Mike,
We get bursts of red tide on the Lower Columbia also. They are typically late in the season, when the flow in the river is quite low. However, the outbreaks are in the salt water, not the fresh, and only very low in the estuary, where salt water is present on high tides. At low tide, we do not see them here; the red coloration is then out to sea or on the bar between the jetties of the Columbia.
The critters responsible are dinoflagellates, and they can also "bloom" in fresh water. However, this class of critters is very diverse. What is causing a red tide in Florida where you live may be a very different bug than what we see here. And, marine biologists claim there are several factors which influence whether dinoflagellates will suddenly grow exponentially in number to produce a visible red tide. Some are related to input of "nutrients" from human activity ... so it is possible the reduction in water release out of Lake O explains why you are not seeing red tide right now. Some factors are related to input of nutrients from the ocean, which seems to be the case where I live. (The Columbia is much less affected by human - produced nutrients than waterways with very low flow.) We get a lot of upwelling in the summertime, which produces a lot of microscopic feed offshore, eventually producing, farther up the food chain, more feed for salmon. We like salmon up here, so the upwelling is a good thing, not a bad thing, most of the time.
Here is a Wikipedia link with more information on red tides and their origin, focusing on harmful algal blooms:
http://en.wikipedia.org/wiki/Red_tide#.22Red_Tides.22
Not all red tides cause respiratory problems. As kids, we used to swim in red tide-affected water in Southern California, but I do not recall any one showing symptoms. Must have been a different one than what Jim has been experiencing. It sounds pretty ugly down there on the Gulf, for sure. Hope it goes away soon.
Oh, yeah, in case anybody is curious, a link to coastal upwelling, the kind we get:
http://en.wikipedia.org/wiki/Upwelling# ... _upwelling