Dear colleague:

Simultaneously using formaline and Lugol is no problem for zooplankton. In fact, many authors have recommended using  Lugol in the field as an initial preservation that decreases the contraction of animals, the release of eggs or the regurgitation of food. Then in the laboratory, it is fixed with the formaline (4%) as a definitive preservative.

 In the case of phytoplankton, the use of formalin is not recommended because it affects the pigments. Preferably, use lugol for phytoplankton.

Best regards,

Carlos

Dear Anjila, Greetings to you. Lugol's iodine is best for preserving both phyto and zooplanktons, it will also bring everything settled down in the container. Formalin is good for preserving filaments and macroalgae. Thank you.

Such double preservation is precisely what our team does for phytoplankton samples. When we collect a water sample by boat we add enough Lugols solution to bring the concentration to 1%. Then, back at the lab we add enough 37% formalin to bring that concentration to 1%. Combined, these preservatives provide great long-term preservation for phytoplankton. Lugols alone is fine for a few years, but without refrigeration it is not ideal.

Dear Smruti,

If you meant initial fixing' of the algal samples, Lugol's Iodine is the best - for counting and to measure or describe the morphology. 

'm not sure about using both Lugol's as well as Formaldehyde in preservation/fixing. & I second Dr. Naganawa here with his answer. You can try using both. In fact, that's all Research is! 

& you can read some interesting answers from here also

https://www.researchgate.net/post/Do_you_have_any_protocol_for_preserving_algal_samples

Best Wishes

Anila P Ajayan

Lugols is always better for phytoplankton. it is known to retain flagelle which are reqiured for their Identification

Both are not required simultaneously. For phytoplankton the preservative lugol's solution is required and for zooplankton formalin or lugol's solution is required.

In Russia is very popular for phytoplankton sampling and preservation upgraded lugol's solution with formaline. A lot of phytoplanktonologists work with it.

Sorry, i didn't see your request on time. I'm sure you already have more than enough responses. Lugol's solution is best with phytoplankton but formalin at 3.5% to 4% is ideal for both phyto and zoo. The formalin could preserve for as long but not lugol's. Lugol's fades off with time and alters the colour of the organism. You may wish to try the combination as earlier suggested but the main preservative is most likely to be formalin. If you are actually looking for the very best try universal fixing and preserving solution like FPA.: commercial Formalin 5 parts, propionic acid 5 parts, 50% ethyl alcohol 90 parts. Glacial acetic acid may be used in place of propionic acid. Note that the use of 2.5% formalin is a good preservative with little or no shrinkage. All the best in your esearch.

It is no problem to use them at the same time. As already remarked, formaldehyde then functions as a postfixing agent. Aldehydes do oxidise lugols though, so you cannot store a mixture of the two, you will have to prepare a mix immediately beforehand, or add the formalin afterwards. The Lugol sample will become colourless in a few days after addition of aldehydes. From my perspective I do not see a gain in postfixing phytoplankton.

Some remarks: it does work well for stabilising internal organelles of already well preserved species. Fragile phytoplankton species generally are better preserved in acidified Lugols than in formalin, or mixtures thereof. For those organisms, use low conc of glutaraldehyde (0.25%), and do add a proper pH buffer in case of freshwater samples.

HTH, René

Lugols iodine is the best option for   phytoplankton preservation

I typically use Lugol's for microzooplankton samples and formalin for zooplankton; however, in one instance I used Lugol's to stain a zooplankton sample that was preserved with formalin so that I could look at some larger phytoplankton that had been captured in the 153 um zooplankton sample. A precipitate formed after adding the Lugol's, which made it a bit challenging to see everything properly.

I've heard who use both at the same time. But I don't know how meaningful. They are ideally used separately according to the desired protection level.

All best

In my experience when I've used Lugol's with formaldehyde, an annoying precipitate has formed, but perhaps you can rinse the formaldehyde off once the sample is preserved and then add Lugol's...I'm not sure I ever tried that, but maybe it will prevent or reduce the precipitation. Good luck!

It is better used separately. The only difference is that 4% formalin will preserve longer without fading away whereas plankton preserved using Lugol's solution with time may start fading away or become fainter in color.

How many months could be preserve (phytoplankton/zooplankton) using formaldehyde?