Template for reporting the MS assessment method
in the case where the Intercalibration exercise
is not possible (Gap 3)
1. INTRODUCTION



Member State: Spain (ES) – Catalan region;
BQE: Benthic invertebrate fauna, QAELS index.
Water body category (type): TW: Coastal lagoons.
2. DESCRIPTION OF NATIONAL ASSESSMENT METHODS
QAELS is a multiple habitat approach sampling the benthos (sediments and macrophytes) of littoral
band. The index considers the sensitivity and tolerance of major and indicator organisms, as well as
abundance and richness of some selected taxa. Littoral hand net samples address multiple habitats
sampling in proportion to their representation in the field. The index is related to eutrophication and
pollution by organic matter. It classifies coastal lagoons intro one quality category among five, according to
WFD. Quality boundaries are derived from metric variability only at near-natural reference sites,
using percentile 75 as good-moderate boundary.
2.1. METHODS AND REQUIRED BQE PARAMETERS
Table 1. Overview of the metrics included in QAELS method.
MS
Spain – Catalan
region
Taxonomic
composition
Metrics ACCO and
RIC includes
microcrustaceans,
macrocrustaceans
and insects.
Abundance
Sensitive taxa
Tolerant taxa
Diversity
For 3 major taxa
(microcrustaceans)
yes
yes
Not strictly – only
taxa richness of
crustaceans and
insects
Combination rule used in the method: QAELS=(ACCO+1) x log10(RIC+1)
Where ACCO takes into account the relative abundances and the sensitivity/tolerance of major
crustacean groups, and RIC takes into account the richness of crustaceans and insects.
Conclusion on the WFD compliance (are all the indicative parameters included; if not, why): QAELS
index uses all parameters included for benthic invertebrate fauna in transitional waters. Some of them
are used with some limitations. The restricted use of taxonomic composition, abundance and diversity
estimations responds to the use of data that provide information consistent with less effort.
2.2. SAMPLING AND DATA PROCESSING
Description of sampling and data processing:
 Sampling time and frequency: Sample collection takes place twice a year. Permanent lagoons
are sampled at late winter (March) and at the end of spring (June). Temporary lagoons are
sampled at the beginning of hydrologic period and before being dry;
 Sampling method: Invertebrate sampling is performed using a 20 cm diameter dip-net (250
µm mesh size). At each lagoon, three sweeps per visit are carried out along transects. Each
sweep consists of 20 dip-net “pushes” in a rapid sequence, to cover all the different habitats in
the littoral zone of the lagoon. Each sweep is preserved separately;
 Data processing: Organisms of the first sweep are identified and counted, and they are used to
estimate the index based on relative abundances of microcrustaceans. If necessary, this sample
could be sub-sampled. The other two samples (sweeps) are used to identify organisms, and to
calculate the index based on taxon richness;
 Identification level: Microcrustaceans are identified at genus level. Macroinvertebrates are
identified at family level (insects – larval, pupae and nymph stadia) or at genus level
(crustaceans, and adults of Coleoptera and Heteroptera).
2.3. NATIONAL REFERENCE CONDITIONS
The procedure to derive reference conditions consists of two analyses, an initial a priori evaluation of
pressures at the landscape and field-local level, and a posteriori contrast with local physico-chemical,
hydro morphological and biological data and conditions.
A priori criteria
The initial screening was based on existing regional coastal lagoons inventories. The analysis
consisting on:
0. Evaluation at the catchments level of pressures:
As a first step, it is necessary the identification and assessment of the risk of each coastal lagoon to be
influenced by the catchment’s activities. The origin of water to the lagoon is considered the main
driver connecting adjacent aquatic ecosystems through water fluxes (i.e. rivers with coastal lagoons),
and the dynamism of their interaction. As a consequence, we expect that some types of coastal lagoons
will be more susceptible of being influenced by human pressures in the catchments (Table 1).
Table 1. Types of coastal lagoons in relation with the water origin and water connectivity
Type of coastal lagoons
Use of thresholds
Main river axis (high risk)
Annually flooded (medium risk)
Inter-annually flooded (low risk)
Episodically flooded (very low risk)
Hypogenic water origin (relates to quantity and quality of aquifer)
apply
do not apply
For those coastal lagoons susceptible to be influenced by landscape level human pressures, a check
procedure should be performed when looking for reference lagoons. This procedure follows a similar
methodology as the one developed by the CB GIG Rivers based on the REFCOND criteria. This
methodology will require the use of pressure thresholds to quantify human activities and land uses in
the catchments able to influence the ecological status, such as percentage cover of artificial areas and
2
of intensive agriculture fields (irrigation), existence of direct points of pollution, aquaculture, and
recreational activities (including boats) among others.
