Chironomid larvae stimulate biogeochemical and microbial processes in a riverbed covered with fine sediment

Abstract

We determined if the influence of chironomid larvae on biogeochemical and microbial processes in fine surface sediments of a riverbed depended on the characteristics of the sedimentary habitat. The influence of chironomids was measured on sediment reworking, biogeochemical processes and bacterial characteristics in infiltration sediment columns having three different surface sediments (with different organic matter characteristics). The results showed that chironomids exhibited similar bioturbation activities (construction and irrigation of U-shaped tubes in the upper layers of sediments) and significantly stimulated O 2 uptake and percentage of active bacteria in all sediment treatments. In contrast, the release of NH 4 + in anoxic sediment layers was strongly increased by chironomids in the presence of organicrich sediments, whereas they had no effect on this process with organic-poor sediments. Our results indicated that the influence of chironomids on biogeochemical processes in river bed sediments are linked to the redox conditions of the system. Moreover, when the effects of chironomid larvae are compared to those measured with tubificid worms in the same experimental conditions, we conclude that the mode of bioturbation (sediment reworking, biogenic structure building, burrowing depth, bioirrigation) can also determine the impact of benthic animals on microbial activities and biogeochemical processes in the sediment.

Direct observations of the effect of fine sediment deposition on the vertical movement of Gammarus pulex (Amphipoda: Gammaridae) during substratum drying

“…However, while the physical effects of fine sediment on benthic habitat and organisms have been widely recognised (Richards & Bacon, 1994;Descloux et al, 2013), it is also important to acknowledge the effects that fine sediment deposition has on interstitial flow and the transport of nutrients and dissolved oxygen through subsurface habitats (Olsen & Townsend, 2003). However, some taxa actively utilise fine sediments as a habitat (e.g., tubificid worms and Chironomidae) and in some instances construct galleries creating hyporheic flow paths and increasing connectivity (Nogaro et al, 2006(Nogaro et al, , 2008. Therefore, further species-specific experiments are needed to quantify the effect of sedimentation on macroinvertebrate fauna.…”

Riverbed Clogging and Sustainability of Riverbank Filtration

“…In 2015, a median leakage coefficient of L = 4 × 10 −6 s −1 was determined during a summer long low-flow period with moderate abstraction. Even though one may expect stronger clogging under these drought conditions, the high water temperatures, higher biological activity [20][21][22] and the ship traffic during lower river stage with stronger impact of propulsion systems on the riverbed [23] are assumed to have a positive effect on riverbed leakage.…”

“…Based on one-dimensional, horizontal groundwater flow, [18][19][20] used w to transform the head loss caused by clogging into the "characteristic leakage length λ (m)" (Equation (2)). If a virtual image of a clogged river is shifted away from the PW by a distance of λ, it can be treated as an unclogged river boundary.…”

Caddis larvae (Trichoptera, Hydropsychidae) indicate delaying recovery of a watercourse polluted by pulp and paper industry

“…those which could nowadays be exposure sources to fish or benthic invertebrates either by bioturbation or by other disturbances. Burrowing freshwater invertebrates are most abundant in the uppermost five to ten cm of sediment, for instance chironomids commonly stay in the uppermost two cm (Nogaro et al 2008), whereas oligochaetes may burrow down to 10 cm . Also other disturbances, like heavy floods or runoffs may remarkably increase the water flow and hence the sediment remobilization and bioaccessibility of the chemicals present there .…”