Open-pond Algal Biomass Production: Lessons from Nature and Nurture Amha Belay, Ph. D. Microalgae are ubiquitous in distribution being able to survive in extreme habitats. They are found in extremes of temperature, light and salinity. Not only do they survive in these extreme environments but they can have high productivities under these conditions. Some also show a degree of flexibility in their tolerance to temperature and light conditions. There are some lakes of the world that support unialgal populations of microalgae throughout the year under changing chemical, environmental and biological conditions. Some of these lakes like some crater lakes in Ethiopia, for example, not only support unialgal populations of Arthrospira, but also have the highest photosynthetic efficiencies ever recorded in nature. These same lakes operate under very different levels of alkalinities and yet show similar productivities. For example, Lake Arenguadie in Ethiopia supports unialgal populations of Arthrospira platensis at an alkalinity of about 60 meq/L while nearby Lake Chitu supports A. platensis at alkalinities well above 250 meq/L. A deeper understanding of the factors that are involved in such adaptations/acclimations will have great implication to economic production of microalgae in outdoor mass culture. There are also Arthrospira strains that tolerate low temperatures without much effect on overall productivities making them useful to grow them economically in colder climates. The difficulty of growing microalgae like Botryoccocus in mass culture is often reported and yet some strains form blooms in natural lakes. For example, Lake Awasa (Ethiopia) blooms with Botryococcus at times. Such a bloom usually happens within a short period of time and disappears quickly as well. An understanding of the eco-physiology of this alga in its natural habitat may shade light on the conditions necessary for its mass culture outdoors. One feature of phytoplankton is the partitioning of their distribution in space and time within the same environment so as to increase overall productivity. Thus seasonal succession of phytoplankton in open waters and their occupation of particular niches within the same system are features that make them successful. An understanding of the factors affecting such succession may have implications in mass production of microalgae as polyculture. This presentation will highlight the importance of understanding the functioning of microalgae in nature to their economic production by drawing examples from observations in nature and nurture. |