Talk:Algal bloom

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The intro is a majority of this article... we need to reorganize it. -- Anonymous 02:28, 9 October 2006 (UTC)

I removed the italicized sentence:

Coastal pollution produced by humans appears to be a causal factor in red tides in some parts of the world, but red tides also occur in places where there are no associated human activities. Some red tides produce large quantities of toxins, which kill fish and are accumulated by filter feeders, like shellfish. This bioaccumulation of toxins is why one must be careful eating shellfish collected at certain times of the year.

Can someone find a reference backing this up? Surely this can't be true of all shellfish as that would include crab which are not filter feeders. This statement sounds like the adage that one should consume raw oysters only in months that end with 'r', but that concern is over bacteria – not cyanotoxins. Kent Wang 04:31, 10 Mar 2005 (UTC)

I guess in many places crabs are considered "shellfish", so the statement really should read clams and oysters (specifically). You are correct that concern over bacteria in clams and oysters, especially where sewage contamination is a potential problem, is real. However, you are incorrect in associating the old adage(s) about safe and unsafe months in which to consume oysters has anything to do with bacteria. Reason it out. Eating oysters in certain months is a climatic thing related to blooms of phytoplankton containing toxins. These blooms are largely under control of climate and have been for a long time (months not ending in "r" are Spring and Summer months), predating human environmental influences in some cases (thus the adages). Harmful (to human consumers) bacteria come from human waste contamination. How that would be associated with certain months is difficult to imagine. I'd feel no safer eating an oyster collected from near a sewer outfall in December than I would in June. - Marshman 19:39, 10 Mar 2005 (UTC)
I still disagree. Did you simply deduce this conclusion or have found actual scientific studies? The explanations for the 'r' rule that I've read in both Saveur and Cook's Illustrated attribute the origin of the rule to the increased chance of bacteria development in warmer seasons but they also state that as long as specimens are refrigerated properly the rule can be ignored (and that the rule only makes sense in the northern hemisphere), which indicates that algal blooms are not a common concern. I'd be happy with the inclusion of the statement if either scientific evidence is produced or if the statement is modified so that only those oysters collected in areas prone to algal blooms need be concerned. Kent Wang 18:32, 14 Mar 2005 (UTC)
Of course I did not deduce it (I did not even add it to the article). I assumed the explanation was so well known to everyone living near certain sea coasts (I'm familiar with Northern California) that I find your explanation strange (who are Saveur and Cook?; are you in the Southern Hemsiphere?). Apparently there may be different explanations for different places/concerns. I'll need to get some references together, obviously. It would certainly NOT be safe to collect an oyster contaminated as result of a "red tide" and freeze it to make it safe. Of course the same would go for bacterial contamination, but safety there could be enhanced by vigorious cooking whether starting with fresh or frozen product. Your (or their?) comment as well about only making sense in the northern hemisphere is of dubious merit if bacterial contamination is of concern, although obviously the "r" rule would not pertain to southern hemisphere temperate zones or languages other than English for red tide concerns - Marshman 19:04, 14 Mar 2005 (UTC).
Saveur and Cook's Illustrated are two of the most popular magazines in the professional culinary world in the United States. I lived on Galveston Island on the Texas coast for seven years and have never heard of algal blooms to be a concern for oyster-lovers. Here's my proposed revised statement:
This bioaccumulation of toxins causes bivalves – like oysters and clams – collected in areas affected by algal blooms to be potentially dangerous for human consumption.
This wording ties the warning directly to algal blooms, not indirectly through seasons. Also, I just remembered that bivalve is really the term that you're looking for. The shellfish article explicitly states that it includes crabs, lobsters and shrimp. I love to eat shellfish and would hate for inaccurate warnings to unnecessarily discourage others from eating them. Kent Wang 03:12, 16 Mar 2005 (UTC)
Your wording is just fine. I may add to it if I can get some refernce(s) for the "old adage" stuff, but for now, I would certainly agree we are talking only about 1) biivalves and 2)algal blooms. I love them all, but I'd prefer others go easy on consumption so I don't get left out! 8^) - Marshman 05:10, 16 Mar 2005 (UTC)
The article has been edited to reflect the above agreed upon wording. Kent Wang 05:47, 18 Mar 2005 (UTC)

