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PISIAD [id:]

Method: Proportions of Impact-Sensitive and Impact-Associated Diatoms [Procentuele abundantie van impact-sensitieve en impact-geassocieerde diatomeeŽn]

1. General information

1.01 GIG: Central-Baltic
Relevant intercalibration types: RC1, RC4
1.02 Category: Rivers
1.03 BQE: Benthic Diatoms
1.04 Country: Belgium (Flanders)
1.05 Specification: Flemish Region
1.06 Method name: Proportions of Impact-Sensitive and Impact-Associated Diatoms
1.07 Original name:
Procentuele abundantie van impact-sensitieve en impact-geassocieerde diatomeeŽn
1.08 Status: Method is/will be used in First RBMP (2009), Second RBMP (2015)
1.09 Detected pressure(s):
Acidification, Eutrophication, Flow modification, General degradation, Heavy metals, Hydromorphological degradation, Pollution by organic compounds (e.g. DDT, PCB), Pollution by organic matter Specification of pressure-impact-relationship:
See Hendrickx & Denys (2005) for significant relations to nutrients, BOD, EC, chloride in 49 brooks
Yes, with quantitative data (e.g. against range of sites reflecting continuous gradient of pressure).
Other detected pressures: salinity change
1.10 Internet reference: n.a.
1.11 Pertinent literature of mandatory character:
VMM, 2009. Biological assessment of the natural, heavily modified and artificial surface water bodies in Flanders according to the European Water Framework Directive. September 2009. Vlaamse Milieumaatschappij, Erembodegem, Belgium.
1.12 Scientific literature: n.a.
1.13 Method developed by: Luc Denys
Email of developer:
Institute of developer: Research Institute for Nature and Forest
1.14 Method reported by: Wim Gabriels
Email of person reporting the method:
Email of institute reporting the method: Flemish Environment Agency
1.15 Comments: none

2. Data acquisition

Field sampling/surveying

2.01 Sampling/Survey guidelines: EN 13946:2003.
2.02 Short description:
The order of preference for the substrate to be sampled is as follows: (1) stones: five different stones that were found spread throughout the location are sampled. These stones are lifted from the water and are sampled to the flow side (upstream side). With a (pocket) knife or sharpened spoon the epilithon is removed from the stones and stored in a container (60 ? 100 ml) with a wide screw cap and extra closing lid. (2) non-wooden artificial structures (e.g. bridge pillars): in some cases no (suitable) stones will be present within the stretch. In this case bridge pillars can alternatively be sampled. This is done in the same way as with stones, only this will be carried out under water. (3) living reed: If no stones or bridge pillars are present, one can sample living reeds. These are cut with scissors. Only the zone about 10 cm below the water surface is collected. (4) other similar, living helophytes (monocotyls such as cattail (Typha), rushes (Scirpus, Juncus),?) are used in absence of reed; (5) artificial substrates are used in absence of all the above: preferably permanent, vandal-resistant constructions are chosen of inert material on which a biofilm can develop undisturbed during the whole year.
2.03 Method to select the sampling/survey site or area: Stratified sampling/surveying Other method to select the sampling/survey site or area: Additionally in function of accessibility
2.04 Sampling/survey device: Scraper, Spoon
2.05 Specification: Knife
2.06 Sampled/surveyed habitat:
Specification of sampled habitat: Epilithon, or when this is not available, epiphyton
Sampled habitat: Single habitat(s)
2.07 Sampled/surveyed zones in areas with tidal influence: not relevant
2.08 Sampling/survey month(s): June - September
2.09 Number of sampling/survey occasions (in time) to classify site or area: At least 1
2.10 Number of spatial replicates per sampling/survey occasion to classify site or area: 1 per site (3 per water body)
2.11 Total sampled/surveyed area or volume or total sampling duration to classify site or area:
About 10 cm2 epilithon or epiphython

Sample processing

2.12 Minimum size of organisms sampled and processed: All valves observed in the microscope
2.13 Sample treatment:

The sample is cleaned using oxidizing agents and homogenised and part of the sample is embedded in naphrax for identification with microscope. 500 valves are identified and counted.
Sample is divided (sub-sampling) and organisms of a sub-sample are identified.
2.14 Level of taxonomical identification:
Level: Other, Species/species groups
Specification of level of determination: Including subspecific taxa
2.15 Record of abundance:
Determination of abundance: Relative abundance
Abundance is related to: n.a.
Unit of the record of abundance: percentage, proportion
Other record of abundance: number of valves
2.16 Quantification of biomass: n.a.
2.17 Other biological data: none
2.18 Special cases, exceptions, additions: Flemish river type 'Mlz' (tidal rivers) is not addressed using diatoms
2.19 Comments: none

3. Data evaluation


3.01 List of biological metrics:
Percentage of impact-associated diatoms (IAD); percentage of impact-sensitive diatoms (ISD)
3.02 Does the metric selection differ between types of water bodies: No
3.03 Combination rule for multi-metrics: n.a.
Other rules:
If IAD exceeds a predefined threshold, EQR gets a value between 0-0,60 based on a transformation of IAD; otherwise EQR gets a value between 0,60-1 based on a transformation of ISD.
3.04 From which biological data are the metrics calculated:
List of biological metrics:
Data from single sampling/survey occasion in time
Data from single spatial replicate

Reference conditions

3.05 Scope of reference conditions: Surface water type-specific
3.06 Key source(s) to derive reference conditions:
Scope of reference conditions: Expert knowledge, Least Disturbed Conditions
Other reference source: foreign sites
3.07 Reference site characterisation:
Number of sites: n.a.
Geographical coverage: n.a.
Location of sites: n.a.
Data time period: n.a.
Criteria: n.a.
3.08 Reference community description:
Reference conditions are characterised by a relatively low relative abundance of impact-associated diatoms and a relatively high relative abundance of impact-sensitive diatoms
3.09 Results expressed as EQR: Yes

Boundary setting

3.10 Setting of ecological status boundaries: n.a.
Other boundary setting:
Class boundaries based on IAD and ISD threshold values are based on expert judgement and comparison to foreign reference sites; they are transformed in such a way that equidistant division of the EQR gradient (boundaries at 0,8; 0,6; 0,4 and 0,2) is obtained.
3.11 Boundary setting procedure:
EQR gradient is assumed to represent a continuous trend with general degradation.
3.12 "Good status" community:
The EQR values at good status are characterised by a relatively low IAD and a ISD that is slightly reduced in comparison to reference.


3.13 Consideration of uncertainty: No (to be done)
3.14 Comments: none

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