The CorMedNet database includes published scientific papers, grey literature, and technical reports based on surveys of SCUBA diving and remotely operated vehicles (ROVs). A literature survey was conducted in March 2023 using different search strategies with the Web of Science and Google Scholar, following the methodology described in Supplementary material S1. A total of 584 references have been included, with ongoing efforts to collaboratively and continuously expand the database. In this initial search, we focussed on the three main macroinvertebrate phyla inhabiting coralligenous assemblages: Cnidaria, Porifera, and Bryozoa, the most affected by marine heatwaves (Garrabou et al., 2022b). This includes both MHF species, such as the red gorgonian Paramuricea clavata (family Acanthogorgiidae, class Octocorallia), and species that may not meet the criteria for habitat formation, such as the encrusting sponge Crambe crambe (family Crambeidae, class Demospongiae). However, considering the collaborative nature of the CorMedNet database, it is designed to incorporate any relevant phyla from coralligenous assemblages, such as coralline algae or tunicates, and their inclusion is foreseen in future updates.

The references were screened and classified into three types of studies: distribution, demographic, and population genetics, according to the information provided. The CorMedNet database houses information on local populations for various target species alongside contextual metadata (e.g., site, depth, sampling year), providing a biogeographic framework for analysis. A local population was defined as a group of colonies, specimens, or individuals of the same species, ranging from tens to thousands, depending on the species dwelling in a particular location (identified by its latitude and longitude coordinates) and depth range – identified in the source reference as belonging to the same population. In this sense, information from multiple populations of a single species to various species could be extracted from the same source and subsequently classified into different population-specific database entries. Species entries in the database are linked to valid species according to the World Register of Marine Species (WoRMS) matching tool (https://www.marinespecies.org/aphia.php?p=match; as of 17 November 2025; see AphiaID in Supplementary Table S2.1). When the original source did not specify the species, only the genus was recorded in the database. The type of information extracted depended on the corresponding study type. For distribution studies, we collected data on the specific geographic location of the populations, defined by their latitude and longitude coordinates (in decimal degrees) and depth range (in meters). The date of the observation was also added as contextual metadata information. For demographic studies, besides the previous information, we collected data on sampling technique and main demographic parameters (e.g., density, size, mortality metrics), which were homogenised using the same metrics (see Supplementary material S1). Notably, the number of replicates and deviation measures were included in the CorMedNet database, where they are available in the original source. Population genetics studies are currently flagged to indicate only whether a record contains genetic information (e.g., observed or expected heterozygosity, allelic richness, etc), with a view to integrating comprehensive genetic data in the near future. Finally, marine ecoregion information (Spalding et al., 2007) has been added to each record based on location. The CorMedNet database primarily focuses on records from the upper 150 m of depth, where coralligenous assemblages are typically found (Ballesteros, 2006). However, we extended the depth range to 200 m, which is the lower limit depth distribution of the mesophotic zone, where coralligenous habitats have been recently documented (e.g., De Falco et al., 2022; Piazzi et al., 2022). Additional records have been included on an exceptional basis when the original publications explicitly described the species as part of deeper coralligenous assemblages (e.g., Pierdomenico et al., 2021; Piazzi et al., 2022), or when the species occur in other habitats (e.g., Corallium rubrum; Knittweis et al., 2016), in order to maintain the most complete possible overview of species associated with coralligenous habitats, even if some records originate from other environments.

A first version of the CorMedNet data is published in the European Marine Observation and Data Network (EMODnet) Biology international database https://www.emodnet-biology.eu/toolbox/en/download/occurrence/dataset/6462, adhering thus to the F.A.I.R. data principles (Wilkinson et al., 2016) and the Darwin Core Archive (DwC-A) standards for biodiversity informatics data. An updated version presented in this study is publicly available on a dedicated website https://cormednet.medrecover.org.

The CorMedNet website allows users to easily visualise the collected data through an interactive map and by applying different filters (e.g., phyla, species, depth range, study type, etc). Besides, CorMedNet has explicitly been designed as a collaborative web platform where users can update the database by editing and uploading functionalities. Indeed, users should register before uploading their data and complete several obligatory fields to ensure data quality and facilitate data entry. In the current version, the system is set to enter both single observations, which can be added individually through the ‘Add data’ in the menu bar, to multiple observations using spreadsheets [contacting the administrator at cormednet (at) gmail (dot) com to prepare the appropriate file format]. We encourage users to reference the original data source (e.g., scientific publications) along with the data descriptor. For unpublished data, users must confirm that they are the creators and owners of the content or otherwise have sufficient rights to make the content available under the database licence (see below). The platform includes the option of uploading data in private mode, facilitating the reporting of data awaiting publication. It is expected to become public when the reports and papers containing it are published. This approach seeks to provide the most updated and harmonised dataset on the coralligenous assemblages.

