In recent years phytoplankton have been investigated as a potential source of en

Question

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



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.

Explanation / Answer

a)I'd be thinking something like this: you need an answer in energy (kilojoules) per metre per year. So if you take the GPP by weight (per gram), per metre, per year and multiply it by the amount of energy created by that weight of biomass, you'll get your answer. GPP = 4102 g/(m^2 yr) GPP = ? kJ/(m^2 yr) So, only thing that changes is g to kJ. You are told that 1 g -> 6 kJ How much kJ would 4102 g produce? That's what it's asking. b)So you know the energy produced by the biomass per gram. And you know how much energy you need. You divide the total energy needed per day, by the amount of energy produced per gram, per day and you have an answer.After you get the value you got, you need to find the proportion of her weight which equals that mass of plankton. 1 person needs 10 000 kJ a day. 1 g of phytoplankton represents 6 kJ Work out the mass of phytoplankton. Now, work out that mass over a year, and find the relationship in terms of percentage with the mass of 60 kg given.

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