Proving the Ocean Nourishment concept
Vast regions of the sea are barren because of a lack of essential nutrients. Ocean
Nourishment is the concept of injecting nutrients into the photic zone of the ocean to
store carbon and increase the base of the marine food web. It is elaborated in Jones &
Young (1997). The first step in demonstrating this concept is to see if the limiting
nutrients can be recognised and provided to the oligotrophic ocean. To this end water
samples from three sites were collected in ultraclean polycarbonate culture bottles and
enriched with various mixtures of nutrients. They were then placed in a water bath and
subjected to natural sunlight for a number of days. Fluorescence levels were measured
daily. Previously Thomas (1969) carried out enrichment experiments in and out of high
nutrient water in the North Pacific and again Thomas (1970) cultured on the deck of his
ship nutrient poor waters in the Pacific. He found nitrogen was the most important
limiting nutrient in the poor waters but that micronutrients produced growth in the
nutrient rich waters. Ryther and Dunstan (1971) in the Atlantic cultured coastal water
with only nitrogen and phosphorus separately. The addition of nitrogen without
phosphate produced growth in all cases. To increase the geographic coverage of
enrichment experiments, samples were collected off Morocco twice, in the Tasman Sea
and in the Sulu Sea. The samples enriched with different concentrations of urea (typically
10 microM) and phosphorous. An increase concentration of chlorophyll is the result of
growth of phytoplankton exceeding death and grazing by zooplankton. At five sites an
increase of chlorophyll was observed in the macronutrient enriched bottles over that in
the control. At the sixth site the control grew at much the same rate as the enriched
sample possibly due to contamination by the fluorometer. The maximum chlorophyll
level was observed after 4 or 5 days. Replicate samples showed different levels of
chlorophyll growths. It was concluded that there were sufficient micronutrients present to
support some additional photosynthesis at the sites investigated. These results suggest
that it will be practical to nourish broad regions of the ocean to increase primary
production.
References
Jones, I. S. F. and H. E. Young (1997) Engineering a large sustainable world
fishery.Environmental Conservation, 24, 99-104.
Ryther, J.H. and W. M.Dunstan (1971) Nitrogen, Phosphorus and Eutrophication in the
coastal marine environment, Science, 171, 1008-1013.
Thomas, W H (1970) Effect of Ammonium and Nitrate Concentration on Chlorophyll
increase in Natural Tropical Pacific Phytoplankton Populations, Limnology and
Oceanography, 15, 386-394.
Thomas, W.H., (1969). Phytoplankton nutrient enrichment experiments off Baja
California and in the eastern equatorial Pacific Ocean. J. Fish Res. Bd. Can., 26: 11331145.
Acknowledgement
A Eddington made a number of the observations. The Ocean Nourishment Corporation
Pty Ltd funded some of the research.