Waterwatch Australia national technical manual

Module 3 - biological parameters
Waterwatch Australia Steering Committee
Australian Government Department of the Environment and Heritage, 2004
ISBN 0 6425 4856 0

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Monitoring macro-invertebrates

Broadly speaking, Waterwatch groups monitor macroinvertebrates for one of two reasons – awareness raising for education outcomes or waterway assessment monitoring and action. You need to decide why you are monitoring. You can do this by developing a Monitoring Plan (see Module 2, or for a summary, Table 2 in this Module). The Monitoring Plan should be developed in consultation with your local Waterwatch Coordinator.

Macro-invertebrate monitoring can tell you about the impact of human activities and how well your community is looking after the waterway. Monitoring can also raise awareness of life in the waterway and promote a sense of stewardship towards the health of the aquatic environment.

Macro-invertebrate monitoring includes:

  1. planning what to do, for example, deciding how, where and when you are going to collect and analyse macro-invertebrate samples
  2. collecting (and possibly preserving) the organisms
  3. sorting and identifying macro-invertebrates in the sample either in the field or the lab
  4. developing findings, conclusions and recommendations. Macro-invertebrates can be monitored in all types of waters but the focus of this manual is on flowing waters. Different procedures for monitoring macro-invertebrates under wide-ranging conditions from shallow streams with rocky bottoms to large deep rivers with sandy or muddy bottoms are described.

Strengths and limitations of macro-invertebrate monitoring

Macro-invertebrates are good indicators of water quality as they:

Macro-invertebrates can be used to monitor changes in streams from headwaters to lowlands, and above and below pollution sites. They reflect changes and problems in the river. For example, stonefly larvae are unlikely to be found if dissolved oxygen has fallen to low levels, turbidity is high, toxic pollutants have contaminated the river, or temperatures are elevated. Be aware however, of the limitations of macroinvertebrate sampling. For example, the absence of stoneflies indicates there has been an impact on the stream, but it does not tell us exactly what caused the impact.

You should combine macro-invertebrate monitoring with an assessment of the catchment (see Module 1) and the physical and chemical conditions (see Module 4) to provide further clues about the causes of changes in the waterway. Assessing the habitat will help you decide if differences in macro-invertebrate samples from one site to another are due to different habitat conditions or some other cause. To be certain that habitat is not causing differences in your macro-invertebrate samples, always compare data from the same habitats.

There are advantages in combining different monitoring methods. Macro-invertebrates provide a short- to mediumterm record of the pollution history of the site. Chemical testing on the other hand, only provides a snapshot of specific pollutants trapped in your water sample. Some macro-invertebrates have a life span of up to four years. This, together with their relative lack of mobility, can make them useful indicators of intermittent pollution. For example, a 'slug' of toxic waste released into a stream after an accident may have an impact on diversity and abundance, an effect that remains evident for several months. By contrast, chemical and physical testing at the site may fail to detect pollutant because it has moved downstream.

How can you use information from macro-invertebrate monitoring?

Sampling for macro-invertebrates can be used for:

What is the best habitat to sample?

Two habitat types have been identified as providing good macro-invertebrate sites for sampling: riffles and edgewaters. Each habitat is home to a distinct group of macroinvertebrates.

Riffles have the most diverse habitats for macro-invertebrates, and are the most desirable collecting places. Under good conditions, they contain organisms that vary from tolerant to very sensitive. By comparing riffle samples from one site to the next, the impact of human activities will become obvious.

For example, macro-invertebrate diversity found in a riffle upstream of a sewage treatment plant will probably be greater than that in a riffle downstream.

Sometimes there are no riffles where you would like them. If this is the case, choose an edgewater habitat and sample organisms living in and around vegetation on the edges of water bodies. Muddy bottom water bodies usually have fewer types of macro-invertebrates because the habitat is less suitable. The same type of habitat must be selected at different sites if you want to meaningfully compare results.

What methods and equipment can be used?

To get a representative collection of macro-invertebrates in your waterway, there are two methods available:

Nets for kick sampling of macro-invertebrates in riffles is recommended where possible or sweep sampling for edgewaters if no riffles occur at the site of interest.

Nets

For groups mainly interested in awareness and education, the type of net is not critical. It can even be a kitchen sieve or be made, at home, from a nylon stocking attached to a coat hanger and broom handle (see Figure 3 ). Alternatively, you may choose to simply pick waterbugs from rocks or leaf packs collected from the stream (see Waterbug awareness).

