Marine agriculture: Land plants cropped floating at sea

摘要

Growing demands on world agriculture confront increasing freshwater limitations. To contribute alternatives, we have explored with considerable success the growth of land plants at sea off the Pacific coast of Costa Rica. Two different approaches were followed. For the first, potted horticultural crops were grown avoiding contact with saltwater on a variety of floating structures, some of which were used for other mariculture activities. To provide freshwater for irrigation, floating seawater distillation and rainwater harvesting devices were designed and tested. Freshwater produced by this method is stored in floating black-plastic bags and can have many uses. In the second approach halophyte plants were grown directly at sea, tying them to floating nets, ropes or other devices, with their roots fully immersed in saltwater as in hydroponics. As part of an ongoing trial of local species, two promising mangrove species and a grass continue to be tested, while a purslane variety that grows particularly well directly at sea has been selected. Current research aims at developing cost-effective culture techniques for the species. At the same time, the purslane is being planted on extensive coastal flats that are covered twice daily during high tides. Floating crops were also multi-cropped with other mariculture options, such as caged fish and shrimp. Though the results presented here are preliminary and require further development, they are extremely promising in their scalability and replicability.