Freshwater Aquatic Invertebrate Surveys

Aquatic invertebrate surveys are typically carried out to assess the water quality of a particular waterbody, either as a one off assessment or ongoing surveys over a period of several years to monitor the effect of land and water use from mining, agricultural or recreational activities. They may also be carried out for monitoring the effects of mitigation or simply in assessing the aquatic invertebrate diversity of a site, particularly as part of a planning application affecting a watercourse.

EMEC Ecology is able to undertake a range of freshwater aquatic invertebrate surveys including the following:

Water quality monitoring using macroinvertebrates as biological indicators and the Biological Monitoring Working Party (BMWP) procedures to determine the quality of a watercourse, indicative of pollutant levels. This industry standard method relies on the principle that different aquatic invertebrates have different tolerances to pollutants and water oxygen concentrations. In addition to the BMWP score the Average Score Per Taxon (ASPT) score is calculated from the collected samples. The ASPT equals the average of the tolerance scores of all macroinvertebrate families found, and ranges from 0 to 10. The main difference between both indices is that ASPT does not depend on the family richness. Recent work involves surveying moving water systems and the effect of large scale mineral extraction on the watercourses, to water quality monitoring of man-made watercourses within a series of holiday complexes.

The BMWP and ASPT values gathered from survey work carried out by EMEC Ecology can be used in reports relating to the Water Framework Directive (WFD). The WFD is a European Union (EU) directive that has been incorporated into English and Welsh law. It aims to enhance and prevent deterioration of aquatic ecosystems, reduce water pollution, promote the sustainable use of water and ensure progressive reduction of groundwater pollution.

In addition to BMWP and ASPT, EMEC Ecology has experience of using the Extended Trent Biotic Index (ETBI), and Community Conservation Index (CCI), as well as statistical techniques such as the Shannon Weiner diversity index, as appropriate and as required by our clients.

Species compilation to determine the effect of management of watercourses on the invertebrates found therein. Previous work has included before and after surveys of watercourses and the impact of structural and vegetation changes on species composition.

Compilation of species lists to determine the invertebrate "richness" of a site.

All EMEC Ecology aquatic invertebrate surveys are carried out according to standard Environment Agency and Natural England procedures, therefore making them suitable for inclusion in Water Framework Directive (WFD) reports. In running water, each sample comprises a three minute period of 'kick-sampling', where the surveyor places the net against the riverbed and then kicks at the substrate, with dislodged invertebrates being carried into the net by the current. This is then followed by a one minute period of hand and net searching for invertebrates, e.g. among vegetation or under overhanging banks where water beetles aggregate.

In static water the sample is taken by sweeping with a long handled pond net for a cumulative three minutes at each sampling location, (broken down into several 30 second or one minute sweeps). Sweeps are made through aquatic vegetation, sediment and the water column. This gives three minutes "net in water" sampling time, again followed by a minute searching for aquatic invertebrates that might be missed by netting, for example by looking under logs for leeches, or scanning the water surface for whirligig beetles.

The sampled invertebrates are then identified and the results of the survey assessed using a scoring system such as the BMWP and ASPT as described above, as required.

Water Chemistry

Typically, as part of an aquatic invertebrate survey EMEC Ecology will use probes to measure water chemistry indices including pH, dissolved oxygen concentration and electrical conductivity.

These measurements give a useful context to the main survey in assessing water quality. Oxygen is vital to all life and while a few are able to directly breathe air, high concentrations of dissolved oxygen are important to almost all aquatic invertebrates. Oxygen saturation varies with temperature, but low oxygen levels usually indicate eutrophic conditions due to organic pollution, for example from fertiliser or sewage run-off, as oxygen is depleted by population explosions of algae and bacteria. The pH is a measure of the acidity, or levels of hydrogen ions present in the water, which will vary with the underlying geology, but natural waters usually lie between 6.5 and 8.5. Electrical conductivity measures the dissolved salts and or ions in the water, which varies naturally with soil conditions but can also give an indication of increased pollutant levels if elevated unexpectedly.

Following an aquatic survey, extensive mitigation advice on freshwater systems can be given, not only including in improving the invertebrate diversity of the site, but also reducing the impacts of pollution and improving the 'health' and appearance of the water.

Our clients currently range from individual landowners, farmers and small to medium sized businesses, up to large multi-national companies and government agencies, including Natural England.

Our invertebrate surveyors are able to undertake aquatic and terrestrial surveys throughout Nottinghamshire, Derbyshire, Leicestershire and further afield including the whole of the East Midlands and throughout the United Kingdom.

If you require a freshwater aquatic invertebrate survey, then the invertebrate ecologists at EMEC Ecology are here to meet your needs in a cost effective and timely manner. Please get in contact via email or phone 0115 964 4828 to discuss your needs.