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Soil salinity is a key environmental factor influencing germination and seedling establishment in salt marshes. Global warming and sea level rise are changing estuarine salinity, and may modify the colonization ability of halophytes. We evaluated the effects of increasing salinity on germination and seedling growth of native Spartina maritima and invasive S. densiflora from wetlands of the Odiel-Tinto Estuary. Responses were assessed following salinity exposure from fresh water to hypersaline conditions and germination recovery of non-germinated seeds when transferred to fresh water. The germination of both species was inhibited and delayed at high salinities, while pre-exposure to salinity accelerated the speed of germination in recovery assays compared to non-pre-exposed seeds. S. densiflora was more tolerant of salinity at germination than S. maritima. S. densiflora was able to germinate at hypersalinity and its germination percentage decreased at higher salinities compared to S. maritima. In contrast, S. maritima showed higher salinity tolerance in relation to seedling growth. Contrasting results were observed with differences in the tidal elevation of populations. Our results suggest S. maritima is a specialist species with respect to salinity, while S. densiflora is a generalist capable of germination of growth under suboptimal conditions. Invasive S. densiflora has greater capacity than native S. maritima to establish from seed with continued climate change and sea level rise.

Halophytes are able to survive in the high salted areas of the world, and have been recognized as sources of bioactive metabolites. There is a need to design sustainable strategies for the use of wild populations of halophytic species in order to avoid irrational gathering. Seed banks are essential for resilience and regeneration in salty ecosystems. We sampled annual seed production, aerial and soil seed banks and seed dynamics for a year in four wild populations of the annual halophyte Salicornia ramosissima growing in saltpans, in order to develop sustainable management practices for the use of its populations.The seed production of S. ramosissima depended mainly on plant density rather than on the number of seeds produced by each individual plant. In three of the four study populations, most of the annual seed production was exported out of the saltpans (> 79%) and only between 14-20% was accumulated in the initial aerial and soil seed banks. These initial seed banks were highly depleted during the year until the next fruiting period, when they accumulated less than 1% of the annual seed production (from 19 to 15302 seed m − 2 ). Salicornia ramosissima established a persistent soil seed bank in two of the four locations. Annual seed production would be key for the preservation of those S. ramosissima populations that do not establish persistent soil seed banks. In view of our results, each population of S. ramosissima should be studied independently to design population-speci c management plans.