The Green And Silent Sea

 

 

Back in 2022-23 the Murray River flooded, pouring warm, nutrient-rich water into the sea at the river mouth.  I pedaled along the foreshore at Goolwa and marvelled at the plume of muddy water while surfers swam in the chocolate waves amongst fish that didn't survive the sudden change in water temperature and salinity.

Then in 2024 a summer cold water upwelling brought more nutrient-rich waters to the surface.  This was not something I noticed as I pedaled along the foreshore paths in Adelaide.  I didn't notice a marine heatwave happening out to sea, either, but a little marine algae callen Karenia found itself thriving in conditions ripe for multiplying.  Multiply it did, filling the waters of Gulf St Vincent with foam and discolouration, stripping the water of oxygen, damaging the gills of marine creatures, and producing toxins that affected the nervous systems of animals lucky enough not rely on gills to breath.  

By the time I was walking along the beach at Port Julia scuba divers were posting pictures of underwater deserts of green algal water, as dead sea life sank to the bottom or washed up onto the beach with every turning tide.

We were not allowed to walk Dog on the beach due to his propensity to gobble up dead sea life with lightning speed and nary a thought as to how sick it would make him.  And once I started looking there was a lot of dead sea life amongst the shells and seagrass left behind by the tide. 

There were crabs; 

a sting ray;

fish I didn't recognise, which didn't mean much because I'm not good at recognising fish;

and more fish.

I walked on the jetty every day and saw one solitary fish and not a single fishing person, which in Port Julia was almost unheard of.  The sea slapped, green and silent, at the jetty piers and the algal bloom spread its microscopic fingers further up the Gulf St Vincent, and inched its way into the Spencer Gulf.  Winter weather arrived with cold winds and everyone crossed their fingers and hoped for drops in water temperatures such that Karenia would find the water incompatible with algal life.  "Don't count your chickens," said marine biologists and other knowledgeable people.  "It will be back when the weather warms up.  We can't do anything, it's not possible to flush out the ocean and get a refill."

That was a sobering thought, wasn't it?  We cleaned up the house, patted the dog, and left him to his returning owners.  As we drove back to Adelaide early morning sunlight sparkled on the waters of the Gulf and the radio told us that Karenia had been found in the waters of the Dolphin Sanctuary at Port Adelaide and that a few nights ago the water around Kangaroo Island had sparkled with (Noctiluca scintillans) a bioluminescent algae that feeds on Karenia and could help to break down the Karenia bloom. The dolphins were not considered to be in immediate danger, and we were warned to not get too excited about the sea sparkles.

"All we can do," said the marine biologists, "Is let nature take its course".

There are no easy answers, more's the pity.

Rainbow on the Yorke Peninsula.