Physical and Chemical Monitoring of Wetland Water - Wetland Techniques - page 331

Fluctuations in the presence and depth of water can also lead to greater variability in
the physical, chemical and biological attributes of wetlands as compared to other
surface waters. For example, Reeder ( 2011 ) identified the generally shallow nature of
the wetland water column as a key driver of temporal and spatial variability in
parameters such as dissolved oxygen. This can pose a challenge for wetland monitor-
ing programs aimed at detecting anthropogenic disturbance since natural variation in
biotic and abiotic assessment metrics can make it difficult to detect human effects.
Within and between-site variability has also been identified as a key challenge in
developing wetland water quality standards (Trebitz et al. 2007 ; Kusler 2011b ).

6.4 Key Factors That Determine Wetland Water Quality

An understanding of the factors that influence the physical and chemical nature of
wetland water can help identify sources of variation in these characteristics and
assist in the design and implementation of wetland monitoring studies and interpre-
tation of data derived from those studies. For the purposes of discussion, these
factors are considered separately, although it is important to realize that these often
work together and influence each other. As such, landscape effects on wetland
water quality can occur due to effects on the chemistry of water entering the
wetland as well as localized effects on biological processes within the system.

6.4.1 Hydrologic Influences

Surface water quality of a wetland integrates the combined influences of geologic
setting, hydrology, presence and activity of biota, and human activity within or near
the system (Carter 1996 ; Boon 2006 ; Azzolina et al. 2007 ). Of these, hydrology
stands as the dominant factor that establishes the “baseline” levels of dissolved and
particulate materials in wetland water. As presented by Bedford ( 1996 ) and further
discussed by Boon ( 2006 ), climate and hydrogeologic setting establish key “hydro-
logic variables” that drive biogeochemical properties of wetlands. These variables
include water source, the mineral and nutrient status of that water, and the spatial
and temporal dynamics of water in the system.
Wetland water sources include precipitation, groundwater, and overland flow
and, as would be expected, the mineral and nutrient status of each is often quite
different. For example, vernal pools and other depressional wetlands that fill largely
from precipitation commonly have low levels of dissolved solids and are more
acidic (pH 7) (Whigham and Jordan 2003 ; Colburn 2004 ), while wetlands receiv-

ing mostly groundwater input may have variable pHs and dissolved ion levels
based on underlying basin and catchment geology (LaBaugh 1989 ; Bedford 1996 ;
Carter 1996 ; Winter et al. 2001 ; Whigham and Jordan 2003 ; Cabezas et al. 2009 ;
Nelson et al. 2011 ). Groundwater-fed wetlands may also have lower temperatures

<