Marine biodiversity in the dark: an ecological assessment of a unique submerged cave system in the eastern Mediterranean Sea

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Published: Apr 22, 2026
DOI: https://doi.org/10.12681/mms.39343
Keywords:
Dark habitats Benthic communities Scientific diving Marine biodiversity Hard substrates
VASILIS RESAIKOS
Enalia Physis Environmental Research Centre, Nicosia, Cyprus & Department of Marine Sciences, University of the Aegean, Lofos Panepistimiou, 81100 Mytilene, Greece
STELIOS KATSANEVAKIS
Department of Marine Sciences, University of the Aegean, Lofos Panepistimiou, 81100 Mytilene, Greece
MARIOS PAPAGEORGIOU
Enalia Physis Environmental Research Centre, Nicosia, Cyprus
GEORGIOS OIKONOMIDIS
Hellenic Centre for Marine Research, Anavyssos, 19013, Greece
CARLOS JIMENEZ
Hellenic Centre for Marine Research, Anavyssos, 19013, Greece
Abstract

Submerged caves in the Mediterranean Sea are unique ecosystems, sustaining diverse benthic communities shaped by environmental gradients. This study focused on the Jubilee Shoals cave system in the eastern Mediterranean (Cyprus), providing a quantitative analysis of benthic community composition, spatial distribution across cave zones, and the influence of environmental factors. The data were collected using closed-circuit rebreathers; 341 photo quadrats were analysed with specialised software to assess biodiversity within this cave system. Overall, 59 sessile taxa were identified at different rank, with sponges comprising 33% of richness. Phototrophic species dominated the entrance zone, while sponges and other low-light-adapted organisms prevailed in the darker areas. Light availability significantly influenced community structure. A progressive decline in biotic coverage from entrance to dark zones and an increase in non-living substrates highlighted the environmental limitations of more remote cave sections. Detailed 2-D and 3-D mapping enhanced our understanding of the structural complexity of the cave and species distribution. These findings emphasise the ecological vulnerability of sea caves and highlight the need for focused conservation efforts. This study establishes a foundation for future ecological studies in deep marine cave systems.

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References
Bianchi, C.N., Morri, C., 1994. Studio bionomico comparativo di alcune grotte marine sommerse; definizione di una scala di confinamento. Memorie dell’Istituto italiano di Speleologia, 6, 107-123.
Bianchi, C.N., Morri, C., 2000. Marine biodiversity of the Mediterranean Sea: situation, problems and prospects for future research. Marine Pollution Bulletin, 40 (5), 367-376.
Bianchi, C.N., Morri, C., Sartoni, G., 1986. La grotta marina semioscura delle Grotte di Bergeggi (Savona): 2. Le comunità bentoniche. Bollettino dei Musei e degli Istituti Biologici dell’Università di Genova, 52 (Suppl.), 95-106.
Bianchi, C.N., Cattaneo-Vietti, R., Cinelli, F., Morri, C., Pansini, M., 1996. Lo studio biologico delle grotte sottomarine del Mediterraneo: conoscenze attuali e prospettive. Bollettino dei musei e degli istituti biologici dell’Università di Genova, 60 (61), 41-69.
Budaj, M., Mudrak, S., 2008. Therion – Digital Cave Maps [Therion – cartographie souterraine digitale], Spelunca mémoires No 33 (2008), n° 33: IV Congrès européen de spéléologie Vercors 2008, 138-141.
Bussotti, S., Terlizzi, A., Fraschetti, S., Belmonte, G., Boero, F., 2002. Spatial and temporal variability of sessile benthos in shallow Mediterranean marine caves. Marine Ecology Progress Series, 236, 19-29.
Cáceres, M.D., Legendre, P., 2009. Associations between species and groups of sites: indices and statistical inference. Ecology, 90 (12), 3566-3574.
Clarke, K.R., 1993. Non‐parametric multivariate analyses of changes in community structure. Australian Journal of Ecology, 18 (1), 117-143
Costantini, F., Rugiu, L., Cerrano, C., Abbiati, M., 2018. Living upside down: patterns of red coral settlement in a cave, PeerJ, 6, p. e4649. De Cáceres, M., Legendre, P., 2009. Associations between species and groups of sites: indices and statistical inference. Ecology, 90 (12), 3566-3574.
