Microbial nutrient limitation in Arctic lakes in a permafrost landscape ofsouthwest Greenland

摘要

Permafrost is degrading across regions of the Arctic, which can lead toincreases in nutrient concentrations in surface freshwaters. Theoligotrophic state of many Arctic lakes suggests that enhanced nutrientinputs may have important effects on these systems, but little is knownabout microbial nutrient limitation patterns in these lakes. We investigatedmicrobial extracellular enzyme activities?(EEAs) to infer seasonal nutrientdynamics and limitation across 24 lakes in southwest Greenland during summer(June and July). From early to late summer, enzyme activities that indicatemicrobial carbon (C), nitrogen (N), and phosphorus (P) demand increased inboth the epilimnia and hypolimnia by 74? % on average. Microbial investmentin P acquisition was generally higher than that for N. Interactions amongEEAs indicated that microbes were primarily P-limited. Dissolved organicmatter (DOM, measured as dissolved organic carbon) was strongly andpositively correlated with microbial P demand (R2 ?=??0.84 in July),while there were no relationships between DOM and microbial N demand.Microbial P limitation in June epilimnia (R2? =??0.67) and Julyhypolimnia (R2? =??0.57) increased with DOM concentration. Theconsistency of microbial P limitation from June to July was related to theamount of DOM present, with some low-DOM lakes becoming N-limited in July.Our results suggest that future changes in P or DOM inputs to these lakesare likely to alter microbial nutrient limitation patterns.