A biological assessment of sites in the Judith River watershed, Judith Basin County, Montana : August-September 2003

22 Pages·2003·2.2 MB·English

by  Bollman, Wease

A Biological Assessment of Sites in the Judith River
Watershed, Judith Basin County, Montana August-
September, 2003
By W. Bollman
2003
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A BIOLOGICAL ASSESSMENT OF SITES IN THE JUDITH
RIVER WATERSHED,
JUDITH BASIN COUNTY, MONTANA
August-September, 2003
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DOCUMENTS
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1 2004
MONTANA STATE LIBRARY
HuEciLEANfAP..M^O-N^TtfAiNAAVE5.9620
A
report to
The Judith Basin Conservation District
Stanford, Montana
Theresa Wilhelm, Project Officer
by
Wease Bollman
Rhithron Associates, Inc.
Missoula, Montana
December 2003

INTRODUCTION
This report summarizes data collected in late August and early September, 2003
from 7 sites in theJudith River watershed, Judith Basin County, Montana. The
purpose is to describe the ecological condition ofseveral locations in the Judith River
basin using characteristics ofa biologic assemblage. This study also qualitatively
compares the datacollected in 2003 with similarly collected datafrom 2001(Bollman
2002).
Aquatic invertebrates are aptly applied to bioassessment since they are known
to be important indicators ofstream ecosystem health (Hynes 1970). Long lives,
complex life cycles and limited mobility meanthat there is ample time for the benthic
community to respond to cumulative effects ofenvironmental perturbations. A
multimetric approach to bioassessment such as the one applied in this study uses
attributes ofthe assemblage in an integrated way to measure biotic health. A stream
with good biotic health is "...a balanced, integrated, adaptive systemhaving the full
range ofelements and processes that are expected in the region's natural
environment..." (Karr and Chu 1999). The approach designed by Plafldn et al. (1989)
and adapted for use in the State ofMontanahas been defined as '... an array of
measures or metrics thatindividually provide information on diverse biological
attributes, and when integrated, provide an overall indication ofbiological condition."
(Barbour et al. 1995). Community attributes that can contribute meaningfully to
interpretation ofbenthic data include assemblage structure, sensitivity ofcommunity
members to stress orpollution, and functional traits. Each metric component
contributes an independent measure ofthe biotic integrity ofa stream site; combining
the components into atotal score reduces varietnce eind increases precision ofthe
assessment (Fore et al. 1996). Effectiveness ofthe integrated metrics depends on the
applicabilityofthe underl3dng model, which rests on afoundation ofthree essential "' '
elements (BoUman 1998a). The firstofthese is an appropriate stratification or
classification ofstream sites, typically by ecoregion. Second, metrics must be selected
based upon their ability to accurately express biological condition. Third, an adequate
assessment ofhabitat conditions at each site to be studied enhances the interpretation
ofmetric outcomes.
Implicit in the multimetric method and its associated habitat assessment is an
assumption ofcorrelative relationships between habitat measures and the biotic
metrics, in the absence ofwater qualityimpadrment. These relationships may vary
regionally, requiring an examination ofhabitat assessment elements and biotic metrics
and atest ofthe presumed relationship between them. Montana's bioassessment
protocols for macroinvertebrate assemblages were initially developed without rigorous
examination or testing and have existed as aflexible working draft for over a decade
(Bahls et al. 1992).The basic guidelines have been periodically updated (Bukantis
1998). BoHmam (1998a) has recently studied the assemblages ofthe Montana Valleys
and Foothill Predries (MVFP) ecoregion, and has recommended a battery ofmetrics
applicable to the montcine ecoregions ofwestern Montana. This metric battery hasbeen
shown to be sensitiveto impairment, related to measures ofhabitat integrity, aind
consistent over replicated saunples. There has also been recent progress in improving
bioassessment for Plains ecoregions streams. Multimetric indices usingaquatic
invertebrateswere developed by Bramblett etal. (2002) for streams ofthe Plains
ecoregions ofMontiana. These indiceswere evaluated for responsivenessto
anthropogenic disturbances, lack ofresponsiveness to natural factors, and temporal
stability. Although both ofthese revised assessment tools probably need refinement,
their use, coupled with qualitative inferences based on the taxonomic and functional
characteristics ofthe invertebrate assemblage, cein provide valuable insight into the
effects ofwater quality and physical habitat condition on the biotic integrity ofstreams.
