Satellite observes agricultural runoff causing algal blooms

Space Daily ^ | December 9, 2004 | SPX

[cogitator]

You wrote a lot. In general, the issue with normal, non-toxic algal blooms is like a lot of other things; when they're normal, they aren't a problem. When there's too much, that can cause problems (likewise with too little).

It talks about red tides and hypoxia, but it doesn't say that they saw evidence of those occurrences in the areas they were observing.

They didn't; but the study supports the linkage between agricultural runoff and blooms that induce hypoxia elsewhere.

They mention problems with hypoxia at the end of Mississippi river, but they don't really show that they have any evidence to show that it's related to algal blooms or nutrient runoff. I suspect that there are a lot of different pollutants in the Mississippi river, what ties the hypoxia to the nutrients?

Pollutants that don't enhance phytoplankton growth don't participate in the process that causes hypoxia; they're just pollutants. Excess nutrients like nitrogen and phosphorus do enhance phytoplankton growth.

The article mentions bacteria that eats the algae uses up oxygen. However green algae is the biggest source of oxygen in the oceans. I'm having a hard time buying the argument that more green algae results in a net loss of oxygen levels in the water.

Hypoxia is a problem on the sea floor. The algae die and sink to the bottom and get consumed by the bacteria. That's where the oxygen depletion occurs, not at the surface where the algae are growing.

Shrimp eat algae. So unless the runoff is causing toxic blooms, I would think that the shrimp population would thrive during algal blooms.

Shrimp breathe (respire), too, and they inhabit the bottom of the water body. If they are in waters that become hypoxic, they have to leave.

It sounds like they gathered some good information with their research. However the tone of the article seems to imply that these algal blooms are bad. All they've done so far is show that the nutrients appear to effect algae growth, but they don't know what type of algae or if it's good or bad.

I think it's more appropriate to say that excess algal blooms can be (but aren't always) bad. They don't really say that they've seen detrimental effects from this process in the Sea of Cortez, leading me to think that they haven't.

[untrained skeptic]

Thanks for the clarification. If I understand correctly there is bacteria feeding not just on the algae, but on other nutrients in the runoff. The net result is the bacteria uses more oxygen than the algae produces.

I wonder if it's possible to tailor the fertilizers used to be appetizing to good algae, but unappetizing to bad algae and harmful bacteria?

[untrained skeptic]

Thanks for all the info. A lot of my skepticism did result from not having enough knowledge on the subject to be able to follow the reasoning of the author as well as he probably expected his audience to be able to follow along.

It sounds like the still have some work to do to show cause and effect, but it seems like they're gathering good information.

[PigRigger]

We experience the same problems in the Great South Bay off of Long Island every few years; we call it brown tide.

The blooms have decimated the shell fishing industry in the region. It has also added to the decline in the fishing industry; although over fishing was probably the main culprit.

What was once a very bountiful ecosystem was experiencing a slow death.

Laws have helped in stabilizing the bay; in time it may one day came back. Only time will tell.

[Aracelis]

a lot of ugly yellow stuff was being washed down the parking lot drains and into the lake! It appeared to be coming from our beautiful pine trees! What program does the Federal Government have in place to stop this detrimental substance from polluting the lake?"

ROFL! Pollen...Pollution...coincidence?

[SierraWasp]

"ROFL! Pollen...Pollution...coincidence?"

At a meeting headlined by one of the most corrupt Pollititions in history... Bill Clinton!!!