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Thread: Understanding String Algae

  1. #11
    Honmei ricshaw's Avatar
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    Is there a difference between pond filamentous string algae and the mat scum type of algae?


  2. #12
    Daihonmei MikeM's Avatar
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    Metaphyton: Mat Scum Algae

    A lot of subjects have been raised by comments posted. I'll try to set out what I know on a few.

    What is shown in the photo above is well-described as mat scum algae. It likely has string algae as a component, but is actually a phenomenon more than a type of algae. These mats are sometimes called metaphyton. These are floating masses of algae (and other organisms) typically composed of several types. Metaphyton are created in several ways. One way where string algae plays a major role is when filaments break off and then rise to the surface where the water is still. There it becomes a raft, and a habitat for all sorts of algae. It is an algal community with cyanobacteria and other life forms taking up residence. The string algae is just a foundation. The type of metaphyton we normally see in shallow ponds begin differently as clumps on the bottom, or around plant stems, which dislodge and float to the surface. These have a more wispy or cotton-candy type of appearance at first, and then get really scummy on the surface as cyanobacteria take hold. Articles often refer to these as indicating hyper-eutrophic ponds.

    Whichever way the metaphyton begins, they become very dense and accumulate dead or dying stuff, with the cyanobacteria releasing various poisons, and can become so thick that light is blocked despite being on the surface in full sun. So, decomposition sets in, and it truly is a rotting, stinking mess. As they rot, the metaphyton can sink or disappear. Studies of such ponds have found that the metaphyton continually reappear as more are produced at the pond bottom and rise to the top. The process stops if the over-abundance of nutrient is eliminated.

    String algae actually do not thrive in such conditions, but do become a substrate for other more noxious algal and bacterial organisms. The competition is not good for the long term success of string algae, but it does hold on waiting for its chance.
    Last edited by MikeM; 05-14-2013 at 09:36 AM. Reason: typos

  3. #13
    Daihonmei MikeM's Avatar
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    Airborne String Algae Spores

    I have not researched whether Cladophora spores become airborne. It is common in ponding circles for folks to say that algae spores are in the air and will be present in every pond. And, we know it turns up eventually in nearly every pond. But, there are anecdotal reports of ponds that have never had string algae. I have read reports of algae spores being found throughout the atmosphere, and algae spores are a significant constituent of what is found in air sampling done in studies of allergens. However, I have not seen any article or report specifically identifying Cladaphora spores as among what has been captured in such air sampling. I recall reading one article some time ago (which is in a drawer someplace, but I cannot find it now, of course) which assembled the results of numerous air sampling studies identifying something like 25 or so algae species' spores having been identified. Some of these were the so-called 'terrestrial alga', species that grow in constantly damp areas and are exposed to the atmosphere continually. Some were from aquatic algae. But, none were identified as Cladophora. That only 25 or so algal species' spores have been specifically identified does not necessarily mean that only that many were retrieved. Folks doing such air sampling studies are not always concerned about species identification. It is enough for their purpose to be able to say there was so much pollen, so much dust, etc., etc. Obtaining identification certainty on everything found in one air sample, all the pollen grains, the spores, the chemicals, the mineralology of each dust particle... it could take an entire lifetime.

    Although I am not aware of a study confirming the existence of airborne string algae spores, I think they likely exist, probably in akinete form rather than an actual spore. One can readily imagine that since akinete formation is triggered by stress, akinetes would be formed in many circumstances where string algae would end up drying out, such as in ponds that dry up seasonally, or as a result of drought. The same type conditions would exist along the edges of waterways that experience a seasonal lowering of water elevations. All sorts of conditions would leave string algae exposed to the atmosphere to dry, where wind can readily pick up the infinitesmally small akinetes like a dust particle. Since Sahara Desert dust can be found throughout the atmosphere, it seems to me the akinetes of string algae would travel as much.

    However, that is just speculation on my part. If I come across a report confirming the existence of airborne Cladophora, I'll post about it.

  4. #14
    Tategoi hewhoisatpeace's Avatar
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    Truly enjoying this thread, Mike. Thanks to all other contributors, too.

  5. #15
    Sansai almostgeorgia's Avatar
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    OK, Mike, had to look up the new (to me) biological term you are throwing around here, and wouldn't you know it, the Wikipedia page makes a brief reference to filimantous green algae under the entry for 'akinete'.

