Agro-Physiological Performance of Iceberg Lettuce (Lactuca sativa L.) Cultivated on Substrates Amended with the Invasive Algae Caulerpa prolifera from the Mar Menor

The beneficial effects of algae on plant growth are widely known, so the combination of coconut fiber with algae waste from a species such as Caulerpa prolifera, which is an invasive species in the Mar Menor, could become an ideal substrate for leafy vegetable cultivation. The aim of this study was to evaluate the effect of an “algae waste + coconut fiber” combination in different proportions on the cultivation of iceberg lettuce. The proportions studied consisted of 0% algae waste + 100% coconut fiber (0% AW), 50% algae waste + 50% coconut fiber (50% AW), 75% algae waste + 25% coconut fiber (75% AW), and 100% algae waste + 0% coconut fiber (100% AW). Physiological parameters were evaluated. The results obtained showed that the mixture of algae waste and coconut fiber is a great alternative in the production of iceberg lettuce, since the proportion of 50% AW considerably improved the size of the lettuce (54.4%), the total phenol concentration (24.8%), the antioxidant activity (28.2%), the total sugars (14.1%) and reduced its nitrate concentration (24.6%), with respect to the 0% AW plants. These findings support the feasibility of reusing Caulerpa prolifera as a bio-enriched substrate for high-quality lettuce production.