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Benthos biomonitoring is an interesting and fun way to collect information related to the biological health of an ecosystem such as a stream or lake. Benthos are large, bottom dwelling insects, crustaceans, worms, molluscs and related aquatic animals. They are good indicators of aquatic ecosystem health because they are sedentary, their life cycles range in length from months to years, they are easy to collect and identify, they are responsive to changes in water and sediment quality, they are ubiquitous, and they are not typically seen as an economic or recreational resource themselves. Benthos are used extensively to assess water quality in streams and lakes. ref
References
Ont. benthos biomonitoring network
chare@conservationontario.ca
Mayfly Stonefly Caddisfly
Biomonitoring involves the use of indicators, indicator species or indicator communities.
The presence or absence of the indicator or of an indicator species or indicator community reflects environmental conditions. Absence of a species is not as meaningful as it might seem as there may be reasons, other than pollution, that result in its absence (e.g., predation, competition, or geographic barriers which prevented it from ever being at the site) (Johnson et al., 1993). Absence of multiple species of different orders with similar tolerance levels that were present previously at the same site is more indicative of pollution than absence of a single species. It is clearly necessary to know which species should be found at the site or in the system.
Benthic macroinvertebrates are spineless animals that live on the bottom of rivers, streams, lakes and wetlands. Some of these include larval and nymph forms of insects, while others live in the water their entire lives such as crayfish, clams, and leeches. There are several advantages to using benthic macroinvertebrates as indicators of stream health.
They are present in nearly all types of water bodies year round, generally in large quantities so removing some from a sampling site will not impact the ecosystem. They are large enough to be seen and identified with the naked eye with some training. Lastly, different groups can be associated with water quality and ecosystem health because they have known and different levels of tolerance of poor living conditions and pollution.
Many insects spend their larva stage in water so their presence or absence can be an indicator of water quality. The presence of the three above larva are indicators of good water quality.
According to the Hilsenhoff Biotic Index:
Ephemeroptera (or Mayfly) has a general pollution tolerance rating of 5 (moderately sensitive)
Plecoptera (or Stonefly) has a general pollution tolerance rating of 1 (extremely sensitive)
Trichoptera (or Caddisfly) has a pollution tolerance rating of 4 (sensitive)
There are a variety of protocols one can use for collecting larva:
the Citizen’s Environment Watch (CEW) Water Quality Monitoring with Benthic Macroinvertebrates’ protocol
the Ontario Benthos Biomoni-toring Network (OBBN) protocol and
the Ontario Stream Assessment Protocol (OSAP) Rapid Assessment Approach.
Site Selection
Initial site selection was performed using GIS Arc Map (with layers from the OMNR) and Google Earth. This was followed by ground surveys to
ensure that sites existed and could be sampled. Some limitations were encountered including road accessibility, stream morphology, time and
scale of project, safety and trespassing concerns. Sites were able to be sampled throughout the watershed with a variety of adjacent land use types
noted in the field. A GIS-based analysis of land use would be a useful addition to this information. The 26 sites sampled in the 2009 season and
used in this report were chosen from over seventy possibilities. In 2010, some of these sites were revisited and three new sites were added. In
2011, 26 sites were sampled including two new ones to extend catchment coverage. Sampling site locations in 2011 can be viewed on the interac-
tive RiverWatch map on the BRWP website at Bonnechereriver.ca .
Sampling Methods
Though the RiverWatch program has been consistently focused on biomonitoring using BMIs, the physical methods of collection has been evolving
to best suit the watershed, survey goals, and time/funding available. In 2009, sampling was carried out according to the Citizen’s Environment
Watch (CEW) Water Quality Monitoring with Benthic Macroinvertebrates’ protocol (CEW 2009). Samples were collected using a “Kick and Sweep”
method, and a 500 micron mesh D net. Sample effort was based on covering a standard 40m of creek bed at each site. With this method, sampled
sections of the creek were random, which sometimes meant that more productive parts of the stream (e.g. riffle seg-
ments) were not visited. Samples were counted until 100 specimens was reached. The method of “sub-sampling ”
was somewhat crude, and left room for bias (e.g, counting the biggest specimens first).
In 2010, a method based on the Ontario Benthos Biomonitoring Network (OBBN) protocol (Jones 2010) was used to
standardize site characteristics sampled. The Kick and Sweep method was used, but sampling targeted only three
specific sections on a creek, two riffles (faster moving, shallower) and one pool (slower moving, deeper) improv-
ing habitat representation in less time. A Marchant box was used to reduce bias in counting live samples in the
field. This required transferring the sample and selecting cells to count using a random number table, until 100
specimens had been identified. While this method helped to reduce bias, it required more time at each site.
