Large-scale patterns in diversity and community structure of surface water copepods from the Atlantic Ocean

Abstract

Diversity and structure of copepod assemblages were investigated using 259 WP2 zoo- plankton samples collected from the top 200 m of the Atlantic Ocean between 60°N and 63°S. Whilst richness at a number of taxonomic levels (genera-superfamily) demonstrated a smooth latitudinal cline from the tropics towards the poles, other diversity indices such as evenness and taxonomic dis- tinctness showed abrupt changes around 40°N and 40°S, coincident with sea surface temperatures of 17 to 20°C. In the tropics and subtropics, copepod communities were characterised by high stable taxonomic diversity and a relatively even distribution of genera within samples. In contrast, at high latitudes and low temperatures communities showed large variation in overall diversity, evenness and distinctness. Multidimensional scaling and cluster analysis of transformed generic abundances, pooled into 5° latitudinal means, produced ordinations consistent with the recent subdivision of the oceans into 4 primary biomes based on temporal and spatial patterns of primary production. The copepod community corresponding to the Trades biome, where primary production is broadly con- tinuous, exhibited high generic richness and evenness. In contrast, community structure in the Polar biome, where primary production is highly seasonal, was highly variable and dominated by a few genera. These genera tended to be herbivorous or omnivorous and stored lipid. The Westerlies biome and the Benguela province had intermediate copepod community characteristics. We therefore sug- gest that copepod diversity and community structure are closely tied not to temperature or energy input, but to the temporal patterns of primary and secondary production.