Public data is available for download and use by registered users. The citation system is under the specific License Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) to guarantee transparency of the data’s origin.

We used the CorMedNet database, presently containing georeferenced records for Cnidaria, Porifera, and Bryozoa, to obtain geographical, bathymetric, and taxonomic distribution data for coralligenous species, which includes records of these phyla.

The observed biogeographic distribution of macroinvertebrates in the Mediterranean Sea was mapped for the selected phyla using QGIS (QGIS Development Team, 2023).

Spatial patterns were summarised by phylum for each ecoregion and depth range (every 30 m, up to 120 m, between 120 and 200 m, and > 200 m). The type of study - distribution, demographic, or population genetics - was summarised for each ecoregion and phylum. Since georeferencing was mandatory for data records, each entry was inherently associated with the distribution study type. When records also included demographic data such as density, size, or mortality, they were additionally listed under demographic study types (see CorMedNet metadata in Supplementary Material S1 for a complete list of demographic variables). Population genetics studies included records that focussed explicitly on the genetic diversity of macroinvertebrate species dwelling in the coralligenous assemblages. Thus, a single record could span multiple study types.

The taxonomic distribution was represented in a circular bar plot showing the total number of records per species in each target phylum. While all 384 species of cnidarians, bryozoans, and poriferans were included, only those with more than 100 database records were explicitly labelled in the figure. This threshold was selected to ensure a minimum level of representativeness and data robustness for visualisation purposes, and to provide a meaningful overview of the species most commonly reported in the database.

We select the most recorded variables and species to explore the demographic information of Mediterranean coralligenous species. The demographic variables reported in this preliminary analysis are density (colonies/m²) and mean height (cm), as these metrics were the most frequently available in the dataset (see Supplementary Table S2.1). Additionally, only species surpassing a cumulative value of records > 100 for any of these variables were selected. Furthermore, values were grouped into three geographical areas with contrasted environmental conditions (e.g., Coll et al., 2010; Lazzari et al., 2016; Pastor et al., 2019): Western (Alboran Sea and Western Mediterranean ecoregions), Central (Adriatic Sea, Ionian Sea, and Tunisian Plateau/Gulf of Sidra ecoregions), and Eastern (Aegean Sea and Levantine Sea ecoregions). Finally, raincloud plots were computed for each selected species and ecoregion aggrupation.

To explore potential biases in current knowledge driven by protection status (e.g., more research being done in protected areas), we separated the records from the distribution, demographic, and population genetics studies according to whether they were conducted in protected or unprotected areas. The level of protection was assessed based on the data for Marine Protected Areas from the Mediterranean GIS database (MAPAMED/MEDPAN; https://mapamed.org/) MAPAMED (2019). Specifically, only georeferenced records in MPAs with a national status and Marine Nature 2000 sites were considered as protected.

Concerning the importance of long-term demographic studies, we examined the number of sampled years for each population of the selected species (i.e., in those with more than 100 demographic values). Specifically, we assigned a value of one to those populations that were sampled only once, and periods of 2 – 5, 6 – 10, 11 – 15, 16 – 20, 21 – 25, and ≥ 26 years, to populations that were sampled for at least 2 years. For instance, a population sampled between 2007 and 2013 would be included in the 6–10 period category. Indeed, we define long-term studies as those conducted for over 10 years (Bonebrake et al., 2010).

The CorMedNet database currently compiles 8575 georeferenced records representing local populations of 418 species of macroinvertebrates inhabiting Mediterranean coralligenous assemblages. This includes primarily species from the phyla Cnidaria (4201 records from 72 species), Porifera (2862 records from 233 species), and Bryozoa (1306 records from 79 species). In addition, there are also records from the class Ascidiacea (Tunicata, Chordata; 206 records from 34 species), but these were not considered for the following analyses. Within the phylum Cnidaria, most records are from the subphylum Anthozoa (4148 records from 64 species), with records from the class Hydrozoa (53 records from 7 species) being less common. The records were sampled between 1882 and 2023, mainly from shallow coastal areas (Figures 1, 2; Supplementary Figure S2.1).

