title: Susceptibility to acidification of groundwater-dependent wetlands affected by water level declines, and potential risk to an early-breeding amphibian species.
abstract: Eggs of the Western spadefoot toad (Pelobates cultripes) reached a 100% mortality in all 29 clutches deposited at a pH below 5.0 in a temporary pond of the Doñana National Park (SW Spain) throughout the wet season of 2006-2007. A similar trend was detected in a neighbouring pond. The proximity of these two ponds to a groundwater pumping area (<1.5km), prompted us to elucidate the possible links between the reduction in pond hydroperiod over past decades (1989-2008) and the decrease of groundwater pH-buffering capacity. The average hydroperiod had decreased by 4months since 1998-99 in the pond where the extensive egg mortality had occurred. The total alkalinity, and the Mg(2+)concentration had also significantly declined in the shallow water-table since 1998-99, from an average of 8.56 to 0.32meql(-1), and of 3.57 to 1.15meql(-1), respectively. This decline of the shallow groundwater buffering capacity could turn this pond more susceptible to the inorganic acidity associated with pyrite oxidation as the sediment S content was often above 0.03%. The initial ratio of S/Ca+Mg in the summer dry sediment was a good predictor of pore-water pH on re-wetting after desiccation (r(2)=0.802, p<0.01). Therefore, this ratio can give some anticipation to mitigate the impact of acidity on toad hatching before these temporary ponds are reflooded on the next wet season. Our results suggest that the long-term damage to pond water levels can trigger a potential risk of soil acidification in the presence of iron-sulphide minerals.
authors.affiliation: Department of Plant Biology and Ecology, University of Sevilla, Sevilla, Spain. Electronic address: serrano@us.es.
authors.forename: L
authors.initials: L
authors.lastname: Serrano
authors.affiliation: Doñana Biological Station-CSIC, Sevilla, Spain. Electronic address: poli@ebd.csic.es.
authors.forename: C
authors.initials: C
authors.lastname: Díaz-Paniagua
authors.affiliation: Doñana Biological Station-CSIC, Sevilla, Spain. Electronic address: carola.gomez@usc.es.
authors.forename: C
authors.initials: C
authors.lastname: Gómez-Rodríguez
authors.affiliation: Doñana Biological Station-CSIC, Sevilla, Spain. Electronic address: margarita@ebd.csic.es.
authors.forename: M
authors.initials: M
authors.lastname: Florencio
authors.affiliation: Doñana Biological Station-CSIC, Sevilla, Spain.
authors.forename: M-A
authors.initials: MA
authors.lastname: Marchand
authors.affiliation: Department of Aquatic Ecology and Environmental Biology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, The Netherlands.
authors.forename: J G M
authors.initials: JG
authors.lastname: Roelofs
authors.affiliation: Department of Aquatic Ecology and Environmental Biology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, The Netherlands. Electronic address: E.Lucassen@b-ware.eu.
authors.forename: E C H E T
authors.initials: EC
authors.lastname: Lucassen
mesh_terms: D000818:Animals; D001001:Anura / Q000502:physiology*; D060587:Groundwater / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008136:Longevity; D010063:Ovum / Q000502:physiology; D012098:Reproduction; D012621:Seasons; D012987:Soil / Q000737:chemistry*; D013030:Spain; D053833:Wetlands
chemical_list: D012987:Soil
keywords: Acid sulphate soil; Iron-sulphide oxidation; Quartz-sandy aquifer; Temporary ponds; Water-table drawdown