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Abstract

Plankton bioniass and indices of metabolism and growth [electron transport system (ETS), glutarnate dehydrogenase (GDH) and aspartatc transcarbarnylase ( A T C ) activities] were studied over a 2,800 km east-west section of the tropical North Atlantic Ocean (21°N) in <200,200-500 and >500 pm size classes. On the large-scale, zooplankton (>200 p) enzymatic activities increased westward in thestudysection, where large cyanobacteria chains (Trichodesmiumspp.) wereobserved. Parallel toit, an increase in rnediurn calanoids (1-2 mrn iength) was observed towards the western part o€ the transect, whereas srnall calanoids (<1 rnrn) were dominant throughout the boundary area of the subtropical gyre.Microplankton ETS and mesoplankton ETS and ATC activitiesseerned to match the wave length of low frequency waves. O u r results suggest that such waves a r e related to the observed enhancement of metabolic activity of rnicro-and mesoplankton. The large-scale and rnesoscale variability observed give evidence of the inadequacy of assurning a steadystate picture of the euphotic zone of tropical and subtropical waters.

Carbon Budgets of Mesozooplankton Copepod Communities in the Eastern Atlantic Ocean—Regional and Vertical Patterns Between 24°N and 21°S

“…In total, 34-63% of carbon produced by global marine primary production (PP) is consumed by epipelagic mesozooplankton communities (Hernández-León & Ikeda, 2005). Lower estimates were reported from oligotrophic regions, where 21-50% of PP was ingested (Calbet, 2001;Dam et al, 1995;Hernández-León et al, 1999Lenz et al, 1993). In these regions, 59-75% of PP was grazed by microzooplankton, whose carbon is then transferred to higher trophic levels (Calbet & Landry, 2004).…”