title: Fossil clam shells reveal unintended carbon cycling consequences of Colorado River management.
abstract: Water management that alters riverine ecosystem processes has strongly influenced deltas and the people who depend on them, but a full accounting of the trade-offs is still emerging. Using palaeoecological data, we document a surprising biogeochemical consequence of water management in the Colorado River basin. Complete allocation and consumptive use of the river's flow has altered the downstream estuarine ecosystem, including the abundance and composition of the mollusc community, an important component in estuarine carbon cycling. In particular, population declines in the endemic Colorado delta clam,Mulinia coloradoensis, from 50--125 individuals m-2in the pre-dam era to three individuals m-2today, have likely resulted in a reduction, on the order of 5900-15 000 t C yr-1(4.1-10.6 mol C m-2yr-1), in the net carbon emissions associated with molluscs. Although this reduction is large within the estuarine system, it is small in comparison with annual global carbon emissions. Nonetheless, this finding highlights the need for further research into the effects of dams, diversions and reservoirs on the biogeochemistry of deltas and estuaries worldwide, underscoring a present need for integrated water and carbon planning.
authors.affiliation: Department of Earth and Atmospheric Sciences , Cornell University , Ithaca, NY 14853 , USA.
authors.forename: Jansen A
authors.identifier: 0000-0003-3771-2039
authors.initials: JA
authors.lastname: Smith
authors.affiliation: Department of Ecology and Evolutionary Biology , Cornell University , Ithaca, NY 14853 , USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Auerbach
authors.affiliation: Department of Geosciences , University of Arizona , Tucson, AZ 85721 , USA.
authors.forename: Karl W
authors.initials: KW
authors.lastname: Flessa
authors.affiliation: Department of Ecology and Evolutionary Biology , Cornell University , Ithaca, NY 14853 , USA.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Flecker
authors.affiliation: Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853, USA; Paleontological Research Institution, Ithaca, NY 14850, USA.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Dietl
keywords: carbon emission; carbon sequestration; estuary; geohistorical records; mollusc; water diversion