Assessing ecological risk in watersheds: A case study of problem...

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Environmental Toxicology and Chemistry, Vol. 19, No. 4(2), pp. 1082–1096, 2000Printed in the USA

0730-7268/00 $9.00 1 .00

ASSESSING ECOLOGICAL RISK IN WATERSHEDS: A CASE STUDY OF PROBLEMFORMULATION IN THE BIG DARBY CREEK WATERSHED, OHIO, USA

SUSAN M. CORMIER,*† MARC SMITH,‡ SUE NORTON,§ and TIM NEIHEISEL††U.S. Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268

‡Ohio Environmental Protection Agency, 1685 Westbelt Drive, Columbus, Ohio 43228, USA§U.S. Environmental Protection Agency, Office of Research and Development, Washington, DC 20460

(Received 26 March 1999; Accepted 27 May 1999)

Abstract—The Big Darby Creek watershed, a highly valued ecosystem in central Ohio, USA, threatened by intensive agricultureand suburban encroachment, served as an example of how case specifics can be applied to refine and direct the planning andproblem formulation stage of the U.S. Environmental Protection Agency’s ecological risk assessment framework. Big Darby Creekwas selected as one of five national pilot risk assessments designed to provide specific examples of how to perform an ecologicalrisk assessment and, at the same time, to refine and improve the assessment process. The case study demonstrates how characteristicsof the watershed were used to give direction to the components of establishing goals, identifying and characterizing the resourceand threats to it, selecting appropriate assessment endpoints, and developing conceptual models. The hypotheses generated in theconceptual model describe expected relationships and interactions between the ecosystem at risk, identified potential stressors, andecological effects and set the groundwork for the analysis phase that follows problem formulation.

Keywords—Ecological risk assessment Problem formulation Assessment endpoints In-stream stressors Concep-tual model

INTRODUCTION

Emphasis in the risk assessment process has increasinglyshifted from single media-based, stressor-driven approaches toa larger, ecosystem scale-approach. The U.S. EnvironmentalProtection Agency’s (U.S. EPA) guidelines, published in theFramework for Ecological Risk Assessment [1], described aprocess for ecological risk assessment that was based primarilyon single stressors in a regulatory management context. Todetermine if these guidelines could be expanded and appliedsuccessfully to a large-scale ecosystem with multiple stressorsin a community-based management context, the U.S. EPA’sOffice of Water and Office of Research and Development co-sponsored five prototype studies at the watershed scale. Thisdocument describes the application of the risk assessmentguidelines and the results of moving through the problem for-mulation process of the risk assessment, using one of thesecase studies, the Big Darby Creek watershed, Ohio, USA, asan example.

In 1993, the Ohio Environmental Protection Agency(OEPA) and the Office of Research and Development nomi-nated the Big Darby Creek watershed for inclusion in the U.S.EPA-sponsored project to develop watershed-level ecologicalrisk assessment case studies. Big Darby Creek was selectedas one of five pilot studies in the nation because of the interestdemonstrated by numerous private and public groups, a largeexisting database developed by the OEPA, the type of water-shed (small river), the diversity of stressors and sources in thewatershed, and the willingness shown by the U.S. EPA andOEPA to provide leadership. The purpose of the assessment

* To whom correspondence may be addressed([email protected]).

Presented at the American Society for Testing and Materials–U.S.Environmental Protection Agency–Society of Environmental Toxi-cology and Chemistry Symposium on Ecosystem Vulnerability, Se-attle, Washington, USA, August 17–20, 1998.

was to evaluate the potential risks to the aquatic ecosystemposed by current and future land use and management prac-tices. By clearly identifying the risks to the stream and theirpotential causes, it was hoped that the research managers andthe public could come to agree on management approachesthat would sustain the Big Darby Creek ecological system.

The Big Darby Creek watershed in central Ohio (Fig. 1)has been described by The Nature Conservancy (TNC) asOhio’s healthiest ecosystem and one of the most diverse sys-tems of its size in the United States. The watershed, whichencompasses 1,443 km2, is highly valued for its scenic beauty,high water quality, and its recreational opportunities. Big Dar-by Creek boasts exceptional aquatic diversity and is home to86 species of fish and 38 species of molluscs [2,3]. The wa-tershed also harbors 34 species of threatened and endangeredanimals and plants [4] (Appendix 1). Despite draining a majoragricultural watershed only 27.5 km from downtown Colum-bus, Ohio, it remains one of the few free-flowing rivers in theMidwest and retains a narrow strip of forest along much ofits banks [5]. Covered 200 years ago by a hardwood forestbroken only by isolated patches of tallgrass prairie, today thewatershed retains less than 10% forest cover. Still, the rivercorridor retains much greater plant and animal diversity thanmost other areas throughout the state and the Midwest [6].The watershed is located within the larger Eastern Corn BeltPlains ecoregion [7]. In Ohio, the ecoregion consists of thearea covered by the Wisconsin and Illinoisan glacier, exceptfor the north central portion that was covered by glacial lakeMaumee [8]. The ecoregion is characterized by rolling till plainwith local end moraines and contains, in addition to Columbus,the urban areas of Dayton and Cincinnati. This area is wellstudied by the OEPA and serves as the extended study locationfor some of the other papers, resulting from this problem for-mulation, in this series.

Although diversity in the Big Darby Creek watershed is

Big Darby Creek Watershed problem formulation Environ. Toxicol. Chem. 19, 2000 1083

Fig. 1. Map depicting the Big Darby Creek watershed. Big Darby andLittle Darby creeks as well as significant tributaries are identified.Small inset map shows location of the watershed in the state of Ohio,USA.

Fig. 2. The generalized ecological assessment framework from U.S.Environmental Protection Agency’s Framework for Ecological RiskAssessment [1].high compared with other watersheds, more than 10% of the

historic fish species have not been collected in recent years[8]. Mussels have also declined in diversity in the Big Darbyand Little Darby creeks since 1986. Although agricultural landuse constitutes 80% of the watershed, encroachment from Co-lumbus’ western suburbs is suspected in degradation of a majortributary that is below Ohio aquatic life use criteria [9].

