An examination of fixatives and sample storage temperatures for marine phytoplankton preservation; comprehensive policies on quality and risk control
2016
Kawanobe, K. (Micro Sea Green, Aizuwakamatsu-shi, Fukushima (Japan)) | Ikeya, T.
Cell counts of marine phytoplankton in formaldehyde, formaldehyde-glutaraldehyde, and acid Lugol's iodine fixatives were carried out for natural seawater samples, which were stored at room- and cooled-storage temperature for 3, 6, and 12 months and were concentrated with the Utermoehl method. The number of species in the taxonomic groups identified for the 3 and 6 months samples of 0.1-1 % formaldehyde increased, mainly due to diatoms at the cooled storage temperature. The loss rates of the dominant diatoms (Leptocylindrus danicus and Pseudo-nitzschia complex) in the acid 1 % Lugol's iodine fixatives under the room temperature storage for 3 months was almost the same (87-100 %) as those in the cooled temperature storage, but were 1.5-2 times as high as those in 0.1 % formaldehyde or the mixtures of 0.1 % formaldehyde and 0.025 % glutaraldehyde in cooled temperature storage. Cooled-storage temperature could decrease the loss rate of diatoms in 0.01-1 % formaldehyde. The abundance of the Pseudo-nitzschia seriata complex in 0.01 % formaldehyde-0.025 % glutaraldehyde was lower than that in 0.1 % formaldehyde-0.025 % glutaraldehyde (P < 0.03). The loss rate of the cell numbers of diatoms (Leptocylindrus danicus and Pseudo-nitzschia complex) in 0.1 % formaldehyde (0.1 % formaldehyde-0.025 % glutaraldehyde) at cooled storage after 12 months was as low as 19 % (25 %) on average. The loss rates of Gephyrocapsa oceanica in formaldehyde fixatives for 3 months were insensitive to the storage temperature, the concentrations of formaldehyde, and the addition of glutaraldehyde. The adoption of 0.1 % formaldehyde and cooled storage could keep the preserved phytoplankton in good condition and even minimize risk management of chemically hazardous materials as well as improve working environments for counting.
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