Cover - Characteristic species - Opportunistic species WFD - coastal waters - GIG NEA
Erwan Ar Gall & Michel Le Duff IUEM (European Institute for Marine Studies) – UBO (University of Western Brittany - Brest)
Technopôle Brest -Iroise
(November 2010 version) 1. In situ sampling procedure
Monitoring sites: shores exhibiting essentially bedrock surfaces (reduced surface of boulders, sand, mud or gravels, large boulders being acceptable at lowest levels), if possible within the range 30 – 100 m width and 100 – 300 m length, and comprising most of the intertidal belts occurring in a given area.
Sampling period: from early March to late July, once every three years for each site.
Replicates : both diversity and structure of each macroalgal community (corresponding to a given belt) are noted on the field within three 33 cm X 33 cm squares per spot, determined by drawing lots, within three 1.65 m X 1.65 m permanent spots per belt, so within 9 squares and 0.9 m2 per belt and per year.
Points are materialized on the soil by a removable 1.65 m X 1.65 m frame comprising 5 X 5 squares.
A field sheet is annexed to the document. 1.2. Global plant covering of the belts (covering percentages, ca. a few %)
Laminaria digitata (Ld) / Laminariales :
NB : in Brittany (and Armorican Massif, including western Channel waters and North of the Bay of Biscay), all sites exhibit at least 5 of these 6 typical belts, the lowest of them being reached only during great tides (tide coefficients > 95). In areas outside Brittany, the minimal number of belts may be drastically reduced (e.g. 2 levels in the Basque Country).
Even in Brittany, belts may overlap and then must be grouped (e.g. no He belt and no Ld belt but a Rhodophyceae / Laminariales level)
An / Fves, Fser / Rhodophyceae, He / Bb / Rhodophyceae, Ld / Laminariales are usually named An, Fser, He and Ld, respectively.
1.3. Surface of each bathymetric level * (m2) Pelvetia canaliculata (Pc) :
*: for each level, all bedrock surfaces potentially covered by seaweeds (dominating species or other species) must be taken into account, at the exclusion of large sand / gravel / small boulder areas.
1.4. Observations in the sampling squares In each square, cover of all characteristic and opportunist species identified on the field, expressed as covering percentages as follows:
2. Quality index calculation for EQ intertidal macroalgae
in coastal waters
This index has been adapted to the Breton shore line and more largely to Atlantic and Channel coasts of France from the CFR index developed in Spain. It takes into account the contribution of each macroalgal community, referred to as a belt, to the global plant covering of a given intertidal rocky shore (maximum 40 points), the number of characteristic species (maximum 30 points) and the total cover of opportunist species in every belt (maximum 30 points). The index corresponds therefore to a notation on 100 summarizing the points obtained in the calculation of the above three sub-indexes.
N.B.: only crude data are collected on the field (cf. field sheet) and all calculations can be done afterwards.
2.1. Global plant covering All levels of the intertidal zone are concerned, and the relative importance of each belt is converted into points using a sub-index table taking into account the rank of each belt determined from its surface (bedrock) within the limits of the site and then the covering percentage of the vegetation in the corresponding area.
Points obtained in all belts are cumulated in order to give a global value for the site out of 40. If one belt lacks (or more), a rule of three must be applied to get the notation out of 40. When more than 50 % of the substratum surface is unconsolidated (sand, mud, gravels, small boulders) or friable (stratified limestone), the level can be disqualified and so not taken into account. However, either a high turbidity or a 1 – 2cm sand layer over the rocky substrate cannot be considered as disqualifying, since Rhodophyceae often replace dominating Phaeophyceae in those cases.
Each belt is therefore ranked according to the importance of its surface. In that way, it is possible to take into account the relative extension of the plant covering in each belt, while enabling a simple calculation of the sub-index, using entire numbers and a total not exceeding 40. A maximum of 5 index tables can be used for the calculation, one for each level, following a decreasing expansion ranking. When present, the sixth level (i.e. with the less extended plant - covered surface) shares the same table as the fifth one. When one belt (or more) lacks on the site, a rule of three will be applied to get the notation out of 40.
Index table for the global plant covering of each belt.