MBTHODS
Samples were collected on August 8 and 9, 2003 by personnel ofthe Judith
Basin Conservation EHstrict. Sample designations and site locations are indicated in
Table 1 and Figure 1. The site selection and sampling method employed were those
recommended in the Montana DepartmentofEnvironmental Quality (Montana DEQ)
Standard Operating ProceduresforAquatic Macroinvertebrate Sampling (Bukantis
1998). Aquatic invertebrate samples were delivered to Rhithron Associates, Inc.,
Missoula, Montana, for laboratory and data analyses. In the laboratory, the Montana
DEQ-recommended sorting method was used to obtain subsamples ofat least 300
organisms from each sample, when possible. Organisms were identified to the lowest
possible taxonomic levels consistentwith Montana DEQ protocols.
TheJudith River is tributary to the Missouri River. Four sites in this study lie
within the Northern Rockies ecoregion, one site lies within the MontanaValley and
Foothill Pradrie ecoregion, and one site lies within the Northwestern Great Plains
ecoregion (Woods at al. 1999).
Table 1. Sample designations and locations. Sites are listed in upstream-to-
downstream order. Judith Riverwatershed. August 2001 and August-September, 2003.
Site
ID
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in this report incorporates multiple attributes ofthe sampled assemblage into an
integrated score that accurately describes the benthic community ofeach site in terms
ofits biologic integrity. In addition to the metrics comprisingthe index, other metrics
shown to be applicable to biomonitoring in other regions (Kleindl 1995, Patterson 1996,
Rossano 1995) were used for descriptive interpretation ofresults. These metrics include
the number of'dinger" taxa, long-lived taxa richness, the percent ofpredatory
organisms, and others. They are not included in the integrated bioassessment score,
however, since their performance in western Montana ecoregions is unknown. However,
the relationship ofthese metrics to habitat conditions is intuitive and reasonable.
The six metrics comprising the bioassessnaent index used for MVFP sites in this
study were selected because, both individually and as an integrated metric battery, they
are robust at distinguishingimpaired sites from relativelyunimpaired sites (Bollman
1998a). In addition, they are relevant to the kinds ofim.pacts that are present in the
Judith Riverwatershed. They have been demonstrated to be more variable with
anthropogenic disturbance than with natural environmental gradients (Bollman 1998a).
Each ofthe six metrics developed and tested for western Montana ecoregions is
described below.
1. Ephemeroptera (mayfly) taxa richness. The number ofmayfly taxa
declines as water quality diminishes. Impairments to water quality which have been
demonstrated to adversely affect the ability ofmayflies to flourish include elevated
water temperatures, heavy metal contamination, increased turbidity, low or high
pH, elevated specific conductance and toxic chemicaJs. Few mayfly species are able
to tolerate certain disturbances to instream habitat, such as excessive sediment
deposition.
2. Plecoptera (stonefly) taxa richness. Stoneflies are particularly
susceptible to impairments that affect a stream on a reach-level scale, such as loss
ofriparian canopy, streambankinstability, charmelization, and alteration of
morphological features such as pool frequency and function, riffle development and
sinuosity. Just as sdl benthic organisms, they are eJso susceptible to smaller scale
habitat loss, such as by sediment deposition, loss ofinterstitial spaces between
substrate particles, or unstable substrate.
3. Trichoptera (caddisfly) taxa richness. Caddisfly taxa richness has been
shown to decline when sediment deposition affects habitat. In addition, the presence
ofcertain case-building caddisflies can indicate good retention ofwoody debris and
lack ofscouring flow conditions.
4. Number ofsensitive taxa. Sensitive taxa are generallythe first to
disappear as anthropogenic disturbances increase. The list ofsensitive taxa used
here includes organisms sensitive to awide reinge ofdisturbemces, includingwarmer
water temperatures, organic or nutrient pollution, toxic pollution, sediment
deposition, substrate instability auid others. Unimpaired streeims ofwestern
Montana typically support at least four sensitive taxa (Bollman 1998a).
5. Percent ftlter feeders. Filter-feeding organisms are a diverse group;
they capture small particles oforganic matter, or organically enriched sediment
material, from thewater column by means ofavariety ofadaptations, such as
silken nets or hairy appendetges. In forested montane streams, filterers are expected
to occur in insignificant numbers. Their abundance increases when canopy cover is
lost and when water temperaturesincrease and the accompanying growth of
filamentous algae occurs. Some filtering organisms, specifically the Arctopsychid
caddisflies (Arctopsychespp. and Parapsychespp.) build silken netswith large mesh
sizes that capture small organisms such as chironomids and early-instar mayflies.
Here they are considered predators, and, in this study, their abundance does not
contribute to thepercent filter feeders metric.
6. Percent tolerant taxa. Tolerant taxa are ubiquitous in stream sites, but
when disturbance increases, their abundance increases proportionately. The list of
taxa used here includes organisms tolerant ofa wide range ofdisturbances,
includingwarmer water temperatures, organic or nutrient pollution, toxic pollution,
sediment deposition, substrate instability and others.
