biomonitoring

Biomonitoring the "bugs" living in the substrate at the bottom of a lake or stream is one of the most common and accurate ways of assessing the health of a lake's aquatic ecosystem.  These bugs, called macroinvertebrates, are almost always present, and are easy to sample and identify.  Done over time a credible collection of macroinvertebrate data can be can be collected by volunteers.

Benthic macroinvertebrates include larval and nymph forms of insects, while others are creatures that 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 bodes year round, generally in large quantities,
  • they are large enough to be seen and identified with the naked eye with minimal  training,
  • different specimens are easily associated with water quality and ecosystem health because they have different levels of tolerance of poor living conditions and pollution.
Site selection

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RiverWatch has collected baseline data for Kruger, Neilan and Hurds Creeks which would be ideal streams to begin adding data to and to also develop confidence in one's monitoring skill.

  • Sampling Method:

    At all but two of the sample sites, the “Travelling Kick and Sweep” method (Fig. 22) was executed using a standard D net with a 500micron mesh. Collection was performed at both pool and riffle segments to create a representative sample community of specimens. The other two sites sampled employed an Ekman Dredge, as the kick and sweep method was found to be unsafe or impractical. Kick and Sweep transects were placed at pool and riffle sections along a segment of each sample creek. Specimens from each transect were placed in a large sample bucket together. A representative sub-sample of 100 specimens were selected using a teaspoon counting method in 2009, and the Marchant Box random counting method in 2010. Benthos were identified and tallied on a field data sheet, then entered into a computer database for further analysis. The data sheet used in the 2009 sampling season can be found in the appendix.
Site Selection.
.

ite Selection:

RiverWatch has collected baseline data for Kruger, Neilan and Hurds Creeks which would be ideal streams to begin adding data to and to also develop confidence in one's monitoring skill.

Sampling Method:

At all but two of the sample sites, the “Travelling Kick and Sweep” method (Fig. 22) was executed using a standard D net with a 500micron mesh. Collection was performed at both pool and riffle segments to create a representative sample community of specimens. The other two sites sampled employed an Ekman Dredge, as the kick and sweep method was found to be unsafe or impractical. Kick and Sweep transects were placed at pool and riffle sections along a segment of each sample creek. Specimens from each transect were placed in a large sample bucket together. A representative sub-sample of 100 specimens were selected using a teaspoon counting method in 2009, and the Marchant Box random counting method in 2010. Benthos were identified and tallied on a field data sheet, then entered into a computer database for further analysis. The data sheet used in the 2009 sampling season can be found in the appendix.

 


Figure 22: RiverWatch team member performing ‘Kick and Sweep’ method of sample collection.






Figure 18, 19 & 20: Some of the interesting specimens studied as part of the biomonitoring portion of the RiverWatch Stream Assessments. Fig. 18: a large stonefly nymph; Fig. 19: the nymph of a relatively uncommon species of dragonfly; Fig. 20: A Hellgrammite larva.






Indices Used For Data Interpretation:

Methods for data collection and analysis for this study were based on that of ‘The Citizen’s Environment Watch (CEW) Water Quality Monitoring with Benthic Macroinvertebrates’ protocol and the Ontario Benthos Biomonitoring Network (OBBN) protocol. In 2009, data sheets of our own design were filled out and kept on file. In 2010, it was decided to use data sheets from OBBN so that our data may be more easily compared province-wide. Both protocols used are very similar. Below is a list of parameters we examine in our benthic samples. Each is an indicator of one or more of the following: water quality, habitat quality, presence of organic pollution, or nutrient enrichment. By investigating each of the following 10 indices, a measure of overall stream health is achieved. Each test is given the result of unimpaired, potentially impaired, or impaired. Afterwards, these ratings are used to give an indication of overall stream health. If 5 or more of these indices are unimpaired, then the stream is deemed to be Unimpaired.

% Worm:

Figure 23: Flatworms


Aquatic worms, flatworms and roundworms are included in this category. High numbers of aquatic worms in a sample can indicate excessive organic inputs and a low oxygen level. Less than 10% worms in a sample is preferred.