RiverWatch Report 2011 Biomonitoring and Assessment
Bonnechere River Watershed Project Pg 5
‘Kick and Sweep’ method of sample
collection. (Photo: Nascimento 2010)
In 2011, the goal was to visit as many sites as possible from the previous two years and to add a few sites to extend catchment coverage. This
meant that stream assessment times needed to be reduced as much as possible while still retaining comparability to data collected in the past. The
Ontario Stream Assessment Protocol (OSAP) Rapid Assessment Approach (OMNR 2007) was the method chosen. Sampling was done in a riffle
segment at a site and thus focuses mainly on the presence or absence of sensitive BMIs such as EPTs (mayflies, stoneflies, and caddisflies). Where
stream substrate allowed (cobbles or larger), 10 rocks were taken from the stream bed and specimens were picked off, identified, tallied and re-
leased in-situ. A rapid (20 second) kick and sweep was performed in riffle segments at sites with smaller particle sizes (gravel, sand or clay).
Indices Used For Data Interpretation
Since the use of benthic macroinvertebrates to assess stream condition is not yet standardized in Ontario, data analysis was custom designed by
the RiverWatch coordinator. Hence, as methods for collecting benthic samples changed from year to year, so did the approach for interpreting
data. In 2011, a suite of indices was selected that were appropriate for use on riffle samples, focused on the presence or absence of sensitive BMIs
such as EPTs (mayflies, stoneflies, and caddisflies) and have been used by the CEW and in the Hilsenhoff Biotic Index (Appendix C).
Data for 2009/2010 were analyzed as reported in RiverWatch 2010 (available on the BRWP website at BonnechereRiver.ca). For the 2011 data,
each of the following indices was considered separately and assigned a rating of Good, Fair or Poor. Then, the 10 indices were considered as a
suite, and a rating of overall stream health was assessed for each site.
Number of Specimens: This is a simple count of the number of specimens collected in the sample. In 2011, the OSAP rapid assessment collec-
tion method is limited by number of rocks (10 per assessment), or in finer substrates, time spent on a kick and sweep (20 seconds), in a riffle seg-
ment . A total 51 or more specimens in a sample was rated as Good, 26-50 as Fair, and 25 or less as Poor.
Number of Taxa: Higher biodiversity is considered a good indicator of ecosystem health, therefore, more taxa, or groups were considered bet-
ter. If this value is low, it could indicate that habitat or water quality is degraded. In 2011, the ranges reflected sampling of a single (riffle) habitat
only: 7 or more was rated as Good, 5-6 as Fair, and 4 or less as Poor.
% Dominant Taxon: This index considers the group that is most prevalent in a sample. If the dominant taxon is a sensitive type of BMI, it is of
less concern than if the dominant taxon was pollution tolerant. Pollution tolerance values for each group is from the Hilsenhoff Biotic Index
(Appendix C).
% EPT: Ephemeroptera (mayflies), Plecoptera (stoneflies) and Tricoptera (caddisflies) all require a rocky substrate with good concentrations of
dissolved oxygen to thrive in their nymph stage. The presence of any of these species in a sample indicates good water quality and good habitat.
For 2011, sampling methods targeted prime EPT habitat so less than 50% EPT was rated Poor, 50%-80% as Fair and more than 80% as Good.
E, P and T Presence: This index is focused on the presence of Ephemeroptera, Plecoptera, and Trichoptera separately. Where %EPT groups
these three together, this index gives one point for each of the three groups represented in a sample. This not only considers the presence of sensi-
tive BMI, but also biodiversity. If all three groups were in a sample, the rating was Good. If one or two were represented, the rating was Fair, and
if none of the groups were represented, the rating was Poor.
RiverWatch Report 2011 Biomonitoring and Assessment
Bonnechere River Watershed Project Pg 6
Plecoptera Presence: The Hilsenhoff Biotic Index (Appendix C) gives Plecoptera (or stoneflies) a pollution tolerance of 1, making stoneflies the
least pollution tolerant and therefore the most sensitive BMI group. The presence of this BMI group in a sample indicates good stream health. If
any are found, a Good rating was given. If there are none in a sample, a rating of Fair was given (to allow for seasonal variablilty, or if they have
been missed by chance). There was no Poor rating for this index.
