Reduced viz - algal growth or spawning?

[Storker]

Spring has come and visibility is deteriorating in the cold mid-Norwegian waters, from at least 15-20 meters down to about 10. This is completely natural, particularly in the fjords where the rivers bring lots of fresh nutrients to the sea, coinciding quite nicely (for the plankton) with longer days and more light.

However, on last Saturday's dives I was a little bit surprised that it has started already. We've had an uncommonly cold spring, and the rivers are still quite dry since the snow hasn't started melting in the mountains. It's only during the recent half week or so that we've seen any significant reduction in the amount of snow even in the lowlands. I was honestly expecting viz to keep for a couple more weeks. Also, the particles appeared to be larger and whiter than the usual algal soup I was seeing last summer. The experience was slightly snowstorm-y.

So I started wondering. Could it be the beginning of some type of spawning, or have the algae managed to start growing despite the still cold water and no big influx of fresh nutrients? To put it bluntly: Was I swimming in vegetable soup or marine jizz?

 

[supergaijin]

Norwegian fjords are pretty region specific- maybe copy this in the regional forum?

 

[TSandM]

I don't know if the two places are very similar, but we're already into spring plankton blooms in Puget Sound. We also have the combination of snowmelt runoff bringing particulates into the water, but that hasn't really started to happen very much here yet (it's still snowing in the mountains).

 

[3D diver]

The water has been pretty green lately down Monterey way too. I've been wishing I had a microscope to see who was there---not that I'd actually recognise anything.

Had blue water Friday, though, upwelling and all that...

 

[Storker]

OK, I guess it's algal blooming after all. I'm no biologist, but is it probable that the dark winter has prevented consumption of the moderate amounts of nutrients that after all are transported into the sea during wintertime? If so, the increased daylight alone should be enough to start the blooming.

 

[TSandM]

Again, I don't know the biology of your waters, but where I dive, this algae bloom phenomenon is a normal part of the rhythm of the year. As the light in the water increases, the algae multiply until they use up the available nutrients (or live out their lifespan, or something -- I'm not sure what limits the blooms), upon which they die and coalesce into long, stringy structures we give the elegant sobriquet of "whale snot". This stuff then settles out and we have a few days of excellent visibility before the next bloom begins.

 

[Storker]

Again, I don't know the biology of your waters, but where I dive, this algae bloom phenomenon is a normal part of the rhythm of the year. As the light in the water increases, the algae multiply until they use up the available nutrients (or live out their lifespan, or something -- I'm not sure what limits the blooms)

Same thing here. Spring algal blooming is comme il faut here as well. I just thought that it depended on fresh nutrients from the land in the spring when the snow melted, but given some afterthought there's always some influx of nutrients, and practically none of that is used in the winter when the light is low.