A ghostly tide in Calabash Creek

It’s true what they say: you can’t step into the same river twice. Especially if that river is really an estuary, briny water moving up and down between the mangroves.

Last time I was in Calabash Bay, back in February, it was full of stingrays. The bigger rays were over a metre from head to tail, the smallest a quarter of that size, sliding along the silty creek bed bottom at a surprising speed as I wrestled with the manual focus on my camera.

Little black cormorant

The entrance to Calabash Bay

Stingray in Calabash Creek

Upper reaches of Calabash Creek

But this Sunday, in the golden hour, I floated alongside a parade of hundreds of thousands of jellyfish. Not the jelly blubbers that gather in the bends and eddies of the Hawkesbury proper, orange and beefy and disturbingly solid under the paddle. These were moon jellies, aurelia aurata, diaphanous as mermaids’ undergarments, their shadows on the sandy bottom more substantial than themselves, tumbling and drifting downstream.

A flock of moon jellies

Moon jelly and reflection

Moon jellies flaunting their horseshoe shaped gonads

Stinging tentacles on display?

They’re common enough, moon jellies. They’re easy to see and easy to study because they like to hang out where we humans do. Harbours and jetties give them somewhere to latch onto in the polyp phase of their intriguing two part life cycle. And blooms of millions of the medusa form – like the one I saw this weekend – are not unusual either, especially in enclosed and not too salty waters, where the nutrient level is high, the oxygen level low and predators are few. But I’d never seen so many moon jellies in one place before, and never seen them here. Perhaps the stiff south easterly breeze and a rising tide blew them implausibly high into the tree-lined reaches of Calabash Creek.

Burns creek during a burnoff

Maybe it was a coincidence, but along with the mysterious tide of jellyfish, Calabash Creek and the trees and rocks that flanked it were draped with garish green algae. The creekbed and mangrove roots were coated in it and dried mats of it hung like fragments of ripped clothing from low branches. Water quality is much better in the Hawkesbury these days, but it seems like Calabash Bay is a hotspot for algal blooms, both toxic and less so, thanks to sewage outfalls upstream and a legacy of nutrients from earlier, dirtier days buried in the sediment.

Whatever the cause, the creepy drapery and the feeling of being entirely surrounded by slowly moving, half-invisible jellies lent an otherworldly feel to these quiet waters.

Whitefaced heron in a monochrome landscape

Dried mats of algae looking like torn clothes

Algae draped over a rock

Baby mangroves

So I guess I can’t say for sure whether you get to step in the same river twice. My feet never went near that water. They were tucked up in the canoe with no chance of touching ghostly jellies, stinging tentacles or strangling slime.