Figure 3: Sampling nets
Figure 3: Sampling nets. Source: TVA Clean Water Initiative, 1995

For kick and sweep sampling a long-handled net is best. It should have a triangular or a D-frame with a 0.25 millimetre or 0.3 millimetre nylon mesh size. This mesh catches smaller waterbugs like midges but does not quickly plug up with sediment. A handle that extends to about 2 metres is useful.

Kick sampling method for riffles

The best riffle habitats for kick sampling:

Method. Wearing rubber boots, stand in knee deep water facing downstream. Hold the net in front of you with the opening facing upstream. Disturb the rocks underfoot by vigorously shuffling and kicking. The current will sweep dislodged macro-invertebrates into the net. Move slowly upstream while you do this to sample a 10m length of the stream bed.

Sweep sampling method for edgewater habitats

The best edgewater habitats for sweep sampling:

Method. Vigorously sweep your net against aquatic plants, roots, logs and the substratum at the water’s edge to dislodge any attached animals. Use upward scooping movements to sweep any dislodged animals into your net. Sample a 10 metre length of water’s edge.

Where is the best place to locate monitoring sites?

The type of monitoring site you select will depend on a number of factors such as why you are monitoring and what you are wanting to find out about your waterway.

The following sections provide you with some helpful guidance when selecting your monitoring sites.

Locating sites for baseline monitoring

Riffle sites are best for sampling, so locate and add these to your catchment map. Riffle sites for river baseline monitoring should represent the full range of conditions in the catchment. Sites should be chosen from:

Results from reference sites located in the natural or least disturbed areas of your catchment can be compared with results from other sites. Reference sites need not be on your river, but the habitat should be similar. Consult an experienced aquatic biologist who is familiar with the characteristics of rivers in your area.

Locating sites for pollution impact monitoring

First, you need to locate and map all the suspected sources of pollution affecting your river. Then identify riffles at sites above and below the suspected source of pollution – these are the reference, impact and recovery sites (see Figure 4).

Figure 4: Ideal location of riffle sampling sites for macro-invertebrate sampling to measure pollution impacts
Figure 4: Ideal location of riffle sampling sites for macro-invertebrate sampling to measure pollution impacts. Source: Redrawn from Dates, G & Byrne, J, 1996

Locating sites for whole-catchment impact

To locate sites for whole-catchment impact you need to pair up an impacted catchment with a relatively natural catchment (paired catchments). For example, a small sub-catchment may be entirely converted to forest harvesting but a nearby subcatchment is untouched. The catchments should be similar in every way except the impact being measured. To show the extent of catchment impact, sample at four sites – a reference or control site, an integrator site, an impact site and a recovery site (see Figure 5).

Figure 5: Location of sample sites for a paired catchment study
Figure 5: Location of sample sites for a paired catchment study. Source: Waterwatch Tasmania Reference Manual 2003

When should you sample?

Ideally, macro-invertebrate sampling should occur twice a year, with recommended times being spring and autumn. Spring samples will have larger specimens of insects that were hatched last summer, making them easier to identify. Autumn samples will show the effects of lower flows and higher temperatures, when pollution inputs may have a greater impact.

Sampling should occur no more than four times a year to minimise the physical damage to a site.

What factors affect your choice of monitoring methods?

The general approach taken to monitoring macro-invertebrates depends on your goals, skills of group members and resources available (see Table 2 ). In particular, two important considerations will influence your choice of monitoring method:

Table 2: Monitoring plan and macro-invertebrate sampling methods
Questions
to be
considered		 Waterbug
awareness		 Macro-invertebrate
rating		 Macro-invertebrate
intensive sampling
(to be developed for community use)
Why are you monitoring? To educate/raise awareness

To identify grossly polluted spots		 To educate/raise awareness

To identify the impact of pollution and pollution control activities and report to land managers to determine the general condition of the site		 To educate/raise awareness

To identify the impact of pollution and pollution control activities

To determine the precise severity of pollution problems and rank sites on the waterway

To identify whether waterways are meeting standards to support designated uses

To identify water quality trends

To select sites for remedial action

To support government agency monitoring efforts
Who will use the data? Teachers, students, group members Teachers, students, the general public, land owners, natural resource managers, catchment and rivercare groups Teachers, students, the general public, land owners, natural resource managers, catchment and rivercare groups
How will the data be used? To educate and raise awareness of students and group members

To plan future monitoring efforts		 To screen potential problem areas for possible future intensive studies

To identify areas for possible corrective actions by local and state agencies		 To help government agencies make management decisions about waterways

To help develop catchment management plans

For state of environment reporting

For selection of sites for remedial action
What will you monitor? Presence of macro-invertebrates by gross body shape Abundance and diversity of macro-invertebrates to order level (and some families) Abundance and diversity of macro-invertebrates to family level
What data quality do you need? As identification is based on gross body shape, data only provide very general indications – the activity of collecting data is more important than results The data are capable of indicating the general condition of the site on a four-point scale (excellent, good, fair or poor) Quality controlled sampling and analysis ensures a high level of confidence in numerical data for decision-making purposes
What methods and equipment are used? Pick macro-invertebrates from rocks, leaf packs or from net samples.