Scoring criteria for each ofthese metrics are presented in Table 2. Metrics differ
in their possiblevalue ranges as well as in the direction the values move as biological
conditions change. For example, Ephemeroptera richness values may range from zero to
ten taxa or higher. Lcirger values generally indicate favorable biotic conditions. On the
other hand, the percentfilterers metric mayrsinge from 0%to 100%; in this case, larger
values are negative indicators ofbiotic health. To facilitate scoring, therefore, metric
values were transformed into a single scale. The range ofeach metric has been divided
into four parts and assigned a point score between zero and three. A score ofthree
indicates a metric value similar to one characteristic ofa non-impedred condition. A
score ofzero indicates strong deviation from non-impaired condition and suggests
severe degradation ofbiotic health. Scores for each metric were summed to give an
overall score, the total bioassessment score, for each site in each sampling event. These
scores were expressed as the percent ofthe maximum possible score, which is 18 for
this metric battery.
Table 2. Metrics Etnd scoring criteriafor bioassessment ofmontane streams ofWestern
Montana (Bollman 1998a).
Score
Metric 3 2 1 6
Ephemeroptera taxa richness >5
Plecoptera taxa richness
Trichoptera taxa richness
Sensitive taxa richness
Percent filterers
Percent tolerant taxa
Assessing sites in the Northwestern GreatPlains ecoregion
Two bioassessment methods were employed in evaluating the data from the
Northwestern Great Pladns ecoregion site (JR 2). First, the metric battery recommended
in the Montana DEQ standard operatingprocedures (Bukantis 1998) was used. Metrics
and scoring criteriafor this method are given in Table 2. These metrics should be
considered provisional, since correlative relationships between them and meaningful
measures ofhabitat condition and water quality have not been evaluated. Assurance of
the validity ofassociations between meaningful habitat measures and biotic metrics is
particularly compelling in the Plains ecoregion, since impairment ofthe biotic health of
streams in this region is generally the result ofnon-point sources ofwater quality
degradation and habitat disturbance. Agricultural activities, including cattle grazing
and flow alteration, are predominant causes ofdisturbance. The benthic assemblages of
the Plains ecoregions etnd the performance ofthese bioassessment metrics have not yet
been examined thoroughly enough to determine whether or not the individual metrics
or their integrated scores can discriminate impaired conditions from good biotic health.
Thus, conclusions concerning bioassessment based upon these metrics must be
reggu-ded as tentative.
To facilitate scoring, metric values were transformed into a non-dimensional
scale. The range ofeach metric has been divided into four parts smd assigned a point
score between zero and three. A score ofthree indicates a metric value similar to one
characteristic ofanon-impaired condition. A score ofzero indicates strong deviation
if- from non-impaired condition and suggests severe degradation ofbiotic health. Scores
for each metric were summed to give an overall score, the total bioassessment score, for
each site in each sampling event.
Recently, multimetric bioassessment indices using aquatic invertebrateswere
developed by Bramblett et al. (2002) for streams ofthe Plains ecoregions ofMontana.
These indices were evaluated for responsiveness to anthropogenic disturbances, lack of
responsiveness to natural factors, and temporal stability. Although the indices probably
need further refinement and have notyet been accepted for steindard bioassessment
use by the State, metric values, scores, and assessmentsusing the appropriate index
are given here inTable 5. To allow for comparison with the Montana DEQ standard
procedure. Figure 1 pairs scores from each method for the Plains stream site.
For all bioassessment methods, total scores were expressed as the percent ofthe
maximum possible score and these were converted into use support classifications.
Criteria for use-support designationswere developed by Montana DEQ and are
presented inTable 3a. Scores were edso translated into impairment classifications
accordingto criteria outlined in Table 3b.
Qualitativeinterpretations
In this report, certain other metrics were used as descriptors ofthe benthic
^ community response to habitat or water quality but were not incorporated into the
bioassessment metric battery, either because they have notyet been tested for
reliability in streams ofwestern Montcina, or because results ofsuch testing did not
show them to be robust at distinguishing impeiirment, or because they did not meet
i .
other requirements for inclusion in the metric battery. These metrics and their use in
predicting the causes ofimpairment or in describingits effects on the biotic community
are described below.
• The modified biotic index. This metric is an adaptation ofthe HilsenhoffBiotic
;
'"" Index (HBI, Hilsenhoff 1987), which was originally designed to indicate organic
i
enrichment ofwaters. Values ofthis metric are lowest in least impacted
~~ "' conditions. Taxa tolerauit to saprobic conditions are also genersdly tolerant of
warm water, fine sediment and heavy filamentous algae growth (Bollman
1998b). Loss ofcanopy cover is often a contributor to higher biotic indexvalues.
The taxavalues used in this report are modified to reflect habitat and water