Stream Macroinvertebrate Protocol

Contents

1. Why Monitor macroinvertebrates?
2. Types of Methods
3. Mentor Contacts
4. Selecting Sites
5. Selecting Specific Sample Locations
6. When Are Sites Sampled?
7. Equipment needed:
8. Field Sampling Methods
9. Data Sheet

Why Monitor macroinvertebrates?

Evaluating the biological community of a stream through assessments of algae, macroinvertebrates, and fish provides a sensitive and cost effective means of determining stream condition. Such evaluations are particularly effective when stream impacts are from non-point sources, sporadic events, or cumulative low level pollution. Each biological community has its own advantages and disadvantages for assessing stream conditions, and they all have published protocols (Plafkin et al. 1989; EPA 1990). The protocols described here are for macroinvertebrates - invertebrates large enough to see with the naked eye.

macroinvertebrates are fairly stationary, easy to collect, and are responsive to human disturbance. In addition, the relative sensitivity or tolerance of many macroinvertebrates to stream conditions is well known. In general, they provide a simple "hands-on" approach to understanding and measuring stream health without the problems often encountered when measuring fish communities impacted by sport fishing, stocking sport fish, and the introduction of exotic fish species.

In order to adequately evaluate the overall ecological integrity of aquatic systems, a monitoring program that encompasses chemical, physical, and biological integrity should be developed (EPA 1990). The macroinvertebrate bioassessment protocol described here is part of a comprehensive approach that involves analyzing the stream habitat conditions, its physical and chemical parameters, and the biological community. The biological community evaluation methods described in this manual are adapted from the EPA Bioassessment (1996).

Types of Methods

Three different levels of macroinvertebrate sampling procedures are described in this protocol. They have unique objectives and require different levels of expertise.

Level I
Level I methods are the simplest to use and require the least experience. They also provide the least amount of information about the health of the macroinvertebrate community. Education is the main goal for Level 1. If the monitoring objective is to inform citizens or students about the various animals that live in streams, and only a very basic assessment of stream conditions is needed, Level I methods will be appropriate.

Level 2
The Level 2 protocol is designed to provide a screening level assessment of stream conditions. Sites can be classed as heavily disturbed, slightly disturbed, or non-disturbed. Finer levels of impairment will be difficult to detect. If the objective is to screen the condition of a variety of sites for prioritizing more in-depth studies, or if the budget or expertise to complete Level 3 studies is unavailable, then the Level 2 protocol will be appropriate.

Level 3
The Level 3 protocol provides a sensitive measure of stream condition using macroinvertebrate communities as the primary indicator. Four classes of conditions can be determined no disturbance, slight disturbance, significant disturbance, and severe disturbance. Applied correctly, studies following this protocol can be used for a variety of objectives such as identifying levels of stream disturbance within a watershed or region, effectiveness monitoring of restoration projects, trend assessments, and evaluating whether the state's standards for protecting aquatic life (fish, macroinvertebrates, algae, amphibians, etc) are met.

Mentor Contacts

As with any monitoring project, questions will come up that are not answered or covered sufficiently in this protocol. Therefore, a group of mentors that are agency experts in monitoring have been identified. These mentors may be contacted with specific questions about particular monitoring goals and efforts. Questions about macro-invertebratre monitoring should be directed to one of the following:

Selecting Sites

The concepts presented here apply to any of the bioassessment Levels (1, 2, or 3). Level 1 studies, designed primarily for education, don't require the same consideration as studies designed to assess conditions within or between different streams. A site with easy access and a good diversity of invertebrates will be adequate for most educational (i.e. Level 1) projects.

For Level 2 or Level 3 studies, remember that stream habitats are complex and change over distance and time. Different communities can inhabit different portions of the same stream, due to natural and human-caused factors. Also, the composition and abundance of the macroinvertebrate species present can change dramatically between seasons due to life- cycle patterns of the different species.

Careful site selection and monitoring timing is critical to insure that the data collected are not biased, and that the differences noted between sites are not due to some artifact of the monitoring program design.

Selecting Specific Sample Locations

Streams with flowing water can generally be divided into several habitat types: pools, runs, glides, riffles, bends, undercuts, etc. Within the major habitat types other habitat categories can be created. Examples would be inorganic substrate like rocks and gravel, or organic substrate like submerged logs and leaf packs. Since each habitat type can have a different macroinvertebrate assemblage, deciding what habitat(s) to sample is necessary.

Two approaches to habitat selection are commonly followed: multiple and single habitat assessments.

Assessing multiple habitats involves a sample design that evaluates two or more habitat types. Each habitat is sampled, processed, and evaluated separately. Pools and riffles are the most common habitat types sampled in a multiple habitat design, but other habitats might be included. The habitats most typical of the study stream should be chosen.

Riffles are usually the only habitat sampled in a single habitat assessment: Riffles tend to contain the most diverse and sensitive invertebrate assemblage compared to other habitats (Plafkin et al. 1989). In most cases, a single habitat assessment of riffles will be adequate when sampling streams. However, sampling only riffles may not always be adequate. Defining the questions in the sampling plan will help determine whether single or multiple habitats should be collected.

Note: The analysis procedures presented in this chapter apply to "riffle" habitat only. If monitors plan on sampling other habitat types, they should contact one of the monitoring mentors to determine the best sampling and assessment methods.

When Are Sites Sampled?

