Unidentified Floating Objects can be a bit of a challenge to identify. By the time they reach shore and are washed up, features have often been pecked off or removed by wave action, or the creature has just rotted away and what’s left is a bit of a mystery. In the case of the latter, a rotting whale carcass washed up on a beach may sometimes be mis-identified as some sort of fabulous sea monster.
Hundreds, possibly thousands, of clear, stiff, gelatinous ‘medallions’ have been washing up at Ballina – and, it turns out, in many places along the east coast.
In my quest to find out what these are, I emailed Ceridwen Fraser, associate professor in the Marine Science Department at the University of Otago and author of a new book called Beachcombing.
In her book, I had noticed a photo of a salp, which looked somewhat similar, but she thought my critters were jellies. She kindly put me onto the Facebook post of Coolum and North Shore Coast Care, which says:
These jellyfish are a relatively new species called Aldersladia magnificus, a genus and species within hydromedusa and within the Aequoreidae family found in tropical and subtropical waters (Gershwin, L. 2006).
What causes these blooms to happen? There are multiple causes, some contributing factors are ‘Eutrophication, climate change, overfishing, and habitat modification’ (Qu CF, Song JM, Li N. 2014).
When washed up they appear to have no tentacles, but when seen in the water they have long tentacles that can retract. These tentacles can sting so please be careful whilst swimming at the moment. Don’t be too scared though, Jellipedia rates them as a 1/5 on their sting-o-meter.… they are … bioluminescent. If you head down to the beach at night time at the moment to a spot where there are plenty of them you will see for yourself.
In 2006, Lisa-Ann Gershwin identified the new genus and published a paper, ‘Aldersladia magnificus: A new genus and species of hydromedusa (Cnidaria: Hydrozoa: Leptomedusae: Aequoreidae) from tropical and subtropical Australia’, and if you want all the gritty details you can download it for free from here.
Thank you to Ceridwen for pointing me in the right direction. It’s great fun finding and tracking down things I haven’t seen before. Now I can add one more thing to my bucket list: a salp!