[§ 1] Amateur divers and/or diving centers will be provided with the underwater tables to report the observations and of all the necessary didactic material about coralligenous habitats and about the observational protocol (see “Sampling” section).
[§ 2] The essential infrastructure for the approach is the CIGESMED CS website which : (a) lists the necessary scientific information on the coralligenous habitat^? in a comprehensive and approachable manner, and (b) provides the platform for the online submission of participants’ observations.

The CS website requires registration from the user in order to be able to submit, view and review data.

[§ 3] During the initial registration process, the following information is requested :
• Personal data (name, place of residence, affiliation)
• Profession (relevant studies or scientific experience)
• Experience from other CS projects
• Diving certification level
• Diving experience (no. of total dives in classes, e.g. 0‐20, 20‐50, 50‐100, >100)
• Dive computer brand and model
• Ability to upload raw dive computer data

[§ 4] The online form then provides fields for the submission of data relevant to the characterization of the site^? and of the coralligenous assemblages, organized in two sections : (a) basic data and parameters, and (b) ecological observations. It is clearly stated that the most of information fields requested within those two sections are optional, i.e. at each recording event the participant is free to submit whichever data he/she was able to collect during the dive or is willing to share

a. Basic data and parameters
[§ 5] Those are mainly topographic data that provide a description of the reported location, along with several easy to describe abiotic environmental parameters which can allow a preliminary characterization of the site, or the formation of data series for sites receiving multiple visits.

• Date of observation
• Geographic reference (coordinates and/or selection on interactive map)
• Name of location or dive site
• Maximum dive depth
• Water temperature at the depth of the observation
• Water temperature at predefined depths (e.g. 0, 10, 20, 30, 40, 50, 60 m)
• Depth of the lower limit of the thermocline (if met)
• Current (three observation ranks : none, weak, strong)
• Visibility (three observation ranks : clear water, some suspended particles, turbid)
• Observed vertical extent of coralligenous habitats (min and max observed depth)
• Horizontal extent of coralligenous habitats (in length, e.g. <5, 5-10, 10-20, >20 m)
• Habitat continuity (selection through a number of illustrations, representing three observation ranks : isolated patch, discontinuous, continuous)
• Slope (selection through a number of illustrations, representing four observation ranks : horizontal, sloping, vertical, overhanging)
• Rugosity (selection through a number of illustrations, representing four observation ranks : tiny, small, medium, large, referred to the size of substrate crevices)
• Orientation (selection through : N, NE, E, SE, S, SW, W, NW)

b. Ecological observations
[§ 6] Those focus on the assessment of the main characteristics, of the structure and of the health state of coralligenous communities and include the following fields :
• Presence and relative abundance of typical species
• Reporting of disease (necrosis) or mortality events for sessile invertebrates
• Presence and characterization of pressures
• Other observations (free text)

[§ 7] Typical species are given in a list (see below), accompanied by photographs of specimens in situ and linking to galleries providing additional photographic material, covering as many viewing angles and morphologic variations of the species as possible. The semi-quantitative abundance of species is requested in classes : absent (0), scarce (+), abundant (++), very abundant (+++). Furthermore, the option of uploading photographs is provided to the user and encouraged as the recommended practice. Additionally, a field of free text is provided for each observation, in order to allow commenting or providing any kind of additional information.

[§ 8] The list includes typical coralligenous species, with particular attention to builder, eroder, indicator, protected and valuable species. The scope of this list is not to be as comprehensive as possible but rather to validate the presence of coralligenous habitats and to roughly characterize them. The list is restricted to the minimum number of species possible, so as not to overwhelm citizen scientists with a large amount of information. The taxa comprising the list are conspicuous and properly selected in order to assure : (a) easy identification underwater, (b) common presence in approachable coralligenous formations, and (c) potential presence in all Mediterranean study areas. However, the list can be modified by CIGESMED partners according to regional specific composition of coralligenous communities in different biogeographic areas.

Taxon/a	Image	Role
Calcareous red algae (Lithophyllum spp., Mesophyllum spp.)		Primary builders, typical
Peyssonnelia spp.		Typical
Agelas oroides		Typical
Axinella spp.		Typical
Cliona spp.		Destroyer, typical
Corallium rubrum		Endangered, valuable, typical
Eunicella cavolini		Near threatened, valuable, typical
Eunicella singularis		Near threatened, valuable, typical
Leptogorgia sarmentosa		Indicator of turbidity, valuable, typical
Paramuricea clavata		Vulnerable, valuable, typical
Savalia savaglia		Near threatened, valuable, typical
Scleractinians (e.g. Leptopsammia pruvoti, Polycyanthus muellerae, Madracis pharensis, Hoplangia durotrix, Phyllangia Americana mouchezii)		Secondary builders, typical
Homarus gammarus		Valuable, typical
Palinurus elephas		Vulnerable (IUCN red list) regulated exploitation, valuable, typical
Scyllarides latus		Regulated exploitation, locally protected (e.g. France), valuable, typical
Myriapora truncata		Indicator of mechanical disturbance, secondary builder, typical
Other erect bryozoans (Adeonella spp., Smittina spp., Pentapora fascialis, Reteporella spp.)		Indicators of mechanical disturbance, sensitive to pollution, secondary builders, typical
Centrostephanus longispinus		Protected, eroder, typical
Other sea urchins		Eroders
Anthias anthias		Typical
Scorpaena spp.		Valuable, typical
Epinephelus marginatus		Endangered (IUCN red list), regulated exploitation, valuable, typical
Shark eggs cases (e.g. Scyliorhinus canicula)		Typical

List of pressures commonly affecting coralligenous habitats :

Type of pressure	Image
Caulerpa cylindracea (invasive species)
Asparagopsis spp. (periodically invasive species)
Mucilaginous aggregates (periodically invasive)
Organism necrosis and mortality events
Fishing gear (e.g. ghost nets, fishing lines)
Diver recklessness (mechanical damage)
Anchoring
Litter (e.g. plastics, metals, batteries)
Urban waste sources nearby (e.g. waste water drainage)

[§ 9] Also for the pressures, a rough estimation of quantification is required, according to three classes : absent (0), limited (+), extended (++).
Observers are further encouraged to upload relevant photos.