An alternative approach to reconstructing organic matter accumulation with contrasting watershed disturbance histories from lake sediments.
A number of proxies, including carbon to nitrogen ratio (C:N) and stable isotopes (delta(13)C and delta(15)N), have been used to reconstruct organic matter (OM) profiles from lake sediments and these proxies individually or in combination cannot clearly discriminate different sources. Here we present an alternative approach to elucidate this problem from lake sediments as a function of watershed scale land use changes. Stable isotope signatures of defined OM sources from the study watersheds, Shawnigan Lake (SHL) and Elk Lake (ELL), were compared with sedimentary proxy records. Results from this study reveal that terrestrial inputs and catchment soil coinciding with the watershed disturbances histories probably contributed in recent trophic enrichment in SHL. In contrast, cultural eutrophication in ELL was partially a result of input from catchment soil (agricultural activities) with significant input from lake primary production as well. Results were consistent in both IsoSource (IsoSource version 1.2 is a Visual Basic program used for source separation, (http://www.epa.gov/wed/pages/models/isosource/isosource.htm) and discriminant analysis (statistical classification technique).
Water and Aquatic Sciences Research Program, Department of Biology, University of Victoria, PO Box 3020, Station CSC, Victoria, BC, V8W 3N5, Canada. biplobdas@gmail.com
Biplob
B
Das
Rick
R
Nordin
Asit
A
Mazumder
D000818:Animals; D002170:Canada; D002247:Carbon Isotopes / Q000032:analysis; D016002:Discriminant Analysis; D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water; D019015:Geologic Sediments / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D008962:Models, Theoretical; D009587:Nitrogen Isotopes / Q000032:analysis; D014872:Water Movements
D002247:Carbon Isotopes; D006812:Humic Substances; D009587:Nitrogen Isotopes