Water "bugs" (macroinvertebrates such as insect larvae, snails, crawfish, sowbugs, clams, aquatic worms and leeches) are excellent indicators of water quality, as they live much of their life cycle in the same area of a stream or lake. This lesson demonstrates how to collect stream debris samples, locate, identify and sort "bugs" within the samples, and evaluate water quality based on species diversity and population. Students of all ages can also gain some understanding of the basic causes and significance of water quality problems, as well as potential solutions.

Objectives:

Collect stream debris samples from suitable habitats (or have the sample brought to them)

Locate and identify macroinvertebrates in the samples

Evaluate water quality based on species diversity and population

Understand basic causes and significance of water quality problems along with potential solutions

Method:

Ideally, students will be taken to a suitable (safe and wadeable) stream or lake where collection techniques will be demonstrated. If possible, students will be able to collect samples on their own in order to better learn collection techniques. If students cannot go to a water body, instructor can go before the demonstration and collect a large enough sample to divide evenly between groups. After sample collection is complete, students will pick through the debris to locate and then identify macroinvertebrates that can be used to estimate water quality.

Background:

Macroinvertebrates are a large group of organisms whose common element is that they lack a backbone. They range from such varied creatures as jellyfish, octopus, worms and leeches, to oysters, clams and snails, to crabs, crawfish and insects. They can be as large as giant squid in the ocean which reach several feet in length or smaller than a flea. Fortunately, what this experiment is looking for falls somewhere in between.

Aquatic macroinvertebrates include primarily larval forms of both common and uncommon insects. Commonly seen insect larvae include dragon flies and damselflies. Less common insects include stoneflies, mayflies, alderflies, midge fly and blackfly larvae. Non-insect indicators include snails, crawfish, sowbugs, clams, aquatic worms and leeches. These and a variety of other macroinvertebrates can be identified using an easy to read "Bug Sheet" which gives generalized body patterns for each of the indicator organisms along with brief characteristics. The sheet also shows which water quality group each indicator organism falls in. Water quality groups include: 1) pollution sensitive ("good water bugs"); 2) somewhat pollution tolerant ("moderate water bugs"); and 3) pollution tolerant ("bad water bugs").

Macroinvertebrates living in any body of water provide excellent indicators of water quality because they are generally forced to live out much if not all of their life cycle in the same area of a stream or lake. Many otherwise terrestrial insects such as stoneflies, dragon flies and midge flies pass through an aquatic larval stage during which they develop into winged adults then fly away to mate and lay eggs, thereby completing their life cycle. In most cases, especially with the mayflies, the largest part of their life span is spent as larvae living in the water. Mayflies take this to such an extreme that the adults generally do not have mouth parts and die within a day or two of emerging and mating, hence their taxonomic name of Ephemoptera.

Other macroinvertebrates live their entire lives in the water. Aquatic snails, crawfish, sowbugs, clams and leeches are all dependent on water for their entire life. However, among these creatures there is still a variety of tolerances to pollution. Gilled snails are dependent on good water quality because they must obtain all of their oxygen from the water. Pouch snails on the other hand can tolerate poor water quality with little oxygen because they are capable of leaving the water and obtaining oxygen from the air. These two types of snails can be separated by the side on which their shells open when the pointed tip is away from the viewer; right for good water snails, left for poor water snails. They can also be separated by the presence of an operculum or "door" on their shell opening. Pouch snails lack an operculum.

Crawfish, sowbugs and clams are all macroinvertebrates generally found in water of at least moderate quality. Crawfish are well known in Louisiana as a delicious meal. Sowbugs are related to common wood lice, otherwise known as "pillbugs" and "roly-polys." Clams are generally small, easy to locate creatures which are obviously dependent on water. Finally, aquatic worms and leeches are both indicators of poor water quality; and no the leeches will not suck your blood, unless you give them a good chance.

Because these organisms depend to varying degrees on clean water, it is possible to evaluate a water body's health based on the type and number found through sampling. However, because each type of macroinvertebrate has a different lifestyle it is important that samples be collected systematically from all suitable habitats so that each habitat type is evenly represented. For example, if collections are only made along steep banks you may find a few mayflies, stoneflies and crawfish, while a much larger population of midge fly and blackfly larvae are living on rocks in the middle of the stream. This could result in an evaluation of good water quality, when in fact the water is of moderate or even poor quality. The important point to remember is that just because you have one good water indicator you do not necessarily have good water. Likewise, having a few poor water indicators does not always mean you have poor water. Ideally, there should be a range of organisms, with a higher percentage of good or moderate water quality species. An evaluation form is utilized to help in this determination.

