The water in our oceans is not still. They are dynamic systems made up of large masses of water moving across the ocean basins on currents, as well as vertically in areas of sinking and upwelling. There is a pattern and predictability to these movements, but they do also shift over time and have a profound effect on water temperature, concentration of nutrients and, as a result, the abundance of marine species.
The waters around Ascension are strongly influenced by the Atlantic South Equatorial Current, which is a complex system of alternating bands of westward and eastward flows that extends from approximately 4oN to 20oS of the equator (Scullion, 1990; Stramma & England, 1991). Within the MPA, there appear to be two distinct regions: a northern zone between latitudes of 4–6oS characterised by consistently strong westward flows and high surface productivity, and a less energetic southern zone.
