"Profile’s characterisation" Method

mercredi 27 mai 2015
par  Dorian GUILLEMAIN, Romain DAVID
popularité : 12%

Index of "Profile?’s characterisation"
1. Principle
2. Method
3. Sampling
4. Deliverables
5. To summarize
Back to protocols Index
How to cite this content :

David R., Arvanitidis C., Çinar M.E., Dubar J., Dubois S., Erga Z., Guillemain D., Sartoretto S., Thierry de Ville d’Avray L., Zuberer F., Chenuil A., Féral J.-P., (2014), with contributors : Açik Çinar S., Andral B., Aurelle D., Aysel V., Bakir K., Bellan G., Bellan-Santini D., Bouchoucha M., Celik C., Chatzigeorgiou G., Chatzinikolaou E., Chenesseau S., Dağli E., Dailianis T., Dimitriadis C., D’Iribarne C., Doğan A., Dounas C., Egea E., Elguerrabi W., Emery E., Evcen A., Faulwetter S., Gatti G., Gerovasileiou V., Güçver S.M., Issaris Y., Katağan T., Keklikoglou K., Kirkim F., Koçak F., Koutsoubas D., Marschal C., Önen M., Önen S., Öztürk B., Panayiotidis P., Pavloudi C., Pergent G., Pergent-Martini C., Poursanidis D., Ravel C., Reizopoulou S., Rocher C., Ruiton S., Sakher S., Salomidi M., Sarropoulou E., Selva M., Sini M., Sourbes L., Simboura N., Taşkin E., Vacelet J., Valavanis V., Vasileiadou A., Verlaque M. Protocols for monitoring of coralligenous habitats of mediterannean (Coralligenous based Indicators to Evaluate and Monitor the "good ecological status" of the MEDiterranean coastal waters) Protocoles de suivi du coralligène en méditerranée (Coralligenous
based Indicators to Evaluate and Monitor the "good ecological status" of the MEDiterranean coastal waters).

[§ 1] For each profile, data must be noted on a notepad, and properly annotated with the name of the observer?(s), date, site?, transect? and depth. The cartography should consider the widest environmental variability possible : therefore, study sites should be chosen around small islands and shoals, or along the coastline in sites where all orientations (North, South, East, West and the four intermediates) are represented. In each site, two depths will be considered, according to the local vertical distribution of coralligenous habitats : in Marseilles, 28 m (+/- 1m) (CIGESMED’s team), and 43 m (about 40 to 50 m) (+/- 1m) (INDEXCOR’s team). At each depth, an imaginary 50 m long (at least) transect will be followed, starting from a notable point. The point will be chosen for its strategic position, preferably at a corner, in order to allow exploring habitats with different orientations (Figure 1). The notable point should be described, photographed, and its GPS? coordinates should be recorded as precisely as possible (by a person in surface according to diver’s bubbles or floating object). Reporting the coordinates on a 3D DTM?, WGS84? format, would enable to find it easily later.

[§ 2] From the notable point, the transect can develop in two ways :
- following a single direction from the notable point ;
- following two opposite directions, having the notable point in the middle (Figure 1) ; this solution is preferred for divers safety and precision of segment location. In this case, two groups of observers can work at the same time.

[§ 3] Transects will be cut into 5 m long segments, which will have a vertical extent of 1 m, centered at the target depth (+/- 1m). This 5 m × 1 m band will be the sampling unit for the cartography. Along each segment, visual observations will be carried out to collect topographic and biological data ; video will be recorded to eventually integrate in situ observations. The combination of topographic and biological characteristics of a segment will define the profile of this segment.

PNG - 12.5 ko Figure 1 : transects positioning in two opposite places (for “one direction” transect, the starting point is at one of its extremity).

