Determining and Using Reference Condition in Biological Assessments IV
Presiding: T Whittier, Dynamac Corporation; B Hughes, Oregon State University
NB32C-01 INVITED 10:30h
Identifying Reference Conditions in Highly Disturbed Coastal Great Lakes Regions
Identification of reference conditions in highly modified landscapes poses a challenging problem. We identified "least disturbed" conditions within Great Lakes coastal wetland basins, based on the degree of anthropogenic disturbances, including road density, agricultural and urban land use, population and point source density. Reference sites were identified for the entire Great Lakes Basin and then uniquely in two ecoregions (the Northern Great Lakes (NGL) and Erie-Ontario Lowlands (EOL)). The reference threshold metric for all NGL wetlands combined was 0.03, while that of the EOL wetlands was 0.37, approximately a 10-fold difference, illustrating the high level of underlying disturbance in the EOL. In the absence of minimally impacted conditions in the EOL, we are evaluating the possible use of reference communities characterized for the entire Basin as an alternative. To eliminate differences due to underlying variation and climate, we included only those fish species that were distributed across the entire Great Lakes Basin. Fish community composition and species traits at EOL reference sites were than compared to those for the entire Basin. Observed versus expected species and traits were related to the human disturbance gradient (HDG) to diagnose potential causes of impairment and assess potential for restoration for the EOL reference wetlands.
NB32C-02 INVITED 10:45h
Zoobenthic Indicators of Environmental Condition At Great Lakes Coastal Margins Derived From Standardized Multivariate Analyses Across Anthropogenic Stress Gradients.
We used multivariate methods to derive and map multiple indices of zoobenthic community composition across anthropogenic stress gradients at Great Lakes coastal margins (shorelines - 10 m depth). We collected up to 24 benthic samples and measured environmental characteristics in each of 150 "segment sheds", ranging from minimally disturbed (=reference) to greatly modified. "K" distinct suites of co-occurring biota from minimally stressed locations were identified using cluster analysis. Discriminant function analysis identified the environmental attributes of sample locations best distinguishing each of the suites (=habitat types). Benthic community data of all samples from each habitat type (ranging across the entire stress gradient) were individually ordinated. The benthic taxa best characterizing the ends of each stress gradient were used to create a gradient-specific biotic index with a standardized scale (0=minimum, 100=maximum stress) for each habitat type, providing a stress-specific score for each sample. Contour surface analysis of mapped sample-specific scores shows the spatial pattern and limits of the overall biotic response to stress, independently of habitat type. The spatial concordance between biotic index scores and environmental stress can indicate the degree to which equivalent-to-reference conditions exist in a particular area.
NB32C-03 11:00h
Determination of Diatom Reference Communities and Restauration Goals for Streams in Quebec
The aim of the study was to determine biological reference conditions of 126 stream sites using diatom community structures. To address these questions, we created stream typology using eco-physiographical characteristics based on ecoregion, watershed physiographical characteristics (area, geology, etc.) and hydromorphological characteristics (width, substrate, etc.). Twenty-two groups were created: five in the Canadian Shield (CS), seven in the Appalachians (AP) and ten in the St. Lawrence Lowlands (SLL). This study allowed to identify restauration goals based on diatom communities for each of the eco-physiographical groups. These reference communities represent biological restauration goals adapted for each eco-physiographical type. The results showed that CS sites should have similar community structures in natural conditions, dominated by generalist and acidophilic oligotrophic taxa due to the dominance of granitic rocks in this ecoregion. AP and SLL sites should have similar community structures in natural conditions, dominated by generalist and alcalin oligotrophic taxa due to the dominance of sedimentary and metamorphic alcalin rocks in those ecoregions. One group of sites located in the North-eastern part of AP and two groups located at the foot of SLL should have generalist, alcalin and acidophilic oligotrophic taxa due to the presence of granitic rocks and wetlands in the watershed.
NB32C-04 INVITED 11:15h
Site Classes, Reference Conditions, and Multimetric Indexes for Mississippi Wadeable Streams
In December 2000, Mississippi initiated a project to develop reference conditions for quantitative biological evaluation of the impairment status of its wadeable streams. Five hundred thirty-five (535) samples were collected from 475 sites and included field chemistry, laboratory analytical chemistry, physical habitat quality assessment (including particle size distribution), and benthic macroinvertebrates. Physical and chemical criteria were used to define sites as reference, subreference, and stressor sites; Bray-Curtis similarity coefficients and non-metric multidimensional scaling (NMDS) were used to group reference and subreference sites into five site classes, or bioregions. A suite of 82 metrics was calculated for all samples and tested for their capacity to detect stressor conditions; a final set of 20 metrics distributed among the five bioregions (6-7 per site class) was identified. Four alternate metric suites per bioregion were tested for discrimination efficiency (DE), and a single index (Mississippi-Benthic Index of Stream Quality [M-BISQ]) selected for each. The five separate multimetric indexes have an overall coefficient of variation of 10.6%, a 90% confidence interval of ±10 points on a 100-point scale, and a mean DE of 91.8%. The 25th percentile of the reference site M-BISQ distribution for each site class is specified as the impairment/nonimpairment threshold.
NB32C-05 11:30h
An Examination of References for Ecosystems in a Watershed Context: Results of a Scientific Pulse in Redwood National and State Parks, California
A multidisciplinary pulse examined three pristine streams in old-growth redwood forests in northern California to motivate discussions about the characteristics of reference sites for stream and riparian ecosystems. We concluded that useful reference sites need not be pristine, but must be rich in data linking physical and biological processes and frame conditions in a watershed context. It is particularly important that the data constitute the present status of an historical array. Not requiring pristine conditions allows data-rich watersheds with a spectrum of conditions to be incorporated into a regional reference framework. Reference watersheds offer real-world examples of how ecosystems function over time. Reference parameters taken from various locations in a region offer first-cut comparisons that can lead to deeper, more contextual analyses. Analytical references can reveal disturbance-related departures from conditions predicted with simple assumptions about some aspects of system behavior. All three reference types (reference sites, reference parameters, analytical references) have their strengths and weaknesses and can be used in combination to inform management decisions regarding these complex systems.