End Date : 30.12.2014
Start Date : 11.02.2012
Phosphorus Biogeochemistry in Surficial sediments in the Okavango Delta, Botswana (2012-2014).
Department : Okavango Research Institute
Researcher : Dr Mangaliso Gondwe
This study aims to understand the current status of phosphorus (P) biogeochemistry in surficial sediments in floodplains in the Okavango Delta. P limits primary production in freshwater ecosystems, including the Okavango Delta, because it is naturally available in shortest supply (compared to nitrogen (N), carbon and other elements) relative to the demand by plants, particularly algae. Whole-ecosystem experiments at the Experimental Lakes Area, Canada, have clearly shown that excessive input of P, not N, generally leads to eutrophication and loss of ecological services from aquatic ecosystems. While low P concentrations have been measured in the Okavango River water, P inputs from surficial sediments and atmospheric deposition to the delta remain unknown. The University of Botswana has recently funded a project to measure atmospheric deposition of P, N and silicon (Si) in the delta. The knowledge from these studies will facilitate development of appropriate strategies for nutrient management to mitigate expected increased nutrient inputs from development activities in the Okavango Delta basin. This knowledge is particularly important because the Okavango Delta is currently threatened by increasing anthropogenic pressures for water and other resources in the delta by human populations in the riparian countries of Angola, Namibia and Botswana. It is currently not clear how the ecosystem will be affected by the increasing anthropogenic pressure in conjunction with the climate change. It can be expected that intensification of the anthropogenic pressure will subsequently increase nutrient loading, particularly P, into the delta as has been observed in many ecosystems including Lakes Erie, Winnipeg and Ontario in North America and Lake Victoria in Africa.