There has been a steady presence of publications since 1882, but it was not until the mid-1990s that a marked rise in the number of publications and records was observed (Supplementary Figure S2.1). Notably, following the first compilation of Mediterranean coralligenous assemblages in 2006 (see Ballesteros, 2006), which encompasses multiple phyla, the number of related publications has increased by more than threefold, rising from 167 in 2006 to 584 in 2023 (Supplementary Figure S2.1).

The number of available records associated with macroinvertebrates inhabiting coralligenous assemblages is higher in the western ecoregions (Western Mediterranean: 6085 records, and Alboran Sea: 683 records). This is in marked contrast to the central and eastern ecoregions, which show a notable paucity of available data, especially emphasised in the southern ecoregions (i.e., Tunisian Plateau/Gulf of Sidra: 41 records, and Levantine Sea: 85 records; Figures 1, 2A). The differences between Western and Eastern basins are also evident regarding the information available for the different phyla. Specifically, observations in the western ecoregions tended to be related to cnidarians, while in the east, poriferans seem to dominate. Interestingly, Bryozoa records are relatively evenly distributed across the Mediterranean (Figures 1, 2A). Finally, although the compilation of data is mainly focussed on the Mediterranean Sea, there are few records from outside this region (n = 57, particularly from the South European Atlantic Shelf and Saharan Upwelling ecoregions).

The bathymetric distribution pattern predominantly peaks between 0 and 30 m and gradually decreases at greater depth (> 60 m). For bryozoans and poriferans, there are very few observations below 60 m. In the case of cnidarians, they exhibit a more gradual decline, with records persisting until depths exceeding 200 m (Figure 2B) inhabiting other deeper habitats.

Regarding the type of study, those records reporting distribution data are consistently predominant in all ecoregions (Figure 2C) and phyla (Figure 2D). By contrast, demographic records are mainly available for cnidarians and in the northern ecoregions (Western Mediterranean, Adriatic Sea, and Aegean Sea). However, in lower proportions, they are present in all ecoregions (Figures 2C, D). Fewer than 100 records report demographic variables for the other ecoregions and phyla, except for bryozoans in the Western Mediterranean ecoregion (n = 233; Figure 2D). Population genetics studies are underrepresented at both ecoregions and phyla levels, particularly for the case of bryozoans (Figures 2C, D). Proportionally, the Western Mediterranean, Adriatic Sea, Aegean Sea, and Tunisian Plateau/Gulf of Sidra are the ecoregions with more representation of this type of study (Figure 2C).

In terms of taxonomic coverage, 55.9% of the database records are concentrated in 14 highly sampled species (each with > 100 records; Figure 3; Supplementary Table S2.1). These species include cnidarians from the class Octocorallia Corallium rubrum (n = 1456), Paramuricea clavata (n = 903), Eunicella cavolini (n = 387), E. singularis (n = 257), P. macrospina (n = 115), as well as two species from the class Hexacorallia, Parazoanthus axinellae (n = 166), and Leptopsammia pruvoti (n = 101); the poriferans from the class Demospongiae Spongia (Spongia) officinalis (n = 233), Crambe crambe (n = 183), and Petrosia (Petrosia) ficiformis (n = 107); and the bryozoans from the class Gymnolaemata Pentapora fascialis (n = 343), Myriapora truncata (n = 308), Smittina cervicornis (n = 130), and Reteporella grimaldii (n = 104). Despite a higher proportion of Cnidaria records, the Porifera category displays a greater species diversity (72 vs. 233 species; Figure 3). Bryozoans reached a total number of 79 georeferenced species (Figure 3).

The Western Mediterranean ecoregion reports the highest number of demographic records, particularly for cnidarians, with 776 records documenting density values, 552 mean height, and 341 mortality data (i.e., mean percentage of injured surface and/or percentage of affected colonies or individuals by mortality; Figure 4). This ecoregion also has a relatively high number of density records for bryozoans (n = 233) and poriferans (n = 70). Poriferans are also similarly represented in density values in the Aegean Sea (n = 103). In contrast, the other ecoregions and phyla report fewer than 50 records for these demographic variables, except the height variable for bryozoans in the Western Mediterranean (n = 124). It should be noted that some ecoregions do not report any data (e.g., the Alboran Sea ecoregion for density and height variables; Figure 4).