% Midge:

Figure 24: Red 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 your sample (>40%), could be an indicator of poor water quality. Inversely, it is highly unexpected to find none of these creatures at a site, so this may also be an indicator of negative stream impacts. Less than 10% in a given sample is best.

% Aquatic Sowbug

Being that this animal is a scavenger, it is associated with organic decomposition and low oxygen levels. These benthos are fairly uncommon in healthy systems, so finding even one in a sample indicates the possibility of impairment. Five or more will give an impaired result for this index.

Figure 25: Sowbugs


% Snail

Figure 26: Small aquatic snail


Aquatic snails feed by scraping algae from rocks, leaves, or anything else found in the substrate of their home. They have a relatively high tolerance to low levels of oxygen in the environment. Snails are said to be quite common in stream


environments, though heavy enrichment and low water velocity can result in higher numbers. It could reflect poor stream health if snails were either absent, or found in large numbers at a site. It should be noted however, that the absence of snails in a given benthic sample is generally not of major concern, unless there are other ‘red flags’ (such as presence of pollution tolerant benthos, high midge or worm count, extremely low number of taxon, etc).

Number of Taxon

High biodiversity is always a good indicator of ecosystem health, therefore, the higher the number of taxon, the better. If this value is low, it could indicate that habitat or water quality is degraded. If 11 or more taxon are found in a given sample, the site would be deemed Unimpaired. This measure is inversely related to dominant taxon.



% Dominant Taxon

A high value for dominant taxon is a concern because it indicates that one taxon is doing considerably better than the others, which creates an imbalance in the ecosystem. This can occur for different reasons such as poor water quality, limited range of habitat, or merely a recent hatch of a certain species. The type of benthic that is the most dominant in the sample makes a difference as well. For instance, it would be of more concern if the dominant taxon is a highly tolerant species, than if it were a mid to low tolerant species. This measure is inversely related to number of taxon.


% EPT

Figure 27: Mayfly Nymph


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 these species in a sample indicates good water quality and good habitat. A sample with less than 10% of these creatures would be a concern, and less than 5% would be considered impaired.

% Diptera

Figure 28: Cranefly Larva



This group describes members of the fly family who spend their larval stage in the water. This includes midges, mosquitoes, blackflies, horseflies, and craneflies. Because dipterans are an important component to a healthy stream community, extremely low or extremely high values for this group would indicate poor stream quality. For a stream to be considered unimpaired, there would have to be 20-45% dipterans in a given sample.

% Insect

Figure 29: Dragonfly nymph


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This parameter includes a large portion of the benthos we study, such as dipterans, beetles, dragonflies and EPT, just to name a few. As with the previous index, extremely low or high values are of concern. This is because benthos which are insects tend to have a lower tolerance to poor conditions and degraded water quality. An unimpaired site will have between 50-80% insects in its sample.

Hilsenhoff Biotic Index

In this portion of the study, each benthos is given a specific numerical value that indicates its pollution tolerance (PT). High numbers indicate more tolerance, whereas lower numbers indicate lower tolerance and therefore higher sensitivity. Weighted average calculations are carried out that consider the relative abundance of each benthic group, which is then summed into a single value. This reflects the relative nutrient status of a stream. If by the end a value of 6 or higher is attained, this could indicate excessive nutrient conditions, and would be of concern. See the ‘Hilsenhoff Tolerance Values Table’ in the appendix.

Summary of Indices

Though each of these indices depict important aspects of stream health, careful interpretation of the results combined with other factors such as site characteristics, history, and observations, is required. No single parameter can define the health of a sampling site.

It is also important to note that microhabitats, in which benthos live, are continuously changing. Changes can take place between 10 and 100 years, or as often as several times per year depending on individual tributaries. Ongoing studies will produce a more average rating, and help to identify non-representative results and irregular outliers. This is why it is important to gain an overall average of health and condition of the watershed through biomonitoring. Ideally, benthic sampling will be conducted once more in the Bonnechere River Watershed in another 5 years (2016) to monitor any changes.



 




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