FOOD POTENTIAL OF AQUATIC MACROPHYTES

To facilitate the use of other aquatic macrophytes (AM) in food production, this paper reviews existing literature for methods to convert AM"s, generally thought of as weeds and so as warranting destruction, into human food, livestock fodder, fertilizer, and herbivorous fish food. The potential for integrated AM-herbivorous fish systems and the possible health hazards associated with aquatic macrophyte cultivation are also reviewed. Loosely defined, AM"s are aquatic plants which grow in water or in soils covered with water for a large portion of the growing season in tropical and semitropical areas. Since AM"s may be cultivated in waterlogged or swampy soils not suitable for either terrestrial crops or aquaculture, their cultivation increases the amount of productive land in a given area. Although more than 40 AM species are edible, only certain ones (taro, Chinese water chestnut, water spinach, and Neptunia oleracea) have clear potential for widespread use due to the social unacceptability and cost inefficiency of most varieties. Water spinach and N. oleracea are identified as the most promising varieties and further research on their protein content and yield capacity is recommended. Given their high moisture content, however, AM"s are not economically feasible livestock fodder because their low nutritive quality does not justify the harvesting, transporting, and processing costs required to convert fresh plants into dry feed. The most promising fertilizer use of AM"s is composting in fish ponds, and further research on the use of AM"s and slurry in biogas production is recommended, as is study of the feasibility of stocking herbivorous fish to control AM"s in irrigation systems with large macrophyte populations. While the presence of AM"s may lead to mosquito breeding, contamination from the use of animal and human wastes as fertilizer and the accumulation of toxic chemicals by AM"s in waste recycling systems are more likely AM-related health hazards. Recommended countermeasures, respectively, are rendering wastes innocuous prior to use and separating domestic from industrial wastes. An 202-item list of references (1918-80) is included.