The selected species with more than 100 demographic records to further explore the demographic data are: the cnidarians Eunicella singularis, E. cavolini, Paramuricea clavata, and Corallium rubrum, and the Bryozoa Pentapora fascialis. Mortality was excluded from the analysis because most records corresponded to the same species and ecoregion (P. clavata in the Western Mediterranean; see Supplementary Table S2.1). Notably, density and height data are consistently available for the five selected species in the western ecoregions, and to a lesser extent in the central and eastern ecoregions (Figure 5). Density values are consistently higher in the western ecoregions. In contrast, height values are generally higher in the central and eastern ecoregions. The highest mean density value is 441.5 colonies/m², reported for C. rubrum in the western ecoregions (Betti et al., 2019), while the highest colony maximum height is reported for P. clavata in the western ecoregions, reaching a value of 150 cm (Previati et al., 2007).

Regardless of the type of study, the number of records is heterogeneously distributed across protected (66.02%) and unprotected (33.98%) populations. Notably, studies containing demographic information are predominantly conducted within MPAs (70.36%) rather than outside (29.64%). A similar trend is observed in population genetics studies, 68.05% of records from protected populations and 31.95% from unprotected ones (Figure 6A).

Long-term demographic studies of the most frequently sampled species (Eunicella singularis, E. cavolini, Paramuricea clavata, Corallium rubrum, and Pentapora fascialis) are scarce in the current CorMedNet database. Most populations have only been studied once (51.2%) or twice (24.5%). From this point, the number of records decreases considerably. Less than 6% of the examined populations were monitored for over 10 years; Figure 6B).

This work underscores the growing scientific effort to expand our understanding and provide basic knowledge on the coralligenous assemblages, one of the most emblematic habitats in the Mediterranean Sea. Since the first comprehensive biodiversity synthesis of Mediterranean coralligenous assemblages (Ballesteros, 2006), the number of studies on macroinvertebrates has tripled. Thanks to the data collected in the CorMedNet database, we can now update the total number of species thriving in these habitats from 1666 (Ballesteros, 2006) to 1786. This represents more than 10% of the total number of species described in the Mediterranean ( ̴ 17000 species; Coll et al., 2010). This growth largely reflects studies on the macroinvertebrate phyla currently represented in CorMedNet (Cnidaria, Porifera, and Bryozoa). Nevertheless, it is reasonable to assume that the number would be substantially higher if additional phyla, such as calcareous algae, were incorporated. For instance, Piazzi et al. (2009) reported a total of 187 macroalgal epiphytes of encrusting Corallinales along the coast and the islands of Tuscany in the north-western Mediterranean. These findings further confirm the role of coralligenous assemblages as one of the most important biodiversity hotspots in the Mediterranean Sea. In terms of species richness, the number of species compiled here approximately doubles the numbers listed in Ballesteros (2006) for poriferans (n = 233 in CorMedNet; n = 142 in Ballesteros, 2006) and cnidarians (n = 72 in CorMedNet; n = 43 in Ballesteros, 2006). However, only 79 of the 171 species of bryozoans listed in Ballesteros (2006) are georeferenced in the CorMedNet database, probably due to the challenges associated with establishing a precise position in historical studies and the difficulties associated with their research (e.g., species-level identification, variability of colony forms and habitat types; see Lombardi et al., 2020; Taylor and James, 2013). Notably, the species richness of poriferans reported in CorMedNet is approximately three times higher than that of the other two taxa, in alignment with previous findings reported in the Mediterranean Sea (e.g., Antoniadou et al., 2006; Çinar et al., 2020; Sini et al., 2015). Bearing in mind that CorMedNet has not yet incorporated information for other phyla present in the coralligenous (e.g., coralline algae, tunicates, etc.), as well as the ongoing efforts to characterise the structure and functioning of coralligenous assemblages across the Mediterranean ecoregions are increasing (e.g., Casas-Güell et al., 2015; Piazzi et al., 2012; Pierdomenico et al., 2021; Valisano et al., 2019), it is very likely that the number of identified species will increase in the coming years.