Early interest in the Big Darby was promoted by MiltonTrautman, who, in The Fishes of Ohio, described and catalogedmost of the species in the watershed [8]. The Darby CreekAssociation was formed in 1968 for the protection of the farm-ing way of life in the Big Darby Creek watershed. This grouporganized efforts to oppose the construction of dams for floodcontrol, recreation, and water supply for the city of Columbusfor more than 20 years. In the late 1980s and early 1990s, anumber of organizations were beginning to come together tobetter protect the river. Several state agencies, along with TNC,formed the Darby Partners in January 1990, as a forum for allconcerned parties to exchange information and ideas concern-ing the watershed and its future. This partnership of more than60 public agencies and private organizations had the goal ofdeveloping a cooperative approach toward the protection andmaintenance of the watershed. In part because of the effortsof this partnership, and through the efforts of the Ohio De-partment of Natural Resources Scenic Rivers and the DarbyCreek Association, the Big Darby Creek was named both anOhio and a National Wild and Scenic River and was identifiedas a Last Great Place by TNC [10]. Meetings and cooperativeresearch between the Big Darby Partners and the risk assess-ment team have continued throughout the development of thecase study.

The watershed ecological risk assessment case studies wereinitiated not only to provide useful information to risk andresource managers in the area, but also to refine and help

improve the risk assessment process. This paper describes themethods used to complete the planning and problem formu-lation phases of the ecological risk assessment, the results, andthe implications of this work for improving both the Big DarbyCreek assessment and the field of watershed ecological riskassessment.

METHODS

The ecological risk assessment performed in the Big DarbyCreek watershed follows, as did the other national pilots, theguidelines provided in the U.S. EPA’s Framework for Ecolog-ical Risk Assessment [1], which are summarized by the gen-eralized ecological assessment framework (Fig. 2). This casestudy focuses on the processes involved in the planning andproblem formulation phases of this framework (Fig. 3). Theseprocesses provide the organization for this paper and includediscussions between the risk assessor and manager; compila-tion of available information on stressor characteristics, theecosystem potentially at risk, and the ecological effects; end-point selection; and conceptual model development.

The planning and problem formulation phases of the as-sessment were coordinated by a risk assessment team that wasrecruited in July 1993, after selection of the Big Darby Creekwatershed as a pilot study. Team members included aquaticbiologists, a city planner, and environmental scientists, butconsultations with experts in other disciplines occurred fre-quently. The knowledge of the team members was supple-mented with literature searches and with interviews with spe-cialists in particular areas. The team interacted with the BigDarby Partners, who represented a significant portion of the

1084 Environ. Toxicol. Chem. 19, 2000 S.M. Cormier et al.

Fig. 3. Details of the Problem Formulation Stage of the ecologicalrisk assessment framework from U.S. Environmental Protection Agen-cy’s Framework for Ecological Risk Assessment [1].

management community, throughout the planning and problemformulation process.

Discussion between the risk assessors and managers(planning)

The objective of initial discussions with the managementcommunity was to identify and reach consensus on manage-ment goals that could be used to focus the assessment. Al-though such large, regional scale goals are, by nature, valueladen and subjective [11], they must be objective and conciseenough in language and scope to be understood and acceptedby all interested parties if they are to be effectively pursued.Management goals were identified by reviewing relevant reg-ulations and the history of public interest in the Big DarbyCreek, by participating in community meetings, and throughnumerous informal conversations with residents and managersin the watershed.

Problem formulation

Describing the watershed. Having established goals, thefirst steps in problem formulation are to assess available in-formation to identify and characterize the ecosystem poten-tially at risk, ecological effects, and the associated stressorspotentially contributing to the effects (Fig. 3). Available in-formation was compiled from an extensive literature review,which included unpublished reports produced for organizationssuch as TNC, and through the best professional judgment ofwork group members. This analysis of available informationled to the selection of appropriate endpoints and drove thedevelopment of conceptual models.

Assessment endpoint selection. Assessment endpoints pro-vide the focal point for ecological risk assessments by linkingthe management goals to the specific measurements used toanalyze risk. In this stage of problem formulation (Fig. 3),

information is gathered in characterizing the ecosystem po-tentially at risk. Detected ecological effects and the stressorsand their sources are used to help select appropriate, ecolog-ically based endpoints that can provide empirical, as well asqualitative measures, relevant to the stated management goals.Suter [12] described assessment endpoints as ‘‘. . . explicitexpressions of the actual environmental value that is to beprotected.’’ In some instances the selected assessment endpointcan be directly measured. However, in many cases, an as-sessment endpoint cannot be directly measured, so a mea-surement endpoint (or suite of endpoints) is chosen that isconsidered to be directly reflective of the assessment endpoint[1].

Effective ecological risk assessment endpoints should meetcertain criteria. The endpoints should be ecologically relevant,susceptible to important stressors, and represent managementgoals and societal values [1]. Additionally, they should havean unambiguous operational definition and be amenable toprediction and measurement [12].

Conceptual model development. Specific information aboutecosystem components gathered in describing the watershedis used to relate one component to another and each to theselected endpoints in a conceptual model (Fig. 2). A conceptualmodel is a series of hypotheses based on the relationshipsamong sources of stress, stressors, effects, and endpoints. Themodel is often expressed in a diagram that graphically dem-onstrates the hypothesized relationships in the context of therisk assessment [1]. Development of a conceptual model forthe Big Darby Creek watershed was an iterative workgroupprocess conducted in association with intensive literaturesearches.

RESULTS

Establishing management goals (planning)

The management goals eventually recommended by theplanning team were refined from a rich history of interest andactivism that had grown up around the watershed. Big DarbyCreek had been locally recognized as an exceptional resourcefor more than 40 years. A dominant theme of the regulatoryand nonregulatory activity within the Big Darby Creek wa-tershed was the protection of native stream communities, bothfish and invertebrate. Ohio’s Water Quality Standards forAquatic Life [9] are based upon assessments of both fish andinvertebrate assemblages in streams. Because of this emphasis,the comprehensive management goal became protection andmaintenance of the native stream communities in the Big Dar-by Creek ecosystem. This goal did not encompass all the eco-logical values in the watershed but did provide a necessarypoint of focus for the risk assessment and one that could bewidely supported. The U.S. EPA, in conjunction with the BigDarby Partners and constituent groups, held several publicmeetings with watershed participants (Appendix 2) to developmanagement goals and achieve consensus on their formulation.Based on these discussions, management objectives were pro-posed by the risk assessment team and adopted by the BigDarby Partners in November 1994.

Management subgoals were developed that included spe-cific statements on the water quality criteria to be maintainedin the system and a qualitative statement on maintenance ofnative species. These subgoals were, of necessity, couched interms of measurement of ecological quality criteria currentlyin use in the state of Ohio. In keeping with the stated goalsand interests of the stakeholders, the subgoals were to attain


Fig. 4. Longitudinal trends by river mile for index of biotic integrity(IBI) scores measured by the Ohio Environmental Protection Agencyin (A) Big Darby Creek (1992–1993, 1986, 1979), (B) Little DarbyCreek (1992–1993), and (C) Hellbranch Run (1992–1993). In 1992to 1993, Big Darby and Little Darby creeks met the criteria for Warm-water Habitat (WWH) and in many instances exceeded the criteriafor Exceptional Warmwater Habitat (EWH). Hellbranch Run did notmeet the criteria for WWH at all locations.

criteria for designated uses throughout the watershed; maintainExceptional Warmwater criteria for stream segments havingthat designation between 1990 and 1995; and ensure the con-tinued existence of native species in the watershed.