Equipment includes:

  • sampling nets or kitchen sieve
  • shallow white tray or bucket
  • ice cube tray or ice-cream or yoghurt containers
  • plastic pipettes
  • small paintbrush
  • tweezers
  • plastic spoons
 Standard sampling methods are used at all sites.

Field identification of macro-invertebrates.

Equipment includes:

  • sampling nets (or artificial substrates)
  • shallow white tray
  • ice cube trays
  • plastic pipettes
  • small paintbrush
  • forceps
  • plastic spoons
 Standard sampling methods are used at all sites. Sampling and preservation of fauna in alcohol for laboratory identification to family level

Equipment includes laboratory and preserving equipment in addition to sampling and sorting implements
Where will you monitor? As determined by your goals, e.g. to educate students, sites must be accessible, safe and close to the school. Choose sites as required by the question you want to answer, e.g. if point source pollution impact is being assessed, riffles at reference, impact and recovery sites bracketing the impact are best. Choose sites as required by the question you want to answer, e.g. baseline monitoring sites will be located in representative areas of the catchment.
When and how often will you monitor? Timing depends on the education or awareness needs of the group, e.g. field days, school projects, on-ground catchment survey. It is not designed as a regular monitoring tool Twice yearly in autumn and spring – maximum is four times a year (once per season) to avoid depleting populations Twice yearly in autumn and spring – maximum is four times a year (once per season) to avoid depleting populations
Who will be involved and how? Suitable for all – new groups, schools etc. Demonstration by Waterwatch coordinator. Best suited for trained community members, secondary students and older. Training by Waterwatch co-ordinator. Suitable for experienced groups willing to undertake rigorous training needed and work under direction of freshwater ecologists
How will the data be managed and presented? Not essential to record data but generally helpful in preparing reports for presentations to sponsors, the community and officials Keep complete and accurate records of result sheets. Interpretation of results should be done in conjunction with habitat assessment and water quality results – site ratings can be indicated on your catchment map using different colours Sites are compared with reference conditions to estimate level of impact – site ratings can be indicated on your catchment map using different colours
How will you ensure your data are credible? No training is needed but is strongly recommended. Data are not used for decision making by others Field training by Waterwatch coordinators ensures comparability and accurate identification

Replicate samples by sampling teams provide a check on representativeness

As well as using diagrams with this manual, a comparison of macro-invertebrates with a verified reference collection is highly desirable for accuracy		 Formal field and laboratory training with freshwater ecologists

10% of macro-invertebrate samples to be preserved for identification to the same taxonomic level by an freshwater ecologist

External field duplicate samples taken by ecologist to ensure data confidence

Level of identification

The main choice you will need to make depends on the level to which you want to identify the animal – broad groups with similar overall body shape, or order or family. This, in turn, depends on the identification skills of group members.

Ability of the method to detect differences in macro-invertebrates between sites

Identification of macro-invertebrates according to overall body shape will only give an indication of the most heavily polluted sites. Identification of macro-invertebrates to SIGNAL 2 major group level will give more resolution but family level identification (SIGNAL 2 family) is the most sensitive method.

The sensitivity of the method refers to its ability to detect differences in the macro-invertebrate community from site to site. Sometimes these differences are subtle. For example, your sample may contain a number of mayflies belonging to the order Ephemeroptera, which is composed of nine families in Australia (Hawking & Smith 1997, Colour Guide to Invertebrates of Australian Inland Waters). Most mayfly families are sensitive to pollution, although a few families are fairly tolerant. You will need to identify which families make up your sample to be sure about the ‘message’ mayflies convey about your site.

For monitoring the impacts on waterways, it might be useful to think of identification to SIGNAL 2 major group level as a first step. This level will be sensitive to moderate to heavy pollution. If the pollution is more subtle, and you suspect there is a problem that does not show up from identifying to order level, you might want to go further and identify families.

Checklist for Macro-invertebrate Sampling

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