Primary Productivity

Primary production in Arctic lakes, Lost Pack Lake, Nunavut

Chlorophyll a (mg/g, difference from the mean value)
Graph: primary production in Lost Pack Lake, Nunavut. Click for graphic description (new window).
Note: chlorophyll a is the main pigment found in plants and algae and is a measure of primary production. Values are inferred through spectral analysis of lake sediment cores.
Source: adapted from Michelutti et al., 200510

The figure shows chlorophyll a reconstructions from Lost Pack Lake, one of six Baffin Island lakes examined for long-term trends. All lakes show dramatic increases of inferred primary production within the most recently deposited sediment, following prolonged periods of comparatively low values.10 Dating of the sediment cores indicates that these rapid increases started in the late 19th century and continue to the present. The increases are a departure, in most lakes, from relatively stable levels of primary production that persisted for millennia. A widespread increase in freshwater production over much of northern Canada is also inferred from major shifts in species composition of algae in ponds and small lakes in many areas (also detected from studies of sediment cores).11, 12 The best explanation for this change in algae is climatic warming leading to longer ice-free growing seasons and associated changes in lake ecosystems.13, 14 The changes are most pronounced in the High Arctic, but similar shifts in algal species are found in many locations in the Northern Hemisphere – with changes being more recent in temperate latitudes.15