Intermittent riverine resuspension: Effects on phosphorus transformations and heterotrophic bacteria

Abstract

Intermittent riverine resuspension (IRR), a common phenomenon, was applied to investigate its effects on sedimentary resources availability and bacteria in the water column. This lab experiment used organic-rich lowland river sediment in a newly designed erosion chamber, the Benthic Water Column Simulator, generating well-defined ratios of shear velocity u* to turbulence intensity. Eight consecutive resuspension events, 1-8, were initiated at u* 5 1.1 cm s 21 . Sedimentary and phosphorus entrainment decreased from 20.4 g m 22 h 21 and 111.6 mg m 22 h 21 at event 1 to 1.31 g m 22 h 21 and 18.7 mg m 22 h 21 at event 8, suggesting an exhaustion of particulate and dissolved sediment constituents. Entrainment of particle-associated (PA) bacteria (132.7 3 10 9 -251.1 3 10 9 cells m 22 h 21 ) was strongly correlated to that of particles. Free-living (FL) bacteria (227.6 3 10 9 -36.4 3 10 9 cells m 22 h 21 ) were fractionally entrained. Numbers of PA bacteria remained low after each event, whereas those of FL bacteria strongly increased 5-15 h after an event because of growth due to increased availability of dissolved organic carbon and inorganic nutrients following each event. FL bacteria community structure also changed during IRR. The systematic changes over consecutive IRR cycles show a strong effect in all considered parameters that elude the typical single-event, steady-state experiments. IRR should thus be considered in two respects: experimental protocols on riverine water quality should be revised. In ecosystem modeling, IRR should be considered to better predict extent and effect of resuspension. Only IRR adequately reflects the natural interplay between hydrodynamics and organisms in rivers.

The sensitivity and stability of bacterioplankton community structure to wind-wave turbulence in a large, shallow, eutrophic lake

“…Disentangling the ecological effects of wind wave turbulence can provide new insights on bacterioplankton responses to physical forcing in lakes, which may be essential for quantifying and understanding lake ecosystem process and its recovery from eutrophication. The usefulness of mesocosms as a tool to investigate community responses has been thoroughly tested, and the current gradient-based design is an effective tool for inferential studies of ecological processes 48 , 51 .…”

Microbial Carbon Metabolic Functions in Sediments Influenced by Resuspension Event

“…Shallow lakes are characterized by frequent sediment resuspension events, causing the release of large amounts of nutrients. Nevertheless, there have been few studies about the potential impacts of sediment resuspension events on the functional activities of microbial communities [33,34]. Based on the above, an indoor annular flume was used in this study to simulate the sediment resuspension event process.…”

Organic matter quality structures benthic fatty acid patterns and the abundance of fungi and bacteria in temperate lakes

“…All water samples were pooled at equal amounts, immediately pre-filtered through a 500 µm mesh to exclude coarse POM, and then filtered through 0.45 µm pre-washed cellulose-acetate filters (Sartorius, Göttingen, Germany) using a vacuum pump for further processing (see below). To analyze the sediment samples, the uppermost 2 cm of each sediment core was sliced with a core cutter because sediments up to 2 cm have the highest microbial densities (Haglund et al, 2003) and the potential of oxygenation and resuspension within the water column via turbulence (Schallenberg and Burns, 2004;Kleeberg et al, 2013). Slices were pooled at equal weights and stored at -20 °C until further processing.…”

“…For littoral lake sediments, a strong correlation was observed between allochthonous OM input and benthic OM concentration (Cole et al, 2006). Additionally, littoral sediments are subjected to frequent resuspension depending on turbulence strength and sediment densities (Kleeberg et al, 2013), further affecting the OM quantity and quality of the sediments and hence of the BMC.…”