Seven persistent misconceptions about Ocean Nourishment

Ian S F Jones

Ocean Technology Group

University of Sydney, F09

Australia

The productivity of the open ocean is dependent on the flow of nutrients most of which are upwelled from the deep ocean. The natural limitation posed by the restricted supply of nutrients in the soil has been overcome in agriculture by supplying mined or manufactured nutrients. This has increased the productivity of the arable land by a factor of five. Purposeful ocean fertilisation, in contrast, has rarely been practiced in part because of a number of concerns about the potential environmental impacts. In some regions of the ocean iron is the limiting nutrient while in the majority of the ocean, the macronutrient nitrogen limits phytoplankton growth. The fertilization with macronutrients, has been termed Ocean Nourishment and has a number of differences to fertilisation by iron. Some misunderstandings arise because analogies of coastal eutrophication and iron fertilisation are uncritically assumed to apply to macronutrient fertilisation. Seven misunderstandings persist and now can be discounted;

• Export will be low due to enhancement of the microbial loop.
• Phosphate and silica will need to be supplied.
• The quantity and cost of nitrogen make carbon sequestration uneconomic
• Fertilisation with urea encourages dinoflagellates.
• Size distribution will unsuitable (too small) for zooplankton and herbivorous fish.
• Fertilization will cause alarming levels of oxygen consumption.
• Implementation carries large ecological risk.

For low fertilisation concentrations, away from shallow water, in a prevailing current, in temperate waters, the seven concerns above can be shown to be mild enough to justify open ocean small scale scientific experimentation.