Water quality can be impaired by a variety of causes and sources. High levels of nutrients from sewage or fertilizers can lead to algae blooms which block sunlight preventing normal aquatic vegetation growth. Reductions in normal vegetation can lead to reduced hiding places for macroinvertebrates and fish, thereby reducing their populations. When this excess algae dies, decay processes caused primarily by bacteria can severely reduce the amount of oxygen in a stream or lake leading to fish kills and reductions in populations of macroinvertebrates sensitive to oxygen levels.

Another source of water quality impairment, one that many people don't think about, is removal of stream bank vegetation. When landowners or flood control managers strip away riparian vegetation from a stream or lake many things happen to the water body. Removal of sheltering limbs and tree roots which provide hiding places for macroinvertebrates, fish, turtles, frogs, snakes, birds and a host of other wildlife frequently leads to loss of these creatures. Removal of streamside vegetation causes water temperatures to rise due to increased sunlight. Rising temperatures reduce the amount of oxygen in the water, cause fish to move away and may promote more algae blooms. Loss of vegetative structure on a stream bank will lead to increased erosion which places more sediment in the stream. Excess sediment can harm fish and other creatures, smother eggs, block sunlight from aquatic vegetation, and actually increase flooding as sediment is redeposited and fills up basins which normally hold back excess water. Finally, removal of riparian vegetation allows pollutants which might otherwise be trapped and degraded by the plants to enter a stream where they can kill fish and other stream life.

Improper use of pesticides around homes, businesses and farms is one form of water quality impairment which may be harder to detect because you cannot readily see the impact. However, macroinvertebrates, fish and other wildlife living in or around a water body will feel it. Pesticides by definition kill pests, whether insect pests or weeds. Unfortunately, many pesticides are extremely toxic to birds, fish and macroinvertebrates, so when used improperly they can enter a water body and kill much of the life found there. This is where macroinvertebrate sampling can really come in handy. A stream or lake may look almost pristine if the water is clear with little or no vegetation and algae, but if pesticides have been periodically introduced it is possible that sensitive indicators like mayflies, stoneflies and caddisflies have been killed off. Proper sampling will detect this and alert investigators to look for sources of the problem.

There are many examples of water quality impairment which macroinvertebrate sampling can help detect. Perhaps the most important aspect, however, is becoming familiar with a water body's habitats, ecology and watershed. By doing so, students can take action toward protecting the overall environment of a water body, thereby protecting much more than just the water.

Materials:

     * 1. Sturdy D-frame aquatic sampling net - at least one for instructor.

     * 2. For every five students need one of each item listed - plastic dishpan approximately 12" x 14" x 5" for sorting samples, forceps (preferably soft tip entomology forceps but ordinary ones will work (available from Bioquip, 310-324-0620)), medicine dropper and or kitchen baster, two ice cube trays, and in order of preference - a plastic two-way microscope (available at Nature Company Store in New Orleans) or Discovery Scope (available from Delta Education, 1-800 442-5444) or hand lens magnifier

     * 3. 1 bug sheet, 2 sample recording sheets and a pencil for each student

     * 4. Large washtub or buckets, if sample must be collected in advance and brought to classroom

     * 5. Waders, if desired, for any one planning to wade in the stream

Procedures:

     *1. Overall concept of project based on Background, above, is presented to students in classsroom or streamside. Emphasis can be placed on experimental nature of project because leader usually does not know what the results will be. Even if sampling has been previously done on the same stream conditions could have changed between tests. Basic environmental aspects can be presented now or held until after sampling and analysis is complete.

     *2. Sampling procedure with net is demonstrated either in the water or on land as appropriate. Different habitat types should be pointed out and described, including: vegetated margins and banks silty substrates with organic debris sandy/gravel bottoms woody debris with associated leaves, algae and fungi

     *3. If possible, each habitat type should be sampled according to the following procedures. In each case, be sure to look at the inside of the net after dumping a sample into the dishpan. Many of the invertebrates can be found clinging to the netting. Vegetated margins and banks should be vigorously scooped from the bottom up, starting 2-3 feet down and finishing at the surface. Sand, silt, mud and vegetation should be retained in the net with water allowed to drain away. This should be done for approximately 10 feet of stream bank, working upstream. Retain this sample in one pan or divide among several if needed. Record or remember what type of sample is in each pan. This area will usually have a good diversity of several macroinvertebrate types particularly mayflies, stoneflies, dragon flies, and damselflies. In slow streams, lakes and ponds vegetation may be the best location to find suitable habitat and macroinvertebrates, especially dragon flies and damselflies, but also scuds and sowbugs. If you want to find something quick and easy try here first.

