To apply an aeroponic system to a marine culture, it is necessary to use plants that have value as a cash crop and can develop in saline effluents. However, halophyte plants differ in their degree of salt tolerance. This study aimed to assess the growth of three halophyte species when irrigated with water in different salinities, and thus evaluate their potential for integration with aquaculture.
The aeroponic system was constructed in three 3-floor shelves, where 27 plastic boxes with lids were placed (30 x 40 x 22 cm, 0.12 m² of planting area, three boxes per floor). Inside of the boxes, six nozzles were installed on a ring of 16 mm pipes that were connected to the water reservoir. A commercial fertilizer was used as a nutrient source. Every hour, a pump was activated with a timer and the nutrient solution was sprayed on the roots of the plants for 5 minutes. Three salinities were tested (freshwater (0 ppt), 10 ppt and 20 ppt) for the growth of three species (Salicornia europaea, Plantago coronopus and Crithmum maritimum), with three replicates each. Six plants per box were placed in hydroponic baskets attached to the lids. The light intensity was 180 µmols photons.m-2.s-1, and the photoperiod was adjusted to 12h during the 6-week trial.
The increase in salinity impaired the growth of most plants, although S. europaea showed a favorable response to the salt in the nutrient solution (table 1). Nonetheless, its low productivity is possibly due to the quality of the light used, featuring a higher spectrum of red. This can promote the flowering of plants, which was observed in this study, thus reducing their vegetative growth. P. coronopus proved to be the most salt-sensitive among the species tested, presenting a substantial reduction in biomass under the 20 ppt treatment. Based on these findings, as far as salinity is concerned, P. coronopus and C. maritimum are viable species for integrated aquaculture up to 10 ppt, and S. europaea up to 20 ppt when a suitable light source is used.