Dear Cristian,

You will have to simulate the natural physical conditions as found in nature, in laboratory set up. Ulva gives out spores at or near about the highest tide (both high & low) which comes about once in 15 day Lunar cycle. This is because the spores gets the widest distribution in nature. Coming to the point: the alga can be cultured in a white porcelain shallow tank directly under sunlight with total seawater change once every 2 to 3 days. Depending upon the exposure of alga in your area, lift the culture agla from the tub for 5 minutes once in 12 hours ( if it is diurnal tide system in your area), on first day of the 15 day Lunar cycle. On next day lift out the weed for 7 minutes/12 hours & so on thereby increasing the period successively, until you expose it up to the 14 or 15th day. Near about these 2 days, soon after introduction into water, spores will be released in the tub. You will have to check for the release of spores from 13th day onwards, as after release of spores, the water turns greenish.

If you need constant supply of spores, batteries of tubs will have to be used, with change in exposure cycle.  

I did my PhD on physiology of Enteromorpha.  I found that putting it in seawater with high nitrate (3-5 mM) was usually enough - about 2-3 days.  Ripe Enteromorpha and Ulva have a characteristic smell you will learn to recognise and the edges of the thallus are white and ragged from sporulation.  Just put them in a plastic bag in the sun with a little water and the water will turn green.  For substrate use broken pottery or even better find a potter and ask them to roll out some potting clay and cut into 1 x 1 cm squares and fire them for you.

 it sounds great. Thanks! I will try it.

Hi, I know this thread is a few years old, but I am interested in this topic. I need to produce Ulva spores for use in drop settlement assays. Does anyone have a protocol/advice etc they could share?