Woody debris should be collected from any area of the water body where it can be found. Debris piles should be approached from downstream with the sampling net held below and downstream while leaves and other loose items are pulled into the net. Small pieces of wood approximately 3 inches in diameter should be collected until you have a total of 4 or 5 feet of wood. Retain samples in one or more pans and remember sample type. Like stream banks, woody debris is usually a good place to sample, especially in slow streams. Look for mayflies, stoneflies and beetle larvae, but large dragonflies can be prowling for other insects and caddisflies can be found filtering the water with tiny nets. Again, like stream banks, this is a good source for quick and easy sampling.

Sandy/gravel bottoms in still water can be sampled by vigorously scooping substrate from the bottom. Move the net approximately three feet across the bottom trying to dig in 1-2 inches. In moving water, scoop as before working upstream so organisms are swept into the net or position the net downstream of a 3-foot sampling area and kick around in the sand and gravel to disturb the substrate and force organisms up into the current. Retain sample as before. This area is not as productive as the previous two locations, but you can find midges, clams, swimming mayflies and very interesting case-building caddisflies.

Silty substrates are found where current is very slow or absent. Samples can be collected as described under sandy/gravel bottoms. This is usually the least productive area, but you may find burrowing mayflies if enough oxygen is present. This is an important area to check for the adequacy of oxygen levels in the stream or pond because this will usually be a low oxygen area. If mayflies are found here the oxygen level in the rest of the water body should be very good.

As was noted in the background section, it is important to try and sample all of the habitat types in order to be most accurate. However, if time is a factor and you want to just find something concentrate on the first two habitats above. These two areas will almost always have something to look at. If comparisons are being made between two different water bodies it is very important to sample the same habitat types, with the same intensity, in each water body.

1. After all samples have been collected and divided into dishpans, groups of no more than 5 or 6 should begin picking through the samples. Students should be told that they are looking for creatures anywhere from about 1/8 inch to 2 inches, with an emphasis on the smaller. Scuds and beetle larvae will usually be on the small side, mayflies and stoneflies are usually about 1/4 - 1/2 inch, while dragonflies and damselflies are usually the largest thing found. However, hellgrammites and craneflies can both be very large but are rarely found. To possibly help alleviate fears of putting their hands in the debris, students can be told that hellgrammites are the only thing that may bite and these are usually large and easy to spot. (Hellgrammites have large pincers on their heads and can give a nasty bite.)

Picking should be done by removing small portions of the debris, one or two leaves at a time, and looking it over closely. Forceps or medicine droppers can be used to pick-up smaller organisms. Woody debris should be scanned carefully on the surface and then loose pieces broken away to find mayflies, stoneflies and caddisflies which hide in crevices. When looking at debris remember the idea of camouflage. Most of the organisms will be brown or black and blend in very well with their surroundings. In green vegetation, damselflies will frequently be green and just as hard to see. Without care, you can almost look right at a mayfly on a stick and not see it. Look for movement to give the creatures away. Water should be kept to a minimum in the pans because it is usually murky, however, if the water is clear enough macroinvertebrates can usually be seen swimming around in the bottom. For this reason, any water present in a pan should be kept as calm as possible to avoid stirring up the mud.

As organisms are located they should be separated into look-alike groups by placing them in individual cells of an ice cube tray. The bug sheets will come in handy here. Microscopes or hand lens can be used to help identification or observe behaviors. Ice cube cells should be filled with tap or clear stream water so that the organisms can be seen and counted. For example, all dragon flies should go in one cell, all mayflies in another, etc. The reason for this is two fold: one, dragon flies, damselflies and hellgrammites will eat anything in a cell with them; two, this facilitates counting the organisms according to taxonomic and water quality groupings. And watch some of the creatures, they are surprisingly mobile and may crawl out of their cell or even the tray. When asked, try not to simply tell students what a particular organism is. Instead, try to guide them to find the answer themselves. For most of the larger macroinvertebrates it is really pretty easy. As the invertebrates are located, identified and separated students should keep a tally of how many of each type they find. This can be done individually or by a group recorder.

2. After at least 20-30 minutes of picking bugs students should be told to complete there tally of each organism type and select one person to call-out their results when asked to. A few more minutes is usually required to complete the tallies. Time spent picking bugs can be highly variable depending on the age and interest of the students. To be completely accurate may take an hour or more of picking for each pan, especially those with a lot of debris, but few groups can sustain their interest that long.

