Biological availability and humic properties of dissolved organic carbon in Lake Balaton (Hungary)

Abstract

The biological availability of dissolved organic carbon (DOC) was experimentally studied in water samples collected at the mouth of the River Zala and in the western and eastern basin of Lake Balaton (Hungary) in four seasons. The water samples were filter-sterilized and inoculated with the in situ bacterial population. The concentration of fulvic and humic acids were analyzed at the beginning of the experiment. The bacterioplankton biomass and DOC concentration were measured on day 0 and 28. The decrease in the DOC concentration and the ratio of the bacterial C/initial DOC concentration showed the microbial utilization of DOC. No seasonal changes in DOC availability were found at any of the sampling stations. The DOC bioavailability was higher in the river than in the lake water. A strong positive correlation was found between the bioavailability and the humic properties of DOC. The observed changes in the organic matter composition of Lake Balaton support the view that much of the not readily utilizable 'refractory' DOM resides in the nonhumic pool in standing waters.

Changes in Chemical Composition and Spectral Characteristics of Dissolved Organic Matter From Soils Induced by Biodegradation

“…Our results are similar to the range (11-17% DOC loss) found by Kiikkilä et al (2006) in the humus layer under deciduous (silver birch) and CF (Norway spruce and Scots pine), while lower than the range (24-50% DOC loss) in the litter layer found by Kiikkilä et al (2005) and Don and Kalbitz (2005). 1) are attributed to microorganisms preferentially using labile DOC for their own biosynthesis and then being released as the cells lyse (Tóth et al, 2007;Bowen et al, 2009). Higher UV absorption (A 254 ) and HIX syn of DOM from CF soils are related to a lower rate of DOC decomposition ( Fig.…”

“…During biodegradation, the RFI of fulvic acid-like materials in DOM increased for CF and AM soils, whereas it decreased for EBF and DF soils in which there was greater RFI at the beginning of incubation (Fig. Tóth et al (2007) found a strong positive correlation between the organic carbon concentration of fulvic acids and biodegradable DOC, but no significant relationship between humic acids and biodegradable DOC, which suggested that fulvic acids are more important components of the biodegradable DOC pool than previously thought. Dissolved humic substances have conventionally been considered to be recalcitrant and largely unavailable for bacterial degradation (Geller, 1986).…”

Effects of pH on aquatic biodegradation processes

“…During the 20 th century, large volumes of lake-water have been extracted through the artificial outflow and discharged into the River Danube. Simultaneously, a shrinking of the open lake area due to accumulation of organic-rich sediments in the littoral zone has been observed (Weisser, 1973 In order to estimate the time-dependent changes of the lake's salt stock, we performed a trend analysis on a large base of hydrochemical data. A detailed ion analysis of the lake-water was conducted using flame atomic absorption spectroscopy (F-AAS; Perkin Elmer AA300) and ion chromatography (IC; ICS1000, Dionex Corp., CA, USA).…”

Impact of drying/rewetting cycles on the bioavailability of dissolved organic matter molecular-weight fractions in a Mediterranean stream

“…However, the bioavailability of DOM is actually affected by numerous factors, including its molecular-weight fractions, biochemical composition, inorganic nutrients, and temperature (Tranvik and Kokalj 1998, Tóth et al 2007, Dawson et al 2008. Researchers have hypothesized that selective bacterial uptake of DOC depends on its molecular weight (MW) (Romaní et al 2006, Vázquez et al 2007).…”