Question: Years ago I was reading an article in The Economist, I am pretty sure it was about red tide, it had a headline that read something like: "A Known Killer, It's Killed Before, It'll Strike Again". The point was that the algae was killing fish intentionally (if I may so anthropomorphize). The mechanism being to poison fish, they fall to the bottom, and provide food for the algae. Was this red tide? Is it true? Kent Borg 5 June 2005.

Satellite image[edit]

Satellite image of a large coccolithophore bloom in the Bering Sea in 1998.

While cleaning up the bloom article and turning it into a proper disambiguation page, I removed the rather fetching image that was on that page. Perhaps it can be of some use? I'm not familiar with the territory, so I'll just stick it in here.

Bz2 23:38, 19 December 2005 (UTC)

I changed the picture from Nasa in the article to this one, because the algal bloom is easier to see than in the other one. BabySinclair 15:55, 21 March 2007 (UTC)

I've just removed this image as it doesn't appear to be a bloom at all. As the image's caption makes clear, as it's from early in the year, it's more likely to be a resuspension of material from the seafloor than a bloom. The image's caption links to a research paper on the subject. Cheers, --PLUMBAGO 12:18, 10 April 2013 (UTC)


I corrected and revised the references today and inserted footnotes into the body of the text by using the <ref>-tag. Hope that was okay! Ioverka 01:19, 10 June 2007 (UTC)


I have noticed a lot of algal bloom in the UK recently and recall reading something about the damage it is doing to the ecosystem. Does anyone know of more information about this, possibly in the form of a link or a section on the subject? —Preceding unsigned comment added by (talk) 16:17, 9 September 2007 (UTC)


From the first paragraph: "...algae can be considered to be blooming at concentrations of hundreds to thousands of cells per milliliter...". Is that per square millimeter or cubic millimeter? It certainly isn't just millimeter. I'd correct it myself, but there's no citation for that statement. —Preceding unsigned comment added by (talk) 17:10, 2 July 2008 (UTC)

Milliliters measure volume, so the statement is accurate. You might have misread milliliter as millimeter. (talk) 22:22, 25 March 2009 (UTC)

Possible Deliberate Bloom Triggering in Deep Waters?[edit]

Years ago I conversed with someone who talked about the possible benefits of manually, deliberately, triggered algal blooms in deep international waters to provide food for other marine life (fish in particular). I don't know if this was purely speculative on his part or if he was referring to established lines of research.

The basic idea was to haul a large quantity of powdered iron rust (ferrous oxide) and disperse it into the water (possibly with selected strains algae that are best suited to the region). The argument is that the primary limiting factor in algae populations in these areas is the relatively low amounts of oxygen dissolved in those waters.

He described this as an "algea bloom" proposal.

My question here is: are there ongoing lines of research into the use of artificial algal blooms? Are there proposals? What are the risks and how do they compare to the possible benefits?

JimD (talk) 19:14, 29 July 2010 (UTC)

There are, yes, as it was initially believed that such fertilization could reduce atmospheric carbon concentrations, as the algae would presumably carry the carbon to the ocean floor upon expiring. Several corporations have already designed equipment for large-scale oceanic fertilization, but the efficacy of this strategy has not yet been determined. The World Resources Institute has a [short article] on it. A group of scientists in Science pointed out in 2008 that granting carbon credits to fertilization projects would be premature, and, more recently, an article in PNAS reported that experimental iron enrichment in high-nitrate, low-chlorophyll areas stimulated the growth of toxic diatoms. Oh, hey, and I just noticed that there's a Wikipedia page on it: Iron fertilization
Napzilla (talk) 05:55, 30 October 2010 (UTC)

New merge discussion[edit]

See Talk:Harmful algal bloom#New merge discussion. Dcoetzee 01:23, 27 July 2009 (UTC)

Causes of Algal bloom[edit]

There are fundamental contradictions on this page.

