Seventeen marine experts met in Sorrento, Italy, in mid April 2015, at the invitation of CIESM to review the latest knowledge on submarine canyons dynamics in the Mediterranean and Black Seas.

Submarine canyons are important features of continental margins from a geological, biological and oceanographic perspectives. They are focal points for fisheries and are critical habitats for threatened cold water coral communities. The Mediterranean Sea is estimated to contain more than 800 canyons that are quite distinct from those occurring in the rest of the world: in particular they are steeper, more closely spaced, and are amongst the most dendritic; they also reflect in part the effects of the dramatic Messinian low stand which occurred some 6-5 My ago. Many gaps in knowledge remain, concerning the controlling factors underlying canyon formation, development and ecological functioning, both for long-term processes (tectonics, sea level changes, sedimentary dynamics) and short-term processes (flash floods, surge waves, internal waves, upwelling/downwelling, ecosystems functioning, trawling damage, etc.).

Critical knowledge gaps identified are:

1. An inventory of canyons in the Mediterranean and Black seas of different types based on geological, physical oceanographic and biological data to enable regional comparisons between canyon systems to be made.
2. Understanding of the natural drivers that control canyon ecosystems (e.g. sediment transport, seabed composition, near-bed current flow, fluxes of particles including nutrients).
3. Data required for geohazard assessment, ecosystems preservation, trawling damage, etc. such as repeated high resolution geophysical and mapping surveys long-term time series observations and monitoring programmes, systematic ROV surveys.
4. Integrated biophysical data sets (eg. multibeam sonar mapping, physical oceanographic data together with biological sampling of canyons) to gain a better understanding of canyon environmental status.

Priorities for conservation include:

1. Improved understanding of canyon biodiversity and ecosystem function in relation with canyon ‘s type.
2. Coordination between geology, biology, chemistry and physical oceanography investigations for an integrated approach to canyon monitoring and management.
3. To investigate any potential relations between canyons and anoxic layers, particularly in the eastern Mediterranean (and the Black Sea).
4. To connect existing mapping and monitoring programs at European and/or national level (EMODNET, ESONET, EMSO) with specific actions linked to submarine canyons.