Conference Proceedings - IAD

Topic 1: Ecological processes in riverine conditions
Linking sediment mineralization processes with nutrient
dynamics of a Danube oxbow (Gemenc, Hungary)
ÁGOSTON-SZABÓ EDIT, DINKA MÁRIA, SCHÖLL KÁROLY, KISS ANITA, BERCZIK
ÁRPÁD
Danube Research Institute, Hungarian Academy of Sciences, Centre for Ecological
Research H-2163 Vácrátót, Alkotmány u. 2-4, Hungary, agostonszabo.edit@okologia.mta.hu,
dinka.maria@okologia.mta.hu
Keywords: microbial activity, sediment, oxbow, Danube
Introduction
Sediments play an important role in mineralization of organic matter and as a
consequence in the nutrient dynamics of the aquatic ecosystems (Wetzel 2001).
The mineralisation of sediment organic matter with allochthonous or
autochthonous origin is realised by microorganisms, which release nutrients to
the water column. These processes are regulated mainly by the physicochemical
properties of the water and sediment and by the substrate quality and
availability for the sediment associated microbiota.
In sedimentological studies the measurement of microbial activity and biomass
are commonly used techniques for determination of the intensity of organic
matter mineralization (Håkanson & Jansson 1983). Numerous studies have
investigated the metabolic activity of the sediment by using the ETS (electron
transport system) activity method (Zimmerman 1975, Olanczuk-Neyman &
Vosjan 1977, Trevors 1984, Broberg 1985, etc.), which is based on the reduction
of an artificial electron acceptor (INT: 2-p-iodophenyl-3-p-nitrophenyl-5-phenyl
tetrazolium chloride) by homogenate samples in the presence of electron donors
(NADH, NADPH, succinate) added in excess and gives the maximal rate of
respiration (Packard 1971).
The main objective of the work were: (1) to study the organic matter content and
the carbon, nitrogen, phosphorus concentrations and stoichiometry, (2) the
mineralization of sediment organic matter, (3) the possible linkages between the
organic matter mineralization and the nutrient concentrations of the sediment
and water column and (4) to identify which among the investigated factors
influence the mineralization of sediment organic matter of Nyéki-Holt-Duna
(Nyéki Danube Oxbow Lake).
Study area and sites
Gemenc is the largest natural forested floodplain of the Danube situated in
southern part of Hungary (rkm 1489-1460). In 19 th century the river regulation
processes at this reach of the Danube shortened the length of riverbed, which
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