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Impact of nutrients (N+P) on algae colonization/growth

Discussion in 'General Plant Topics' started by Marcel G, Dec 15, 2012.

  1. Marcel G

    Marcel G Banned

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    In 2008 Dr. Bergey found out, that diatoms (Bacillariophyceae) with non-limiting supply of nitrogen (in the form of 0.1M NaNO3 = 8.5 g/L ?) grew by 40% faster then Diatoms with limited amount of N. Diatoms with non-limiting supply of phosphorus (in the form of 0.1M KH2PO4 = 13.6 g/L) grew/colonized by 160% faster. And algae with non-limiting supply of both N+P grew by 180% faster => this means that their amount (i.e. the amount of their chlorophyll) triplied → from 50 mg/m2 to 140 mg/m2.

    Also between the "amount of algae biomass" on one hand, and "amount of shade (10-70%)", water depth (5-30cm) and the rate of water flow (0.01-0.04 m/s)" on the other hand, they found no direct correlation.

    Also the type of rocks has no significant impact on the algae colonization (be it greywacke, schist, glass or pumice ... the algae colonize them the same).

    For more information see the source article at http://www.springerlink.com/index/10.1007/s10750-008-9450-9

    View attachment 3980

    I don't say that excess of nutrients is the "trigger". Also we could not compare the plant density of the natural streams in the study with the plant density in our tanks. So it's hard to draw direct line between these two environments, and say that excess of nutrients significantly fuels the growth/colonization of algae. Also as I understand it now, if we would have an environment with high density of plants, then adding more N+P would probably lead to increased growth of plants (and not so much algae). Still it seems the study implies that P has much "bigger" impact on growth rate of algae then N.

    Still I was not able to figure out what exactly means "limiting supply" of nutrients in this study. Also I'm not sure if "non-limiting supply" was used in this study, because as I understand it they gave some agar with NaNO3/KH2PO4 on paving blocks, and the algae had direct access to them (so I suppose the algae had enought nutrients).
     
    #1 Marcel G, Dec 15, 2012
    Last edited by a moderator: Dec 15, 2012
  2. Tom Barr

    Tom Barr Founder
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    There are no plants in these streams, at all. So it's like a fish tank with out plants and LOTS of light and ferts. 10-70% light = about 200-1500 umols of light.
    Diatoms are rarely visible in planted tanks, but they are always present in quite high densities if you take leaf samples and put them under a scope.

    Try it, take what you think is a nice clean leaf sample, then see if you can find Tabellaria. You should be able to. Diatoms seem to be eaten a fair amount by a number of herbivores we keep.
    Ole did a test on periphyton using various species of herrbivore(See AGA's TAG for the article), the amano shrimp did very well.

    This is similar:
    http://educationally.narod.ru/freshwaterecoprimproductionphotoalbum.html

    Nothing really surprising.

    They seemed to be more interested in testing the various rock's nutrient content, but dissolution is so slow, that it is non significant. I'm not sure why they bothered doing that since it was not likely to occur unless the rocks dissolved easily, vinegar and other acids can be added to test that much faster to see if there is potential.
     
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