title: Effects of salinity on leaf breakdown: Dryland salinity versus salinity from a coalmine.
abstract: Salinization of freshwater ecosystems as a result of human activities represents a global threat for ecosystems' integrity. Whether different sources of salinity with their differing ionic compositions lead to variable effects in ecosystem functioning is unknown. Therefore, the present study assessed the impact of dryland- (50μS/cm to 11,000μS/cm) and coalmine-induced (100μS/cm to 2400μS/cm) salinization on the leaf litter breakdown, with focus on microorganisms as main decomposer, in two catchments in New South Wales, Australia. The breakdown of Eucalyptus camaldulensis leaves decreased with increasing salinity by up to a factor of three. Coalmine salinity, which is characterised by a higher share of bicarbonates, had a slightly but consistently higher breakdown rate at a given salinity relative to dryland salinity, which is characterised by ionic proportions similar to sea water. Complementary laboratory experiments supported the stimulatory impact of sodium bicarbonates on leaf breakdown when compared to sodium chloride or artificial sea salt. Furthermore, microbial inoculum from a high salinity site (11,000μS/cm) yielded lower leaf breakdown at lower salinity relative to inoculum from a low salinity site (50μS/cm). Conversely, inoculum from the high salinity site was less sensitive towards increasing salinity levels relative to inoculum from the low salinity site. The effects of the different inoculum were the same regardless of salt source (sodium bicarbonate, sodium chloride and artificial sea salt). Finally, the microorganism-mediated leaf litter breakdown was most efficient at intermediate salinity levels (≈500μS/cm). The present study thus points to severe implications of increasing salinity intensities on the ecosystem function of leaf litter breakdown, while the underlying processes need further scrutiny.
authors.affiliation: Institute for Applied Ecology, University of Canberra, ACT 2601, Australia; Institute for Environmental Sciences, University of Koblenz-Landau, Fortstrasse 7, 76829 Landau, Germany.
authors.forename: Felix G
authors.initials: FG
authors.lastname: Sauer
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Fortstrasse 7, 76829 Landau, Germany; Department of Aquatic Sciences and Assessment, Swedish University of Agriculture Sciences, Uppsala, Sweden.
authors.forename: Mirco
authors.initials: M
authors.lastname: Bundschuh
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Fortstrasse 7, 76829 Landau, Germany.
authors.forename: Jochen P
authors.initials: JP
authors.lastname: Zubrod
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Fortstrasse 7, 76829 Landau, Germany.
authors.forename: Ralf B
authors.initials: RB
authors.lastname: Schäfer
authors.affiliation: National Research Centre for Environmental Toxicology, The University of Queensland, 39 Kessels Road, Coopers Plains, Queensland, 4108, Australia.
authors.forename: Kristie
authors.initials: K
authors.lastname: Thompson
authors.affiliation: Institute for Applied Ecology, University of Canberra, ACT 2601, Australia. Electronic address: Ben.Kefford@canberra.edu.au.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Kefford
mesh_terms: D001315:Australia; D018533:Biomass; D002840:Chromates / Q000633:toxicity; D003032:Coal Mining; D017753:Ecosystem; D004875:Ergosterol / Q000032:analysis; D005052:Eucalyptus / Q000187:drug effects / Q000378:metabolism*; D005658:Fungi / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D009517:New South Wales; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D054712:Salinity; D012965:Sodium Chloride / Q000633:toxicity; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D002840:Chromates; D014874:Water Pollutants, Chemical; D012965:Sodium Chloride; C016104:sodium bichromate; D004875:Ergosterol
keywords: Freshwater; Leaf breakdown; Major ions; Microorganisms; Salinization