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ESAW/HESNW Culture Medium
Enrichment stocks can be refrigerated. Adjust Solution #5 to pH 6 using solid NaCO3 (about 2 g). Solution # 4 can be heated to dissolve the iron.
* Can be replaced with an equimolar stock of Na2HPO4
** Add before the trace metals.
*** Can be replaced with an equimolar stock of FeCl3
Vitamin stocks should be stored frozen.
TO MAKE 1 LITRE OF HESNW
1) Filter natural seawater through 0.45 µm membrane filter with a glass fiber prefilter.
2) Use a flask that has been acid-washed in 10% HCl and rinsed in distilled water before first use.
3) Pour 1 L filtered seawater or artificial seawater into flask. Add the following while mixing with a stir-bar:
a) 6 ml Combined Stock (Enrichment stocks #1,2,4-7)
(OR 1 ml of each individual stock solution)
b) 2 ml Silica Stock (Enrichment stock #3)
c) 2 ml Vitamin Stock
4) To reduce precipitation during autoclaving add:
d) 1.44 ml of 1N HCl
e) 0.12 g Sodium bicarbonate
5) Autoclave 20 minutes for one litre, ~ 30 minutes for 2 litres. Autoclaving for longer periods will result in more precipitation. Flasks should not be filled up more than 2/3 of their capacity, to avoid boiling over during sterilization.
6) Let stand for 2 days to allow pH to equilibrate (should be ~ pH 8.2).
7) Filter aseptically through a glass fiber filter to remove precipitate. Some taxa appear to be sensitive to it (optional).
Harrison, P.J., R.E. Waters and F.J.R. Taylor. 1980. A broad spectrum artificial medium for coastal and open ocean phytoplankton. J. Phycol. 16:28-35.
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