Freshwater Aquatic Invertebrate Surveys

Background

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.

Timing

The optimal period for aquatic invertebrate surveys is May to August. Surveys can be carried out in late March to April and September to mid-November, but many species will not be present at this time so additional surveys within the optimal period may be required to provide a complete picture of the invertebrate species present.

Methodology

Aquatic Invertebrate Scoping Survey

A scoping survey for aquatic invertebrates of habitats on site is used to assess the potential for a site to support an important invertebrate assemblage, and to determine the need for further survey to fully assess the invertebrate assemblages present. The scoping survey will involve an assessment of habitat suitability for invertebrates and recording of casual observations.

Aquatic Invertebrate Full Survey

A full aquatic invertebrate survey is undertaken if the scoping survey determines the site as suitable for an important species assemblage. Every attempt will be made to make the site visit in weather conditions conducive to invertebrate surveying.

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

Water quality monitoring & other indicators

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.

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 several other statistical techniques, including the Extended Trent Biotic Index (ETBI), and Community Conservation Index (CCI), as well as statistical techniques such as the Shannon Weiner diversity index, Whalley, Hawkes Paisley, Trigg (WHPT) index, Lotic Invertebrate Index (LIFE), and Proportion of Sediment Sensitive Invertebrates (PSI) index as appropriate and as required by our clients.

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.

Survey methods will follow Environment Agency standard protocol of three-minute kick-samples using FBA standard nets. River topography and botanical content will also be recorded. Specimens collected will be retained in iso-propyl alcohol for later identification (except those where definite identification in the field is possible). All collecting methods are in line with Natural England’s collection protocols. The survey will be undertaken by a suitably experienced entomologist, with an assistant for health and safety when working near water.

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.

Species richness surveys

Surveys to discover species composition in order to ascertain the invertebrate “richness” of a site or the effect of management of watercourses on the invertebrates found therein can also be undertaken. We can carry these out before and after any known changes to watercourses to determine the impact of structural and vegetation changes on species composition.

Following the Survey

An individual species list will be produced for all sampling locations as well as a pooled list of all macro-invertebrate species recorded. Biological Monitoring Working Party (BMWP), Average Score Per Taxon (ASPT), Proportion of Sediment-sensitive Invertebrates (PSI), Lotic-invertebrate Index for Flow Evaluation (LIFE) and Community Conservation Index (CCI) can be calculated for each sample if required.

Following an aquatic survey, a report would be produced to interpret the results and provide mitigation advice on freshwater systems, 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.