The seas around the Maltese islands continue to stun and mesmerise marine biologists with the discovery of two new jellyfish species – the nomadic jellyfish (Rhopilema nomadica), a painful stinger and an alien species, and the barrel jellyfish (Rhizostoma pulmo), an innocuous and indigenous species.
The barrel jellyfish report was submitted online to Spot the Jellyfish recently, while the nomadic jellyfish was recorded on video by Calm Seas staff members in 2004 at two locations, but was only detected recently.
Both jellyfish are similar in appearance but can be distinguished through a number of subtle differences, including a marginal blue ring around the bell, found only in barrel jellyfish.
Such reports bring the total number of new jellyfish species in Maltese coastal waters to seven.
Both are relatively large jellyfish species, with a bell diameter of around 40-60 cm, which can even reach the 90-cm mark.
The nomadic jellyfish has an infamous reputation – it entered the Mediterranean sea via the Suez Canal in the late 1970s and has appeared in swarms along the coast of Israel and Lebanon since the late 80s.
Like most other non-indigenous marine species entering the Mediterranean through the Suez Canal (the so-called Lessepsian migrants), it has also spread west and is popular in Turkey and Greece.
The nomadic jellyfish was also the cause of the temporary shutdown of a coastal electrical power station in Israel in 2001 – it had clogged its cooling water intake pipes.
Fishermen in Israel, Lebanon and Turkey very often discard netfuls of fish due to large quantities of this jellyfish among their catch.
Water temperature plays a crucial role in the reproduction of the nomadic jellyfish, with the medusa stage appearing once the water temperature exceeds 24˚C. In fact, it was previously thought the species would only limit itself to the eastern Mediterranean, normally characterised by very warm water temperatures, but it seems to have also penetrated the Sicilian channel.
Marine biologist and researcher Alan Deidun said there was no cause for alarm, especially since the nomadic jellyfish appears to be quite rare in Maltese waters. It is also easy to spot, unlike other more cryptic species.
If spotted, bathers are urged to call members of the Spot the Jellyfish team on 2340 2843 or 7960 4109 or to e-mail ioimoc@um.edu.mt.
The Spot the Jellyfish initiative is coordinated by Aldo Drago and Alan Deidun and staff members of the International Ocean Institute – Malta Operational Centre.
The initiative is supported by the Malta Tourism Authority, Nature Trust, Friends of the Earth, Ekoskola and the Blue Flag Malta programme.
For more information, visit www.science20.com/citizen_science_journal/jellyfish_reporing_citizen_scientists_malta or www.scienceforcitizens.net/blog/2010/08/spot-the-jellyfish-here-or-in-malta/, e-mail moc@um.edu.mt or send an SMS to 7922 2278.