Distribution of Macroalgae in the area of Calvi (Corsica, Mediterranean Sea)

Study Extent

The study is based on 2 sampling campaigns. Both campaigns covered the same area (see "geographic coverage"). The lenght of the transects is variable but is around 100m in general.
The first one occurred in july 2016 and was performed over several days. Each transect was observed 1 time. The second campaign took place in june 2019. Again, several days were needed to observe the different transects. Each transect was observed 1 time.

Sampling

Each transect was filmed by GoPro cameras attached to an underwater Remotely Operated Vehicle (ROV). Videos were visualised and annotated using the software "COVER" (Carré 2010). For each transect, species were identified and relative cover and abundance were estimated.

Quality Control

In some videos, species identification was validated by another algae specialist (Damien Sirjacobs, Université de Liège). We also replicated one transect with a team of divers who did their own identifications. This proved that our ROV/video method was strong and provided similar results.

Method steps

1. For each transect : - an underwater ROV was navigated at approximately 1m from the bottom in a straight line perpendicular to the shore. It was equipped with cameras filming the bottom and the surroundings. - in the lab, down-looking video was analysed and annotated. Species are identified. Information about depth, salinity, temperature and cover were retrieved for each algae observation. - abundances of different macroalgae were compared between transects (spatial comparisons) and between different years (temporal comparisons).

Most algae were identified to genus or species, encrusting algae were identified as “Corralinales”.

1. Acetabularia acetabulum
   rank: species
2. Amphiroa rigida
   rank: species
3. Caulerpa prolifera
   rank: species
4. Caulerpa cylindracea
   rank: species
5. Codium bursa
   rank: species
6. Colpomenia sinuosa
   rank: species
7. Corralinales
   rank: order
8. Cystoseira brachycarpa
   rank: species
9. Cystoseira crinita
   rank: species
10. Cystoseira spinosa
    rank: species
11. Cystoseira zosteroides
    rank: species
12. Dictyota
    rank: genus
13. Flabellia petiolata
    rank: species
14. Halopteris
    rank: genus
15. Halopteris scoparia
    rank: species
16. Jania
    rank: genus
17. Osmundaria volubilis
    rank: species
18. Padina pavonica
    rank: species
19. Peyssonnelia squamaria
    rank: species

The area of interest is the Bay of Calvi. Total coverage of the dataset is the extent of 17 ROV transects (12 carried out in 2016, 5 in 2019), perpendicular to coast line. Transects are distributed in the whole Bay of Calvi, Corsica (Mediterranean Sea). More specifically, the area between Punta Revellata and Punta Spano was the focus of our study.