The Ohio State Water Quality Standards specifically linkwater quality to the ability of a stream to support and maintainnative species. Ohio classifies stream reaches according to theirability to support different uses. Waters that do not meet theirdesignated uses are identified as impaired. For ecological riskassessment, the most relevant classifications are those that arebased on aquatic life [9], which specify the ability of streamsto support and maintain a community of aquatic organismssimilar to those naturally occurring in least impacted areas.The Big Darby, Little Darby, and most of the Little Darby’stributaries are classified as Exceptional Warmwater Habitat:waters having species composition, diversity, and functionalorganization comparable to the 75th percentile of statewidedesignated least impacted reference sites. Most tributaries ofthe Big Darby Creek are classified as warmwater habitat: wa-ters comparable to the 25th percentile of the identified leastimpacted sites.

Problem formulation

Land use and history. A description of the nature and his-torical and present condition of the watershed establishes thecontext within which ecological changes are detected. Big Dar-by Creek flows approximately 125 km from its headwatersnorthwest of Marysville, Ohio, to its confluence with the Sci-oto River at Circleville, Ohio. The watershed, drained by BigDarby Creek, Little Darby Creek, and 24 smaller tributaries(Fig. 1) includes part of six counties in central Ohio. Thewatershed is located in the Eastern Corn Belt Plains ecoregion[7], at the eastern edge of what was once tallgrass prairie andburr oak savannah. Native Americans are thought to havemaintained the relict prairies by setting planned fires to retardforest encroachment. With European settlement (around 1800)the fire regime was halted. The abundant marshes of the north-ern portion of the watershed were drained by the mid 1800sfor agricultural use. A productive agricultural industry existstoday, supported by the fertile but erodible soil of the glacialtill plains. Currently, the western tributaries drain almost ex-clusively agricultural areas. The northern and eastern tribu-taries drain areas of agriculture with increasing suburban andcommercial–industrial land use. The southernmost portion ofthe drainage is narrow with short tributaries draining agricul-tural land and small towns. Agricultural land use currentlycomprises more than 80% of the land use of the watershed[4].

Ecological effects. The Big Darby Creek system contains adiversity of fish and molluscs that is considered exceptionalfor streams of its size [2]. Historically, as many as 104 fishspecies [5,8] and 41 mollusc species [2] have been collectedin the watershed, although these numbers have declined inrecent years. Appendix 1 provides a list of the state and federalthreatened and endangered species occurring in the system.

Diversity of fish and molluscs has declined in the water-shed. Species counts have declined in the most recent surveysto 86 fish species and 38 mollusc species [2,3]. The federallyendangered Scioto madtom (Noturus trautmani), known onlyfrom the Big Darby Creek, and the eastern sand darter (Am-mocrypta pellucida) (under review for federal listing) havenot been collected in the watershed since 1957 and 1960, re-spectively [2]. Biological surveys by the OEPA have indicated

decreases in biological indices of fish and macroinvertebratecommunities in some stream reaches, whereas others haveshown improvement (OEPA draft report, 1999) [13]. Althoughthe total number of fish species has declined over the past 50years, longitudinal profiles of the Big Darby suggest that morerecently, improvement has occurred in the fish (Fig. 4) andmacroinvertebrate (Fig. 5) assemblages. An overall significantdecline in diversity of unionid molluscs was noted betweensurveys in Big Darby and Little Darby creeks between 1986and 1990 [3].

Stressors. Several stressors associated with urban and sub-urban land development, as well as with agriculture, affect theBig Darby Creek and its biota. Degradation of tributarystreams has been noted by the OEPA and residents in severalplaces. The watershed contains eight small cities and is locatedwithin a short distance of the city of Columbus. Although theland area in urban and suburban use is much smaller than thatdevoted to agriculture, urbanization of the Hellbranch Runportion of the watershed is occurring as the outskirts of thecities of Columbus and Hilliard expand westward. Develop-ments in the northern portions of the watershed are also an-ticipated around Marysville as industrial growth continues inthe region. The three highest priority stressors to the Big DarbyCreek system identified by TNC [4] are sedimentation, de-creased water quality, and altered hydrologic regime.


Fig. 5. Longitudinal trends by river mile for invertebrate communityindex (ICI) scores measured by the Ohio Environmental ProtectionAgency in (A) Big Darby Creek (1992, 1986, 1979), (B) Little DarbyCreek (1992), and (C) Hellbranch Run (1992). In 1992, all the sam-pling sites in Big Darby and Little Darby creeks met the criteria forWarmwater Habitat (WWH) and in many instances met the criteriafor Exceptional Warmwater Habitat (EWH). The upper portion of BigDarby Creek achieved higher ICI scores in 1992 than 1979. HellbranchRun met the criteria for WWH at only one sampling location.

Fig. 6. Longitudinal trends in minimum, median, and maximum dis-solved nitrate and phosphorous concentrations measured in the BigDarby mainstem by the Ohio Environmental Protection Agency in1992. Noteworthy elevations occur below river mile 25.

Sedimentation is listed as the highest priority stressor. Sed-iment inputs occur from soil erosion on construction sites,roadways, and agricultural fields [5]. The Qualitative HabitatEvaluation Index, used by the OEPA, includes evaluation ofsedimentation among its metrics. The Qualitative Habitat Eval-uation Index uses seven interrelated metrics that assess sub-strate type and quality; in-stream cover type and amount; chan-nel quality; riparian width and quality, and bank erosion; pool–riffle characteristics including depth, current, pool morphol-ogy, substrate stability, and riffle embeddedness; and gradient[14]. Based on these metrics, a total score is assigned to astream reach out of a possible 100 points. The QualitativeHabitat Evaluation Index scores were generally high along theBig Darby Creek mainstem, ranging from 98.5 to 63.5, withonly three scores falling below 80. One notable indicator ofsedimentation was the low occurrence of silt-free substrates.This positive habitat attribute was found only at three sites bythe OEPA in 1992, river miles 23.6, 13.5, and 3.5 (OEPA draftreport, 1999).

