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PT-PB-RI [id:]

Method: Rivers Biological Quality Assessment Method - Diatoms [Método de Avaliação da Qualidade Biol&oaute;gica de Rios - Diatomáceas]

1. General information

1.01 GIG: Mediterranean
Relevant intercalibration types:
Small mid-altitude Mediterranean streams (R-M1); Medium lowland Mediterranean streams (R-M2) and Small, lowland, temporary (R-M5)
1.02 Category: Rivers
1.03 BQE: Benthic Diatoms
1.04 Country: Portugal
1.05 Specification: Not applicable to Very Large Rivers (>10000 km2)
1.06 Method name: Rivers Biological Quality Assessment Method - Diatoms
1.07 Original name:
Método de Avaliação da Qualidade Biol&oaute;gica de Rios - Diatomáceas
1.08 Status: Method is/will be used in First RBMP (2009)
1.09 Detected pressure(s):
Acidification, Eutrophication, Flow modification, Pollution by organic matter Specification of pressure-impact-relationship:
Relation between diatom indices and several pressure variables was examined (type-specific). Best Spearman Correlation Coefficients were mainly obtained for nutrients parameters (ranging from 0.3 and 0.6). Results were statistically significant except for types with a low number of sites.
Yes, with quantitative data (e.g. against range of sites reflecting continuous gradient of pressure).
1.10 Internet reference:
1.11 Pertinent literature of mandatory character:
National sampling protocol:
Inag, I.P., 2008. Manual para a avaliação biológica da qualidade da água em sistemas fluviais segundo a Directiva Quadro da água - Protocolo de amostragem e análise para o fitobentos - diatomáceas. Ministério do Ambiente, do Ordenamento do Território e do Desenvolvimento Regional. Instituto da água, I. P. (available online). Based on CEN Standards: EN 13946 (2003) and EN 14407 (2004).
National Ecological Status Classification Guidelines:
Inag, I.P., 2009. Critérios para a Classificação do Estado das Massas de água Superficiais- Rios e Albufeiras. Ministério do Ambiente, do Ordenamento do Território e do Desenvolvimento Regional. Instituto da água, I. P. (available online).
1.12 Scientific literature:
CEMAGREF, 1982. Etude des methodes biologiques d?appreciation quantitative de la qualite des eaux. Rapport Q. E. Lyon. Agence de l?Eau Rhone-Mediterranee-Corse-Cemagref. Lyon. France.
Descy, J.P. & M. Coste, 1991. A test of methods for assessing water quality based on diatoms. Verh. Internat. Verein. Limnol. 24: 2112-2116.
Ferreira, J., J.M. Bernardo & M.H. Alves, 2008. Exercicio de intercalibracao em rios no ambito da Directiva-Quadro da Agua. Acta do 9º Congresso da Agua, Lisboa.
1.13 Method developed by:
Not applicable. Sampling and analysis procedures are based on CEN Standards EN 13946 (2003) and EN 14407 (2004). Quality evaluation methods are based on available indices. The chosen indices were tested within a national wide project promoted by the Water
Email of developer: n.a.
Institute of developer: n.a.
1.14 Method reported by: João Ferreira, Salomé Almeida
Email of person reporting the method:,
Email of institute reporting the method:
Water Institute (Instituto da Água, I.P.) / University of Aveiro
1.15 Comments: none

