Spatial distributions of copepod genera along the Atlantic Meridional Transect

The distribution of copepod taxa at a basin scale was analysed using three Atlantic transects (U.K. - Malvinas 1997, Malvinas - U.K. 1997, and South A frica - U.K. 1998). Integrated 200 m to surface zooplankton samples were ta ken daily, using WP2 nets (200-mum mesh). The zooplankton were size-fractio nated and sub-samples taken for carbon analysis. The remainder of the sampl es was preserved for taxonomic analysis of copepod genera. Multidimensional scaling (MDS) was used to identify zoogeographic regions from the copepod genera. Seven regions were identified: northern temperate, northern subtrop ical, equatorial, southern tropical, southern sub-tropical, southern temper ate and Benguela upwelling. Analysis of similarity showed that most regions were significantly different from each other except: northern temperate an d southern temperate, northern temperate and southern subtropical, and nort hern subtropical and southern subtropical. The genera significant in determ ining the regions were identified. These regions were compared to other sch emes of biological and hydrographic areas. The MDS also showed that the cop epod composition in the tropical and subtropical regions was less variable than the temperate and Benguela stations. Latitudinal trends in diversity a nd size were also investigated. Copepod genera showed a reduction in richne ss at higher latitudes. Copepod size did not show any substantial or consis tent change with latitude along these transects, as demonstrated by both th e numerical abundances in each size category, and the carbon biomass per in dividual. The proportion in each size fraction was quite uniform over the t ransect.