Decrease of concentration and colloidal fraction of organic carbon and trace elements in response to the anomalously hot summer 2010 in a humic boreal lake

Small Boreal Lake Ecosystem Evolution under the Influence of Natural and Anthropogenic Factors: Results of Multidisciplinary Long-Term Study

“…DOC and dissolved inorganic carbon (DIC) concentrations were measured using methods routinely used in the Geosciences and Environment Toulouse (GET) laboratory to analyze boreal water samples [10,12]. The nutrient determinations were based on colorimetric assays [13,14].…”

“…The international geostandards SLRS-4 and SLRS-5 (Riverine Water Reference Material for Trace Metals certified by the National Research Council of Canada) were used to check the validity and reproducibility of each analysis (see refs. [10][11][12] for analytical pH was measured in the field using a combined electrode calibrated against NIST (National Institute of Standards and Technology, Gaithersburg, MD, USA) buffer solutions (pH = 4.00 and 6.86 at 25˝C). The accuracy of pH measurements was˘0.02 pH units.…”

“…The international geostandards SLRS-4 and SLRS-5 (Riverine Water Reference Material for Trace Metals certified by the National Research Council of Canada) were used to check the validity and reproducibility of each analysis (see refs. [10][11][12] for analytical details). There was good agreement between our replicated measurements of SLRS-5 and the certified values (relative difference <15%).…”

“…These dialysis experiments were performed using 20 to 50 mL pre-cleaned dialysis bags placed at various depths during the different seasons. The duration of the dialysis procedure was between 72 and 96 h, following kinetic experiments of dialysis equilibrium attainment for DOC, Si, and trace metals [10,12]. For dialysis experiments, EDTA-cleaned trace-metal pure SpectraPor 7 ® dialysis membranes made of regenerated cellulose with pore sizes of 1 kDa were thoroughly washed in 0.1 M double-distilled HNO 3 and ultrapure water, and then filled with ultrapure MilliQ deionized water and placed into the lake at the desired depth.…”

“…In particular, we demonstrated the impact of the anomalously hot summer in 2010 on the increase of low molecular weight (potentially bioavailable) forms of dissolved organic carbon (DOC) and metals, primarily linked to enhanced photo-and bio-degradation of large size allochthonous soil dissolved organic matter (DOM) coupled with production of phytoplankton exometabolites [10]. In addition, observations of the diel photosynthetic cycle of the shallow zone of this lake during the hot summer's cyanobacterial bloom revealed the existence of coupled DOC-Fe-Mn speciation cycle in the surface water layer linked to alternative photosynthetic activity and heterotrophic aerobic plankton respiration [11].…”