Global warming is likely the largest contributor to the increase in algae blooms, in that warmer air temperatures mean warmer water temperatures, stimulating more algae growth. Increased levels of carbon dioxide are a major contributor to the problem as well. Remember that plants eat C02, so the more of it there is in the atmosphere, the more plants, especially fast-growing plants like algae, grow. But wait, there's more: Damming rivers leads to less water movement. Many rivers have been dammed worldwide, and this, not only slows water down, or in some cases stagnates it, which makes it easier for algae to grow. It also means that wastewater nutrients and agricultural fertilizers have a chance to concentrate, meaning more nitrogen. The only thing that causes plants, especially algae to grow faster than more C02 is concentrated nitrogen.
So those are the causes. They're bad, but the picture the new study paints gets darker still: There are currently no state or federal mandates requiring municipalities to test for cyanobacteria in their drinking water, nor are there any regulations requiring the reporting of disease outbreaks associated with algal blooms. But, the researchers pointed out, as more toxic algae blooms occur and more people get sick, local and federal governments may be forced to pay greater attention to this issue.
Drought and low snow pack in 2015 has led to large and toxic algal blooms earlier than in previous years throughout the West. Also, this is the second consecutive year that toxic blooms have occurred in the Willamette River near Portland, Ore., and in Upper Klamath Lake.
All along the West Coast shellfish harvests have been closed due to an ongoing domoic acid shellfish poisoning, which is producing the largest algal bloom in recorded history.
How bad is the problem? Well, a national survey carried out by the EPA in 2007 found microcystin, a recognized liver toxin and potential liver carcinogen, in one out of every three lakes tested. Though most toxic strains of cyanobacteria can cause gastrointestinal illness and acute skin rashes, some strains can also produce neurotoxins. For pets or wildlife that drink water contaminated with cyanobacteria the results are often fatal. Recorded human fatalities directly attributed to cyanobacteria exposure so far have been rare, but not unheard of. Although that may be due to the clear thinking of local officials in situations like one last year when the drinking water supply of Toledo, Ohio, a city of 500,000 people was temporarily shut down due to cyanobacterial contamination. Toledo's drinking water comes from a particularly shallow part of Lake Erie. It prompts the question: as the earth heats up, will places like Toledo start losing their drinking water supplies for large parts of the year on a regular basis?
There are certainly other concerns as well. A major one is, what are the long-term effects of drinking low levels of these toxic substances? "At this point," says Tim Otten, a postdoctoral scholar in the OSU Department of Microbiology, and lead author on the study, "we only have toxicology data for a handful of these toxins, and even for those it remains unclear what are the effects of chronic, low-dose exposures over a lifetime. ... We know some of the liver toxins such as microcystin are probable carcinogens, but we've really scratched only the surface with regard to understanding what the health effects may be for the bioactive metabolites produced by these organisms."
Source: Phys.org