Recent paleoenvironmental changes recorded in three non-anadromous lakes in Southwest Alaska: effects of climatic and vegetation dynamics on lake productivity

Abstract

"Paleolimnological investigations, landscape analyses, and repeat photographs were used to provide a long-term view (~150 yrs. BP to present) of nutrient dynamics and lake ecosystem change in southwest Alaska. Recent major changes in lake ecology and landscape are generally attributed to climate warming since the end of the Little Ice Age and to the recent warm phase of the Pacific Decadal Oscillation. Disturbances driven by climate, glacial retreat, and volcanism also contribute to changes in aquatic-driven processes. Sediment cores reveal a complex yet progressive set of changes that are expressed in the study lakes. Changes in the biogeochemical proxies began in the mid-19th to early-20th century, but major inflections occurred significantly later, most pronounced after 1950. Among these changes are increases in biogenic opal, and indicators of enhanced C and N cycling. These systems act as integrators of climatic, terrestrial, and aquatic processes without additions of marine-derived nutrient subsidies from spawning salmon and thus allow us to isolate and identify factors (e.g. productivity, spawning and rearing success of salmonids, or terrestrial nutrient inputs) important for interpreting sediment records in anadromous systems"--Leaf iii