NRE

Hydrographic data collected during a dedicated research cruise in the Agulhas Retroflection region in February/March 1987 are analyzed in conjunction with Geosate altimetry from December 1986 to December 1988. Estimates of the heat and salt anomalies of eddies and rings observed in this hydrographic survey, are combined with the altimetric tracking of these features to provide insight into and quantification of the climatically important interbasin exchanges occurring in this region. Over the 2-year period a total of 14 anticyclonic eddies were generated by the Agulhas Current, approximately 50% of these were observed in the satellite altimetry analysis not to migrate father than 1500 km west of northwest of the Agulhas Retroflection region. Altimetry data show a number of eddies being shed south of the Agulhas Retroflection; all were observed ultimately to move westward rather than southward across the Subtrpoical Convergence. The estimated net heat fluxes (300 W m-2) and evaporative losses (1 cm day-1) to atmosphere from eddies with the Agulhas Retroflection region in February-March 1987 were appreciably larger than the austral summer climatological means (25 to 100 W m-2 and 0.6 cm day-1, respectively) for this region. From the combined altimetric and hydrographic analyses, the volume flux of Indian Ocean water warmer than 10°C into the South Atlantic Ocean via the Agulhas eddy field is estimated to be 6.3 Sv (1 Sv=10-6 m3 s-1) and 7.3 Sv for water warmer than 8°C. Similarly, estimated fluxes of heat and salt into the Atlantic Ocean via the Agulhas eddy field are 0.045 PW and 78×1012 kg per annum, respectively.

Abstract This study applied ecological niche models to determine the potential invasive range of Nile tilapia, Oreochromis niloticus, with a particular focus on river systems in southern Africa where it is now established and spreading. Computational tools such as niche models are useful in predicting the potential range of invasive species, but there are limitations to their application. In particular, models trained on native records may fail to predict the full extent of an invasion.

Ammonia-oxidizing bacteria (AOB) are essential in the biogeochemical cycling of nitrogen as they catalyze the rate-limiting oxidation of ammonia into nitrite. Since their first isolation in the late 19th century, chemolithoautotrophic AOBs have been identified in a wide range of natural (e.g., soils, sediments, estuarine, and freshwaters) and man created or impacted habitats (e.g., wastewater treatment plants and agricultural soils). However, little is known on the plant-species association of AOBs, particularly in the nutrient-starved fynbos terrestrial biome. In this study, we evaluated the diversity of AOBs in the plant canopy of three South African fynbos-specific plant species, namely Leucadendron xanthoconus, Leucospermum truncatulum and Leucadendron microcephalum, through the construction of amoA-gene clone libraries. Our results clearly demonstrate that plant-species specific and monophyletic AOB clades are present in fynbos canopy soils.

The combined effects of climate change, the continued volatility of fuel prices, the recent food crisis and global economic turbulence have triggered a sense of urgency among policymakers, industries and development practitioners to find sustainable and viable solutions in the area of biofuels. This sense of urgency is reflected in the rapid expansion of global biofuels production and markets over