"Freshwater algal blooms

Algae tend to grow very quickly under high nutrient availability, but each alga is short-lived, and the result is a high concentration of dead organic matter which starts to decay. The decay process consumes dissolved oxygen in the water, resulting in hypoxic conditions."


In the marine environment, single-celled, microscopic, plant-like organisms naturally occur in the well-lit surface layer of any body of water. These organisms, referred to as phytoplankton or microalgae, form the base of the food web upon which nearly all other marine organisms depend."

These two paras contradict each other. Why do phytoplankton die and decompose if they are food for all other marine organisms? A bloom of algae ought to result in bloom of higher organisms such as zooplankton and fish.

The fact is that most algal blooms are of Cyanobacteria or Dinoflagellates, especially most of the Harmful Algal Blooms.

Very few algal blooms are of Diatoms.

This is because Diatoms are good food for zooplankton and fish but Cyano and Dinos are not. This difference between various groups of algae is not well studied and there are few scientific papers on the subject.

--Bhaskarmv (talk) 14:39, 21 June 2012 (UTC)

Algal bloom[edit]

I have been made aware of a large area of bright green algal bloom right off of someones property (fresh water) and it has stayed there for at least three weeks. How would this situation affect a source of well water? — Preceding unsigned comment added by (talk) 12:57, 7 July 2012 (UTC)

Separate updated article on HABs[edit]

I created a very updated article for Harmful algal blooms, along with a hatnote in this article's section for the topic. Anyone willing to help copy edit and improve it is welcome to. You'll notice that I've tried to make it readable for non-scientific readers, and assume that readers who want more details will read the full sources or go to linked articles. I've therefore limited using excessive scientific terms and jargon which would force readers to bounce around to different articles.

It might be worth reviewing this and the new article to see any redundant or updated details should be trimmed.--Light show (talk) 05:48, 24 July 2016 (UTC)

I have a number of reservations about this. I can find no references to what constitutes a HAB - where is the definition and the exclusions? In my view most, if not all, algal blooms are harmful to ecosystems or directly to humans and/or other animals. I would much prefer that the text be incorporated into the existing article. It looks to me like an unnecessary content fork based on a an arbitrary distinction. Regards  Velella  Velella Talk   11:08, 24 July 2016 (UTC)
Since most of the details in this article in the HABs section are included, expanded, and updated in the other article, should we do a full replacement of section, and then delete the other article? I also notice that the two sections not about HABs are either general facts or about HABs. The text in Blooming, for instance, has no sources and the details are included in the other article. The text in Freshwater algal blooms is also covered and is only about HABs in any case.
The distinction between "harmful" and "non-harmful" HABs seems to get down to how we define "harmful." The sources note that in their formation, growth and decay, all algal blooms deplete oxygen and thereby cause harm to the ecology, as you said. The distinction usually refers to whether they produce toxins. --Light show (talk) 18:30, 25 July 2016 (UTC)
@Velella, I might even suggest merging this article with the updated one if indeed most or all HABs are in some way considered harmful.--Light show (talk) 23:41, 26 July 2016 (UTC)
I agree that the original article is sadly deficient in many areas and if there could be a careful merge it would make a distinct improvement on areas of the existing article. My only caveat would be that we need to ensure that the issues about toxicity does not overwhelm the rest of the content per WP:UNDUE. I think that the enhanced article would need to discuss the environmental and other impacts without reference to the terms HABs. Reference to HABs needs to be carefully managed since it is only used in a few sources and appears to principally relate to the toxicity issues of dinoflagellate blooms. Regards  Velella  Velella Talk   08:14, 27 July 2016 (UTC)

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