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
on the way to Makri Island for a dive with tuna
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
macro photo of Maerl coralline red algae 50 m deep off 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.
deep water algal comunity off Rhodes
Vivian and herbarium specimens
deep water community off Rhodes
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.
Womersleyella invading deep water reef at 50 m off Rhodes
on the way back from the last dive
farewell of the team at Athens International Airport
Photographs: Martin D.J. Sayer, NFSD / SAMS
