Journal of Ecological Research, 4, 1-4 (2002)
BIOTIC INDEX, CONDUCTIVITY,
AND BIOLOGICAL OXYGEN DEMAND
IN THREE LOCAL STREAMS
Chad Barshinger and Nicholas Mancino
ABSTRACT
The water quality of three stream sites in Huntingdon County, Pennsylvania was
estimated by three measures: a biotic index based on macroinvertebrate
abundance, ionic conductivity, and biological oxygen demand.
Keywords: biological oxygen demand, biotic index, conductivity, macroinvertebrates,
streams, water quality
INTRODUCTION
Natural springs and streams are an important source of clean water for both animals and humans
alike. Animals living in polluted streams are less abundant and species diversity may be lower than that of
non-polluted streams (Barbour et al. 2001). Animals and humans that obtain their drinking water from
polluted streams may have mild to serious health problems. To calculate a “biotic index” of water quality,
macroinvertebrate abundance was estimated at three different sites including Muddy Run, Emma Spring,
and Ell Spring, located in Huntingdon County, Pennsylvania. Both Muddy Run and Emma spring are
subject to human pollution either from agriculture as in Emma’s case or storm water run off and littering in
the case of Muddy Run. By testing the water of the streams and calculating a biotic index for each, we
aimed to determine whether the presence of human pollution is affecting the water quality of these streams.
We hypothesized that Ell Spring should have the highest biotic index, Emma should have the second
highest index, and that Muddy Run would have the lowest index.
SITE DESCRIPTIONS
The water entering Ell Spring originates from a large, deep aquifer, and thus its flow is largely
unaffected by rain and drought. The spring is located in a forested area that appears to be unaffected by
human pollution and as a result the water in the spring should be free from pollutants associated with
agricultural run-off and other human wastes.
Emma Spring is located in an agricultural area. The source of the water supplying this spring is
probably not very deep because it was observed to have a higher flow rate during periods of rain. This
spring is within a steep ravine surrounded by large trees.
Muddy Run is a stream that runs through Juniata College and is subject to multiple human made
pollution. Muddy Run is greatly affected by rain and runoff from the streets and parking lots that surround
the college. The stream is surrounded on all sides by shrubs and grasses.
METHODS AND MATERIALS
At each of the three sites, pH and conductivity were measured using electronic meters. Maximum
and minimum water temperatures during a 24-h day were estimated at each site using max-min
thermometers. Collection of species for the biotic index was done by drawing out a map of each site and
dividing that map into grid areas. The areas were then numbered and a random numbers table was used to
select the grid area in which to obtain a sample, using a core sampler. Five samples from each site were
taken. Macroinvertebrates were later counted and identified in the laboratory using taxonomic keys. The
number of animals of each taxon collected at each site was used to calculate a biotic index of water quality
at that site (following Anonymous 1999). This index weights the abundance of taxa according to their
sensitivity to pollution.
RESULTS
The biotic index of each stream tended to be inversely correlated with conductivity (r2 = 0.9684, P
= 0.114) and biological oxygen demand (r2 = 0.9549 P = 0.136), although neither association was
significant (Figs. 1 & 2). Table 1 shows the number of organisms of various macroinvertebrate taxa
collected at each site, as well as the total number collected and the calculated biotic index). Table 2 shows
the various physical measurements taken at each site.
Table 1. Number of individuals of various taxa collected at each of the three study sites, as well as the
calculated biotic index for each site.
Ell Spring Emma Spring Muddy Run
Taxa
Amphipods
Trichoptera
Tipulidae
Fontigens nickliniana
Empididae
Chironomidae
Ephemeroptera
Planaria
Oligochaeta
Leech
Gyrinidae
Lymnaeidae
Copepod
Plecoptera
Totals
Biotic Index
22
8
3
133
1
1
1
0
0
0
0
0
0
0
169
344
178
15
3
0
0
9
0
6
0
0
0
0
0
0
211
428
0
0
1
0
0
0
9
0
14
3
1
1
1
1
30
53
Table 2. Physical measurements taken at each of the three study sites.
Physical Data
Spring
Muddy Run
Ell Spring
Emma Spring
pH
7.54
7.58
6.76
Conductivity
436
260
148.9
Biological Oxygen Demand (mg O2/mL) Temperature Max/Min (C)
0.7
18.5/13.0
0.31
9.0/8.5
0.03
10.0/9.0
Biotic Index vs. Conductivity
Biotic Index
500
400
300
200
R2 = 0.9684
100
0
0
100
200
300
400
500
Conductivity (microSiemens)
Figure 1. Association between the biotic index and the conductivity of the water at each of three stream
sites.
Biotic Index vs. Biological Oxygen Demand
500
Biotic Index
400
300
200
R2 = 0.9549
100
0
0
0.2
0.4
0.6
0.8
Biological Oxygen Demand (mg 02/ml)
Figure 2. Association between the biotic index and the biological oxygen demand of the water at each of
three stream sites.
DISCUSSION
Our prediction was partly correct in that Muddy Run had the lowest biotic index. However,
Emma Spring had a higher biotic index than Ell Spring. The biotic index seems to be affected by both the
biological oxygen demand and conductivity, as there is a strong (but nonsignificant) correlation between
these measurements and the biotic index. Another factor that may have an effect on the macroinvertebrate
life are the maximum and minimum temperatures. Muddy Run has a significantly higher temperature than
both Ell and Emma Spring, which may have affected the abundance of various invertebrates living there.
ACKNOWLEDGEMENTS
We thank Dr. Glazier for his support, guidance, and equipment. We also thank Melanie Vrabel for
estimating the biotic oxygen demand of our water samples.
LITERATURE CITED
Anonymous. 1999. Biological Indicators. <http://fluvarium.ca/bioticindex.html >. Accessed April 18,
2002.
Barbour, M.T., J. Gerritsen, B.D. Snyder and J.B. Stribling, JB. 2001. Rapid bioassessment protocols for
use in streams and wadeable rivers: periphyton, benthic macroinvertebrates, and fish.
<http://www.epa.gov/owow/monitoring/rbp/ >. Accessed April 02, 2002.