Decreased water quality results form nonpoint-source im-pacts, including nutrient-enriched runoff from agricultural ar-eas and untreated storm-water runoff from urbanized areas. In1992, few wastewater treatment plants were present in thewatershed and their discharge volumes were low. This stressor

was expected to increase in importance in the future. Elevatedlevels of nitrogen and phosphorus compounds are indicativeof nutrient loading from wastewater treatment plants as wellas nonpoint inputs. These types of loadings were suggestedby longitudinal trends in nitrate and phosphorous concentra-tions along the Big Darby Creek mainstem as recorded by theOEPA in 1992 (Fig. 6).

Altered hydrologic regime can result from changes in tim-ing, frequency, duration, and magnitude of flood events. Inurban and suburban areas, an increased area of impervioussurfaces (e.g., roofs, pavement) increases surface runoff, in-tensifying periods of high flow and decreasing base flow tostreams. In agricultural systems, the loss of vegetative coverin winter can result in an altered hydrologic regime. Finally,the city of Columbus has been investigating the use of BigDarby Creek as a potable water supply [2]. Withdrawal orimpoundment resultant from such use could impact the hy-drologic regime of the watershed.

Other potential stressors identified by TNC [4] includechanges in the hydrologic and alluvial processes that currentlymaintain specific habitats for native species. Stressors such ashabitat fragmentation from construction of low-head dams,agricultural conversion, and residential and road developmentmay hinder migration of fish and mussels. Potential invasionby alien species such as the zebra mussel (Driessena poly-morpha) could overshadow current stressors. The Ohio 1990Nonpoint Source survey [15] listed many stream reaches in


Table 1. Index of biotic integrity (IBI) metrics used to evaluatewading sites, boat sites, and headwater stream sites [21]

IBI metric

Head-watersitesab

Wadingsitesb

Boatsitesc

1. Total number of speciesd

2. Number of darter speciesf

% Round-bodies suckersg

3e

3—

33—

3—3

3. Number of sunfish speciesNumber of headwater species

—3

3—

3—

4. Number of sucker speciesNumber of minnow species

—3

3—

3—

5. Number of intolerant speciesNumber of sensitive species

—3

3—

3—

6. % Tolerant species7. % Omnivores8. % Insectivorous species9. % Top carnivores

% Pioneering species

333—3

3333—

3333—

10. Number of individualsh

11. %Simple lithophils3—

33

33

Number simple lithophils species 3 — —12. % DELT anomaliesi 3 3 3

a Applies to sites with drainage areas less than 20 m2 (51.8 km2).b Sites sampled with wading methods.c Sites sampled with boat methods.d Excludes exotic species.e 3 5 metric measured for this site type.f Includes sculpins.g Includes suckers in the genera Hypentelium, Moxostoma, and Eri-

myzon; excludes white sucker (Catostomus commersoni).h Excludes species designated as tolerant, hybrids, and exotics.i Includes deformities, eroded fins, lesions, and external tumors

(DELT).

Table 3. Macroinvertebrate community metrics and criteria forcalculating the invertebrate community index (ICI) and ICI scores for

evaluating biological condition [21]

Metric

Score

0 2 4 6

1. Total number of taxa Varies with drainage area2. Total number of mayfly taxa Varies with drainage area3. Total number of caddisfly taxa Varies with drainage area4. Total number of dipteran taxa Varies with drainage area5. Percent mayfly composition 0 .0, #10 .10, #25 .256. Percent caddisfly composition Varies with drainage area7. Percent tribe Tanytarsini midge

composition 0 .0, #10 .10, #25 .258. Percent other dipteran and nonin-

sect composition Varies with drainage area9. Percent tolerant organisms Varies with drainage area

10. Total number of qualitative EPTa

taxa Varies with drainage area

a EPT 5 Ephemeroptera, Plecoptera, and Trichoptera.

Table 2. Computational formulae for the modified index of well-being(Iwb) and the Shannon diversity index [21]

Modified index of well-being (Iwb)

Iwb 5 0.5 ln N 1 0.5 ln B 1 H9(no.) 1 H9(wt)

where

N 5 relative numbers of all species excluding speciesdesignated highly tolerant

B 5 relative weights of all species excluding speciesdesignated highly tolerant

H9(no.) 5 Shannon diversity index based on numbers

H9(wt) 5 Shannon diversity index based on biomass

Shannon diversity index (H9)

H9 5 2(ni)/N loge(ni)/N

where

n 5 relative numbers or weight of the ith speciesi

N 5 total number or weight of the sample

the watershed as being impacted by crop production, pasture,urban runoff, and construction. Of the tributaries, Flat Branch,Hellbranch Run, Sugar Run, and Buck Run stand out as highlyimpaired streams.

Assessment endpoint selection. Two assessment endpointswere chosen for the Big Darby Creek watershed assessment:species composition, diversity, and functional organization ofthe fish and benthic macroinvertebrate communities (endpoint1); and sustainability of native fish and mussel species (end-point 2). Each endpoint selected for the Big Darby Creek wa-

tershed is discussed below in terms of how it satisfies thecriteria outlined under the methods section.

The first endpoint includes composition, diversity, andfunctional organization of stream communities, each of whichprovides different insights into how the communities are op-erating and whether they may be impaired. The analysis ofsuch community attributes requires that large quantities of dataon species presence and abundance are reduced into an un-derstandable and useful form. The way these data are reducedresults in an operational definition and makes the endpointamenable to measurement and prediction. The OEPA has doneextensive work to develop several complementary indices [16].These indices and the metrics that comprise them were usedin the Big Darby Creek risk assessment and are briefly de-scribed below.

The index of biotic integrity (IBI) includes 12 attributes offish communities. Species richness and composition are mea-sured by the number of native species, benthic species, pelagicspecies, long-lived species, intolerant species, and percentageof tolerant species. Trophic composition is measured by thepercentage of omnivores, insectivores, and top carnivores. Fishabundance and condition are rated for percentage of hybridsand diseased fish. Each metric is given a rating of 5, 3, or 1with the IBI score being the sum of the ratings for each metric[17]. The OEPA has adapted the original IBI to account forregional and stream-specific conditions in Ohio [12,18–21](Table 1).

The modified index of well-being (Iwb) is another indexof fish communities based primarily on structural character-istics, abundance, evenness, and biomass [20–23]. The com-putational formula for the index of well-being was modifiedby the OEPA to exclude tolerant species [21], which can over-whelm the index under certain conditions (Table 2).

