on the river Loup (Alpes Maritimes, France)
First results on 04/04/2000
On 31st March 2000, the results of following participants (alphabetical order) were arrived at the Agence de l'Eau Artois-Picardie :
- Almeida Salomé, University of Aveiro, Portugal
- Druart Jean-Claude, INRA Thonon les Bains, France
- Honoré Marie-Ange, Institut Pasteur de Lille, France
- Iserentant Robert, Université de Louvain, Belgique
- Lalanne-Cassou Christian, DIREN Ile de France, France
- Lesniak Christophe, Agence de l'Eau Artois-Picardie, France
- Nazart Maxence et Guillard Didier, DIREN Pays de Loire, France
- Nouchet Nathalie, Bi Eau Cie, France
- Peeters Valérie, DIREN Bourgogne, France
- Peres-Weerts Florence, FPW Cie, France
- Prygiel Jean, Agence de l'Eau Artois-Picardie, France
- Rumeau Alain, Conseil Supérieur de la Pêche, France
- Sabater Sergi, Université de Barcelone, Espagne
- Straub François, Lycée Blaise Cendrars, La Chaux de Fonds, Suisse
- Tudesque Loïc, Centre de Recherche Public Gabriel Lippmann, Luxembourg
- Vidal Henri, Conseil Général des Alpes Maritimes, France
- Vizinet Jessica, Aquascop Cie, France.
Two exploitation types are foreseen. A first one concerns the index values and their significance. The other concerns essentially the systematic.
Table 1 : IBD intercalibration results (September 1999) for 13 operators
P= sampling ; L= slide ; I= inventory ; Witness (slide) : slide realized from a unique sampling and transmitted to each operator
A
B
C
D
E
F
G
H
I
J
M
N
O
Witness
19,1
19
19,2
18,6
19,5
16
16,8
16,4
20
17,2
17
19,3
19
P1L1I1
20
18,9
19,3
18,7
19,9
16,2
15,9
17,7
20
16,7
16
19,5
19,3
P1L1I2
20
19,2
19,3
19
19,1
16,3
16,1
17,4
20
16,8
15,6
19,2
19,2
P1L1I3
20
18,9
19,4
19,4
19,6
16,2
16,1
17,3
20
17,1
15,7
19,2
18,6
P1L2I1
20
18,9
19,1
19,6
19,1
16,3
15,3
17,2
20
17,2
16,3
19,1
19,2
P1L2I2
20
17,2
19,5
20
19,5
15,9
15,3
17,1
20
17,2
16,4
19,5
19,5
P1L2I3
20
17,8
19,4
19,8
19,3
16,1
15,8
17,3
20
17,1
16,2
19,3
19,4
P1L3I1
20
18,1
19,4
20
19,3
15,9
15,6
17,2
20
17,2
15,6
19,3
19,3
P1L3I2
20
17,9
19,6
20
19,5
16,1
15,4
16,9
20
17,1
15,6
18,8
19,2
P1L3I3
20
17,6
19,1
20
19,3
16,1
15,3
17
20
17,1
16
19,6
19,1
P2L1I1
20
17,6
19,3
18,5
20
16,4
15,8
17,3
20
16,9
16,8
18,7
19,5
P2L1I2
20
16,8
19,3
18,7
20
15,8
15,4
17,2
19,9
16,9
16,8
18,7
19,3
P2L1I3
20
17,2
19,4
18,3
20
15,6
16,1
17,1
20
17,1
16,9
18,8
19
P2L2I1
20
17,4
19,6
19,1
20
16
15,6
17
19,8
17
16,6
18,8
19,2
P2L2I2
20
16,8
20
19
20
16,2
15,7
17,2
20
16,9
16,5
18,8
19,1
P2L2I3
20
17,4
19,8
18,7
20
16,3
15,5
17
20
16,8
16,6
18,7
19,1
P2L3I1
20
17,5
19,7
18,9
20
15,9
15,4
17
20
17,1
16,3
18,6
19,3
P2L3I2
20
17,4
20
18,6
20
15,9
15,3
17,3
19,9
17,2
16,6
18,7
19,3
P2L3I3
20
18,1
19,6
19
20
15,9
15,8
17,2
20
17
16,5
18,8
19,4
P3L1I1
19,9
19,2
18,8
18,9
20
16,1
15,5
17,1
20
16,9
12,2
19,6
19,7
P3L1I2
19,9
18,7
19
19
20
15,7
14,8
16,8
20
17,3
12,1
20
19,7
P3L1I3
20
18,6
18,8
19,3
20
15,6
15,5
17
20
17,3
12,1
19,6
19,6
P3L2I1
20
18,7
18,5
19
20
16,2
14,9
17,1
20
16,8
11,8
19,6
19,5
P3L2I2
20
19,3
18,6
18,9
20
15,8
15,1
17
20
17
11,7
19,8
19,7
P3L2I3
20
18,8
18,8
18,6
20
15,9
15
17
20
16,7
12,1
19,8
19,6
P3L3I1
20
18,1
18,5
19,1
20
15,8
15,3
17,1
20
17
11,8
20
19,7
P3L3I2
19,9
18,8
18,8
19
20
16
15,4
17,2
20
16,9
11,9
19,6
19,8
P3L3I3
20
18,6
19,1
19,2
20
16
16
16,9
20
17,1
11,9
19,3
19,8
The expressed results in the shape of index values have been reported in Table 1 in a confidential way, a letter has been given to each operator in a random manner. The data of 4 operators could not been entered because a lack of time.
