Seasonal biogeochemical and microbiological studies of small lakes in taiga zone of northwestern Russian (Arkhangelsk Province)

Abstract

Abatract-The results of biogeochemical and microbiological studies of three small lakes in southwestern Arkhangelsk province are presented. The lakes differ in their morphometric characteristics, thermal and oxy gen regimes, and the extent of anthropogenic impact they experience. In the periods of summer and winter stratification, anaerobic water layers with higher phosphates, ammonium, and sulfide sulfur (hydrogen sul fide) are found to form in the bottom horizon of deep water zones of the lakes. The highest concentrations of sulfide sulfur (150-210 µg dm -3 ) were recorded in the shallow Beloe Lake during winter low water period, while in summer, sulfide concentration did not differ from those obtained in other lakes (~10 µg dm -3 ). The abundance of sulfate reducing bacteria in lake bottom sediments varied from 10 to 100000 cell cm -3 , and the rate of sulfate reduction process varied from 29 to 3746 µg S dm -3 day -1 . Seasonal variations were revealed in hydrogen sulfide distribution over the water column and in the rate of sulfate reduction process in the upper horizons of bottom sediments in the examined lakes.

Size Fractionation of Trace Elements in a Seasonally Stratified Boreal Lake: Control of Organic Matter and Iron Colloids

“…5a). Note that the probable contribution of thioarsenic species (as evidenced in sulfidic environments by Wilkin et al 2003) to the observed colloidal As in the bottom water and sediment of lake Maselga could not be tested in this work, although the concentration of thiosulfate in the water column is comparable to that of sulfide (Kokryatskaya et al 2012). However, the independence of colloidal As proportion on depth during most studied season and even its decrease in March, during the maximal anoxy in the hypolimnion (cf.…”

“…Typical biogenic elements (Si, P, and N) and Ba are not associated with colloids; however, they exhibit significant stratification, as they probably originated from degrading sinking plankton debris and/or reflux from the sediments to the water column. The presence of the anoxic zone below 15-18 m, which is especially notable in winter and contains up to 0.67 lmol/L H 2 S (Kokryatskaya et al 2012), may be responsible for the increase in the bottom water concentrations of Cr, V, Mo, and As ( Fig. EA-2-1, E-H).…”

“…The DIC concentration remained quite constant (5 ± 1 mg/L) over the full depth of the lake in summer and during lake overturn. Contrarily, in winter, there was an increase in the DIC concentration by a factor of 3-4 at depths below 14 m, which is most likely linked to the anaerobic mineralization of OC and sulfate reduction (Kokryatskaya et al 2012). Intensive mineralization of dissolved organic matter is further supported by the d 13 C DIC values (Shirokova et al 2009b) that ranged from -9% at the surface to -14% at the bottom in March 2009 suggesting (i) clear disequilibrium with the atmosphere and (ii) importance of benthic respiration and DOM mineralization by heterotrophic bacteria in the water column.…”

“…These FeS nanoparticles are capable of scavenging some trace metals (Balistrieri et al 1994(Balistrieri et al , 1995. Given elevated sulfide and S 0 concentrations in the hypolimnion of Lake Maselga (from 0.15 lM at the surface to 0.45-0.67 lmol/L at the bottom, Kokryatskaya et al 2012), colloidal iron sulfide and elemental sulfur may be potentially important TE carriers and deserve special investigation using size fractionation techniques.…”

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

“…These FeS nanoparticles are capable of scavenging some trace metals [34,35]. Given elevated sulfide concentrations in the hypolimnion of Lake Svyatoe (from 0.24 µM at the surface to 1.18 µM at the bottom [36]), colloidal iron sulfide may be potentially important and deserves special investigation using size fractionation techniques.…”