Standards Development

Scope

This European Standard gives guidance on procedures for the pro-rata Multi-Habitat-Sampling (MHS) of benthic macro-invertebrates in rivers and streams. The term "pro-rata" reflects the intention to sample all the main riverine habitats present at a monitoring site according to the proportion of the site that it covers. It is an objective way to divide sampling effort between the different habitats.

This guidance is applicable to all flowing waters, both artificial and natural. Pro-rata multi-habitat sampling can be applied to all surface waters, including small streams, large rivers, springs, subterranean streams, temporary and intermittent streams. Standard sampling methods for some of these types of habitat are still in development and not all of these habitats are included in national monitoring schemes. It is suitable for national and regional monitoring networks for classifying ecological status under the Water Framework Directive. All water bodies in all EU member states have to be classified under this directive.

In contrast to small streams, large rivers cannot be inspected on foot, even at low-flow. Deeper water with relatively poor visibility sometimes makes the habitats invisible to the observer and prevents the selective collection of samples. Where water depth varies through the year, sessile and less mobile macro-invertebrates are more commonly found below the low-flow water level. For these reasons, representative sampling from the banks is restricted to low-flow periods, but the water level of large rivers is often too high for very long periods to get representative samples from the bank. In such cases, it is advisable to survey with a sampling technique that is independent of the water level, for example using a grab, air-lift sampler or dredge. Deployed from a boat or ship, samples should be taken in cross-section of large rivers to cover the main habitat gradient (flow and depth) even though it is not visible. In all cases, the sampling method should not be changed within one water body.

This European Standard is designed to

• support environmental and conservation agencies meet the monitoring requirements of the WFD (Article 8, Annex II and Annex V);

• generate data sets appropriate for monitoring and reporting of sites designated under the Natural Habitats Directive and the Wild Birds Directive;

• ensure that samples for comparing the overall composition of invertebrates from different stream types are comparable;

• 2. to ensure samples for environmental quality assessments across different stream types are comparable even when sampled by different people;

• support river management and restoration initiatives.

The pro-rata MHS provides

• a consistent way of sampling sites that is not dependent on the presence of particular types of habitat;

• guidance on a user-friendly strategy for collecting biological data depending on the distribution of substratum type.

It is also ideal for

• understanding the distribution of biological community types across different physical river types;

• quality assessments based on deviation from reference, as adopted in the European Water Framework Directive.

Pro-rata MHS is for two purposes:

1. To ensure that samples for comparing the overall composition of invertebrates from different stream types are comparable;

2. to ensure samples for environmental quality assessments across different stream types are comparable even when sampled by different people.

The pro-rata MHS technique does not replace other techniques. If the same habitat is present at all monitoring sites, pro-rata multi habitat sampling is not necessary, because you will always be able to collect samples from this habitat and both reference values and samples associating different environmental qualities will also be based on samples from that habitat. Results will be more directly comparable between sites. Sampling from one habitat type reduces variation and therefore provides a more consistent overall assessment. It also avoids variation caused by observer bias in the assessment of habitat cover. The training burden is also reduced. The best habitat for practical and biological reasons, are shallow riffles with gravel substrate.

If the same type of habitat is not present at every site, you could limit sampling to a selection of habitats. Shallower sites that you can wade into are easier to sample. Again, this approach is only practicable if the few habitats that you choose to use are found in all monitoring sites. The steps that you must take to make data comparable for pro-rata multi-habitat sampling such as expressing results as a proportion of their reference value will still need to be based on reference sites or models covering the same combinations of habitats.

Pro-rata multi-habitat sampling provides the greatest flexibility and allows any site to be used, provided it is adequately covered by your reference sites or models. 

The regional or national river monitoring networks in most countries have to cover diverse river types that have different combinations of habitats. There will be no single habitat type that is present at every monitoring site that could be used to collect samples from. Here, pro-rata multi-habitat sampling enables the effects of differences in combinations of habitat to be taken into account in reference values as an integral part of typology. It is a fundamental requisite of some multi-metric assessment approaches used to evaluate the ecological status of running waters.

The possible combinations are:

1. always sampling the same habitat (the ideal, with much less variation, but not pro-rata multi-habitat and therefore not in this standard). This is only possible if the habitats you use are found at every site on the monitoring network.

2. sampling a very limited number of habitats pro-rata. Essentially and extension of the first option to enable more sites to be covered. This is not covered by this standard.

3. sampling all habitats pro-rata. 

Pro-rata MHS is adopted almost universally for national and regional standard methods for river quality management and ecological status assessment. The pro-rata MHS methodology is based on Rapid Bioassessment Protocols [1], the procedures of the United Kingdom [2], the Austrian Guidelines for the Assessment of the Saprobiological Water Quality of Rivers and Streams [3], the AQEM sampling manual [4], the AQEM & STAR site protocol [5], EN 27828, the Austrian Standards M 6232 and M 6119-2 [6], [7], the German Standard DIN 38410-1 [8] and the French Standard XP T90-333 [9].

The concept of sampling all major habitats in proportion to their cover is simple to understand, so it is easy to give the same instruction to many different ecological surveyors with confidence that they will collect samples correctly. The use of this common concept increases comparability of samples collected by different observers. 

This European Standard also describes in a detailed manner how to sample different habitats that might be suitable for sampling approaches other than Multi-Habitat-Sampling. Previous sentence not easy to understand...

Purpose

The aim of the revision is to explain the principle of pro-rata multi-habitat sampling described in this standard rather than to specify a particular method that follows it, thus broadening its applicability, and to provide more information about the purpose of the standard and when it should be applied. The particular method described in the current draft is retained as an example.

A proposal to revise the EN 16150:2012 was put forward in 2019.

The Results of Voting confirmed that 14 countries and their NSB’s indicated the need for a revision of this standard. However, due to several reasons, the pandemic included, there was a delay in registration of the project and therefore there is now the need to put forward this revision proposal to ballot again. Work is ongoing so we are requesting all experts to inform their NSB’s of their participation/ interest to participate in the revision of EN 16150.

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