Phytoplankton are microscopic autotrophs that are the foundation of many aquatic food chains. The amount of photosynthesis carried out annually by ocean phytoplankton alone is of a similar magnitude to that of all terrestrial plants combined, making them an important subject for ecological research. Ocean phytoplankton photosynthesis can be studied using a wide range of techniques, from satellite imaging to measure whole oceans to collecting small samples and analysing their behaviour in the laboratory.
(a)In recent years phytoplankton have been investigated as a potential source of energy for humans. Researchers have therefore been interested in whether these organisms could be ‘farmed’ to provide food or fuel. In terms of biomass, Gross Primary Production (GPP) in phytoplankton living in a layer just below the surface of a typical ocean area is 4102 g m−2 yr−1 If you . assume the energy value of phytoplankton is 6 kJ g−1, calculate the GPP in terms of kJ m−2 yr−1 .Show your working clearly .
(b) If a human needs to eat about 10 000 kJ per day, estimate (to the nearest gram) the mass of phytoplankton that would be required to meet their daily energy requirements. Based on this value, approximately what proportion of her own body weight in phytoplankton would a 60 kg woman need to eat over the course of a year, if this were her only source of energy? Show your working clearly.
(c) Farming phytoplankton to harness solar energy for human food or fuel would presumably require cultivating large numbers of these organisms in a carefully designed artificial environment. Suggest two features that could be incorporated into the design of a phytoplankton ‘farm’ to optimise the Net Primary Production (NPP). Briefly describe why each design feature would be useful. (One sentence for each)