Do rural impoundments in coastal Bay of Fundy, Canada sustain adequate habitat for wildlife? / Amanda L. Loder, Mark L. Mallory, Ian Spooner, Nic R. McLellan, Chris White, and John P. Smol.

Includes bibliographical references (pages 228-230).

In Canada and elsewhere in North America,
impoundments are created in compensation for
historic wetland loss and for habitat loss due to
development projects, but these new sites are infrequently
evaluated to determine how effectively they
function. The Cumberland Marsh Region (CMR),
located at the head of the Bay of Fundy, Canada, is of
importance to migratory birds and has been subject to
300? years of anthropogenic alteration, including
impoundment creation on diked and drained tidal
marsh in the last five decades. Wetland managers have
noticed a pervasive decline in impoundment productivity
leading to reduced waterbird usage (senescence).
To understand factors that promote
senescence, we analyzed abiotic and biotic proxies
in sediment archives from six freshwater impoundments
in two coastal watersheds to assess spatial
trends across the CMR within recent decades. Our
results demonstrate that impoundment productivity is
driven by autochthonous nutrient sources (C/N
between 7.7 and 14.4), but biogeochemical conditions
can be highly variable among impoundments
despite their proximity. Biogeochemical variation
among top-of-core sediment samples from each
impoundment was generally minimal, and thus we
believe that the aging of impoundments has resulted
in low productivity and organic matter accumulation
due to dike stabilization and declines in nutrient
loading. We conclude that these freshwater
impoundments (in the CMR and likely other similar
settings) are not highly productive, and may not
provide abundant forage and optimal wildlife habitat
which is expected of these systems; adaptive management
strategies and hydrologic rehabilitation
merit consideration to enhance ecological functioning.
Understanding landscape attributes, hydrologic
dynamics, and conditions prior to and after major
human alterations should be a priority in future compensation projects.