A template will be produced describing the main types of human pressures, with quantification with
thresholds of a variety of reference criteria to be fulfilled by the water bodies to be candidates for
reference systems; this can be done in a similar way as in the CB Rivers GIG.
1. Spatial inspection of cartography, satellite and aerial photographs to gather information on
the land use surrounding the wetland.
As a second step in the search for pressures (point and diffuse origin) able to influence the ecological
status of the lagoons, an assessment of concrete existing pressures within defined bands over the
perimeter of the lagoons is performed:
a. Assessment of land uses within a band of <50 m from the perimeter of the lagoon
(buffer)
b. Assessment of landscape use between >50-300 m from the perimeter of the lagoon
Priorised list of pressures to be considered and evaluated within the 50 m, and between 50 and 300 m
bands to select reference systems (Table 2). The approach is based on US EPA (chapter 6).
-
Best: natural landscape, as expected for reference sites with no evidence of human
disturbance
Moderate: mostly undisturbed, low intensity alteration, some human use disturbance
Fair: highly altered, significant human disturbance
Poor: almost no natural habitat present, nearly all or all surrounding landscape in human use
Table 2. Priorised list of pressures to be considered and evaluated within the first 50 m, and between 50- 300 m
bands to identify reference systems, and expected status under increasing levels of pressures
>50-300 m band
Yes
Absence of intensive (irrigation) agriculture
Wooded or trails
Yes
no influence on water connexion
presence of exotics, nor invasive cover
Low use for recreational activities
< 50 m band Pressure
Yes
Yes
Yes
Yes
Yes
Yes
Yes
expected status
Autochthonous vegetation
Absence of agriculture
Absence roads, no trails
Absence artificial/urban use/non point pollution
Absence of channels, sluice gates, concrete structures, quaries
Absence of exotic species
Absence of recreational activities
Restored prairie, young second growth woodlot, shrubland
Active pasture
Asphalted trails
Low artificial/urban use
Reference / best
Moderate
Active pasture
Less intensive agricultures
Medium road density
Medium artificial/urban use
Fair
Tree/shrub removal, Golf course
Intensive agriculture
High road density or impercious surfaces in immediate landscape
High artificial/urban use
Water treatment plants
Channelisation, sluice gates, weirs
Quaries, mines
Poor
3
2. Field ascertainment on the absence of pressures:
Further field validation, taking into account point sources directly influencing the water body and its
morphology, like fishing activities, point pollution sources, dragging and other human constructions
and activities in the perimeter of the coastal lagoon (artificial, agriculture).

The water perimeter of the lagoon is not closed by weirs or levees, and there is no
limitation or canalization either at the entrance or at the exit of the lagoon. When the
water level rises, adjacent lands get flooded without important limitation to the water
body spatial extension.
LEVELS
0
Catchment
influenced
YES
1
< 50 m
2
Field check
>50-300 m
Non catchment
influenced
< 50 m
NO
Field check
>50-300 m
Figure 1. Screening procedure and levels to evaluate pressures on the different types of coastal lagoons (with or
without catchments influencing dominant water fluxes)
A posteriori criteria
The initial screening for reference sites is complemented with an evaluation of a posteriori criteria.
These criteria will allow the final check to assure the consistency of the spatial network of lagoon
systems with the reference condition, and is based on the study of existing data and information from
the systems under study.
Consistency of existing data with ecological functioning under reference conditions:





Check of physico-chemical data and information on the composition of biological
communities
There are not invasive fauna or flora species. The composition and structure of plant
communities is characteristic of the type
The hydrology within the lagoon is not affected by water inputs or outputs, managed or
affected by humans; instead, they depend mainly on natural hydrological disturbances,
like sea storms, rainfall, or rise of water level. There are not extractions, neither input
of water or nutrients from runoff channels of urban, industrial or agricultural origin.
