PP13B-2287
Modern Limnology and Varve Formation Processes in Lake Montcortès (Southern Pyrenees, Spain)

Monday, 14 December 2015
Poster Hall (Moscone South)
MªCarmen Trapote forné1,2, Pilar López3, Eric Puche3, Elisabet Safont3, Núria Cañellas-Boltà4, Joan Gomà3, Teresa Buchaca5, Núria Pérez-Zanón6, Javier Sigró6, Valentí Rull7 and Teresa Vegas-Vilarrúbia3, (1)University of Barcelona, Barcelona, Spain, (2)University of Barcelona, Department of Ecology. Faculty of Biology, Barcelona, Spain, (3)University of Barcelona, Department of Ecology, Barcelona, Spain, (4)Botanical Institute of Barcelona (IBB-CSIC-ICUB), Barcelona, Spain, (5)Centre d’Estudis Avançats de Blanes (CEAB-CSIC), Department of Continental Ecology, Blanes, Spain, (6)Centre for Climate Change (C3). University Rovira i Virgili, Physical Geography Department, Tarragona, Spain, (7)Institute of Earth Sciences Jaume Almera (ICTJA-CSIC), Department of Environmental Geology and Geohazards, Barcelona, Spain
Abstract:
Lake Montcortès is a karstic lake located in Catalonian Pyrenees (Spain). Its sediments consist of biogenic varves composed of a couplet of calcite and organic matter layers and occasional detrital layer. Previous studies of the lake’s sediments spanning the last 1500 years proposed that the lake was meromictic and that calcite layers formed due to endogenic precipitation in the epilimnion during spring/summer, driven by diatom blooms. These processes would have been influenced by variations in calcium saturation, trophic state and water temperature of the lake. The presence of phosphorous and biological differences between planktonic diatoms Cyclotella comta and C.cyclopuncta, would have produced additional differences in calcite sublayering.

In order to improve comprehension of limnological variables that influence varve formation processes, monthly field campaigns including sediment traps deployment have been carried out during two concurrent years (2013-2015).

The lake mixed once during winter. Endogenic calcite precipitation related with high primary production and calcium saturation in metalimnetic water was confirmed. Trapped material composition revealed low but constant calcite precipitation through the year with higher intensities during summer and autumn, coinciding with high relative abundances of C. cyclopuncta and C.ocellata. Nutrient content was very low throughout both years, particularly phosphorous. It seems to be removed by coprecipitation of calcium phosphate with calcite during summer, probably inhibiting part of calcite precipitation reaction. In contrast to previous hypotheses, currently calcite precipitation occurs through the whole year, mainly during summer and autumn months, and may be triggered by nucleation with picoplankton. Our study shows that processes leading to varve formation are highly complex and that any extrapolation to different regions or time periods should be handled with caution

<< Previous Abstract | Next Abstract >>