Environmental Engineering Reference
In-Depth Information
hydroperiod. Based on ordination analysis, dissolved oxygen was the only water
quality parameter found to have a strong influence on amphibian assemblages in the
wetlands. As such, in some cases, differences in plant and animal assemblages
between wetlands with different hydroperiod durations may be driven more by the
actual presence of water and available habitat rather than changing water quality
(see Jackson (
2006
) for further discussion).
Finally, water movement through a wetland can establish important within-site
spatial differences in water quality, with contrasting levels of parameters such as
dissolved oxygen, suspended solids, nutrients, and contaminants observed between
the inflow and outflow zones (Ibekwe et al.
2007
; Diaz et al.
2012
). Trebitz
et al. (
2005
) evaluated the influence of hydrology and geomorphology on water
quality (temperature and dissolved oxygen) and other habitat parameters in Lake
Superior coastal wetlands and in some cases, found within-wetland spatial
differences due to seiche action and tributary inputs that were as large or larger
than differences between wetlands.
6.4.2 Landscape Influences
Attributes of the landscape in which a wetland occurs can influence water quality
through effects on hydrology, characteristics of water entering the system, and
localized effects on wetland microclimate. A number of studies have linked
differences in parameters such as levels of suspended solids and nutrients between
wetlands with landscape-level differences in agricultural intensity, human popula-
tion density, and point source pollution (Trebitz et al.
2007
; Morrice et al.
2008
;
Cabezas et al.
2009
). In their study, Trebitz et al. (
2007
) combined individual water
quality parameters via principal components analysis into a wetland water quality
metric that was more responsive to agricultural intensity than any single parameter
alone. Physical characteristics such as size and drainage slope of watersheds that
feed wetlands have also been found to significantly influence chemical parameters
such as pH and levels of suspended solids and nutrients (deCatanzaro and Chow-
Fraser
2011
). Differences in parameters such as temperature and pH between
forested depressional wetlands have been found to result from subtle differences
in landscape topography, forest canopy cover, and tree age and size (Batzer
et al.
2000
; Skelly and Freidenburg
2000
; Hossack and Corn
2008
). In an investi-
gation of what constitutes appropriate buffer zones adjacent to wetlands, Houlahan
and Findlay (
2004
) found that water column nutrient levels in the systems studied
were influenced by forest cover quality at over 2,000 m from the wetland edge.
6.4.3
Internal Influences
While the hydrologic variables discussed above are significant determinants of
wetland water quality, it is important to also consider the effects of internal
biological processes on chemical parameters and the physical influences that factors
