Spatial and temporal dynamics of major solute chemistry among Mackenzie Delta lakes

Lesack, L. F. W., Philip Marsh, Robert E. Hecky

Limnol. Oceanogr., 43(7), 1998, 1530-1543 | DOI: 10.4319/lo.1998.43.7.1530

ABSTRACT: The Mackenzie Delta of the Canadian arctic is a complex environment, containing -25,000 lakes, where annual river flooding may exert a considerable degree of control over the ecological characteristics of lakes in the system. The solute composition of 92 lakes representing differing frequencies and durations of flooding was determined from among three clusters of lakes distributed over a north-south (N-S) gradient along the eastern margin of the delta. The solute compositions yield an end-member system of dominant solutes (shifting among Ca2+ plus HCO3-, Mg2+ plus HCO3-, Ca2+ plus SO42-) in correspondence with a gradient from frequently flooded lakes to infrequently flooded lakes. This end-member system is consistent between years and along the N-S elevational gradient of the delta. The solute composition of the frequently flooded lakes appears to be stable among years, while the composition among infrequently flooded lakes is not stable. The end-member system is consistent with the seasonal dynamics in solute composition observed for three lakes, representing differing flooding regimes, plus the dynamics of the nearest main distributary channel. The dominance of local hydrological and biogeochemical processes in about one-third of the lakes in the delta, where flooding occurs less frequently than every year, is not consistent with a common paradigm where flooding from river channels is thought to dominate the annual flushing, nutrient replenishment, and reinitialization of lacustrine ecosystems on the floodplains of major world rivers.

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