Effects of agricultural encroachment and drought on wetlands and shallow lakes in the Boreal Transition Zone of Canada / S.E. Bayley, A.S. Wong, and J.E. Thompson.

Includes bibliographical references (pages 27-28).

The ecoregions along the southern edge of the
Boreal Plains have experienced rapid and extensive agricultural
encroachment over the last 60 years. Over 200 wetlands and
shallow lakes in central and northern Alberta and northeastern
British Columbia, Canada were surveyed along an agricultural
encroachment gradient to investigate the effect of land use on
water quality between 2005 and 2007. Study wetlands were
typically small (median 29.8 ha), shallow (median 0.8 m) and
highly eutrophic (median 148 μgTP L−1). Wetlands in the
southern Boreal Plains were regionally variable and dynamic.
Drought in 2006 caused significant increases in TP, TN, chlorophyll
a (chla), conductivity, silica and significant decreases
in maximum depth and light penetration. Increased agricultural
activity within a 1.6 km buffer surrounding wetlands enhanced
nutrients but not chla concentrations or submersed aquatic
vegetation (SAV) coverage. Wetlands with higher amounts of
agriculture in the buffer zone tended to be shallower with
decreased secchi depths. Due to shallow depths, SAV thrived
even under hypereutrophic conditions with high agricultural
encroachment in the buffer zone. Our study suggests that SAV
has a significant role in maintaining clear water states in Boreal
Transition Zone wetlands and shallow lakes through its ability
to suppress concentrations of chla and TP.