Hydrologic variability and the application of Index of Biotic Integrity metrics to wetlands: A great lakes evaluation

Abstract

Interest by land-management and regulatory agencies in using biological indicators to detect wetland degradation, coupled with ongoing use of this approach to assess water quality in streams, led to the desire to develop and evaluate an Index of Biotic Integrity (IBI) for wetlands that could be used to categorize the level of degradation. We undertook this challenge with data from coastal wetlands of the Great Lakes, which have been degraded by a variety of human disturbances. We studied six barrier beach wetlands in western Lake Superior, six drowned-river-mouth wetlands along the eastern shore of Lake Michigan, and six open shoreline wetlands in Saginaw Bay of Lake Huron. Plant, fish, and invertebrate communities were sampled in each wetland. The resulting data were assessed in various forms against gradients of human disturbance to identify potential metrics that could be used in IBI development. Our results suggested that the metrics proposed as potential components of an IBI for barrier beach wetlands of Lake Superior held promise. The metrics for Lake Michigan drowned-river-mouth wetlands were inconsistent in identifying gradients of disturbance; those for Lake Huron open embayment wetlands were yet more inconsistent. Despite the potential displayed by the Lake Superior results within the year sampled, we concluded that an IBI for use in Great Lakes wetlands would not be valid unless separate scoring ranges were derived for each of several sequences of water-level histories. Variability in lake levels from year to year can produce variability in data and affect the reproducibility of data collected, primarily due to extreme changes in plant communities and the faunal habitat they provide. Substantially different results could be obtained in the same wetland in different years as a result of the response to lake-level change, with no change in the level of human disturbance. Additional problems included limited numbers of comparable sites, potential lack of undisturbed reference sites, and variable effects of different disturbance types. We also evaluated our conclusions with respect to hydrologic variability and other major natural disturbances affecting wetlands in other regions. We concluded that after segregation of wetland types by geographic, geomorphic, and hydrologic features, a functional IBI may be possible for wetlands with relatively stable hydrology. However, an IBI for wetlands with unpredictable yet recurring influences of climate-induced, long-term high water periods, droughts, or drought-related fires or weather-related catastrophic floods or high winds (hurricanes) would also require differing scales of measurement for years that differ in the length of time since the last major natural disturbance. A site-specific, detailed ecological analysis of biological indicators may indeed be of value in determining the quality or status of wetlands, but we recommend that IBI scores not be used unless the scoring ranges are calibrated for the specific hydrologic history pre-dating any sampling year.

Standardized Measures of Coastal Wetland Condition: Implementation at a Laurentian Great Lakes Basin-Wide Scale

“…By using vegetation-typespecific faunal indicator metrics, the methods described above are adaptable to these changes (Uzarski et al 2004(Uzarski et al , 2005Albert 2008). Vegetation-based indicators are much more sensitive to wide natural fluctuations in water levels because deep waters and dewatered shorelines can alter plant communities dramatically from year to year with no change in anthropogenic disturbance (Wilcox et al 2002). However, the drawback is that metrics must be established for all vegetation zones and for locations where vegetation has been removed via human alterations.…”

“…This approach relied on inferring that measurable biotic community attributes are responses to varying levels of anthropogenic disturbance. Since the 1980s, numerous organism-based indicators have been developed or evaluated for several Great Lakes ecosystem types, including coastal wetlands (Burton et al 1999;Herman et al 2001;Simon et al 2001;Wilcox et al 2002;Lougheed and Chow-Fraser 2002;Uzarski et al 2004Uzarski et al , 2005Uzarski et al , 2014Chow-Fraser 2006;Seilheimer and Chow-Fraser 2006;Albert et al 2007;Croft and Chow-Fraser 2007;Howe et al 2007a, b;Niemi et al 2007;Martínez-Crego et al 2010;Grabas et al 2012;Calabro et al 2013;Chin et al 2015). These indicators have been calibrated against both water chemistry attributes and anthropogenic land-use gradients to relate specific biological community characteristics to anthropogenic disturbances across the Great Lakes basin.…”

A unifying approach for evaluating the condition of wetland plant communities and identifying related stressors

“…The vegetation diversity of Great Lakes coastal wetlands has long been celebrated by naturalists (Voss 1978), and contemporary Natural Features Inventories have done much to describe it (Epstein et al 2002, Albert 2003. However, the diversity and dynamics of vegetation in Great Lakes wetlands have deterred basinwide generalizations about relationships between vegetation and anthropogenic stress (Wilcox et al 2002).…”

Development of a benthic macroinvertebrate biotic index to evaluate wetland health in Northeastern Thailand

“…The majority of the published findings in the literature suggest that benthic macroinvertebrates are a beneficial tool for the biological assessment of wetlands but that the indices need to be modified (Wilcox et al, 2002; Chipps Marchetti et al, 2008). Many studies show that the structure of the benthic macroinvertebrate communities in wetlands is complex and depends on many factors, such as the vegetation structure, hydroperiod, water body area, food resources and water chemistry (Battle and Golladay, 1999;Heino, 2000;Kazancı et al, 2003;Tarr et al, 2005;Galbrand et al, 2007;Studinski and Grubbs, 2007).…”

“…Many studies show that the structure of the benthic macroinvertebrate communities in wetlands is complex and depends on many factors, such as the vegetation structure, hydroperiod, water body area, food resources and water chemistry (Battle and Golladay, 1999;Heino, 2000;Kazancı et al, 2003;Tarr et al, 2005;Galbrand et al, 2007;Studinski and Grubbs, 2007). Additional problems include the limited number of comparable sites, the potential lack of undisturbed reference sites, and the variable effects of different disturbance types (Wilcox et al, 2002).…”