Data rich, information poor? Phytobenthos assessment and the Water Framework Directive

Figures & data

Table 1. Normative definitions of ecological status for lakes and rivers. The general definitions refer to all biological quality elements in all water body types; definitions for ‘macrophytes and phytobenthos’ apply just to lakes and rivers. From Annex V of the WFD (European Union, 2000).

Class	General	Macrophytes and phytobenthos
High	There are no, or only very minor, anthropogenic alterations to the values of the physico-chemical and hydromorphological quality elements for the surface water type from those normally associated with that type under undisturbed conditions.The values of the biological quality elements for the surface water body reflect those normally associated with that type under undisturbed conditions, and show no, or only very minor, evidence of distortion.These are the type-specific conditions and communities.	The taxonomic composition corresponds totally or nearly totally to undisturbed conditions.There are no detectable changes in the average macrophytic and the average phytobenthic abundance.
Good	The values of the biological quality elements for the surface water body type show low levels of distortion resulting from human activity, but deviate only slightly from those normally associated with the surface water body type under undisturbed conditions.	There are slight changes in the composition and abundance of macrophytic and phytobenthic taxa compared to the type-specific communities. Such changes do not indicate any accelerated growth of phytobenthos or higher forms of plant life resulting in undesirable disturbances to the balance of organisms present in the water body or to the physico-chemical quality of the water or sediment.The phytobenthic community is not adversely affected by bacterial tufts and coats present due to anthropogenic activity.
Moderate	The values of the biological quality elements for the surface water body type deviate moderately from those normally associated with the surface water body type under undisturbed conditions. The values show moderate signs of distortion resulting from human activity and are significantly more disturbed than under conditions of good status.	The composition of macrophytic and phytobenthic taxa differs moderately from the type-specific community and is significantly more distorted than at good status.Moderate changes in the average macrophytic and the average phytobenthic abundance are evident.The phytobenthic community may be interfered with and, in some areas, displaced by bacterial tufts and coats present as a result of anthropogenic activities.
Poor	Waters showing evidence of major alterations to the values of biological quality elements for the surface water body type and in which the relevant biological communities deviate substantially from those normally associated with the surface water body type under undisturbed conditions.
Bad	Waters showing evidence of severe alterations to the values of the biological quality elements for the surface water body type and in which large portions of the relevant biological communities normally associated with the surface water body type under undisturbed conditions are absent.

Table 2. National approaches to fulfilling the WFD’s requirement to assess phytobenthos in rivers. Information from European Union (2008, 2013) and www.wiser.eu. ‘No method’ means that the State has neither submitted a national method to intercalibration nor provided information to the WISER database.

	Diatom-based method
	Reference	Weighted			Non-diatom	Macroalgae included
	species	average			phytobenthos	in macrophyte
State	approach	equation	Multimetric	Other	method	method	Notes
Austria	✓	TI/SI	✓		✓		1
Belgium (Flanders)	✓				0	✓	VMM (2009)
Belgium (Wallonia)		IPS			0		2
Bulgaria		IPS			0		2
Cyprus		IPS			0		2
Czech Republic					✓		3
Denmark					0		no method
Estonia		IPS			0	?	2
Finland		IPS			0		2
France				IBD	0	✓	Coste et al. (2009)
Germany	✓	TI/SI	✓		✓		1
Greece					0		no method
Hungary		TI/SI/IPS	✓		0	?	Várbiró et al. (2012)
Ireland		TDI			0		Kelly et al. (2008a)
Italy		pICM	✓		0	✓	4
Latvia					0
Lithuania					0
Luxembourg		IPS			0	✓	2
Netherlands		IPS			0	✓	2
Norway					✓		Schneider & Lindstrøm (2011)
Poland	✓	TI/SI	✓		0	✓	1
Portugal		IPS			0		2
Romania					0		no method
Slovakia		✓	✓		0	✓	5
Slovenia		TI/SI			0	✓	1
Spain (north)	✓		✓	✓	0		6
Spain (south)		IPS			0		2
Sweden		IPS			0		2
United Kingdom		TDI			0	✓	Kelly et al. (2008a)

Notes

1. TI: Trophic Index (Rott et al., 1999); SI: Saprobic Index (Rott et al., 1997).

2. The standard reference for the IPS is Coste in CEMAGREF (1982) and it is usually implemented via the Omnidia software (Lecointe et al., 1993); outcomes are, to some extent, dependent upon the taxonomic conventions employed by users.

