| Environmental factors influencing the cultivation of many economically important marine algae are not well understood. Cultivation problems are being encountered in the growing of various algae in artificial algal beds or on man-made farming structures. It is necessary to study these cultivation problems under controlled conditions in order to understand and solve them. Aspects of Eucheuma uncinatum as a model organism for cultivation were studied in the laboratory and in a greenhouse. Gradients of different environmental factors, such as light, temperature, salinity, and nutrients, were created in the laboratory and in outdoor water tanks. Plants were exposed both to single gradients and cross gradients and their growth and morphology were monitored. Plants with different morphologies developed under different experimental conditions. High light levels (1500 uEm-2sec-1) caused large, light yellow-brown plants to develop, which became dark red when light levels were subsequently reduced. Young germlings reacted in a similar manner at light levels an order of magnitude lower. Temperatures of 29-31 C caused growth of small, fuzzy plants which were dark red and brittle. The best growth (80.5% increase in wet weight per week) occur at 17-23 C, with light levels of 1000-1500 uEm-2Sec-1, and nitrogen above 30 ugat/l, and 30-35 ppt salinity, all accompanied by active water motion. Transport of substances was demonstrated, with translocation occuring throughout the organism at speeds of up to 65 cm/hr. Spore release was induced by 17-28 C, 17-50 uEm-2sec-1, and 31 ppt salinity. The biology of spore germination and development was studied. The number of erect plants developing from germinated spores was inversely proportional to the density of spores on the substrate. Methods for storing regenerative stock were studied. Large branches were stored for 5 months, and germlings for as long as 3.5 years. It is hoped that the information collected during this study will both enlarge our knowledge of Eucheuma uncinatum as a future marine crop plant, and provide a basis for further studies of algal domestication and cultivation. |