The level of water is not maintained artificially, so during the dry period the lagoon
may dry
There will never be hypertrophy episodes, in the moments previous to dryness or
minimum water level. If important decreases in dissolved oxygen values occur they do
not motivate the disappearing of the type communities of the lagoon, or its substitution
by a typical community of anoxic prolonged conditions
Due to the natural hydrologic fluctuating characteristics of theses systems, no
restriction is imposed over salinity values, nutrient concentration and water
permanence period. However, seasonal patterns in physico-chemical composition
4
should be analysed in water bodies selected as references in order to discard pressures
not detected in the “a priori” evaluation, such as diffuse nutrient or contaminant inputs
Further comments on the criteria
Given the strong human activity developed during centuries in the Mediterranean coast, pristine
transitional water ecosystems without any pressures in their catchments are probably inexistent. This
fact makes sometimes impossible to find reference water bodies. However, some human actions in the
past have changed the ecological characteristics of transitional water ecosystems, modifying initial
conditions and generating new ones which can be considered also under reference conditions:

For example, a freshwater coastal lagoon may become a “near to pristine” brackish
coastal lagoon, as a consequence of ancient changes in water supply, if these changes
are not presently causing any alteration in the “brackish-type” characteristic hydrology

Additionally, there are some man made actions which do not have any impact on water
quality and on the ecological state. This is the case of some old man made structures
currently not in use, or the existence of non productive agricultural practices, such as
grass reap, in the buffer area
2.4. NATIONAL BOUNDARY SETTING
Quality boundaries are derived from metric variability only at near-natural reference sites, following
REFCOND guidance.
High boundary: QAELS values higher than percentile 90.
Good boundary: QAELS values between percentile 90 and 75.
Moderate boundary: QAELS values between percentile 75 and 50.
Poor boundary: QAELS values between percentile 50 and 25.
Bad boundary: QAELS values smaller than percentile 25.
We also tested other methods described in REFCOND guidance (Wallin et al., 2003), based on the
selection of the sites (disturbed and/or near-natural), and the selection of the statistic (percentile,
standard deviation, etc.), as well as a method based on the identification of tolerant and sensitive taxa
in relation to eutrophication (described in Ruse, 2010). Resulting quality categories were correlated to
different trophic indicators (nutrients, chlorophyll, TRIX index, etc.), and finally we chose the method
with higher correlation.
According to the selected methodology, the final boundaries are shown in Table 1.
Table 1. Class boundaries for QAELS index (expressed as EQR)
Type
DP
TA
Type description
Oligohaline coastal lagoon
Mesohaline coastal lagoon
H-G
0,86
0,72
G-M
0,58
0,62
M-P
0,51
0,55
P-B
0,39
0,46
2.5. PRESSURES ADDRESSED
QAELS index responds to eutrophication and pollution by organic matter. The best indicator is TRIX
index, which is based on chlorophyll, dissolved oxygen, nitrogen (DIN) and phosphorous (TP). The
5
Strength of relationship between QAELS and TRIX is, depending on type (oligo or mesohaline coastal
lagoon): r= -0.36 to -0.43; p<0.001.
Table 1: Correlations of QAELS (and its main metric ACCO) with Total Nitrogen, Total phosphorous, chlorophyll
and TRIX, for oligo (DP) and mesohaline (TA) coastal lagoons. p<0.05*; p<0.001***. No significant correlations
are not shown.
LnTN
DP
TA
lnTP
lnPO4
lnCha
TRIXe
ACCO
-0.27***
-0.20*
-0.32***
-0.38***
QAELSe
-0.35***
-0.31***
-0.34***
-0.36***
ACCO
-0.48***
-0.43***
-0.22*
-0.42***
QAELSe
-0.49***
-0.41***
-0.24*
-0.43***
DP
TA
1,2
1
1
0,8
0,8
QAELS
QAELS
1,2
0,6
0,6
0,4
0,4
0,2
0,2
0
0
0
1
2
3
4
5
6
7
0
TRIX
1
2
3
4
5
6
TRIX
Figure 1. Dispersion-plots showing the significant trends of QAELS gradient of pressure (TRIX) for each type
(oligo (DP) and mesohaline (TA) coastal lagoons).
Figure 2. Relationship between index QAELS and its main metric ACCO and trophic variables. Colours and forms
indicate the sense (positive: blue, negative: red) and intensity (narrow and dark: strong, circular and pale: weak)
of the relationship (Boix et al., 2010).
