Yesterday afternoon I was wading through an incoming tide, recalling that it’s best to shuffle your feet when walking in stingray country. A few giveaway clouds of swirling sand just ahead reminded me that I really need to get some appropriate wading footwear.
Then in just a few inches of water I stopped, startled, mid-step before a great brown, mottled, slightly convex disc that I took for a dead or floundering sea turtle.
But nope, it was a stingray, and man, what a commotion it made as it panicked and thrashed its way to deeper water and safety. A not-so-clean getaway.
It’s great witnessing mysterious visitations like these on such a well-trod shore — but this post isn’t about stingrays. Instead I thought I’d share some recent shots of some less lucky visitors, a plague of them in fact — or perhaps a swarm or a bloom, which are the accepted terms.
For the last few weeks Sandgate and other stretches of the east coast have been invaded by jellyfish in their millions:
If you’re a visitor, you might have noticed the stench; thanks for coming and sorry about that. (Just as we were finally rid of a noxious algal bloom that had painted the foreshore in psychedelic and revoltingly fragrant swirls for weeks.)
We locals are used to it — as I’ve noted before, the littoral zone might teem with life, but it’s an open graveyard as well. There are always a few jellyfish carcasses littering the flats and high-tide line, and the odd handful or two bobbing gracefully shorewards or down the creeks…
..but lately it’s been like a jellyfish D-Day all up and down the South-East Queensland coast — it even made the papers.
These swarms, or blooms, or invasions happen periodically. Says this source,
In recent years, certain parts of the world — namely Japan, Australia, and Europe — have seen a problematic increase in jellyfish populations. Scientists believe the increase in jellyfish numbers may have to do with additional nutrients in the water, climate change or fishing along the coastlines.
Noted marine biologist Professor Wikipedia adds,
Jellyfish populations may be expanding globally as a result of overfishing of their natural predators and the availability of excessive nutrients due to land runoff. When marine ecosystems become disturbed, jellyfish can proliferate.
At least they leave good-looking corpses. Hard to imagine a more attractive shade of blue in the animal world:
This is easily the most common and visible species in Moreton Bay — turns out its common names are blue blubber and jelly blubber. When we were kids swimming in Moreton Bay, they were simply jellyfish, an occasional hazard with a decent but not dangerous sting that could even be grabbed from the water if you made sure to grasp the “head” and not touch the tentacles.
(Why would you want to pick up a jellyfish? How else are you going to throw it at your sister?)
Jellyfish distinguished them from the far scarier bluebottles (not actually jellyfish), which Americans might know as Portuguese man-o-wars — what we called Portuguese man-o-wars were in fact some other, larger, weirder and infinitely more disgusting and gelatinous saucer-shaped blobs.
We named a lot of things wrongly in those days, I now realise.
The smell ain’t pretty after a day or two, but I’ve enjoyed the surreal streaks of brilliant colour and the allure of the just-plain mysterious these visitations bring to the tidal flats and shoreline.
There’s so much going on out there that we don’t understand yet:
The blue blubber’s scientific name is Catostylus mosaicus. In southern waters they can be brownish — I’ve seen paler ones, but they’re rare up here.
I’ll leave you with some tasty Jellyfish Ephemera to enjoy with a side helping of recent pictures, just some interesting facts I came across while looking online into these fascinating critters.
Apparently jellyfish are classified as plankton! A defining characteristic is that they are radially symmetrical. They’re 98% water.
“Recent research shows that jellyfish numbers oscillate over time and will be abundant for several years and then not seen for several years – this bloom of jellyfish appears to be part of a recurring series of events at about this time of year in Moreton Bay” ~ marine biologist Paul Thomson.
If they don’t come across as too smart, that could be because jellyfish lack a brain. Instead they employ what’s called a nerve net — a network of neurons, as this source puts it — able to detect light, odour and other stimuli and coordinate a suitable response.
That said, I could be wrong, but yesterday as I was wading past a few living jellies, I imagined that they could detect me and were making attempts at an escape.
Then again, I have this effect on a broad swathe of the animal world, right up to the higher primates.
Jellyfish use a single orifice as both mouth and anus. Spend a lot of time watching TV, as I have lately, and you’ll observe that this trait is not confined to jellyfish.
You probably won’t be surprised to learn that Australia has more than one deadly jellyfish species. The thumbnail-sized irukandji, in northern Queensland waters, killed two people in 2002, but larger and more prevalent box jellyfish or sea wasps are household names in this state. They have been called the most venomous marine animal known to mankind.
In evolutionary terms, jellyfish are the earliest known animals to have organised tissues—their epidermis and gastrodermis—and a nervous system. They’re also the first animals known to swim using muscles instead of drifting with the whims of the waves ~ The Smithsonian
Dried, cooked and (gag) raw jellyfish are popular foods in China, Japan and Korea. Then again, if there’s a variety of sea life not eaten in those countries, it probably hasn’t been discovered yet.
In their own environment, jellyfish predators include tuna, shark, swordfish, sea turtles, and at least one species of Pacific salmon.
Jellyfish medusas (the adult bell-shaped form we all know) are either male or female!
Although they travel mostly by drifting (I can relate to that), they can produce some vertical movement by contracting their “bell”.
Jellyfish exist during their life cycle as polyps and medusas and stages in between. Beginning as coral-like polyps anchored to something solid, they later multiply by budding, and then produce saucer-like larvae which detach and grow into the medusa form we recognise as jellies.
The sensation of a medusa’s “head” bumping into you while you swim stays with you a long while. Who knows what kind of impact it has on the jellyfish. Ships in the night, no doubt…
~ And that’s all the Goat wrote