11 - Dynamics and vertical distribution of particulate organic matter in river bed sediments (Morava River, Czech Republic)

Summary

ABSTRACT Vertical and temporal distribution of paniculate organic matter (POM) in river bed sediments was observed in two different stations in the Morava River. Samples of river sediments from 0–70 cm depths were taken by inserting a steel cylinder with a special grab. The main type of organic matter found in bed sediments was fine particulate organic matter (FPOM < 1 mm). The organic matter had a variable distribution in the hyporheic zone. Generally, the concentration of organic matter was higher in the top 0–40 cm of sediment. The annual mean storage of buried organic matter (0–70 cm depth) was 5352.13 g AFDW.rn⁻³. The exchange of organic matter between surface sediments and deep river bed sediments is influenced mainly by flooding activity. The maximum storage of organic matter in the hyporheic zone appears in the spring when floods are decreasing.

INTRODUCTION

Allochthonous organic matter which is imported in running waters at different times and in different ways (Boling et al, 1975; Cummins, 1974; Moser, 1991) is an important source of energy for sediment fauna (Fisher & Likens, 1973; Cummins, 1974). Fresh imported allochthonous organic matter is not available directly for benthic consumers and must first be processed by the microbial communities, especially fungi and bacteria (Rossi & Fano, 1979; Arsuffi & Suberkropp, 1985).

An exchange of water exists between the surface and hyporheic zone (Grimm & Fisher, 1984; Thibodeaux & Boyle, 1987; White et al, 1987). In these exchange processes, particulate and dissolved organic material are transported into the bed sediments (Welton, 1980; Carling & McMahon, 1987; Mayack et al, 1989; Metzler & Smock, 1990; Smock, 1990; Bretschko & Moser, 1993; Sear, 1993).