Nutrient enrichment in the High Arctic associated with Thule Inuit whalers: a paleolimnological investigation from Ellesmere Island (Nunavut, Canada)

摘要

Cultural eutrophication is one of several environmental stressors that represents a significant ecological threat as the human population continues to grow and encroach on aquatic ecosystems. However, until recently, the environmental impacts of ancient human populations that had low population densities were thought to be largely insignificant relative to those of post-industrial urban society. Based on paleolimnological and archeological data, we have shown that Thule Inuit whalers living in small, nomadic communities were altering High Arctic pond ecology centuries before industrialization. Changes in diatom species assemblage and spectrally inferred aquatic primary production indicate a period of increased production in a pond (E-Knud) on Knud Peninsula, Ellesmere Island, which can be linked to the effects of the Thule from about 810-340 years ago. This site is near the northernmost region of past Thule occupation. Input of nutrients from bowhead whale carcasses, used by the Thule Inuit for sustenance and the construction of winter settlements, as well as other Thule activities (e.g., sealing, human waste, etc.), resulted in an increase in delta N-15, which coincided with ecologically significant diatom abundance changes, including an increase in Amphora ovalis. Diatom and nutrient changes also coincided with increased primary aquatic production, as measured by spectrally inferred chlorophyll a concentration. In addition, we recorded relative increases in diatom taxa such as Craticula halophila and Achnanthidum minutissimum in the more recent sediments, which we attribute to recent climate warming, manifested by lower water levels and associated evapo-concentration. Specific conductivities recorded during three sampling years (2004, 2006, 2009) show a trend of increasing conductivity in pond E-Knud in response to declining water levels. Together these changes in diatom species abundance suggest that multiple environmental stressors, operating several centuries apart, have led to marked limnological changes in E-Knud pond.