  6. #16
    Daihonmei MikeM's Avatar
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    Currents

    I had in mind to eventually do a post on the relationship of string algae with currents. Although I've not gone back to gather up materials on the subject, the question of currents has been raised. So, I'll post now and add more another time when I've had a chance to retrieve some studies. There have been a lot of studies, particularly in regard to marine species that thrive in the constant turbulence of coastal rock zones and tidepools. The freshwater studies are interesting, too.

    The key trait of string algae is the strength of the filaments and their flexibility. Few life forms combine both to such a degree. We have all observed that string algae thrives in strong currents. If it is present, it will be abundant on waterfalls and where currents are strong along pond walls. The strength and flexibility of the filament allows it to resist abrasion where other alga could not. Also, the holdfasts put down by string algae are very strong, and intertwine with those of each plant. The thousands composing a single clump create a strong bond with the substrate like a form of cement. Even if unusually strong flooding currents cause breakage of filaments, the clump is likely to remain held in place.

    The physical appearance of string algae is much influenced by currents. There are a couple of aspects to this. First, as flow velocities increase, the filaments lengthen. Also, the cell walls become more thin. And, third, branching of filaments can occur, resulting in extremely long streamers of filaments. These changes have further consequences. The individual filaments are more able to take in CO2 and nutrients, and both CO2 and nutrients are more available at the molecular surface due to the continual flow over the surface of the filament. Studies have shown that string algae that was utilizing bicarbonates as a carbon source in low current conditions was able to decrease reliance on bicarbonates and directly use more dissolved atmospheric CO2 as currents were increased. This was perhaps due to the greater availability of CO2, and it being a more efficient source of carbon than the more complex bicarbonates formed in water.

    So, with more efficiency in absorbing available nutrient, and increased availability of efficiently used nutrient, string algae thrives in currents. It is not that highly oxygenated water is preferred, oxygen is a waste product of photosynthesis. Rather, it is increased availability of CO2 and other nutrients along the outer cell membrane that seems to generate higher growth rates.

    However, high currents can become a negative over time. The currents cause compaction of the streamers of algae. As compaction occurs, the velocity of water movement within the streamer decreases, meaning a reduction in nutrient availability to the filaments in the center. Also, compaction results in lowered light levels within the streamer. Studies have shown a decrease in the overall rate of photosynthesis in the biomass of filaments as compaction occurs. As the center of a streaming clump declines, there can be dead or dying filaments within it. The branching of filaments that occurs in currents contributes to the mass becoming increasingly intertwined, holding some dead/dying filaments in the interwoven matrix of filaments. So, we see a life stage transition from long flowing streamers to ones that have clumps within the streamers as the algae ages.

    Thus, currents are a mixed blessing, both stimulating growth and contributing to decline.

  7. #17
    Jumbo RobF's Avatar
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    Mike, As you have observed in other threads it is surprising the places that the love of nishikigoi takes the mind.

    And in another thread I recently said that UV was irrelevant when it comes to string algae, but the free swimming zoophores would seem to contradict that long standing belief.

    Airborne Algae: Their Present Status and Relevance. Sharma et al 2007. Not suprisingly says: "Launching of bioaerosols is mainly from terrestrial and aquatic sources". But although they list 60+ genera of Chlorophyta algae, Cladophora is not among them. Emailed the paper to you.

  8. #18
    Daihonmei MikeM's Avatar
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    Quote Originally Posted by RobF View Post
    Mike, As you have observed in other threads it is surprising the places that the love of nishikigoi takes the mind.

    And in another thread I recently said that UV was irrelevant when it comes to string algae, but the free swimming zoophores would seem to contradict that long standing belief.

    Airborne Algae: Their Present Status and Relevance. Sharma et al 2007. Not suprisingly says: "Launching of bioaerosols is mainly from terrestrial and aquatic sources". But although they list 60+ genera of Chlorophyta algae, Cladophora is not among them. Emailed the paper to you.
    Thanks for the article, Rob. I'll need to read it fully when I have more time. Skimming it, I note that at the end of the listing of over 100 genera of algae, cyanobacteria, etc., there is that wonderful category: 'unidentified algae'.... found airborne over every continent, including Antarctica. Who knows?

  9. #19
    MCA
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    I wonder if you find it in ponds with low TDS (<100) and high ORP (>300mV).

  10. #20
    Nisai
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    Great thread!
    I have found that when I use just well water in the pond I have fewer problems with string algae. When I put city water in the pond the string algae starts growing. I know that my city water has a high phosphorus content and think that is what is driving my algae problem.

    I have found the same with my aquarium. City water = algae bloom.

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