Influence of bioturbation on the biogeochemistry of littoral sediments of an acidic post-mining pit lake

Abstract

Abstract. In the last decades, the mining exploitation of large areas in Lusatia (Eastern Germany) but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3). The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macroinvertebrates) under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera) is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O 2 microsensors) was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the diffusive oxygen uptake by sediment, indicating a stimulation of the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation) but with no significant effect on the iron flux at the sediment-water interface, and thus Correspondence to: S. Lagauzère (lagauzere@gmail.com) on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

Biogeochemical changes at the sediment–water interface during redox transitions in an acidic reservoir: exchange of protons, acidity and electron donors and acceptors

“…Diffusive oxygen uptake (DOU) rates at the sediment water interface were in the range or slightly higher than those available in the literature for acid lakes (Kühl et al 1998;Koschorreck et al 2003;Lagauzère et al 2011) and neutral lakes (Sweerts et al 1991;Maerki et al 2009;Matzinger et al 2010;Schwefel et al 2017). The instantaneous increase in O 2 concentration in the HI-OX transition probably induced an increase in the oxidation rates of organic matter and reduced compounds like Fe 2?…”

In situ organism-sediment interactions: Bioturbation and biogeochemistry in a highly depositional estuary

“…Though it is clear sediment biogeochemistry limited macrofauna function in CLB, biogeochemistry and bioturbation are coupled interactions in the sediment [ 95 ]. The presence of macrofauna bioturbators during the summer-reduced period indicates that many of the bioturbative processes discussed earlier were still occurring despite the decrease in macrofauna influence.…”

Effects of artificial substrate and night-time aeration on the water quality inMacrobrachium amazonicum(Heller 1862) pond culture

“…Besides increased detritus and nutrient suspension due to aeration, the increasing of oxygen concentration in the surface layer of the sediment water favours the release of nutrients into the water column due to aerobic decomposition and mineralization of organic matter carried out by benthic macroinvertebrates (e.g. Chironomidae, Chaoboridae, Olygochaeta) (Phan‐Van, Rousseau & De Pauw ; Lagauzere, Moreira & Koschorreck ). The higher availability of nutrients in the ponds with aeration probably favoured the growth of phytoplankton and periphyton.…”