UTEX sells LDM Medium at 1X concentration only. Stock solutions and individual components for this specific medium are currently not available for purchase.

LDM Medium

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LDM Medium

Modification of Lewin's marine diatom medium.


For 1 L Total
  1. To approximately 950 mL of seawater (30 ppt), add each of the components in the order specified (except vitamins) while stirring continuously.
  2. Bring total volume to 1 L with non-pasteurized seawater.
    • For 1.5% (w/v) agar medium, add 15 g of agar into the flask; do not mix.
  3. Cover and autoclave medium.
  4. When cooled add sterile vitamins.
    • For agar medium add vitamins, mix, and dispense before agar solidifies.
  5. Store at refrigerator temperature.

# Component Amount Stock Solution Concentration Final Concentration
1 Seawater (30 ppt) 950 mL
2 NaNO3
(Fisher BP360-500)
1 mL/L 10 g/400mL dH2O 0.29 mM
3 CaCl22H2O
(Sigma C-3881)
1 mL/L 1 g/400mL dH2O 0.017 mM
4 MgSO47H2O
(Sigma 230391)
1 mL/L 3 g/400mL dH2O 0.03 mM
5 K2HPO4
(Sigma P 3786)
1 mL/L 3 g/400mL dH2O 0.043 mM
6 KH2PO4
(Sigma P 0662)
1 mL/L 7 g/400mL dH2O 0.129 mM
7 NaCl
(Fisher S271-500)
1 mL/L 1 g/400mL dH2O 0.043 mM
8 P-IV Metal Solution 6 mL/L
9 Tryptone
(Sigma T 9410)
1 g/L
10 Vitamin B12 1 mL/L
11 Biotin Vitamin Solution 1 mL/L

Important Notes To Consider:

  • The quality of water, including natural seawater, is important. The term 'dH2O' generally refers to distilled, deionized, distilled/deionized water, Milli-Q water (Millipore Corp.), etc. Natural seawater and natural freshwater should be obtained from a non-polluted source.
  • When dissolving chemicals, wait for the first component to dissolve before adding the second. Stirring, and sometimes the addition of heat, is often required to dissolve the chemicals efficiently. Preparation of stock solutions for frequently made algal culture media make preparing media convenient but also necessary to avoid errors from weighing very tiny amounts.
  • Attention should be given to the pH of the final medium. In most cases, if pH adjustment is required, this occurs before sterilization. Please note that autoclaving removes carbon dioxide from media lacking carbonate stabilizing buffers. This would make the medium very alkaline soon after removal from the autoclave. In these cases, you should wait approximately 24 hours for gaseous equilibrium before inoculating the medium.