Long-term leaf litter decomposition and associated microbial processes in extremely acidic (pH <3) mining waters

Publisher： E. Schweizerbart'sche Verlagsbuchhandlung

ISSN： 0003-9136

Source： Archiv fuer Hydrobiologie, Vol.164, Iss.1, 2005-09, pp. : 53-68

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Abstract

Leaf packs were exposed in extremely acidic mining waters, removed at intervals throughout a two-year period and analysed for mass loss, microbial respiration and fungal biomass (ergosterol content). The mass loss followed an exponential trend with asymptotic values of 45–53% of initial mass reached within the first 5 months. After this initial stage, leaves were completely encrusted by iron oxyhydroxide precipitates. The highest respiration occurred during the initial period and subsequently decreased to low levels comparable to those on an inert substrate (plastic strips) that was covered by iron precipitates. These precipitates create a barrier against microbial attack and mechanical abrasion of leaf litter and trap considerable amounts of organic matter. Ergosterol contents were highest after 3 months and varied throughout the subsequent exposure period with higher contents in autumn/winter. Unidentified HPLC-peaks may indicate that dead fungal hyphae are enclosed by iron plaques instead of being degraded. The formation and accumulation of refractory leaf litter/iron plaque layers has implications for the future development of the mining waters.