% Midge: Midges have a relatively high tolerance for changes in water quality, and can survive in virtually any substrate type. Finding this animal
in high numbers in a sample (more than40%), could be an indicator of Poor water quality. Less than 10% midges in a given sample would be con-
sidered Good, and 10-40% would be given the rating of Fair.
% Non-Dipterian Insects: This group includes Zygoptera (damselflies), Anisoptera (dragonflies), Coleoptera (aquatic beetles), Ephemeroptera
(mayflies), Hemiptera (true bugs), Lepidoptera (aquatic moths), Megaloptera (hellgrammites), Plecoptera (stoneflies), and Trichoptera
(caddisflies). As these groups make up an important part of a healthy aquatic ecosystem, more than 45% of these groups in a sample was given a
Good rating, 25-45% a Fair and less than 25% a Poor.
Aquatic Sowbug Presence: This animal is a scavenger associated with organic decomposition and low oxygen levels. Hilsenhoff Biotic Index
gives these creatures a pollution tolerance of 8 or high (Appendix C). These BMIs are fairly uncommon in healthy systems, so finding even one in a
sample indicates the possibility of impairment. Five or more results in a Poor rating for this index.
Hilsenhoff Biotic Index (HBI): Originally developed in 1977 by Dr. William Hilsenhoff of the University of Wisconsin (Mandaville 2011, Shep-
herd 2011), this index assigns each BMI group a specific numerical value that indicates its tolerance to low oxygen levels and organic pollution.
High numbers indicate more tolerance, whereas lower numbers indicate less tolerance and therefore more sensitivity. Weighted average calcula-
tions are carried out that consider the relative abundance of each BMI group, which is then summarized into a single value. This reflects the rela-
tive nutrient status of a stream. Since the 2011 study targets sensitive riffle species, a differently weighted scale was required to compare data to
previous years and throughout the watershed. This was developed using the range of values that resulted by using the standard HBI calculation,
and dividing it into three parts to attain Good, Fair, and Poor ratings, on a relative scale specific to the Bonnechere Watershed. For 2011, an HBI of
4.25 or less was rated as Good, 4.25-4.75 as Fair, and 4.75 or higher as Poor. See Appendix C for the table of Hilsenhoff Biotic Index Tolerance
Values.
RiverWatch Report 2011 Biomonitoring and Assessment
Bonnechere River Watershed Project
For each stream assessment site in 2011, the BMI data is examined according to the 10 indices described in the previous section, and for each in-
dex, a value is calculated. Health ranges for each of the 10 indices have been summarized in the chart below. These ranges have been calculated
with reference to information from the Citizens Environment Watch, the Ontario Stream Assessment Protocol, and the Ontario Benthos Biomoni-
toring Network. Each index value will fall into one of the following categories, depending on its proximity to the health range: Good, Fair, or Poor.
Below is a chart that summarizes the index ratings used for 2011.
Defining Health Status:
In the BMI results tables on each creek sheet, stream health is indicated using colour coding as follows:
● A green dot indicates readings have fallen into the range of what would be found in a healthy site with little to no impairment. An index with a
green dot is deemed Good.
● An orange dot indicates that the value for an index is out of the range that would be expected at a healthy site. This could indicate the beginnings
of degradation, but could also be reflective of an anomaly in the data. Therefore, such an index is given the rating of Fair, and further analysis is
needed to form accurate conclusions.
● A red dot suggests that the index in question is more obviously outside of the range of what would be considered healthy, and is less likely due to
an anomaly in the data. Indices with a red dot are considered to be Poor.
An overall rating for each creek was obtained by examining the full suite of indices as follows:
7 or more green dots indicates a site that is in Good condition; 4 - 6 green dots indicates a site that is in Fair condition; 3 or less green dots indi-
cates a site that is in Poor condition
If a site was assessed in both 2009 and 2010, the 2010 result was used for comparison with 2011.
Index
2011
Good Fair Poor
Number of specimens 51 or more 26-50 0-25
Number of Taxa 7 or more 5-6 0-4
Dominant Taxon 1-4 5-6 7-8
% EPT >80% or more 50-80% <50%
E, P and T presence 3 1-2 0
Plecoptera presence 1 or more 0 N/A
% Midge <10% 10-40% >40%
% Non-Dipterian Insects >45% 25-45% <25%
Sowbug presence 0 1-4 5 or more
Hilsenhoff Biotic Index <4.25 4.25-4.75 >4.75
RiverWatch Report 2011 Biomonitoring and Assessment
Bonnechere River Watershed Project
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