Seasonal relationships between planktonic microorganisms and dissolved organic material in an alpine stream

Abstract

Abstract. The relationships between the abundance and activity of planktonic, heterotrophic microorganisms and the quantity and characteristics of dissolved organic carbon (DOC) in a Rocky Mountain stream were evaluated. Peak values of glucose uptake, 2.1 nmol L-' hr -', and glucose concentration, 333 nM, occurred during spring snowmelt when the water temperature was 4.0 C and the DOC concentration was greatest. The turnover time of the in situ glucose pool ranged seasonally from 40-1110 hours, with a mean of 272 hr. Seasonal uptake of 3 H-glucose, particulate ATP concentrations, and direct counts of microbial biomass were independent of temperature, but were positively correlated with DOC concentrations and negatively correlated with stream discharge. Heterotrophic activity in melted snow was generally low, but patchy. In the summer, planktonic heterotrophic activity and microbial biomass exhibited small-scale diel cycles which did not appear to be related to fluctuations in discharge or DOC, but could be related to the activity of benthic invertebrates. Leaf-packs placed under the snow progressively lost weight and leachable organic material during the winter, indicating that the annual litterfall in the watershed may be one source of the spring flush of DOC. These results indicate that the availability of labile DOC to the stream ecosystem is the primary control on seasonal variation in heterotrophic activity of planktonic microbial populations.

Effects of asynchronous snowmelt on flushing of dissolved organic carbon: a mixing model approach

“…Such processes have large implications for ecosystem function. For example, McKnight et al (1993) showed that flushing of labile DOC from a mountainous landscape to the stream is the primary control on the seasonal variation in heterotrophic activity of planktonic microbial populations, with activity peaking during the time of peak DOC concentration early in the snowmelt runoff event.…”

Regional comparisons of watershed determinants of dissolved organic carbon in temperate lakes from the Upper Great Lakes region and selected regions globally

“…Allochthonous DOC (organic carbon produced on land and released to waterways) can be delivered to lakes via stream inflows (Schindler et al 1996a), groundwater , and shallow subsurface runoff from wetlands (Gergel et al 1999) and uplands (Schindler et al 1996a). In some regions, a large amount of DOC originates in the upper soil horizons from decomposing vegetation and is flushed from the watersheds into streams and lakes, primarily during spring snowmelt (McKnight et al 1993) or major precipitation events . However, we know little about how these processes might differ in importance in different regions worldwide.…”

Drinking Water: Factors Affecting the Quality of Drinking Water

“…During these periods NOC peak concentration is achieved and then after some time it reduces exponentially. To account for such a phenomenon a mechanism of the intensive washing of rocks with large volume of river and ground water was proposed [108,109]. However, the authors of paper [107] propose another view of this phenomenon.…”

“…In this case, both the properties of the rock mineral-water surface interface and the water phase in terms of their reactivity with respect to various effects vary. When assessing adsorption purification ability of the rocks, the researchers propose to take account seasonal changes of the concentration and composition of DOS in natural water which substantially change when snows melt and in the period of floods [108][109][110]. During these periods NOC peak concentration is achieved and then after some time it reduces exponentially.…”