Derrien, M., Chevaldonné, P. Pérez, T., 2024. Patterns of benthic diversity in marine underwater caves of the Marseille Region (France, North-Western Mediterranean Sea), Mediterranean Marine Science, 25 (3), 666-681.
Digenis, M., Arvanitidis, C., Dailianis, T., Gerovasileiou, V.,2022. Comparative study of marine cave communities in a protected area of the South-Eastern Aegean Sea, Greece. Journal of Marine Science and Engineering, 10 (5), 660.
Dimarchopoulou, D., Gerovasileiou, V., Sini, M., Koutsoubas, D., 2018. Spatial variability of sessile benthos in a semi-submerged marine cave of a remote Aegean Island (eastern Mediterranean Sea). Regional Studies in Marine Science, 17, 102-111.
Di Franco, D., Jimenez, C., Albano, P.G., 2021. Unexpected high molluscan diversity in a submarine cave in the Eastern Mediterranean. Marine Biodiversity, 51 (6), 85.
Dufrêne, M., Legendre, P., 1997. Species assemblages and indicator species: the need for a flexible asymmetrical approach. Ecological monographs, 67 (3), 345-366. European Commission, 2013. Interpretation Manual of European Union Habitats: EUR 28. Habitat type 8330: Submerged or partially submerged sea caves. Brussels: European Commission.
Gerovasileiou, V., Bianchi, C.N., 2021. Mediterranean marine caves: A synthesis of current knowledge. Oceanography and Marine Biology: An Annual Review, 59, 1-88.
Gerovasileiou, V., Voultsiadou, E., 2012. Marine caves of the Mediterranean Sea: A sponge biodiversity reservoir within a biodiversity hotspot. PLoS ONE, 7 (7), 1-17.
Gerovasileiou, V., Voultsiadou, E., 2016. Sponge diversity gradients in marine caves of the eastern Mediterranean. Journal of the Marine Biological Association of the United Kingdom, 96 (2), 407-416.
Gerovasileiou, V., Chintiroglou, C., Vafidis, D., Koutsoubas, D. Sini et al., 2015. Census of biodiversity in marine caves of the eastern Mediterranean Sea. Mediterranean Marine Science, 16, 245-265.
Gerovasileiou, V., Chintiroglou, C.C., Konstantinou, D., Voultsiadou, E., 2016. Sponges as “living hotels” in Mediterranean marine caves. Scientia Marina, 80 (3), 279-289.
Gerovasileiou, V., Dimitriadis, C., Arvanitidis, C., Voultsiadou, E., 2017. Taxonomic and functional surrogates of sessile benthic diversity in Mediterranean marine caves. PLoS ONE, 12 (9), e0183707.
Giakoumi, S., Sini, M., Gerovasileiou, V., Mazor, T., Beher, J. et al., 2013. Ecoregion-based conservation planning in the Mediterranean: dealing with large-scale heterogeneity. PLOS ONE, 8 (10), p.e76449.
Gibson, R., Atkinson, R., Gordon, J., Ballesteros, E., 2006. Mediterranean coralligenous assemblages: a synthesis of present knowledge. Oceanography and Marine Biology: An Annual Review, 44, 123-195.
Gili, J.M., Riera, T., Zabala, M., 1986. Physical and biological gradients in a submarine cave on the Western Mediterranean coast (north-east Spain). Marine Biology, 90 (2), 291-297.
Gonzalez-Marrero, Y., Canepa-Oneto, A., Clemente, S., Cristobo, J., Hernandez-Gonzalez, C. et al., 2026. The vulnerability paradox in Atlantic marine caves: A multiscale mechanistic explanation from wave exposure to cave gradients. Marine Environmental Research, 217,107915.
Grenier, M., Ruiz, C., Fourt, M., Santonja, M., Dubois, M. et al., 2018. Sponge inventory of the French Mediterranean waters, with an emphasis on cave-dwelling species, Zootaxa, 4466 (1), 205-228.
Guido, A., Gerovasileiou, V., Russo, F., Rosso, A., Sanfilippo, R. et al., 2019. Composition and biostratinomy of spongerich biogenic crusts in submarine caves (Aegean Sea, Eastern Mediterranean). Palaeogeography, Palaeoclimatology, Palaeoecology, 534, 109338.
