Low diversity or poorly explored? Mesophotic molluscs highlight undersampling in the Eastern Mediterranean

Area of Science:

• Marine Biology
• Ecology
• Invertebrate Zoology

Background:

• Mesophotic ecosystems (77-92m) are underexplored frontiers in the Mediterranean Sea.
• Eastern Mediterranean mesophotic habitats remain largely unknown compared to western areas.
• These deep zones host diverse invertebrate-structured habitats.

Purpose of the Study:

• To describe molluscan assemblages in mesophotic rocky reef and soft substrate habitats off northern Israel.
• To assess the marine biodiversity and species composition at these depths.
• To evaluate the status of native vs. non-indigenous species in this underexplored region.

Main Methods:

• Sampling of molluscan assemblages at mesophotic depths (77-92m) using underwater surveys.
• Species identification and cataloging of recorded mollusks.
• Comparison of findings with existing data from the Mediterranean basin.

Main Results:

• Recorded 172 molluscan species, with 43 (25%) being new records for Israel, increasing its marine diversity by 7%.
• Only 5 species were previously reported in nearby Lebanon, suggesting broader regional significance.
• A low proportion of non-indigenous species (2%) was found, indicating relatively pristine conditions.

Conclusions:

• Mesophotic habitats in Israel harbor rich, native molluscan assemblages, contrasting with impacted shallow waters.
• The findings challenge the presumed west-to-east declining diversity gradient in the Mediterranean.
• Urgent conservation efforts are recommended for these vulnerable deep-sea ecosystems.