2. Data acquisition

Field sampling/surveying

2.01 Sampling/Survey guidelines:
National protocol:
Inag, I.P., 2008. Manual para a avaliacao biologica da qualidade da agua em sistemas fluviais segundo a Directiva Quadro da Agua - Protocolo de amostragem e analise para o fitobentos - diatomaceas. Ministerio do Ambiente, do Ordenamento do Territorio e do Desenvolvimento Regional. Instituto da Agua, I. P. (available online). Based on CEN Standards: EN 13946 (2003) and 14407 (2004).
2.02 Short description:
Observation of field conditions before sampling takes place. In the sampling area look for riffle which contains stones. The area should preferably be unshaded, with water depth between 10 and 30 cm and current velocity between 10-50 cm/s. Five random stones should be chosen, stones with filamentous algae should be avoided. The stones are removed from the water and the upper surface of each stone is scraped using a toothbrush. The stones are washed after scraping is finished. The material which has been scraped is preserved in an identified plastic bottle using Lugol solution.
2.03 Method to select the sampling/survey site or area: Expert knowledge
2.04 Sampling/survey device: Brush
2.05 Specification: Toothbrush
2.06 Sampled/surveyed habitat:
Specification of sampled habitat:
Preferably hard substrate (stones occuring at sampling sites). If natural hard substrate is not available artificial hard substrates are sampled (walls, bridges, etc.). When hard bottom is not available macrophytes can be sampled.
Sampled habitat: Single habitat(s)
2.07 Sampled/surveyed zones in areas with tidal influence: not relevant
2.08 Sampling/survey month(s):
Spring season: February to April in southern rivers and March to June in northern rivers.
2.09 Number of sampling/survey occasions (in time) to classify site or area: One sample per year
2.10 Number of spatial replicates per sampling/survey occasion to classify site or area:
1 replicate. Sampling is performed on 5 stones to guarantee the collection on a representative sample of the site.
2.11 Total sampled/surveyed area or volume or total sampling duration to classify site or area:
Minimum of 100 cm2.

Sample processing

2.12 Minimum size of organisms sampled and processed: Not Apllicable
2.13 Sample treatment:
400 valves are analysed.
Sample is divided (sub-sampling) and organisms of a sub-sample are identified.
2.14 Level of taxonomical identification:
Level: Species/species groups
Specification of level of determination: n.a.
2.15 Record of abundance:
Determination of abundance: Relative abundance
Abundance is related to: n.a.
Unit of the record of abundance: Percentage of valves.
Other record of abundance:
Relative abundance - the abundance of one species in relation to the abundance of the other species. About 400 valves are counted from each sample.
2.16 Quantification of biomass: n.a.
2.17 Other biological data: none
2.18 Special cases, exceptions, additions: none
2.19 Comments: none

3. Data evaluation


3.01 List of biological metrics:
Specific Pollution Index (IPS, CEMAGREF, 1982) for Northern River Types and CEE Index (Descy & Coste, 1991) for Southern River Types.
3.02 Does the metric selection differ between types of water bodies: Yes
3.03 Combination rule for multi-metrics: Not relevant
3.04 From which biological data are the metrics calculated:
List of biological metrics: Data from single sampling/survey occasion in time

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:
Existing near-natural reference sites, Expert knowledge, Least Disturbed Conditions
3.07 Reference site characterisation:
Number of sites: 78 Sites
Geographical coverage:
Reference sites are representative of 7 diatom "river types" spread throughout the country.
Location of sites: n.a.
Data time period: Data from 2004 and 2005.
In order to establish reference conditions the guidelines and pressure screening criteria provided by the Working Group 2.3 ? REFCOND and described on CIS WFD Guidance Document No 10 - Rivers and Lakes ? Typology, Reference Conditions and Classification Systems were followed. The applied reference site identification methodology is integrative including spatial analysis, historical data analysis and expert judgment. Semi-quantitative analysis was used in order to assess the magnitude of 9 pressure variables (Land Use, Riparian Zone, Sediment Load, Hydrological Regime, Acidification and Toxicity, Morphological Condition, Organic Matter Contamination and Nutrient Enrichment, River Continuity) a procedure adapted from European Project FAME - Development, Evaluation and Implementation of a Fish-based Assessment Method for the Ecological Status of European Rivers. A Contribution to the Water Framework Directive (Contract EVK1-CT-2001-00094).
This procedure was applied according to the specificities of the different river types and lack of true reference sites in some river types lead to the selection of ?best available sites?. A final biological screening was also made in order to exclude sites with communities typical of degraded sites. Reference Conditions setting criteria will be updated in view of the work of the 2nd phase of the Intercalibration Exercise.
3.08 Reference community description:
Diatom reference community description was made using available reference sites for each of the 7 "diatom river types". A description of diatom reference community for each "river type" is only available in Portuguese, but not published yet.
3.09 Results expressed as EQR: Yes

Boundary setting

3.10 Setting of ecological status boundaries:
High-good boundary derived from metric variability at near-natural reference sites
3.11 Boundary setting procedure:
No evident discontinuity was detected on the indexes response to the pressure gradient. High-Good classes boundary: 25th percentile of reference sites; the range below was divided in 4 equal classes; Good-Moderate = H/G x 0.75; Moderate-Poor = H/G x 0.50; Poor-Bad = H/G x 0.25.
3.12 "Good status" community: Not available yet.


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

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