The invertebrate community index (ICI) uses 10 metricsthat emphasize structural attributes of macroinvertebrate com-munities in streams. Ratings of 6, 4, 2, and 0 are assigned tothe following metrics: number of taxa for total invertebrates,mayflies, caddisflies, and dipterans sampled; and percent com-postion of mayflies, caddisflies, midges, other dipterans, non-insects, and tolerant species (Table 3). The sum of the ratingsis the final score given to a site. Scores for several ICI metricsare calibrated by drainage area to account for differences in


Fig. 7. Generalized conceptual model of vulnerability outlining linksbetween land uses, management practices, stressors, and condition ofthe valued resource.

occurrence and distribution of taxa affected by stream size ororder [21,24].

Species composition, diversity, and functional organizationare strongly linked to both the regulatory context of the as-sessment and the identified goals. These characteristics ofaquatic communities are mentioned explicitly in Ohio’s waterquality criteria, which specify that the IBI, ICI, and Iwb beused to characterize aquatic communities (i.e., ExceptionalWarmwater, Warmwater Habitat). These measures also addressthe goal of preservation of the native stream communities. Ona more basic scale, fish are the aquatic organisms most likelyto evoke interest and concern among parties involved. Al-though less likely to evoke widespread interest in those sameparties, benthic macroinvertebrates are important sources offood for fish and other aquatic and terrestrial animals.

Fish occupy positions throughout the aquatic food web andare relatively long-lived; thus, they function as well as time-integrated indicators of watershed conditions. Their diets ofteninclude foods from both the terrestrial and aquatic environ-ments [25]. Because many fish species, as top consumers, alsorepresent the end product of most aquatic food webs, the totalbiomass of fishes is highly dependent on the gross primaryand secondary productivity of lower organisms [20,21]. Inaddition, feeding groups present in the community reflect en-ergy sources that predominate the system.

As noted above, many ways exist to evaluate communitycomposition, diversity, and functional organization. The IBIincorporates aspects of all three concepts [25]. In addition tometrics that target species richness and composition, othermetrics target trophic composition (which reflects the energybase and trophic dynamics of a stream), fish condition, andreproductive impairment due to habitat degradation. The OhioICI principally uses metrics of community structural attributes.Both the IBI and ICI analysis retain all the original infor-mation. The biological information routinely is disaggregatedto perform analyses on particular metrics.

Biological communities have several general responses toincreased stress [26,27]. One general response is a reductionin the number of species and increased dominance of a smallnumber of tolerant species [25,28,29]. As human influenceincreases, the number of specialist species is often expectedto decrease with a concomitant increase in the number of gen-eralist species [30]. Another general response is for biomassor total numbers of organisms to be reduced without a changein community structure [31]. In summary, impacted biologicalcommunities are expected to have lower species richness anddiversity and altered functional and/or structural organizationswhen compared with unimpacted or reference areas [17]. Otherresponses may be more specific to particular stressors and mayinvolve particular taxa. The Iwb contains both biomass andcommunity structure components and has been modified toemphasize response of native species that are thought to begenerally intolerant of environmental change.

Although development of endpoint 2 (sustainability of na-tive fish and mussel species) was thoroughly pursued, as de-scribed in detail below, it was ultimately determined to beimpractical and/or inefficient as an assessment endpoint, andwas not included in further research and analysis. Populationsustainability has been operationally defined in several ways.Most commonly, it has been assessed by inference by exam-ining critical life history processes including mortality, re-cruitment, and dispersion. If none of these processes is im-paired, then the population is concluded to be at minimal risk.However, on-going data collection methods in the Big DarbyCreek were not designed for this type of life history approach.In addition, this method does not readily lend itself to directmeasurement, so appropriate measurement endpoints weresought. The information likely to be available or collected forfish is in the form of organism and taxa counts. Karr et al.[25] admitted that biotic indices are not particularly useful forevaluating individual species. However, some of the individualmetrics collected for fish indices could be relevant to the as-sessment of native species. These include the number and bio-mass of native fish species, percent simple lithophils (fish thatrequire riffle substrates that have not been silted in for repro-duction), and number of darter species. Although capture tech-niques employed for species counts and biomass measures aretoo potentially destructive to threatened or endangered fishspecies, handling required to obtain these measures for musselsis relatively harmless [3]. Adult mussels can be sampled, iden-tified, marked, and returned to the stream undamaged bytrained individuals. Because mussels are relatively sedentary,they are likely to be observed repeatedly in the same bed.Potential measurements for mussel species include abundancewithin a bed, relative abundance of small individuals (recruit-ment), and frequency of occurrence (number of sites where aspecies occurs). Therefore the assessment endpoint could beaddressed using a series of metrics such as, for fish, numberand biomass of native fish species, percentage of simple lith-ophils, and number of darter species; and for molluscs, abun-dance of selected threatened or endangered species, distribu-tion (number of sites) of selected species, and percentage ofsmall individuals of the selected species, as a measure of re-cruitment. These metrics could be observed over time and,thus, serve as measures of increases or declines of the selectedspecies. However, they operationally define sustainability ofnative species populations in only a limited way. A strongeranalysis would focus on life history processes and populationheterogeneity for specific species in the Big Darby Creek.


Fig. 8. Conceptual model designed for the Big Darby watershed that uses fish community characteristics as the indicator of biological responseto in-stream stressors and the measure of resource health. By following colored paths, specific land use practices can be linked to in-streamstressors and these in turn can be linked to measurable response in the biotic community.


Fig. 9. Conceptual model designed for the Big Darby watershed that uses benthic macroinvertebrate community characteristics as the indicatorof biological response to in-stream stressors and the measure of resource health. By following colored paths, specific land use practices can belinked to in-stream stressors and these in turn can be linked to measurable response in the biotic community.


Nonlethal techniques for assessing genetic diversity of musselpopulations using a small tissue sample have been developed[32]. Although not currently feasible, such analyses hopefullycan be conducted in the future.

The link between fish and mollusc counts and biomass tothe management goal of sustaining native species is limited atbest. The presence of live organisms of a particular speciesmay indicate that mortality rates do not exceed reproductionrates. However, in the case of long-lived species, simple pres-ence data, without population age or size structure, does notnecessarily mean that reproduction is currently successful.Similarly, immigration or movement from undisturbed areasmay mask local reproductive impairment. For mussel species,representative estimates of total abundance, abundance of newrecruits, and frequency, all observed over time, can providesufficient information on increases and declines of populations.

Because fish occupy positions throughout the aquatic foodweb, the decline in species counts of native populations mayreflect a broader change in the ecosystem from historical con-ditions. Declines in mussel taxa or biomass may also indicatebroader community and ecosystem changes. In particular, be-cause unionid mussels depend on the fish community for dis-persal of their young, the decline of mussels may indicatechanges in the fish community.

