Report on Harmonisation of freshwater biological methods

size of the net range between 250 to 750 µm. The models currently applied in variousnational watercourse monitoring programmes differ in sampled area (0.01 to 0.12 m²)and mesh-size (100 to 500 µm).84. In deeper streams benthic macroinvertebrates are taken using grabs, dredges andartificial substrates. The application of these devices is standardised in ISO 9391(1993) or EN ISO 9391 (1995). These are the same standards, as are the previousones, as a result of adoption by ISO and CEN. The difference in dates is caused by thedifferent dates of publication by the two organisations:85. In many European countries large rivers are monitored by utilisation ofquantitative bottom samplers: Different types such as Ponar Grab, Van Veen Grab,Petersen Grab, Birge-Ekman Grab and core samplers are used. All devices sampledefined areas of the river bottom ranging from 100 to 500 cm².86. To obtain a qualitative sample of the river bed community, dredges representadequate tools in deeper watercourses. Dredges are particularly applied in severalcountries in the Danube catchment (Austria, Bulgaria, Hungary, Romania, Serbia-Montenegro) using mesh-sizes of 225 and 500 µm.87. The use of artificial substrates allows comparability of different sites by providingsimilar habitats is not widely used for monitoring purposes. In monitoring programsonly Moldova (Saprobiological assessment based on various metrics), Austria(Assessment of saprobiological quality of rivers) and France (I.B.G.N.) employ thesecolonisation devices.88. Note that the ISO and CEN standards for sampling invertebrates are currentlyunder revision. This should make them more WFD compliant, but the timescale forpublication will inevitable be several years.Sampling frequency89. Sampling frequency in biomonitoring programmes using benthic invertebrates asindicators of watercourse quality varies from seasonal collections to proceduresconducted every five years. Annual sampling is the most common interval applied inriver monitoring. In particular, programs observing the saprobiological water qualityin Latvia, Moldova, Romania and Serbia-Montenegro as well as the national Italianmonitoring programme based on IBE take seasonal samples of macroinvertebrates.86