Spatial and temporal variability of Net Primary Production on the Agulhas Bank, 1998–2018

Despite the importance of Agulhas Bank (AB) marine productivity in supporting South African coastal fisheries and shelf ecosystems, there are relatively few regional-scale assessments its spatial temporal variability, most studies have been limited scale. Here we use satellite-derived Net Primary Production (NPP) rates calculated using Vertically Generalized Model (VGPM) to examine dynamics NPP over 21-year satellite record (1998–2018) on AB. In calculating VGPM used OCCI Chlorophyll-a product, SST from Operational-Sea-Surface-Temperature-and-Sea-Ice-Analysis (OSTIA) PAR GlobColour level-3 mapped products as these represent longest datasets that fit our extended study period. We trends between eastern central AB, well three areas bank (around Port Alfred, Tsitsikamma coast, ‘cold ridge’) previously identified contributing significantly overall The AB shows only a moderate degree seasonality VGPM, with being highest austral summer (1.7–1.8 g C m?2 d?1) lowest winter (0.9–1.0 d?1), remains high (>1 throughout year, contrasting sharply other systems. Considered annually, was 516 yr?1 (38 Mt when scaled total area) which is higher than many systems though lower neighbouring Benguela system indicative moderately productive fuelled by perennial NPP. Comparing different sections east bank, including upwelling areas, highlighted differences were limited; made similar contributions their relative proportion area, average spatially across notable occur some areas. Interannual variability modest, varying years ?15% two decades assessed. Over data set, slight (?0.26% yr?1) statistically-significant decline time for whole, which, examined pixel-by-pixel basis, indicated 100 m 200 isobaths. summer, an increase occurred EAB (26.5–28°E). conclusion, significant site levels NPP, little interannually time. These factors lead stable environment terms ecosystem so makes contribution regional fisheries.