Though the statistics have not yet been done, some first observations can be made from the results of the 13 operators whose results have been treated.
The sampling seems the most delicate phase. If the sampling formalities described in the IBD standard project are respected, the index results are very homogeneous for the set of the 3 samplings. One single exception is to be mentioned (operator M, sampling P3) : the index results are homogeneous for the samplings P1 and P2 (IBD values between 16 and 17), and for the sampling P3 (IBD value between 11,7 and 12,2). The rapid examination of the floristic lists shows a very perceptible difference in the composition of the floristic suite indicating in particular that the sampling P3 has not been realized in the same conditions than samplings P1 and P2 and in a general way than the whole samplings of the other operators. So all the inventories are dominated by small Achnanthes/Achnanthidium while the inventories corresponding to sampling P3 of operator M are largely dominated by Amphora pediculus, which is a species almost absent in the other inventories. This seems to translate a sampling realized in conditions, which are not conform to the standard.
From these rapid observations, it appears thus that when the sampling formalities are respected, a unique inventory realized from one single slide, itself issued from one single sampling is sufficient to characterize the water quality. The repeating of the sampling formalities has been verified and the formalities can be considered as reliable.
Some variations of the counting formalities have been observed. The IBD standard prescribes a counting of 400 individuals. Only 5 operators (B, C, H, J, N) have respected this number, the other operators having frequently overrun this number, sometimes reaching 450 counted individuals. This seems not to have a big effect on the obtained results (see results of operators C and O for example). This value of 400 had been imposed to minimalize the difference due to the fact that all taxa intervening in the IBD calculation must present in all figure cases a relative abundance superior to 7,5 (3 individuals on 400) and for a great number have a relative abundance superior to an abundance threshold established for each of the taxa of the IBD method.
If the differences between the IBD values are inferior to 1 unit for each operator taken separately, sometimes very perceptible differences have been noted between operators. These differences are only due to the determination of the taxa from the IBD method. In particular, the IBD distinguishes Achnanthes minutissima Kützing var. minutissima = AMIN (under which figures also Achnanthes minutissima Kützing var. affinis (Grunow) Lange-Bertalot = AMAF), Achnanthes minutissima Kützing var. jackii (Rabenhorst) Lange-Bertalot = AMJA, and Achnanthes biasolettiana Grunow var. biasolettiana Grunow = ABIA.
Certain operators (A, B, C, D, E, I, N and O) have distinguished AMIN and ABIA and give high IBD values (from 18,5 to 20). Others (H, J and M) have only considered AMIN and present IBD values comprised between 16 and 17. Others finally (F and G) have distinguished AMIN and AMJA and present IBD values between 14,8 and 16,8. The variations between the IBD values should thus be due to the determination effort. This is confirmed by the examination of the IBD results obtained from the witness slides prepared from a unique sampling by a same operator. Apart from the natural variability from around 1 unit, the variations of sometimes 4 points between the different operators can only result from the manner to determine the IBD taxa. For example, the abundance of taxa AMIN and ABIA which have been distinguished by the operator O have been added and affected to AMIN for the inventories P1L1l1 and P1L1l2. The IBD values pass respectively from 19,5 and 19,2 to 16,9 and 16,7 and thus approach from the IBD values furnished by the operators not having distinguished AMIN and ABIA.
Finally and as a first approach, we can say that :
References
Agences de l'Eau/Cemagref, 2000 - Guide méthodologique pour la mise en uvre de l'Indice Biologique Diatomées NF T 90-354, avril 2000, sous presse.
AFNOR, 2000 &endash; Détermination de l'Indice Biologique Diatomées (norme NF T 90-354), sous presse.
Conseil Général des Alpes-Maritimes, 1995 &endash; Etude de la qualité des eaux du bassin du Loup. Juillet & septembre 1994. Conseil Général des Alpes-Maritimes (DATDE) - Agence de l'Eau Rhône-Méditerranée-Corse, 15 p. + annexes.
PRYGIEL J., COSTE M. & ECTOR L., 1999 &endash; Projets d'intercalibration européens et mise en place d'une charte de qualité pour l'IBD (et l'IPS). In : Ector L., Loncin A. & Hoffmann L. (eds), Compte rendu du 17e colloque de l'Association des diatomistes de langue française. Luxembourg, 8-11 septembre 1998. Cryptogamie, Algologie 20: 139-142.
PRYGIEL J. & ECTOR L., 2000 &endash; Groupement d'Intérêt Scientifique " Diatomées des Eaux Continentales " Présentation et premières orientations. In : Ector L., Compère P. & Vidal H. (eds), Compte rendu du 18e colloque de l'Association des diatomistes de langue française. Nice, 14-17 septembre 1999. Cryptogamie, Algologie 21.