[§ 4] Topographic data :

  • Orientation : North (N), South (S), East (E), West (W) and the four intermediate orientations (Northeast (NE), Northwest (NW), Southeast (SE), Southwest (SW)). To determine the orientation, the diver should stand in front of the wall and measure with a compass the direction that goes towards the wall. If the observed segment has many orientations, take the average one. Finally, the orientation value of the wall will be obtained by adding 180° to the compass value, into the data file in a second column.
  • Slope : unlike Glasby (2000) suggested to limit slope categories to “flat” and “vertical under overhang”, CIGESMED’s protocol adopted four categories (Figure 2) : (i) Horizontal (H) (ideally, slope angle from 0° to 18.45°) : it corresponds to a homogeneous substrate or a set of concretions and rocks that are about at the same level, very exposed to light. Horizontal surfaces are particularly susceptible to fine inputs and mechanical impacts. (ii) ”Sloping” (S) (ideally, slope angle from 18.45° to 71.69°) : surfaces may be differently affected by light, fine sedimentation and currents). (iii) “Vertical” (V) (ideally, 71.69° to 90° inclination angle) : corresponds to an homogeneous substrate (+/- 1m around the same isobath) or a series of rims that overlap. During the dive, when shifting slightly from the wall, this seems to be at equal distance from the diver, 1 m above and 1 m below, and the wall is entirely visible. On vertical surfaces, light exposition and fine sedimentation are reduced. (iv) « Overhanging » (O) : this slope is assigned when there is an overhang above the observer, which is as large as a person at least, and covers most of the segment.
PNG - 14.3 ko Figure 2 : general idea of slope categories.

When a segment is not uniform, the most represented slope should be considered. When it is possible, note if an overhang is present near or above the surface. This information must be noted for each segment, if possible.

PNG - 9.1 ko Figure 3 : slope categories.
  • Rugosity : the size of crevices, holes and faults observed will be classified as follows : (i) "Tiny" (T) : holes and crevices that do not allow introducing a fist (considering the fist about 10 cm wide). (ii) "Small" (S) : holes and crevices that allow introducing a fist at most. (iii) "Medium" (M) : holes and crevices that allow introducing a head (about 30 cm wide). (iv) "Large" (L) : crevices, holes and faults can contain the upper body at least (about 1 m wide with air tank(s)).

When the segment is not uniform in terms of rugosity, the largest holes will be considered, assuming that in a big crevice there are likely some smaller ones.

PNG - 7 ko Figure 4 : holes sizes.

[§ 5] Biological data :
The method used for the estimation of species cover or abundance is conceived to be easy to apply and to reduce the variability among observers. Only conspicuous species (generally, 4 or 5 species, 3 at least) will be considered, belonging to two groups :

  • encrusting species, i.e. species showing prevalent bi-dimentional growth form (e.g. Figure 8). For each conspicuous species, the percent cover will be assessed, considering three ranges : <20%, 20-50%, >50% (Table 1).
  • erected species, i.e. species showing three-dimensional growth forms (e.g. Figure 8). For each conspicuous species, the semi-quantitative abundance will be estimated, considering, again, three categories : “scarce”, “abundant”, “very abundant” (Bianchi et al., 2004) (see Table 1 and Figure 5 for details).

[§ 6] It is important to note any additional information such as exceptional abundance of one species, exceptional organisms (size, shape, etc.), remarkable populations, presence of solid wastes, etc.

Be careful : if the wall is vertical but situated under an overhang (in and out of the water), the assemblage can be tipical of overhangs instead of vertical walls. Remember to point out these characteristics on the notepad.

Table1 : codes used for cover and abundance of encrusting and erected species.
Code++++++
Encrusting species Cover between 0 % and 20 % Cover between 20 % and 50 % Cover greater than 50 %
Erected species 1 to 4 colonies/individuals Uniforme cover, but low density Either high density covering at least 50 % of the segment, or uniforme dense populaton
PNG - 36.8 ko Figure 5 : erects and encrusting species abundance estimation criteria.
JPEG - 208.2 ko Figure 6 : examples of encrusting and erected species. (© Zuberer F.)

WE EXPECT YOUR SUGGESTIONS OF CORRECTIONS !

- Deadline : 14th December 2015
- Please add comments for each paragraph (§) by means of a corrected new version (one form per §)
- It is recommended to add scientific references if necessary

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