Seeds of Cymodocea nodosa (Ucria) Aschers. are abundant throughout the year in several beds around the coasts of the western Mediterranean, but it is rare to find seedlings in situ. Experiments carried out in aquaria have shown that the higher the temperature and the lower the salinity, the faster the germination and the higher the germination rate. At high temperatures and low salinities C. nodosa can show more than 90% germination in 10 days, at all times of the year. Seedlings, however, show good growth only at temperatures between 17 and 25°C and when salinity is also moderately reduced. Thus, in C. nodosa, germination followed by seedling development requires either a reduction of salinity to between 20 and 27‰ for a prolonged period (several weeks-several months) or a more marked reduction to between 10 and 20‰ for a days. These restrictions appear to limit the germination of C. nodosa in the western Mediterranean, in time to the period April–October, and in space to those seagrass beds near sources of freshwater.
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