Susceptibility of the fish metrics was discussed above. Ingeneral, species numbers and biomass are expected to declinewith increasing stress. The percent simple lithophils metricwould be expected to be particularly susceptible to sedimen-tation. Because darters make up a large number of the speciesclassified by the OEPA as intolerant, the percent darters metricwould be expected to be susceptible to nutrient enrichmentand toxic effects. Unionid mussels have been declining inabundance and diversity throughout the United States sinceapproximately 1900 [33]. They have been found to be sensitiveto sedimentation and metal contamination [3]. Because of thelimited number of metrics, the likelihood of identifying spe-cific causes of any effects is reduced. For these several reasons,the endpoint of sustainability of native fish and mussel specieswas not evaluated in this case study.

Conceptual model development

The general model (Fig. 7) is designed to link land use andmanagement practices to the condition of the valued resource,as measured by biotic indicators. The detailed conceptual mod-el developed for the Big Darby watershed was based upon thisgeneral structure. Land use practices, broadly characterized asagriculture, residential development, and industry, generatestressors that then influence the stream community as char-acterized by the IBI, Iwb (Fig. 8), and ICI (Fig. 9). The BigDarby Creek risk assessment focused on six stressors reflectiveof the priority stressors identified by a panel of experts andindependently reviewed by TNC [4]: altered stream morphol-ogy, increased flow extremes, increased sediments, increasednutrients, increased temperature, and increased toxicants (met-als and persistent organic compounds). The general schemeemployed in the rather complex model was to establish linksbetween land use and biological effects through the relation-ship of each to the in-stream stressors. The generalized rela-tionships between these three major components, and the hy-potheses generated by these models will be discussed by thisbreakdown of relationships, although the object of the riskassessment is ultimately to link manageable causes (land use

and management practices) to suspected effect (biological re-sponse).

Relationships between land use and in-stream stressors.The model versions depicted by Figures 8 and 9 share thesame initial components that link different land uses to in-stream stressors. The figures show in greater detail the sourcesand stressors associated with different land uses. These dia-grams are by necessity simplified and not all interactions arereflected. Although the six in-stream stressors noted earlier arediscussed separately here, the physical stressors of morphol-ogy, flow, and sediment are closely interconnected and shouldbe considered together in conceptual model development. Notethat a forested riparian buffer may, in many cases, act to mit-igate the in-stream stressors.

The first stressor is altered stream morphology. Direct al-teration of stream morphology includes channelization, effectsof cattle wallowing, and structures such as bridge abutmentsor levees. Channelization straightens meander patterns, resultsin linear banks, increases the gradient of the stream, removesmost habitat heterogeneity, and alters flow pattern as water isremoved rapidly and efficiently [34,35]. Upstream areas aredewatered and eroded, and downstream areas are subject toincreased channel erosion, flow variability, and sedimentation[35–37].

Increased flow extremes and changes in flow pattern con-stitute the second stressor. In a watershed, soil and groundwateract as a reservoir, providing baseflow during times of littlerain and absorbing rainfall in times of heavy rain. Wetlandsin headwater or riparian areas play a similar function in at-tenuating peak or low flows [38,39]. Construction of imper-vious surfaces in a watershed such as roofs, roads, and parkinglots resulting in unabated runoff and changes the hydrologyof a stream, which in turn alters stream morphology. Imper-vious surfaces increase the amount of water that enters thestream directly through surface runoff. Streams may subse-quently be subjected to flash floods during relatively smallrainstorms. The baseflow is also reduced because less infiltra-tion occurs into groundwater. Flash flooding causes the streambed to degrade and streambanks to erode more rapidly thannormal. The stream eventually loses access to a floodplain.Floods become more frequent and severe and increased down-stream sediment deposition is likely to result [36].

The third stressor is increased sediments. Although somesedimentation naturally occurs in all stream systems, the sed-imentation rate may be altered by changes in land use. Inaddition to loads resulting from flow alteration, sediment mayenter a stream from tributaries or from poor management prac-tices of agriculture or construction [40]. Implementation oferosion reducing no-till or conservation tillage can reduce soilwash-in from fields [5,40–42]. Impervious surfaces enhancesediment input, causing rapid wash off of materials.

Increased nutrients are the fourth stressor. Nutrients can beadded to a stream through surface water runoff, groundwater,and tile discharge, or direct addition. In the Big Darby Creekwatershed, sources of nutrients associated with agriculture in-clude fertilizer application to fields, runoff from pastures, anddirectly by defecation of livestock into the stream. In residen-tial and industrial areas, sources include lawn and garden fer-tilizers, septic systems, municipal treatment plants, and com-bined sewer overflows. Impervious surfaces increase nutrientinput from vegetation litter, garbage, domestic pets, and at-mospheric deposition [43]. Riparian vegetation is thought tomitigate nutrient inputs by trapping nutrient laden particles in


surface runoff, by adsorbing soluble phosphorus, and by en-hancing denitrification [34,44–47]. The effectiveness of suchvegetative buffer strips is reduced when subsurface tile drain-age is present.

The fifth stressor is increased temperatures. Water depthand velocity, as well as substrate type, can influence watertemperature. Stream water temperature is also affected by thetemperature of tributary waters, by the amount of solar radi-ation reaching the water surface, and by the latent heat ofvaporization from foliage. Removal of riparian vegetation rais-es the temperature of streams, often beyond the tolerance ofcool-water–adapted species [34,48–52]. The relative amountsof cooler groundwater and warmer surface water also affectstream temperature. Impervious surfaces such as roofs andpavement absorb heat from sunlight and the heated runoff thencontributes to increased stream water temperatures [53]. Ox-ygen is less soluble in warm water, so warm waters have morefrequent episodes of hypoxia than do cool waters. Warmertemperatures also accelerate release of soluble phosphorusfrom sediments [34,54].

The sixth stressor is increased levels of toxic chemicals.The addition of toxic chemicals to streams occurs not only asa result of industrial and municipal point sources, but alsofrom agricultural and residential nonpoint sources. Pesticidescan enter the stream system by surface runoff from agriculturalfields and residential lawns and gardens. Industrial point sourc-es and combined sewer overflows can introduce toxics directlyinto the stream. Increased impervious surfaces can add to theamount of toxic chemicals entering the system by facilitatingthe runoff of metals, oil, grease, and other materials depositedon the surfaces [43]. Toxic substances adsorbed to particulatematter may be intercepted by riparian vegetation, thereby mit-igating potential adverse impacts.

