The effect of landscape surface age on linking terrestrial productivity to higher trophic levels in lake ecosystems through methanotrophic bacteria

摘要

The landscape on the North Slope of Alaska reflects a complex glacial history, with younger surfaces (<25,000 years before present) interspersed with older surfaces, some exceeding 780,000 ybp since deglaciation. Surfaces differ in vegetation characteristics, soil chemistry, and methane flux. Dissolved organic carbon (DOC) is high in all lakes but higher in lakes on older landscapes. We compared gamma C of benthic macroinvertebrates from lakes across landscape ages to evaluate the importance of methane as a carbon source for macroinvertebrates. Four of five taxa had significantly lower gamma C in lakes on old compared to young landscapes, indicating greater reliance on methane-derived carbon. The filter-feeding clam Sphaerium had higher gamma C than other taxa, indicating less importance of methanotrophy. Other landscape factors had little effect on macroinvertebrate gamma C. Low primary production and high DOC suggest a strong link to terrestrial productivity. Methanotrophy is an important mechanism linking terrestrial DOC to lake benthic foodwebs.