Melting Alpine glaciers enrich high-elevation lakes with reactive nitrogen.
Alpine glaciers have receded substantially over the last century in many regions of the world. Resulting changes in glacial runoff not only affect the hydrological cycle, but can also alter the physical (i.e., turbidity from glacial flour) and biogeochemical properties of downstream ecosystems. Here we compare nutrient concentrations, transparency gradients, algal biomass, and fossil diatom species richness in two sets of high-elevation lakes: those fed by snowpack melt alone (SF lakes) and those fed by both glacial and snowpack meltwaters (GSF lakes). We found that nitrate (NO(3)(-)) concentrations in the GSF lakes were 1-2 orders of magnitude higher than in SF lakes. Although nitrogen (N) limitation is common in alpine lakes, algal biomass was lower in highly N-enriched GSF lakes than in the N-poor SF lakes. Contrary to expectations, GSF lakes were more transparent than SF lakes to ultraviolet and equally transparent to photosynthetically active radiation. Sediment diatom assemblages had lower taxonomic richness in the GSF lakes, a feature that has persisted over the last century. Our results demonstrate that the presence of glaciers on alpine watersheds more strongly influences NO(3)(-)concentrations in high-elevation lake ecosystems than any other geomorphic or biogeographic characteristic.
Saros
Jasmine E
JE
Climate Change Institute, University of Maine, Orono, Maine 04469, USA. jasmine.saros@maine.edu
Rose
Kevin C
KC
Clow
David W
DW
Stephens
Verlin C
VC
Nurse
Andrea B
AB
Arnett
Heather A
HA
Stone
Jeffery R
JR
Williamson
Craig E
CE
Wolfe
Alexander P
AP
D018533:Biomass; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D056890:Eukaryota / Q000378:metabolism; D005580:Fossils; D005618:Fresh Water; D005843:Geography; D057232:Global Warming; D007053:Ice; D046448:Ice Cover; D009511:New England; D010788:Photosynthesis; D026361:Reactive Nitrogen Species
D007053:Ice; D026361:Reactive Nitrogen Species