6
3. WFD COMPLIANCE CHECKING
The first step in the Intercalibration process requires the checking of national methods considering
the following WFD compliance criteria.
Table 2. List of the WFD compliance criteria and the WFD compliance checking process and results
Compliance criteria
Ecological status is classified by one of five
classes (high, good, moderate, poor and bad).
High, good and moderate ecological status are
set in line with the WFD’s normative
definitions (Boundary setting procedure)
Compliance checking
yes
Yes
Yes
Taxonomic
composition
All relevant parameters indicative of the
biological quality element are covered (see
Table 1 in the IC Guidance). A combination
rule to combine parameter assessment into
BQE assessment has to be defined. If
parameters are missing, Member States need to
demonstrate that the method is sufficiently
indicative of the status of the QE as a whole
Abundance
Sensitive taxa
Tolerant taxa
Diversity
Yes for the main groups but not
strictly - only as groups of
different sensitivity
For 3 major taxa
yes
yes
Not strictly - only taxa richness of
crustaceans and insects
The restricted use of taxonomic composition, diversity and
abundance estimations responds to the use of data that
provide information consistent with less effort (see, for
example, the taxonomic resolution below).
The combination rule is:
QAELS=(ACCO+1) x log10(RIC+1)
Where ACCO combines abundances, tolerances and
sensitivities of the main taxa (cladocera, copepoda and
ostracoda), and RIC measures the richness including
crustaceans and insects.
Assessment is adapted to intercalibration
common types that are defined in line with
the typological requirements of the Annex II
WFD and approved by WG ECOSTAT
Yes
The water body is assessed against typespecific near-natural reference conditions
Yes
Assessment results are expressed as EQRs
Sampling procedure allows for
representative information about water
body quality/ecological status in space and
time
All data relevant for assessing the biological
parameters specified in the WFD’s
normative definitions are covered by the
sampling procedure
Yes
Yes
Selected taxonomic level achieves adequate
confidence and precision in classification
Yes
Yes
QAELS uses genus level to optimize the efforts, because
genus level is highly correlated to species level.
7
Fig. 1. Correlation between the main metric of QAELS index
(ACCO) calculated to genus and species level, in oligohaline
coastal lagoon type (DP).
Fig. 2. Correlation between the main metric of QAELS index
(ACCO) calculated to genus and species level, in mesohaline
coastal lagoon type (TA).
4. IC FEASIBILITY CHECKING
The intercalibration process ideally covers all national assessment methods within a GIG. However,
the comparison of dissimilar methods (“apples and pears”) has clearly to be avoided. Intercalibration
exercise is focused on specific type / biological quality element / pressure combinations. The second
step of the process introduces an “IC feasibility check” to restrict the actual intercalibration analysis to
methods that address the same common type(s) and anthropogenic pressure(s), and follow a similar
assessment concept.
8
4.1. TYPOLOGY
Does the national method address the same common type(s) as other methods in the Intercalibration
group? Provide evaluation if IC feasibility regarding common IC types.
QAELS method address to three types of coastal lagoons: Oligohaline, Mesohaline (choked), and
Mesohaline (restricted). The calculation of QAELS index, and also the quality boundaries, is quite
different between types, due to differences in the presence and abundance of indicator species.
However, QAELS metrics and boundaries for mesohaline choked and restricted lagoons are treated in
the same way. So, in order to apply the index, two typologies are considered: oligohaline (DP) and
mesohaline (TA).
4.2. PRESSURES ADDRESSED
Does the national method address the same pressure(s) as other methods in the Intercalibration
group? Provide evaluation if IC feasibility regarding pressures addressed.
Yes, it addresses to eutrophication and pollution by organic matter.
4.3. ASSESSMENT CONCEPT
Does the national method follow the same assessment concept as other methods in the
Intercalibration group? Provide evaluation if IC feasibility regarding assessment concept of the
intercalibrated methods
QAELS was not finally intercalibrated in the second phase IC due to differences on taxonomic
composition in relation with other member states (MSs) (>90% dissimilarity); this decision was based
on ordination plots and in the analysis of common taxa between MSs. However, a complete
justification about habitat preferences of sampled fauna was given. It is transcribed below:
Habitat preferences of animals considered in QAELS index. Benthic vs. planktonic species.
