Keywords: | Anoxia Bacteriochlorophyll Bacterioviridin Karstic lake Pigment markers Sedimentation |
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