The Choice of Standardisation Reveals a Significant Influence on the Dynamics of Bacterial Abundance in Newly Deposited River Sediments

Abstract

After a high water event of the River Danube in April 1994, bacterial cell numbers were determined in newly formed deposits in a backwater near Hainburg (Lower Austria) within a time course of 140 days. This data set shows that expressing bacterial numbers per fresh sediment volume, per sediment dry mass, or per pore-water fluid volume, respectively, yield significantly different results and ecological conlusions. These findings refer particularly to intra-study and time-course comparisons as presented in our case. Bacterial cell numbers expressed per gram sediment dry mass revealed statistically significant differences between the beginning and the end of the study, whereas expressed per cm 3 of fresh sediment or fluid volume of sediment pore water, no statistical difference could be detected. It is argued that these differences were caused by physical sediment compaction and mineralisation processes over the considered time-course. Such mechanisms may simulate biological activity if some basic sediment parameters are neglected and thus standardisation has to be done with caution for the particular situation being observed.

Use of faecal pollution indicators to estimate pathogen die off conditions in source separated faeces in Kathmandu Valley, Nepal

“…The weighted average of the respective colony counts was used when more dilutions were countable on the plates. The counts of the indicators were converted from CFU/wet gram of faeces to CFU/cm 3 to avoid any bias due to standardisation (Farnleitner et al 2003). However, it was observed that the concentrations did not vary much when Chicago, IL) was used for data analysis and the significance level at p # 0.05 was used.…”

Heterotrophic prokaryotic production in ultraoligotrophic alpine karst aquifers and ecological implications

“…The samples were stored at 4°C and processed within three days. Prokaryotic abundance, sediment bulk density, dry mass (DM) and pore water (PW) were determined as described previously (Farnleitner et al 2003). Organic content of sediment samples was calculated by subtracting the sample weight after combusting (500°C, 4 h) from DM.…”