Pelagic Biodiversity and Ecophysiology of Copepods in the Eastern Atlantic Ocean : Latitudinal and Bathymetric Aspects

Abstract

Pelagic copepods play a key role in marine food webs as they transfer energy from lower to higher trophic levels and are responsible for the cycling and flux of a substantial amount of organic matter. Copepod communities are usually characterized by strong latitudinal and bathymetric gradients. Their biodiversity is mainly regulated by environmental parameters, biological interactions and species-specific ecophysiological performances. However, major driving mechanisms generating high biodiversity are still poorly understood, especially in the pelagic deep sea. The present thesis provides detailed information on distributional patterns, community structure and diversity of copepods in four major oceanic provinces of the tropical and subtropical eastern Atlantic and additionally a coastal region of the northern Benguela Current upwelling system. The analysis of community structure was combined with ecophysiological characteristics, i.e. trophodynamics and metabolic demands of key species, to investigate trophic and spatial niche separations, food requirements and the role of copepods in mediating vertical carbon flux from the euphotic zone down to 2000 m. Below the euphotic zone, representatives of the family Spinocalanidae were particularly abundant and species identification of adult and juvenile stages based on morphological features was a real challenge. To elucidate diversity as well as species- and stage-specific vertical distribution patterns of this relatively unknown, deep-sea copepod family, an integrated taxonomic approach was applied, combining morphology, DNA sequence analyses and proteomics using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). As time- and cost-efficient method, proteomic fingerprinting discriminated even putative cryptic species and yielded quantitative information on vertical distributional patterns of Spinocalanidae with high species and stage resolution. Thus, detailed community analyses based on proteomic fingerprinting may shed new light on biodiversity, plankton dynamics, phylogeographic patterns and vertical habitat partitioning, which is particularly promising for taxonomically challenging copepod groups such as cryptic species, juvenile stages and fragile deep-sea species.