Seasonal and interannual production of sea lettuce (Ulva sp.) in outdoor cultures based on commercial size ponds

The many nutritional benefits reported in seaweeds have increased their demand in the western world for human consumption. In order to supply this demand, it is necessary to cultivate seaweeds both offshore and onshore. Offshore cultivation is highly vulnerable to climate variation. Cultures on land can be operated while essential variables can be controlled (nutrient supply) or partially regulated (light and temperature) providing a more uniform quality and continuous production. In this study, we present the results of pond-culture in a commercial pilot-facility on the Pacific, temperate coast of Mexico, which has been continuously running for 2½ years. Ponds of 100 m3 were seeded with 3 kg/m2 of a previously selected strain of Ulva. Pulse fertilization and a full water exchange were made twice a week. Ponds were fully harvested every 3 weeks and re-seeded with the initial density. Seaweed production showed a bimodal distribution with a strong peak in spring (258–290 g m−2 day−1), a minor peak in autumn, and lower production in summer and much lower in winter (40–85 g m−2 day−1). Highest growth performance occurred when the average temperature remained between 17 and 23°C. This study provides a realistic baseline for annual seaweed production on a commercial pilot-scale aquaculture farm.