Sampling method
In order to calculate the QAELS index, samples are taken with a dip-net (250 µm mesh size), on the
littoral zone substrate (sediments or aquatic vegetation).
Three sweeps are needed along transects, each one consisting of 20 dip-net ‘pushes’ in fast sequences,
to cover all the different habitats of the wetland littoral zone (Boix et al., 2005), as stated, mostly
sediments and aquatic vegetation.
Because of the mobilization of the bed sediments due to the hand-net sampling, the sediment fauna are
resuspended and subsequently collected. Moreover, hand-net sampling into the vegetation captures
the animals living on or into it. This sampling method captures mostly macro and meiobenthos
(insects, crustaceans, and other invertebrates such as gastropods, bivalves, polychaetes or
oligochaetes). It may also collect zooplankton species, which are not target species (see next section).
However, mainly at shallow ecosystems, zooplankton species could be considered as meiobenthos
when they spend some time on bottom (Timm et al., 2007), when zooplankton refers to small species
that live suspended in water (Pace & Lonsdale, 2006).
9
Habitat preferences of QAELS key species
QAELS index is based on two metrics: the first is a measure of taxon sensitivity to water quality
(ACCO) and focuses on the relative abundance of Cladocera, Copepoda and Ostracoda while the second
is a measure of taxon richness (RIC), and takes into account insects and crustaceans. Therefore, QAELS
index focuses on both macro and meio-fauna (invertebrates).
Macroinvertebrates collected and considered in QAELS (RIC) are insects and crustaceans.
Macrocrustaceans are especially important in coastal wetlands, while insects are particularly relevant
in inland wetlands (Boix et al., 2005). We collect crustaceans such as Mesopodopsis slabberi, Gammarus
aequicauda or Proasellus coxalis, and insects such as Cloeon inscriptum (Ephemeroptera), Anisops
sardeus, Micronecta scholtzi or Sigara lateralis (Heteroptera), Enochrus bicolour, Hydroporus planus or
Helophorus fulgidicollis (Coleoptera), and Odonates and Dipterans. All these insect families are also
common at benthic samples taken in rivers, and considered by benthic macroinvertebrate indices –
see, for example, the national Spanish index to Mediterranean streams and rivers IBMWP (AlbaTercedor & Sánchez Ortega, 1988; Alba-Tercedor et al., 2004) already intercalibrated (EC, 2008).
ACCO index considers a maximum of 37 genera of Cladocera, Copepoda and Ostracoda, 25 genera
considered in thalassohaline coastal lagoons and 21 genera considered in freshwater oligo or
mesohaline lagoons. These organisms are considered meiobenthos, and may be either exclusively
benthonic (i.e. Ostracoda, Meisch, 2000), or live in both habitats: plankton and benthos (i.e. Cladocera
and Copepoda, Einarsson & Örnólfsdóttir, 2004; Streever & Crisman, 1993; Timm et al., 2007).
Whereas more than 70% of QAELS key organisms are exclusively benthic (i.e. cladocera Pleuroxus
(Alonso, 1996), copepod Cletocamptus and all harpacticoida (Dussart, 1967; 1969), no taxa is
exclusively planktonic.
Table 1 classifies all genera taken into account by QAELS (ACCO), with the indication of their habitat
preferences.