Relationships between in-stream stressors and biologicalresponse in the fish community. Morphologic changes result-ing from channelization, altered flow regime, and increasedsedimentation decrease pool and riffle habitat (Fig. 8). Byreducing the distinction between habitat types, habitat hetero-geneity is reduced or lost [34,35]. Loss of riparian vegetationcauses a loss of cover and shelter areas for many species offish, because of the loss of woody debris and shade [55]. Thedecreased area in pool and riffle habitat results in decreasedabundance of the species dependent on these areas, especiallydarters, madtoms, and sculpins. Simple lithophils also are af-fected.

Flow extremes alter stream morphology, and hence resultin many of the changes to communities noted above. Increasedflooding frequency increases erosion and reduces the perma-nence of habitat, resulting in decreases in pool and riffle habitat[56]. Rainbow darters, which spawn in fast current riffle habitatand forage in exposed microhabitats, are particularly suscep-tible to flash floods [57]. Increased frequency of low- or no-flow conditions increases temperature and hypoxia stress, aswell as temporarily reduces habitat. Reduction in pool andriffle habitat is expected to result not only in reduction ofspecies associated with this type of habitat, but also to increasethe proportion of pioneering species [58].

In a stream, sediment consists of both suspended solids thatcontribute to turbidity and larger particles that settle and con-tribute to siltation. Increased siltation modifies habitat by fill-ing in pools and smothering cobble and gravel substrates inriffles and runs [59]. Herbivores, benthic insectivores, and sim-ple lithophils are most susceptible to siltation. Reported effects

include physiologic stress from clogged gills and smotheringof eggs and larvae [60]. Extreme turbidity can also hindervisually foraging fish.

Increased concentrations of nitrogen, phosphorus, and or-ganic matter increase algal and microbial production. Moderatenutrient loadings tend to increase fish production [26,61]. Om-nivores, which can take advantage of the increased algalgrowth, have been shown to increase in dominance under theseconditions, resulting in higher overall fish biomass. Extremenutrient loading coupled with organic matter loading (e.g.,from untreated sewage or animal waste) promote the growthof filamentous algae and fungi, which can smother substratesand contribute to nocturnal hypoxia from microbial decom-position. Because of the reduced capacity of water to holdoxygen at higher temperatures, temperature increase can fur-ther intensify hypoxic conditions.

Because of the diversity of mechanisms of action of dif-ferent toxic chemicals, much less the toxic solutions comprisedof several chemicals, drawing generalizations of communityresponse is difficult. The metric for the percentage of defor-mities, fin erosion, lesions, and tumors (DELT anomalies) re-sponds to the presence of toxicants, and in heavily impactedareas, many IBI metrics are expected to decrease, includingtotal number of species, number of individuals, and biomass[62].

Relationships between in-stream stressors and biologicalresponses in the benthic macroinvertebrate community. Al-tered stream morphology and increased flow extremes are ex-pected to influence the invertebrate community by increasingerosion and impermanence of habitat and increasing no-flowperiods. The qualitative Ephemeroptera (mayflies), Plecoptera(stoneflies), and Trichoptera (caddisflies) (EPT) metric is ex-pected to be the most sensitive of the invertebrate metricsbecause it uses samples from natural substrates and combinessamples from several different habitats [21,24]. However, be-cause the EPT metric also responds to many other stressors,the EPT metric is not expected to be able to discriminate thisparticular stressor.

Increased sedimentation contributes to the reduction of in-vertebrate habitat by silting of cobble and gravel substrates[63]. Adhering fine particles can cover body surfaces of streaminsects, including their respiratory structures [64]. The qual-itative EPT metric is expected to respond to siltation [64,65].High turbidity reduces feeding efficiency in suspension feedersby effectively diluting the food source with inorganic partic-ulates.

Nutrient loading effects on benthic macroinvertebrate com-munities are similar to those noted above for fish. Moderatenutrient loading generally increases production and has beenlinked with increased diversity of many streams. High nutrientand organic matter loading shifts community composition totolerant organisms, particularly chironomids and oligochaetes,while reducing EPT numbers [54,66]. Nutrient loading canoperate synergistically with sedimentation to reduce substrateavailability for these taxa [67]. The combination of increasesin tolerants and decreases in intolerants would be expected toresult in an overall decrease in the numbers of species. Theresponse of a suite of organisms that are tolerant of organicenrichment is expected to be a good discriminator of thisstressor type. Removal of riparian trees increases sunlight onthe water, which increases algal production and temperatureand also decreases the oxygen-holding capacity of the water.This will contribute to increases in tolerant and decreases in


intolerant organisms. Increased temperature can also changethe temporal segregation of insect species and may interferewith rates of reproduction and growth [67].

Because of the variety of toxic chemicals and organismalresponse, drawing generalizations about the response of theICI and component metrics is difficult. Some of the inverte-brate groups and ICI metrics that respond to organic pollution(low dissolved oxygen and increased ammonia concentrations)also respond to toxic contamination. These organisms tend toinclude dipterans and noninsect species and many of the oli-gochaetes [24,62,68,69].

Risk hypotheses. Seven hypotheses were developed that de-scribed relationships in the Big Darby Creek watershed sug-gested by the conceptual model. The first three have beentested (OEPA draft report, 1999) [13] and the last four are indevelopment.

Hypothesis 1: Community structure and function will de-cline downstream of identified point sources.

Hypothesis 2: No differences exist in community structureand function among subwatersheds.

Hypothesis 3: No differences exist in community structureand function among time periods.

Hypothesis 4: An increase in certain land uses or land useactivities will result in a change in the IBI and/or the ICI.Broad historical changes in the watershed communities hadalready occurred and were not dealt with in the assessment.The analysis would focus instead on specific hypotheses re-lated to more recent and anticipated future changes in land useand land use activities in the Big Darby watershed. An increasein the proportion of land use as urban and suburban will resultin a decrease in the IBI and/or ICI. An increase in the pro-portion of agricultural land in no-till agriculture will result inan increase in the IBI and/or ICI.

Hypothesis 5a: An increase in certain land uses or land useactivities will result in an increase in the intensity or spatialor temporal extent of in-stream stressors. Modeling studiesconducted by Gordon and Simpson [5,6] contributed substan-tially to the description of land use–in-stream stressor rela-tionships and gave direction to the hypotheses generated inthis category. Stronger relationships exist between specificland use activities and in-stream stressors that are connectedby a line in the conceptual model diagrams. More than oneland use activity may contribute to the amount or intensity ofan in-stream stressor. For example, an increase in the amountof channelization and impervious surface will result in in-creased flow extremes, including flood frequency. A key com-ponent of this category of hypotheses is that decreasing theextent of forested riparian area will increase flow extremes,sedimentation, nutrients, and stream temperature.

