Flocculation of marine phytoplankton

Flocculation of marine phytoplankton

Postby Skattejag » Thu Jun 20, 2013 6:27 pm


I am current looking into techniques that can be used to concentrate phytoplankton in order to feed a marine/reef aquarium. I am considering setting up a phytoplankton culture and am doing currently doing research on the subject. The reason why I am considering concentrating the phytoplankton would be because:
1) I do not know what the long-term effects will be if excess fertilizer such as Guillard's F/2 growth medium (containing Copper sulfate, Manganese chloride, sodium Molybdate etc) accumulates in the reef aquarium.
2) Since the phytoplankton changes the pH/ alkalinity(?) of the culture medium adding large amounts of phytoplankton + medium might damage/shock the reef system
3) Makes storage/ freezing of phytoplankton easier, although this process apparently decreases the protein content

Methods used for concentrating phytoplankton:
1) Sedimentation (Rate of settling - approximately "1 hour settling/mm of column depth" from Standard Methods for the Examination of Water and Waste Water)
2) Membrane filtration (May crush organisms if a vacuum is applied - from Standard Methods for the Examination of Water and Waste Water)
3) Centrifugation (i.e. accelerated sedimentation - May damage/ crush fragile plankton - from Standard Methods for the Examination of Water and Waste Water)
4) Flocculation (Wikipedia :"Flocculation, in the field of chemistry, is a process wherein colloids come out of suspension in the form of floc or flake; either spontaneously or due to the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually dissolved in a solution.")

I am interested in Flocullation since I read in "Artificial Reefs and Seafarming Technologies" (from the Central Marine Fisheries Research Institute (CMFRI)- Bulletin 48-1996 ) and other articles (see attached .pdf) that the following procedure results in flocculation (there are other procedures as well):

The addition of a sufficient amount of sodium hydroxide solution to a phytoplankton culture to raise the pH of the culture by 1 (example from pH 8.4 to 9.4), followed by vigorous stirring and a settling period 1 hour will result in concentrated phytoplankton. The supernatant may then be slowly decanted. The pH of the concentrated phytoplankton must then be restored to its original level, i.e. pH of 8.4 (in the case of the example) by the slowly adding dilute hydrochloric acid. This concentrated solution may then be freezed after a few drops of glycerol or Dimethyl sulphoxide (protective agents - Check toxicity (?))

I would like to know if anyone as any experience with this or would be willing to test it out? Apparently tests were performed in the aquaculture environment and no adverse effects were noted. But I suggest researching further before trying this method for breeding purposes.
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Re: Flocculation of marine phytoplankton

Postby Luis A M » Fri Jun 21, 2013 6:50 pm

Welcome to MOFIB-Marine Breeders :D
The reasons for concentrating Phytoplankton are mostly commercial,to minimize the ammount of water in the finished product and their bulk/freight cost.
Methods used for concentration are those you mentioned plus liophylization.
Most require large/expensive equipment and therefore are not suitable for hobbyists.Perhaps flocculation could be tried in a small scale.If you plan to start a project about that,you can post it in our Research Projects forum.
And another interesting project would be to monitor the utilization and decrease of nutrients in the f/2 medium as a thriving phyto culture develops.I suspect it will be close to nil after the culture peaks.
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Re: Flocculation of marine phytoplankton

Postby Skattejag » Sat Jun 22, 2013 7:53 am

Has anyone tested the viability of freezed phytoplankton + glycerol/Dimethylsulfoxide (DMSO) (other than Nannochloropsis) as a culture inoculant. A "few drops" of glycerol has been recommended for a concentrated/flocculated phytoplankton sample, so a larger amount of glycerol may be required for a larger culture volume. Unfortunately, I do not have a phytoplankton setup at the moment.
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