10
Table 1. Habitat preferences of crustaceans considered in QAELS (ACCO) index (for DP and TA lagoons). 1:
Exclusively benthic; 2: Benthic, but may invade plankton (heloplanktonic); 3: Planktonic, but may stay at
benthos; 4: Exclusively planktonic. (Alonso, pers. com.; Alonso, 1996; Dussart, 1967 & 1969; Meisch, 2000)
Type of
lagoon
Habitat
1
CLADOCERA
COPEPODA
OSTRACODA
Alona
Bosmina
Ceriodaphnia
Chydorus
Daphnia
Moina
Oxyurella
Pleuroxus
Scapholeberis
Simocephalus
Acanthocyclops
Calanipeda
Canuella
Cletocamptus
Cyclops
Diacyclops
Ectocyclops
Eucyclops
Eurytemora
Halicyclops
Harpacticus
Macrocyclops
Megacyclops
Mesochra
Nitokra
Pseudonychocamptus
Tisbe
Tropocyclops
Cypria
Cyprideis
Cypridopsis
Eucypris
Herpetocypris
Heterocypris
Loxoconcha
Paracyclops
Sarscypridopsis
Xestoleberis
DP
DP
DP
TA, DP
TA, DP
DP
DP
TA, DP
DP
TA, DP
TA, DP
TA, DP
TA
TA
TA, DP
TA
DP
TA, DP
TA
TA
TA
DP
DP
TA
TA
TA
TA
TA, DP
DP
TA
TA, DP
TA, DP
DP
TA, DP
TA
DP
TA
TA
2
3
4
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
27
(73%)
19
(76%)
15
(71%)
Total:
TA:
DP:
11
2 (5%)
8 (22%)
0
1 (4%)
5 (20%)
0
1 (5%)
5 (24%)
0
4.4. CONCLUSION ON THE INTERCALIBRATION FEASIBILITY
The conclusions of the second phase of intercalibration were the following: The Intercalibration was
feasible in terms of typology. The typology and common types with available data had been agreed in
general terms by the experts. It was also feasible in terms of pressures addressed by the method, because it
addresses specifically eutrophication and organic pollution. Also, it was feasible in terms of assessment
concepts, because it was demonstrated that fauna evaluated by QAELS have benthic habitats in these types
of TW. However, taxonomic differences due to different sampling protocols (e.g. use of hand-net instead of
grabs) made the intercalibration exercise not possible.
5. DESCRIPTION OF THE BIOLOGICAL COMMUNITIES
DESCRIPTION OF THE BIOLOGICAL COMMUNITIES AT HIGH STATUS
High status communities are composed by more than 20% of sensitive species. As in other quality
status, non indicative species represents about 40% of the total richness, and they are not included in
the index. So, the descriptions of the community at each quality level are mainly based only on
indicative species (60% of the total richness).
Taking into account only indicative species, at high status community more than 40% are sensitive
species, with indicator value higher than 7. These sensitive species represent more than 90% of the
total abundance, whereas tolerant species, with indicator values less than 4, only represent 2% in
abundance.
DESCRIPTION OF THE BIOLOGICAL COMMUNITIES AT GOOD STATUS
At good status, indicative sensitive species (with indicator value higher than 7) represent about 25%
of total indicative species, and about 50% of their abundance. The presence of very tolerant species
(indicator value less than 2) is possible but rare, and they represent, in terms of abundance, less than
1%.
DESCRIPTION OF THE BIOLOGICAL COMMUNITIES AT MODERATE STATUS
At moderate status, the abundance of sensitive species is very low, less than 5% in abundance and
about 15% in richness. The main community is composed by mid tolerant species (with indicator
values about 5), representing more than 50% of richness and more than 80% of abundance.
6. REFERENCES
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biológica de las aguas corrientes basado en el de Hellawell (1978). Limnetica, 4: 51-56.
Alba-Tercedor J et al. 2004. Caracterización del estado ecológico de los ríos mediterráneos ibéricos
mediante el índice IBMWP (antes BMWP’). Limnetica, 21 (3-4): 175-185.
Alonso, M. 1996. Crustacea, Branchiopoda. A: Ramos, MA (ed) Fauna Ibérica, 7. Museo Nacional de
Ciencias Naturales. CSIC. Madrid. 486 pp.
Boix D, Gascón S, Sala J, Martinoy M, Gifre J & Quintana X. 2005. A new index of water quality
assessment in Mediterranean wetlands based on crustacean and insect assemblages: the case of
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12
Boix et al. 2010. Avaluació de l’estat ecologic de les zones humides I ajust dels indicadors de qualitat.
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Dussart, B. 1967. Les Copépodes des eaux continentales I. Éditions N. Boubée & Cie. Paris. 500 pp.
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meiobenthic cladoceran assemblages in natural and constructed wetlands in central Florida. Wetlands,
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Timm T, Kumaria M, Kübara K, Soharb K & Traunspurger W. 2007. Meiobenthos of some Estonian
coastal lakes. Proc. Estonian Acad. Sci. Biol. Ecol., 56, 3, 179-195.
Wallin M, Wiederholm T & Johnson RK. 2003. Guidance on establishing reference conditions and
ecological status class boundaries for inland surface waters. Final draft, version 7.0. Technical report.
Common Implementation Strategy Working Group 2.3, European Union. 93 pp.
13