3. Czech assessment system is based on the weighted average equation using sensitivity values originally from the Czech Technical Standard 75 7716 Water quality - Biological analysis - Determination of Saprobic Index (ČSN 75 7716, 1998) but subsequently updated. It encompasses both diatoms and non-diatoms (L. Opatrilova, P. Marvan, personal communication).

4. Italy has adopted the phytobenthos intercalibration common metric (pICM: Kelly et al., 2009b) as its national metric. This is the average of the TI and IPS (see 1 and 2 above) used as a basis for pan-European comparisons.

5. Slovakia uses three metrics from the Omnidia software (Lecointe et al., 1993): IPS (see note 2), CEE (Descy & Coste, 1991) and EPI-D (Dell’Uomo, 1998), with the lowest value determining the final status class.

6. Galicia (NW Spain) uses a multimetric composed of the mean of type-specific lists of ‘sensitive’ diatoms, ‘tolerant’ diatoms and biomass (as chlorophyll a). See Delgardo et al. (2010).

Fig. 1. Schematic diagram illustrating how position on the Ecological Quality Ratio (EQR) scale can affect the confidence of an ecological status classification. It assumes ecological status boundaries are regularly arranged along the EQR gradient (bad status: 0–0.2; poor: 0.2–0.4; moderate: 0.4–0.6; good: 0.6–0.8; high: > 0.8). The upper plot (a) shows a (statistical) sample comprising 30 spatial and/or temporal replicates from a water body, with a mean EQR of 0.58 and standard deviation of 0.027. The mean value suggests moderate status; however, as this is close to the good/moderate boundary, 11 samples have EQRs ≥ 0.6, suggesting good status. There is, in other words, a 63% probability that the ‘true’ status is moderate and a 37% probability that it is, in fact, good status. By contrast, although the standard deviation is larger (0.046) in the lower plot (b), the confidence of class is greater as the mean corresponds to the middle of the class (0.3) and the distribution does not spill into adjacent classes.

Fig. 2. The River Nent at Nentsberry, Cumbria, northern England (UK National Grid reference NY 766449). The green colour on the river bed is due to prolific growth of metal-tolerant populations of the chlorophyte Stigeoclonium tenue, which accounts for approximately 80% of the biovolume of algae in the river (Kelly, 2012).

Table 3. National approaches to fulfilling the WFD’s requirement to assess phytobenthos in lakes. Information from European Union (2008, in prep.) and www.wiser.eu. Only those states with formal assessment of phytobenthos or macroalgae other than charophytes are included in this table.

	Diatom-based method
	Reference	Weighted
	species	average			phytobenthos	Macroalgae included in
State	approach	equation	Multimetric	Other	method	macrophyte method	Notes
Belgium (Flanders)	✓					✓	VMM (2009)
Estonia						✓	1
Finland		IPS					2
France				IBD		✓	3
Germany	✓	See note	✓				4
Hungary		TDIL/IBD/EPI-D	✓				5
Ireland		LTDI				✓	6
Netherlands						✓
Poland	✓	TIJ	✓			✓	7
Slovenia		TI				✓	TI
Spain (south)					0	✓
Sweden		IPS					2
United Kingdom		LTDI					6

Notes

1. Relative abundance of macroalgae recorded as part of macrophytes method.

2. See Note 2 for Table 2.

3. The IBD (Coste et al., 2009) is under evaluation but has not yet been formally adopted.

4. The German method combines a reference index and one of two weighted average metrics that assess trophic status. The Trophic index of Hofmann (1999) is used in most regions except the north-west, where the Trophic index of Schönfelder (2005) is used. Only the method of Schönfelder (2005) has been formally intercalibrated and reported in European Union (2013). Schaumburg et al. (2004) give more information on German methods in lakes.

5. Hungary uses the Multimetric Index for Lakes for all lakes except Lake Balaton. This is the average of the Trophic Diatom Index for Lakes (TDIL: Stenger-Kovács et al., 2007), IBD and EPI-D. TDIL is calculated using DILSTORE software (Hajnal et al., 2009) and other metrics using OMNIDIA (Lecointe et al., 1993). For Balaton, the mean of IBD and TDIL is used.

6. Both Ireland and UK used a version of the TDI optimized for lakes (‘LTDI’: Bennion et al., 2014) and also record cover of macroalgae as part of the macrophytes assessments.

7. TIJ = Trophic Index for Lakes, which is combined with a reference index to produce the final classification (Picinska-Faltynowicz & Blachuta, 2008).

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