Stream habitats will have different macroinvertebrate communities, habitat conditions, and chemical water quality at different times of the year. Bioassessment surveys are typically done over the course of several years, so it is important to repeat sampling at the same time of year to make year-to-year comparisons possible. Sampling several times per year may be desirable to describe the seasonal variability of the stream and to determine the best time of the year to evaluate a specific type of impact. Once the seasonality of a stream has been adequately characterized, it may be possible to reduce the sampling to a single critical season that best indicates impacts.

Effective periods for macroinvertebrate sampling in Oregon include:

Winter: December, January, February

Spring: March, April, May, June

Summer: July, August, September

Fall: October, early November.

Depending on a stream's elevation or region in the state, the months of May/June and October/November can be transition months between seasons, and invertebrate communities may be changing faster than at other times. Most macro-invertebate studies in Oregon are done during summer low flow conditions in July, August and September. Whatever sampling period is selected sampling should be avoided during or immediately after high water, because high flows can significantly effect the ability to collect representative samples.

Equipment Needed:

Level 1 Assessments Total Costs: $100 - $200

Level 2 and 3 assessments Total Costs: $450

Field Sampling Methods

Level I Assessments

Field procedures for Level I assessments can follow a variety of techniques using simple, inexpensive equipment. The main objective is to collect a representative variety of species from the selected area.

Procedure

1. If possible, select a shallow area having a gravel/cobble bottom with a fairly fast current (make sure the current is not too fast for safe wading). Other habitats may also be sampled; for example, wood and leaf debris, pools, and stream margins.
2. If using a kick screen or D- frame net, place the bottom of the net firmly against the stream bottom and disturb the area upstream of the net by picking up pieces of large gravel and cobble and rubbing their surfaces by hand or with a small vegetable brush upstream of the net. After most of the cobble-sized pieces have been moved, continue disturbing the stream bottom immediately upstream of the net with hands or feet to a depth of several inches. Repeat this process at two or three locations in the same habitat type and combine the contents from each net into a single sample.
3. Remove the net from the stream and wash its contents into a small bucket. Clean and discard large pieces of gravel, leaves, twigs, etc. from the sample.
4. If no net is used, pick up pieces of large gravel or cobble and hold over the bucket while rubbing the surfaces clean. Pieces of wood and leaf packs can also be gently washed in the bucket
5. Pour the material in the bucket into the white plastic tray, and remove all the invertebrates found.
6. Turn to Sample Processing Methods section (below) for final processing steps.
   

Level 2 and 3 Assessments

Both Level 2 & 3 assessments follow the same field sampling methods.

Method Overview

The goal of the field sampling technique is to collect an unbiased, representative sample of macroinvertebrates. First, a "representative" stream reach approximately 40 times longer than the average (mean) wet surface channel width should be selected. From within this sample reach choose two riffles (e.g. if pools will be sampled, select two pools). Two 0.18 square meter (2 square feet) kick samples are randomly selected in each riffle or pool. The four kick samples from each habitat type (riffle and pool) are combined, resulting in one composite riffle sample and one composite pool sample to process in either the field or the lab.

Procedure

1. Randomly select two kick-net sites within the downstream riffle or pool. Random numbers in the table used by DEQ have four digits. The first two identify the percent up from the downstream end of the riffle or pool, and the second two are the percent of stream width across the channel. For example, a random number of 3225 would place the sample at 32 percent up from the downstream end and one quarter across the stream width. These percentages are determined by visual estimates.
2. After locating the random sample site, place the net into the stream with the flat part of the hoop perpendicular to the stream flow and resting on the bottom. Collect the macroinvertebrate sample by disturbing a 30 by 60 centimeter area (1 ft x 2 ft) of stream bottom directly upstream of the net so that the current carries the macroinvertebrates and debris into the net.
3. Carefully rub by hand, or with a small scrub brush, all substrate larger than five centimeters (golf ball size and larger) in front of the net to dislodge any clinging macroinvertebrates. After rubbing, place the substrate outside of the sample plot.
4. Thoroughly disturb the remaining substrate to a depth of five to ten centimeters with the hands or feet. This usually takes between 30 seconds and a minute.
5. After the sample is collected and the net removed, the large substrate is returned to the sample plot.
6. The contents of the net are placed in a sieve bucket and the sampling procedure is repeated at three more plots for that habitat. The preferred order for sampling is from downstream to upstream to minimize influences of disturbance to each sample plot.
7. All four samples for the same habitat type are combined in the sieve bucket. Large organic material and rocks are rinsed, carefully inspected for clinging macroinvertebrates and removed. As much fine sediment as possible is washed away. Leaf packs from pool samples may require considerable rinsing and removal of debris before preserving the composite sample.
8. For lab sorting and analysis the composite sample is placed in a labeled jar or double Ziploc bag and preserved with 90% ethanol for sorting and subsampling in the lab. Change the alcohol in the sample with fresh alcohol within one week to ensure adequate preservation. Place a label inside the jar (using paper and pencil), as well as an exterior label. For field sorting, do not preserve the specimens. Keep them alive and follow the subsorting procedures described in the next section. Field sorting is faster since live, moving specimens are easier to see. Field sorted macroinvertebrates also tend to be in better condition than lab sorted specimens, making identification easier.

NOTE: The disadvantage to field sorting is that it adds one to three hours to the field time per site. This is especially true for low productivity streams that may require sorting most, if not all, of the sample to get the minimum number of specimens required for analysis.

Data Sheets