To date, the total number of macroinvertebrate species registered in CorMedNet is 418. However, slightly more than half of the compiled records are associated with only 3.35% of the most frequently sampled species (14), indicating a highly biased sampling effort towards a few key species, mostly MHF cnidarians. The overrepresentation of particular cnidarian species may be partly due to their high abundance in traditionally well-studied regions such as the northern Mediterranean Sea. Additionally, their unique traits (e.g., large size, arborescent morphology; Gómez-Gras et al., 2025), which make them key MHF species (Gili and Coma, 1998), and their high vulnerability to ongoing disturbances (e.g., Garrabou et al., 2022b; Gómez-Gras et al., 2021a; Ramirez-Calero et al., 2024), further increase their research interest. Whatever the cause of the observed disparities in data coverage, they highlight the need to extend the current research to other species and Mediterranean regions. Among the cnidarians, the octocorals Corallium rubrum (1456 records) and Paramuricea clavata (903 records) account for most of the records, reaching a total of more than 2000 records. These numbers are higher than those compiled for the entire group of bryozoans (1313 records), within which the most abundant species are Pentapora fascialis (343 records) and Myriapora truncata (308 records), as previously reported (Ballesteros, 2006). Finally, Spongia (Spongia) officinalis and Crambe crambe are the most studied poriferans (233 and 183 records, respectively), probably linked to the higher abundance of this phyla in the eastern Mediterranean Sea (e.g., Gerovasileiou and Voultsiadou, 2016), and their commercial value and/or utility as heavy metal bioindicators (e.g., Cebrian et al., 2007; Stabili et al., 2008). When looking at the geographical patterns across macroinvertebrate phyla, the CorMedNet dataset (> 8500 records) shows a dominance of cnidarians in the western Mediterranean, with fewer entries in the eastern region, where poriferans were more abundant (this study; Çinar et al., 2020; Pérès and Picard, 1958). The Bryozoa are the least represented phylum in the dataset, with a relatively uniform distribution across the ecoregions except for the Western Mediterranean ecoregion, which exhibits a markedly increased representation. Irrespective of phylum and ecoregions, most records are concentrated within the first 30 meters of depth. These biogeographical and bathymetrical discrepancies in data coverage could be attributed to historical, logistical, and ecological factors.

Specifically, disparities in sampling effort may reflect a historical bias towards the northern Mediterranean (e.g., Abdulla et al., 2008; Di Camillo et al., 2018; Garrabou et al., 2019; Gerovasileiou and Voultsiadou, 2016) and the more accessible shallower depths for scuba diving. Traditional taxonomic shortcomings may be caused by the great attention paid to the key coralligenous species (Ponti et al., 2018) – mirroring global trends (Fisher et al., 2011) – representing another important source of variability. The upper depth distribution limits of coralligenous assemblages could be mentioned among the ecological factors that could partially explain these coverage biases. Irradiance levels primarily influence these limits at the seafloor, which are mainly modulated by nutrient concentration (Zabala and Ballesteros, 1989). In oligotrophic eastern regions, higher irradiance leads to macroalgae dominance in shallower waters, thereby outcompeting coralligenous assemblages dominated by MHF macroinvertebrate species, typically found at greater depths (Ballesteros, 2006). Additionally, poriferans and bryozoans tend to thrive in oligotrophic waters, explaining their higher proportion in those regions (Gili and Ballesteros, 1991; Stambler, 2014; Zenetos et al., 2002). In contrast, cnidarians are overall more prevalent in environments with higher levels of suspended organic matter, a characteristic of the more eutrophic western ecoregions, where coralligenous assemblages are found at shallower depths (approximately 20–55 m) compared to central and eastern populations (approximately 40–120 m; Ballesteros, 2006; Çinar et al., 2018; Laborel, 1961; Salomidi et al., 2009). Regardless of these factors, the widespread lack of records in the southern Mediterranean Sea (i.e., Tunisian Plateau/Gulf of Sidra and Levantine Sea ecoregions) suggest lower research activity in the area, as there is evidence, albeit limited, of the presence of key MHF coralligenous species in some of these southern regions (e.g., Tsounis et al., 2013). This biogeographical pattern aligns with observations for other important species from coralligenous assemblages. For instance, current knowledge of coralline algae in the Mediterranean Sea is concentrated in the north-western basin, particularly in France, Italy and Spain (Rindi et al., 2019). In this context, further exploration should be undertaken to address challenges linked with lower research activity. In addition, increased knowledge will gradually enhance our understanding and elucidate the factors contributing to the currently observed differences.

