Epic Conditions are Approaching

[3D diver]

As I recall, it's something like, offshore (i.e. from land toward sea) wind blows surface water away from shore to be replaced by an up-welling of cooler, clearer, nutrient rich water. This + sun leads to plankton/algae bloom.

 

[g1138]

As I recall, it's something like, offshore (i.e. from land toward sea) wind blows surface water away from shore to be replaced by an up-welling of cooler, clearer, nutrient rich water. This + sun leads to plankton/algae bloom.

Pretty much. To visualize: Next time you get a bowl of miso soup, let the miso settle to the bottom so the top is clear hot water and the bottom is the mucky miso. Then blow over the top of the bowl. You'll see a current form and the miso will be brought up to the top and mix in to form a full consistent bowl of mucky (but yummy) miso soup.

Pretty much the same thing that's been happening right now. Marine snow and nutrients are being brought up to the surface by upwelling. These particulates are molecules small and wouldn't affect vis. However they allow plankton and algae to have a field day and bloom, which does affect the vis.

 

[mahjong]

If upwelling also means considerably cooler water (recently it's been 46-48 degrees at depth; last weekend I even had 46 degrees in 20' of water; today, for the first time, I had a reading of 50 degrees in shallower water), and if bloom requires higher temps (in addition to more light), then would there not tend to be a lag between upwelling and bloom during which the water might be especially clear? After all, the upwelling itself isn't "mucky" like miso. It's what 'eventually' happens, when conditions are right, as a result of the nutrients in the upwelling. Seems there might be a window between upwelling (event) and bloom (process) during which the water might be quite clear, no?

 

[g1138]

If upwelling also means considerably cooler water (recently it's been 46-48 degrees at depth; last weekend I even had 46 degrees in 20' of water; today, for the first time, I had a reading of 50 degrees in shallower water), and if bloom requires higher temps (in addition to more light), then would there not tend to be a lag between upwelling and bloom during which the water might be especially clear? After all, the upwelling itself isn't "mucky" like miso. It's what 'eventually' happens, when conditions are right, as a result of the nutrients in the upwelling. Seems there might be a window between upwelling (event) and bloom (process) during which the water might be quite clear, no?

Correct, but let's not forget the wind's been blowing for a good 3 weeks now, so that window has already passed. Upwelling came and still is coming, life has already started to be effected. And higher temps is not necessarily needed for our local waters to support a bloom. Yes it helps for some species but not all. With the amount of sunlight Monterey's been getting (a lot), plus the wind, plus the confirmed reports of green soupy viz, I think it's safe to say there's an algae bloom already. Later this could evolve into a different bloom of algae-eating plankton or what not, or it could just die off with the algae once the nutrients are consumed. It's always different each time, because weather and conditions are always different each year.

This is just my take from what I managed to grasp from Oceanography class.

---------- Post added April 20th, 2013 at 09:57 PM ----------

So to put it into more perspective. The ocean isn't evenly mixed with all kinds of plankton; phyto- and carnivorous. Same goes with algae. There are pockets of populations that constantly increase or decrease in numbers depending on water quality (nutrients/food), competition, and predation.
Populations are usually mixed with other species populations, which I guess we can call communities.

So when upwelling hits out coast, depending on which pocket of populations are in our area, one of them will beat out the competition and bloom. This starts with primary producers, phytoplankton and algae. Once they consume all the nutrients from upwelling, they no longer can sustain their population growth. The herbivorous plankton, which have also been feasting (on primary producers), will now widdle away the initial bloom; they in turn can be consumed by larger carnivorous plankton on the food chain, so on so forth.

Depending on which species bloom in the cascade, if there is a cascade at all, will effect how long you have to wait for the murk to dissipate after a bloom.

Sometimes we get a "red tide" which is toxic (not always to humans) which would explain why you get one bloom then away it goes. Other times you get one bloom, followed by another in which you notice the murk changes color or consistency.

El Nino and El Nina can effect blooms (your temperature remark). Temperature can help speed a bloom or help slow it. But if there's a large amount of food available you're talking about a just large raw numbers being able to have a growth and reproductive success, so at that point temperature doesn't really matter much because it's all in the same temp range/tolerance of the bloom.


Now for instances where we get very high wind for a very short duration. All that murk already here (not from a bloom, just our usual murk) get's blown down the coast. Wind stops, water settles, and you get clear waters. Then the bloom hits from the upwelling.
Or sometimes, draw of luck, we don't have a population as close to the shore, so the bloom happens farther out at sea and makes it's way over. So we perceive this as a longer time period of clear waters after the upwelling.

 

[mahjong]

Thanks for the thorough explanation! Good stuff!

 

[zf2nt]

The best explanation I found on the web after a few minutes worth of browsing is at Ocean Motion : Background : Ocean in Motion - Ekman Transport. This will explain why NNW winds along our coast will push the green surface gunk out to sea and then have it replaced by cold, clear water from deep in the canyon.

Bruce