A simple method to preserve algal spores of Ulva spp.: in cold storage with ampicillin

Preservation of algal spores of the green seaweed Ulva fasciata and U. pertusa was enhanced by the addition of ampicillin in f/2 medium at 4 degrees C. The viability of preserved spores was determined by a spore germination assay at various time intervals. The germination rate of U. fasciata remained at 5% to 38% for the first five days, dropping to 1% to 6% on the 10th day of storage with various preservation treatments without ampicillin at 4 degrees C during parameter-selecting experiments. In f/2 medium, 53% of U. fasciata spores were still viable on day 5 and 23% on day 10 at 4 degrees C. By adding 100 mu g mL(-1) ampicillin to f/2 medium, 90% of the spores were viable at day 40 and 61% after 100 days of storage at 4 degrees C. Spores of U. pertusa had lower preservation rates, with viabilities of 70% at day 40 and 32% at day 100. Algal spore preservation was heavily dependent on the bacterial contamination and subsequent degradation in stock solutions.