Hypothesis 5b: An increase in the intensity, or spatial ortemporal extent of in-stream stressors will result in a changein the biological community as quantified by ICI and IBI met-rics and species abundances. As with hypothesis 5a, strongerrelationships exist among the in-stream stressors and biologicalresponses joined with a line in the conceptual model diagrams.As can be seen, one stressor can cause an entire suite of bi-ological changes. For example, an increase in the frequencyof low or no flows is expected to result in a decrease in thepercentage of headwater species, minnows, and pioneering fishspecies, and a decrease in the number of species found in thequalitative EPT sampling.

Hypothesis 6: The pattern of response of the stream com-munity can discriminate among the different types of stressors.

The best discriminating responses will be those that respondprimarily to one type of stressor, as shown in the conceptualmodel diagrams. For example, finding a decrease in the per-centage of Tanytarsini midges along with an increase in thepercent of toxic-tolerant invertebrate species, percent Crico-topus species, and percent DELT anomalies found in fish isexpected to be consistently associated with an increase in theconcentrations of toxic chemicals in the water.

DISCUSSION AND CONCLUSIONS

The ecological risk assessment framework was applied atthe watershed scale and the specifics of a case study were usedto describe how the framework served the process at this levelof ecological organization. Biotic community-type metricswere identified as the most effective assessment endpoints formeasurement of effects of land use practices in the Big DarbyCreek watershed. Specific in-stream stressors that can belinked to land use or land use practices were identified asmeasurable median effects. These stressors could in turn belinked to changes to the community-type endpoints and en-hance the possibility of correlating cause and effect from eitherdirection. Hypotheses that evolved in conceptual models sug-gested approaches to analyses that could be first descriptiveand ultimately predictive management tools. The Big Darbyserved as a case study example of how the problem formulationstage of an ecological risk assessment conforms to and is de-fined by a specific ecosystem, while still maintaining a gen-eralized structure that can provide information between andacross different ecosystem types.

The problem formulation stage of ecological risk analysisleads into the analysis stage. The hypotheses generated fromthe conceptual model describe the approach that will be usedfor the analysis phase and the types of data and analytical toolsthat will be needed [1]. With the completion of the Big Darbyproblem formulation, on-going analyses are being conductedthat will ultimately be integrated into risk characterization andimplemented in risk management. Specific analyses that grewout of the problem formulation of the Big Darby Creek wa-tershed ecological risk assessment will be discussed in thepapers that follow [13,27,70,71].

These watershed case studies were initiated not only toprovide examples of ecological risk assessments, but also torefine and help improve the risk assessment process. Applyingthe principles of ecological risk assessment in the context ofthe Big Darby watershed provided benefits to both the as-sessment and to the development of risk assessment methodsfor watersheds. The risk assessment process provided a usefulway to organize and communicate information, articulate goalsand objectives, and link scientific studies to policy goals andobjectives. The Big Darby Creek case study illustrated the needfor up-front discussions with interested parties and managersin the watershed. The study provided an example of an as-sessment that was more effectively focused by identifying wa-tershed attributes valued by the community, rather than by firsttrying to identify all the possible stressors. In addition, theBig Darby Creek study produced conceptual models that canserve as models for other assessments involving multiplestressors.

Finally, the Big Darby Creek case study extends severalchallenges to the risk assessment community. The timelinessof these assessments can be improved by using our experi-ences, as well as those of the other case studies, to reduce theamount of time needed to complete planning and problem


formulation. The analysis of the effects of multiple stressorsat the community level in a watershed will require developmentof models and stressor–response relationships that do not cur-rently exist. A better foundation will evolve for the watershedassessments of the future as the experiences, methods, anddatabases of more watershed risk assessments are integratedand synthesized.

Acknowledgement—We would like to thank Mike Millward for edi-torial assistance, Randy Bruins for an exhaustive literature search andreview, Suzanne Marcy for initiating the project, and the Big DarbyPartners and the folks in the watershed who made this study possible.This document has been reviewed in accordance with U.S. EPA policyand approved for publication. Approval does not signify that the con-tents necessarily reflect the views or policies of the Agency nor doesmention of trade names or commercial products constitute endorse-ment or recommendation for use.

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APPENDIX 1Big Darby Creek watershed threatened and endangered species [4]

(Ohio Department of Natural Resources, unpublished data)a

Scientific name Common nameFederalstatus

Statestatus

FishAmmocrypta pelluci-

dumEastern sand darter C

Erimyzon sucetta Lake chubsucker TEtheostoma camurum Bluebreast darter TEtheostoma maculatum Spotted darter EEtheostoma tippecanoe Tippecanoe darter THiodon alosoides Goldeye EIchthyomyzon fossor Northern brook lam-

preyE

Noturus stigmosus Northern madtom ENoturus trautmani Scioto madtom E E

MusselElliptio c. crassidens Elephant ear EEpioblasma rangiana Northern riffle shell E EEpioblasma triquertra Snuffbox ELampsilis ovata Ridged pocketbook ELigumia recta Black sandshell TMegalonaias nervosa Washboard EPleurobema clava Northern clubshell E EQuadrula c. cylindrica Rabbitsfoot ESimpsonaias ambigua Salamander mussel CTruncilla donaciformis Fawnsfoot EVillosa fabalis Rayed bean E

BirdLanius ludovicianus Loggerhead shrike C E

PlantAmoracia lacustus Lake-cress TAster drummondi Drummond’s aster TCarex bicknellii Bicknell’s sedge TCuscuta glomerata Glomerate dodder TCypripedium reginae Showy lady’s-slipper TDelphinium exaltatum Tall larkspur CGentiana albar Yellowish gentian TLathyrus venosus Wild pea EMelica nitens Three-flowered melic EMyriophyllum hetero-

phyllumTwo-leaved water-mil-

foilE

Rosa blanda Smooth rose TSilene regia Royal catchfly CSporobolus heterolepis Prairie dropseed T

a C 5 species of concern; T 5 threatened; E 5 endangered.

APPENDIX 2Participants in the Big Darby Creek watershed

Watershed levelDarby Creek AssociationOperation FuturePrivate businessesResidents and neighborhood associationsLocal government agencies and officials (township, town, city,

county)

State levelMid Ohio Regional Planning CommissionOhio Department of Natural ResourcesOhio Environmental Protection AgencyOhio State University

National levelThe Nature ConservancyU.S. Environmental Protection AgencyU.S. Geological SurveyU.S. Department of Agriculture (USDA) Agricultural ExtensionServiceUSDA Agricultural Stabilization and Conservation ServiceUSDA Natural Resource Conservation Service

All levelsBig Darby Partners

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