3. While students are completing their tallies the instructor should prepare a black board or flip chart, listing each macroinvertebrate in a fashion similar to that found on the survey form. When ready, each group can call out the number of each macroinvertebrate type they found (ie. 10 stoneflies, 5 gilled snails, 20 dragon flies, etc.). The total for all groups is recorded on the black board and on a master survey form. If more than one water body was sampled, results for each water body should be maintained separately. Students should be asked to complete one survey form based on their own samples. If desired, a second survey sheet can be completed by each student showing overall water body results. By maintaining separate group survey forms it should be possible to show results for different habitat types if each group had a different habitat sample.

4. When all results have been tallied the instructor can explain the use of index letters as shown on the survey forms. See analysis below. If time becomes a critical factor, explanation and use of index letters can be left out and raw numbers and distribution among water quality groups can be used to informally estimate water body quality. If time permits, students can discuss possible impacts to water quality in general and the sampled water body in particular.

5. After completion it is important that all participants wash their hands well with soap and water. This is especially important with small children and when samples were collected from areas of questionable sanitary condition.

Analysis

The survey forms explain the use of letter coding to tally both the presence and population of each indicator group found. The number of letters in each water quality group is determined and then multiplied by the appropriate group factor (ie. # of letters x 3 = index value for sensitive indicators, # of letters x 2 = index value for somewhat tolerant indicators, and # of letters x 1 = index value for tolerant indicators). These values are added together to get a total index value. Values > 22 indicate excellent water, values of 17-22 are good, 11-16 is fair and < 11 indicates poor water quality.

Remember, the important point is not to have all good water species and no bad water species. Instead, a high quality water body will have a wide diversity of all indicator types from sensitive to tolerant, with, hopefully, a larger number of sensitive or moderately tolerant organisms. Also, this survey was originally designed for clear, flowing northern U.S. streams. Although scores and techniques have been modified slightly, it does not always accurately assess Louisiana, and especially South Louisiana waters. Obviously, if you sample a relatively clear, fast moving central Louisiana stream you will have different results than if you sampled a farm pond or bayou. Both water bodies may have perfectly operating environments with no pollution impacts; however, the stream will have many sensitive indicators such as mayflies and probably rank as having excellent quality, while the pond will probably have more moderately tolerant organisms such as dragon flies and give a rank of good or fair. This is primarily due to oxygen levels, water temperature and habitat availability.

Sampling which finds little variety in the type of macroinvertebrates found, but high populations of each may indicate water enriched with organic matter. Locating only one or two types of macroinvertebrates in very high abundance indicates severe organic enrichment. If a good variety of organisms was found but at low numbers then toxic pollution may be indicated; however, other problems could also cause reduced populations. This program works best when the same or very similar water bodies can be sampled over time so that results can be compared. However, since use of the sampling program for demonstration purposes generally precludes that possibility, it is up to the instructor to gain as much familiarity as possible with what can be expected of different water bodies. This will allow reasonable comparisons and interpretation of what is found in the demonstration water body.

Extensions

This program lends itself to a number of possible extensions and discussions. Aspects of water pollution can be discussed in association with what pollution does to the life of a water body. Discussions on food webs can begin with vegetation and algae growing in water and continue all the way to fish and humans. The macroinvertebrates found during the program form a lower or middle area of the food web, between vegetation and minnows or larger fish. Within the macroinvertebrates there are good examples of smaller food webs because some of the organisms are grazers or detritivores on the fungus and plants (mayflies and stoneflies); some are filter feeders (caddisflies); and some are carnivores (dragon flies and damselflies). If a relatively good microscope is available, placing a drop of water on the slide and allowing students to look at it on their own will show an entire new layer of the food web in the diatoms, flagellates and other microorganisms present.

The concept of watersheds is an important aspect of water pollution control which can be discussed either before or after the sampling program. A watershed is the land area which acts as a collection basin for rainwater which eventually flows to a single stream or river. Watersheds can be as small as a single valley and creek or as large as the Missouri, Mississippi and Ohio River system and its myriad tributaries. This watershed encompasses 30 states in the continental U.S. stretching from Montana in the west to New York in the east, and all the way north into Canada.

Nonpoint source pollution is another aspect of water pollution which can frequently be identified by macroinvertebrate sampling techniques. Stream sampling, along with field scouting of the watershed can frequently locate water quality problems not readily identified by conventional water quality sampling. The Louisiana Department of Environmental Quality, Office of Environmental Assessment maintains a Nonpoint Source (NPS) Program which can provide more information on this important form of water pollution. The NPS program also works with citizen environmental groups to establish Citizens' Monitoring Programs on area streams.

This lesson was prepared by:

Al Hindrichs, Louisiana Department of Environmental Quality