Given the difficulties in establishing historical ecological baselines for the coralligenous (e.g., Angiolillo et al., 2023; Di Camillo et al., 2018; Garrabou et al., 2017), compiling basic demographic metrics such as density and height will facilitate comparative analyses of populations across temporal and spatial scales. Data collected in the CorMedNet database demonstrates that density and height vary from the western to the central and eastern Mediterranean ecoregions. Mean density displays a decreasing trend from West to East for the five selected species (i.e., Eunicella singularis, E. cavolini, Paramuricea clavata, Corallium rubrum, and Pentapora fascialis). This pattern, which aligns with studies for E. cavolini (Sini et al., 2015), adds to our knowledge for other species such as P. clavata or C. rubrum. In contrast, the lower mean height values observed in the western ecoregions may be attributed to the shallower depth ranges where these species thrive, exposing them to higher hydrodynamic conditions. The existence of different anthropogenic pressures (e.g., marine heatwaves, severe storms, fishing gears, recreational activities) could also affect large colonies, particularly in those shallower populations (Cupido et al., 2008; Linares et al., 2008a; Tsounis et al., 2006; Weinbauer and Velimirov, 1996). Unfortunately, climate change intensifies some of these pressures, such as marine heatwaves or severe storms (Garrabou et al., 2022b; Teixido et al., 2013). Conversely, the deeper and more stable environment of the populations sampled in the central and eastern ecoregions likely results in the opposite pattern, characterised by higher mean colony sizes and lower population densities. In these populations dominated by large colonies, intraspecific competition may hinder the recruitment of smaller colonies, leading to lower densities (Gómez-Gras et al., 2021b; Linares et al., 2008b). It is important to underscore that establishing accurate biogeographical patterns requires comprehensive and representative datasets. At present, the data collected through CorMedNet is insufficient to achieve this with precision. However, we anticipate that the collaborative nature of this initiative will facilitate the incorporation of new data, thereby enabling more robust biogeographic analyses in the future.

Future endeavours should balance the sampling effort by investing more resources and attention towards underrepresented ecoregions, phyla, species, depths, and studies that adequately address their associated ecological and evolutionary data. Innovative approaches are liable to bridge these gaps. Indeed, marine citizen science, local, and web ecological knowledge represent invaluable tools that could contribute to a better understanding of the species distribution and conservation status (e.g., Brook and McLachlan, 2008; Di Camillo et al., 2018; Figuerola-Ferrando et al., 2023; Turicchia et al., 2021). Furthermore, integrating recent technological advances, such as ROVs, could facilitate the imminent surge of studies focussing on mesophotic depths (Rossi et al., 2021), thereby improving the information on the deeper coralligenous assemblages from the eastern Mediterranean.

As mentioned above, Mediterranean coralligenous assemblages have been recognised as a conservation priority under international policy frameworks such as the MSFD and the Barcelona Convention. These initiatives aim to monitor and ensure the achievement of the Good Environmental Status (GES) in marine ecosystems. Accordingly, considerable progress has been made in developing metrics, indices, and protocols to evaluate the GES of Mediterranean coralligenous assemblages (see Di Camillo et al., 2023), yet a unified strategy remains elusive. As part of these efforts, CorMedNet incorporate key indicators, such as the mean percentage of injured surface and the percentage of affected colonies or individuals, to assess the conservation status of key MHF coralligenous species. Indeed, the latter indicator offers a mortality rapid assessment method that can be applied both by scientists and citizen science volunteers, providing the opportunity for meaningful comparative analysis of conservation status at broad scales (Figuerola-Ferrando et al., 2024; Garrabou et al., 2022a). However, to fully assess the environmental status of these habitats and advance towards a comprehensive strategy for monitoring and management, further investigation and integration of additional metrics and phyla into CorMedNet would be beneficial.

