Marked Post-18th Century Environmental Change in High-Arctic Ecosystems

Abstract

Paleolimnological data from three high-arctic ponds on Cape Herschel, Ellesmere Island, Canada, show that diatom assemblages were relatively stable over the last few millennia but then experienced unparalleled changes beginning in the 19th century. The environmental factors causing these assemblage shifts may be related to recent climatic warming. Regardless of the cause, the biota of these isolated and seemingly pristine ponds have changed dramatically in the recent past and any hopes of cataloging natural assemblages may already be fruitless.

Crossing the final ecological threshold in high Arctic ponds

“…Moreover, our detailed paleolimnological studies (4, 5) do not record any evidence of past desiccation events (e.g., aberrant diatom or invertebrate assemblages, physical changes in sediment structure and texture, etc.). In fact, observations of declining water levels dovetail with our paleolimnological data from these same ponds showing that, following several millennia of relative stability, unprecedented ecological changes began in the 19th century that were consistent with warming, indicating longer-ice free periods and associated limnological changes (4,5). A subsequent metaanalysis of 55 paleolimnological profiles from the circumpolar Arctic recorded similar shifts in indicators showing that a number of ecological thresholds related to post-1850 warming were being crossed, such as changes in ice cover, availability of epiphytic substrates (e.g., aquatic moss proliferation), and/or thermal stratification (9), as well as other associated limnological changes, such as climate-related shifts in ionic and nutrient concentrations (10).…”

“…A subsequent metaanalysis of 55 paleolimnological profiles from the circumpolar Arctic recorded similar shifts in indicators showing that a number of ecological thresholds related to post-1850 warming were being crossed, such as changes in ice cover, availability of epiphytic substrates (e.g., aquatic moss proliferation), and/or thermal stratification (9), as well as other associated limnological changes, such as climate-related shifts in ionic and nutrient concentrations (10). Therefore, our long-term monitoring data, coupled with our current observations of desiccation, track the conclusion of environmental trends that began in the 19th century (4,5), but have greatly accelerated with the most recent climatic warming. Of course, in particularly wet or cool summers, these ponds may refill and maintain water levels longer than those recorded in the 2005 and 2006 seasons.…”

“…A key ''tipping point'' has now been passed: Arctic ponds that were permanent water bodies for millennia (4,5) are now ephemeral. The ecological ramifications of these changes are likely severe, and will cascade throughout the Arctic ecosystem (e.g., waterfowl habitat and breeding grounds, invertebrate population dynamics and food for insectivores, drinking water for animals, etc.).…”

“…The Cape Herschel study sites, many of which have existed for millennia (4,5), are typical of most high Arctic ponds. The basins of most of the Cape Herschel ponds are underlain by granitic bedrock.…”

Climate change and freshwater ecosystems: impacts across multiple levels of organization

“…Indeed, such approaches have revealed that long-term warming is a key driver of changes in Arctic lake communities (Douglas et al 1994;Sorvari et al 2002;Michelutti et al 2003;Smol et al 2005). A metaanalysis of 55 sediment cores, collected from lakes in the circumpolar Arctic, has provided compelling evidence of widespread shifts in algal assemblages since 1850 (Smol et al 2005).…”