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

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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