The current version of the CorMedNet database provides valuable information, but important knowledge gaps remain. A disproportionate focus on studies within MPAs - probably due to the initial designation of these areas based on the presence of coralligenous assemblages - hinders a comprehensive assessment of the effects of protection. To address this problem, the application of such indicators (e.g., the mortality rapid assessment method) in protected and unprotected sites should be expanded. Moreover, although most of the populations currently included in the CorMedNet database appear to be under some protection status, they are mostly subjected to suboptimal management strategies (e.g., Claudet et al., 2020). At present, it seems that efforts are more focussed on expanding the network of MPAs rather than consolidating consistent information on their effectiveness (Dinerstein et al., 2019; Eckert et al., 2023). In this study, we considered all types of protected areas as MPAs, including Marine Nature 2000 sites, as these categories provide the greatest potential for implementing management and conservation measures. However, the available data still tend to focus on the geographic distribution of the species (i.e., where they occur) rather than on ecological or evolutionary metrics (e.g., demographics, population genetics, mortality) that could provide insights into their conservation status (Lande, 1988; Palkovacs et al., 2014; Paz-Vinas et al., 2013). In this context, gaining a more complete picture of the conservation status of a population requires long-term studies that include demographic variables (e.g., density or height), which are more liable to predict the temporal evolution of a population or community. For instance, such studies can provide deeper insights into population dynamics, resilience, and threats, understanding impacts on key ecological processes and evaluating their responses (e.g., Capdevila et al., 2024; Likens, 1989; Lindenmayer et al., 2022).

There is an almost total lack of long-term studies in the coralligenous assemblages. Accounting for the most frequently sampled selected species, long-term datasets spanning over 11 years are only available for 45 populations over the entire Mediterranean (< than 6%). Notably, for populations of the other non-selected species, more than 70% have only been sampled once. This is alarming considering the life history traits (such as long life span and slow growth rates) of the key macroinvertebrate species in this habitat (e.g., Garrabou and Harmelin, 2002; Gómez-Gras et al., 2025; Linares et al., 2007), which demand long time scales to understand their dynamics and resilience in the face of escalating environmental pressures. Indeed, gaining insights into comprehensive long-term ecological data has prompted the development of valuable conservation and management tools (e.g., identifying the species most at risk of extinction, estimation of dispersal and recolonisation capacities, setting realistic conservation targets, or quantifying ecological responses to different drivers of ecosystem change; Lindenmayer et al., 2012; Willis et al., 2007). It is worth noting that several limitations could be influencing this estimate. For instance, some peer-reviewed studies and technical reports may not be included in the current version of the CorMedNet database for various reasons (e.g., not found, lack of specific geographical coordinates, etc). In addition, the same population may have been studied in two or more different studies, which may lead to overestimating the number of short-term studies. As this is a collaborative database, we encourage authors to identify and report such potential errors to refine this information, which may not be evident solely from the information provided in the peer-reviewed studies or technical reports.

Finally, the scarcity of long-term demographic data may be linked to the limited long-term funding offered by governments and the difficulties of maintaining surveys across decades, coupled with a greater interest by scientists in conducting more ‘innovative’ research (e.g., Lovett et al., 2007; Nisbet, 2007). However, despite these barriers, the CorMedNet database calls for the promotion of long-term monitoring programmes, including a representative array of key species across the entire range of distribution in the Mediterranean Sea. We contend that this information is essential to define effective conservation measures.

Although the term coralligenous assemblages is widely used (see Supplementary Figure S2.1), much of our knowledge is based mainly on those locations in the NW Mediterranean (e.g., this study, Ballesteros, 2006; Giaccone, 2007; Casas-Güell et al., 2015). The structure and biodiversity of these complex habitats, which encompass a wide range of communities, still lack an exact consensus on their definition and a standardised list of associated species.

The collaborative nature of CorMedNet provides an excellent opportunity to maintain, update, and consolidate a database of Mediterranean coralligenous assemblages. The design of CorMedNet provides the basic functionalities to engage the collaboration between all the stakeholders involved in the conservation of coralligenous assemblages. The current version of the CorMedNet web platform is expected to evolve continuously to facilitate the updating and visualisation of the data acquired. The first noteworthy outcome of CorMedNet is the identification of several major gaps concerning the lack of data across phyla, Mediterranean ecoregions, depth ranges, and study types. We want to emphasise the importance of delving deeper into demographic and long-term studies and incorporating population genetics and trait diversity measures in the database. The integration of different approaches and disciplines will be essential to address these issues and to capture the full diversity of coralligenous assemblages (see Rindi et al., 2019). The Mediterranean research community and leading local and regional conservation organisations need to work in the most efficient way to fill these gaps. CorMedNet supports this shared goal by serving as a platform to consolidate information, track progress, and effectively contribute to guiding sound conservation actions for this important Mediterranean habitat.