Previously it has been shown that, after long range transportation over the subcontinent of southern Africa, significant atmospheric deposition of phosphorus and nitrogen takes place over the Okavango Delta of Botswana (Garstang et al.,1998). Complex ecosytems in the delta region are thereby nourished to an extent previously unrecognised. Likewise it has been demonstrated that iron in the aerosols recirculating over southern Africa may be transported thousands of kilometres from the east coast of South Africa to be deposited into the central Indian Ocean between South Africa and Australia. The resulting iron fertilization of marine biota in the region is likely to be responsible for the observed carbon sink of the central Indian Ocean (Piketh et al., 2000).

The implications of similar long-range transport and deposition of nutrients into the complex Benguela Upwelling System off the west coast of South Africa, Namibia and Angola remain to be examined. In this paper an attempt is made to quantify possible atmospheric deposition. Case studies of deposition will be modelled and an attempt made to link deposition to long-term climatologies of air transport over southern Africa. It will be shown that the hitherto ignored deposition of nutrients from the atmosphere into the Benguela may have significant implications for the biogeochemical balance of the system and the complex marine ecosystems supported by it.

References:

Garstang, M., Ellery., W. N., McCarthy, T. S., Scholes, M. C., Scholes, R. J., Swap., R. J. and Tyson, P. D., 1998: The contribution of aerosol- and water-borne nutrients to the Okavango Delta ecosystem, Botswana. South African Journal of Science, 94, 223-229.

Piketh, S.J., Tyson, P.D. and Steffen, W., 2000: Aeolian transport from southern Africa and iron fertilisation of marine biota in the South Indian Ocean, South African Journal of Science, 96, 244-246.