Guido, A., Jimenez, C., Achilleos, K., Rosso, A., Sanfilippo, R. et al., 2017. Cryptic serpulid-microbialite bioconstructions in the Kakoskali submarine cave (Cyprus, Eastern Mediterranean). Facies, 63, 1-17.
Harmelin, J.-G., 1985. Bryozoan-dominated assemblages in Mediterranean cryptic environments, in Nielsen, C. and Larwood, G.P. (Εds) Bryozoa: Ordovician to Recent. Fredensborg: Olsen & Olsen, pp. 135-143.
Harmelin, J.G., 1997. Diversity of bryozoans in a Mediterranean sublittoral cave with bathyal-like conditions: role of dispersal processes and local factors. Marine Ecology Progress Series, 153, 139-152.
Harmelin, J.-G., Vacelet, J., 1997. Clues to deep-sea biodiversity in a nearshore cave. Vie et Milieu, 47 (4), 351–354.
Harmelin, J.G., Vacelet, J., Vasseur, P., 1985. Les grottes sous-marines obscures: un milieu extrême et un remarquable biotope refuge, Téthys, 11 (3-4), 214-229.
Harmelin, J.-G., Vacelet, J., Vasseur, P., 1985. Les grottes sous-marines obscures : un milieu extrême et un remarquable biotope refuge. Téthys, 11, 214-229.
Hess, R., 2013. Blender Foundations: The Essential Guide to Learning Blender 2.5.
Iliffe, T.M., Bowen, C., 2001. Scientific cave diving. Marine Technology Society Journal, 35 (2), 36-41.
Jimenez, C., Achilleos, K., Petrou, A., Hadjioannou, L., Guido, A. et al., 2019. A dream within a dream: Kakoskali Cave, a unique marine ecosystem in Cyprus (Levantine Sea). Marine caves of the eastern Mediterranean Sea. Biodiversity, Threats and Conservation, 53, 91-110.
Routledge. Martí, R., Uriz, M.J., Ballesteros, E., Turon, X., 2004. Benthic assemblages in two Mediterranean caves: species diversity and coverage as a function of abiotic parameters and geographic distance. Journal of the Marine Biological Association of the United Kingdom, 84 (3), 557-572.
Mead, A., 1992. Review of the Development of Multidimensional Scaling Methods. The Statistician, 41 (1), 27.
Pérès, J.M., Picard, J., 1964. Nouveau manuel de bionomie benthique de la mer Méditerranée, Recueil des Travaux de la Station Marine d’Endoume, 31 (47), 1-137.
Romano, E., Bergamin, L., Di Bella, L., Frezza, V., Marassich, A. et al., 2020. Benthic foraminifera as proxies of marine influence in the Orosei marine caves, Sardinia, Italy. Aquatic Conservation: Marine and Freshwater Ecosystems, 30 (4), 701-716.
Rosso, A., Sanfilippo, R., Sciuto, F., 2013. Bryozoan assemblages from a submerged cave in the SE Sicily (Mediterranean Sea). Bollettino della Società Paleontologica Italiana, 52 (3), 167-176.
Resaikos, V., Papageorgiou, M., Jimenez, C., 2024. The role of rebreather divers in the study of a marine deep-water cave ecosystem. pp. 296-306. In: Tenth International Symposium “Monitoring of Mediterranean Coastal Areas: Problems and Measurement Techniques” (Livorno, Italy, 11th–13th June 2024). Firenze University Press, Florence. (accessed 2 March 2025).
Riedl, R., 1966. Biologie der Meereshöhlen. Hamburg: Paul Parey. Submerged or partially submerged sea caves (01.01.2013) Europa.eu. Available at: https://eunis. eea.europa.eu/habitats/10172?utm_source (accessed 13 February 2025).
Szukalski, W., 1998. Cave Tools for ArcView GIS Installation and User Guide Version 5.0.
Trygonis, V., Sini, M., 2012. PhotoQuad: A dedicated seabed image processing software, and a comparative error analysis of four photoquadrat methods. Journal of Experimental Marine Biology and Ecology, 424-425, 99-108.
Ward, J.H. Jr., 1963. Hierarchical grouping to optimize an objective function. Journal of the American Statistical Association, 58 (301), 236-244.
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