I am writing this at the end of our latest trip to Greece, reflecting on our diving mission to the southern Aegean Sea. Supported by a professional team from the NERC UK National Facility for Scientific Diving (NFSD, hosted by the Scottish Association for Marine Science / SAMS in Oban), we have been exploring poorly known seabed communities off the Greek island of Rhodes for the last 2 weeks.
Kalymnos Island home of traditional sponge divers community
Led by Dr. Martin Sayer (NFSD) and myself, the team (which also included Elaine Azzopardi and Andrew Mogg from NFSD / SAMS) has been working with Vivian Louizidou (PhD student at Oceanlab / University of Aberdeen and Hellenic Centre for Marine Research), conducting deep diving operations up to 55 m depth, exploring the poorly known communities of maerl (coralline red algae) and associated organisms. Conducting scientific work – sampling, surveys and photography - at such depth required careful planning with larger than usual air cylinders, independent bail-out cylinders and extra air staged for the decompression stops. All diving was conducted using a bottom-reel to ensure that the divers always found their way back to the decompression lines. In total, 46 person-dives requiring staged decompression were completed without incident.
Frithjof Kuepper and Andy Mogg at work 50 m deep off Rhodes
yellowfin tuna with Andy Frit and Savvas under fish farm at Makri Island
The biodiversity and ecology of such communities in the Eastern Mediterranean has been rarely explored. Most of the existing studies had been conducted by bottom grabs or trawling, sometimes also by remotely operated vehicles (ROVs) – but rarely by divers. Scientific diving has a range of advantages – I consider that the major one is to place a thinking scientist in the midst of the site or community that he is studying. Scientific diving is also less intrusive and destructive than sampling by bottom grabs or trawling – and, in most cases, also more cost effective than the use of a larger research vessel.
2 m large ray under fish farm at Makri Island off SW Rhodes
The team managed to conduct extensive collections and photographic surveys, enabling a range of laboratory studies in the nearer future including the taxonomy of calcifying and other algae, their growth rates and contribution to carbon sequestration, and community ecology. The surveys revealed the presence of a number of alien invasive species, including fireworms, the red seaweed Womersleyella and 3 Caulerpa species (several of which are considered among the worst invaders of the Mediterranean). While they were known to impact shallow-water communities in the Eastern Mediterranean, the surveys conducted by the team suggest that their impacts are likely profound also in the low-light and colder-water, deeper communities.
On our last day and with all scientific objectives accomplished, Savvas Hatzinikolaou (from whom we had rented the boat and part of the equipment) took us diving around his fish farm near Makri Island off the SW coast of Rhodes. Since its establishment in the early 1990, the site has been off limits for fishing and, in consequence, has become a safe haven for some large marine life: dolphins, yellowfin tuna, and large rays. As we dived under the large fish cages, we were lucky enough to see 5 yellowfin tuna close up and a resting ray with > 2 m wing span on the seabed – a closure to our dive mission, as spectacular as the deep diving!
I am very grateful to the wonderful team – ευχαριστώ πολύ to Martin, Elaine and Andy for the diving, to Savvas for logistics support, and to Vivian and her mother Irini for most other aspects of working in Rhodes and their great hospitality. I had previously worked with Martin and Elaine in the Canadian Arctic and around Oban, Scotland – we are currently planning a new mission to the Arctic, and to return to Greece next year. To be continued – watch this space.
Photographs: Martin D.J. Sayer, NFSD / SAMS