(Ranks are based on the potentially plant-covered area)
Rather than a global list of characteristic species for a typical shore, the repartition of these species at each level, i.e. in each habitat constituted by belts (linear populations) of structurating Phaeophyceae, has been taken into account. Hereafter are listed from the bottom to the top of the rocky shore the belts occurring on the coasts of both the Channel and the Atlantic Ocean: Laminaria digitata (Ld), Himanthalia elongata - Bifurcaria bifurcata (He + Bb), Fucus serratus (Fser), Ascophyllum nodosum - Fucus vesiculosus (An + Fves), Fucus spiralis (Fspi), Pelvetia canaliculata (Pc). The last two belts are joined here because of their low algal diversity. Beyond that grouping, the relative importance of each belt in the calculation of this sub-index is balanced by an index table adapted to each level, with a given number of characteristic species.
The species taken into account on the field to calculate the index are listed in the table below when they exhibit a minimal cover of 2.5% per belt. Concerning the combined belts Pc and Fspi, species taken into account must cover at least 2.5% in one of these two belts. When species have a heteromorphic life-cycle, surfaces covered by each generation must be added (e.g.Mastocarpus stellatus / Petrocelis cruenta).
Sub-index value = sum of values per belt (or grouped belts) / 5,
when 5 levels occur (at least either Pc or Fspi for Pc + Fspi)
or sub-index value = sum of values per belt / n X 5
The complete list of characteristic species occurring in the intertidal zone on rocky shores in Brittany (and beyond, on the coasts of the Armorican Massif) comprises 33 genera / species of sea macrophytes, including 2 species of Lichens, 10 species of Phaeophyceae, 20 genera or species of Rhodophyceae and 1 species of Chlorophyceae. When additional names are indicated for a given taxon, they can refer to various shapes of the same species, to species which cannot be distinguished on the field (e.g.Laurencia obtusa / L. hybrida) or to common synonymes.
Asparagopsis armata / Falkenbergia rufolanosa
Corallina spp. pour C. elongata + C. officinalis + Haliptilon squamatum
Complete list of characteristic macrophytic species on Breton rocky shores (extended to North of Biscay and West Channel) in the intertidal zone
(microhabitats such as ponds are excluded)
Index tables concerning the number of characteristic species per belt (or level).
Pc - Fspi
An - Fves
5 - 6
3 - 4
1 - 2
6 - 7
4 - 5
1 - 3
He - Bb
7 - 9
4 - 6
1 - 3
7 - 8
4 - 6
1 - 3
2.3. Cover by opportunist species The sub-index takes into account the following taxa, whatever the level.
Phaeophyceae:Ectocarpales (Ectocarpaceae : Ectocarpus spp., Pylaiella spp., Hincksia spp.)
Chlorophyceae: Enteromorpha compressa
Rhodophyceae: Ceramium spp.
Polysiphonia spp. (excluding both P. lanosa and P. elongata)
Colonial microalgae Diatoms (either epiphytic or epilithic)
Values obtained per level are given in the table below. They are then summarized to reach a maximum score of 30, when covers of opportunists are < 5 % in each belt. When a belt is lacking, the total rating is obtained by adding the values of occurring belts and applying to the result a rule of three. In the calculation, the same weight is given to each belt (or group of belts for Pc + Fspi).
opportunist species per belt
< 5 %
5 – 25 %
25 – 50 %
50 – 75 %
75 – 100 %
Index table for the cover of opportunist taxa per belt. In the case of grouped Pc and Fspi, covers of a given taxon will be pooled and averaged (Pc + Fspi / 2).
2.4. Determining the qualitative status (boundaries) The qualitative status of a given site for the EQ "intertidal seaweeds" is obtained by comparing the final mark with CFR boundaries previously established in Spain and at the EC level. The global index corresponds to the three sub-indexes calculated as above and added together: global plant covering (0 - 40), number of characteristic species (0 - 30) and cover by opportunist species (0 - 30).
83 - 100
62 – 82
41 – 61
20 – 40
0 - 19
Annex Field sheet WFD CW NEA Intertidal seaweeds
1. Global plant covering of the belts (covering percentages, ca. a few %)
Remember: three 33 cm X 33 cm squares per spot, taken hazardously at each sampling on the field, within three 1.65 m X 1.65 m permanent spots per belt, so within 9 squares and 0.9 m2 per belt and per year.