Journal of Oceanography, Vol. 55 (No. 4), pp. 471-482, 1999
Santiago Hernández-León1, Lutz Postel2, Javier Arístegui1, May Gómez1, María Fernanda Montero1, Santiago Torres1, Carlos Almeida1, Eugen Kühner3, Ullrich Brenning3 and Eberhard Hagen2
1Facultad de Ciencias del Mar, Campus Universitario de Tafira, 35017 Las Palmas de Gran Canaria, Islas Canarias, Spain
2Institut für Ostseeforschung, Seestr. 15, D 18119, Warnemünde, Rostock, Germany
3Universität Rostock, Fachbereich Biologie, Rostock, Germany
(Received 5 May 1998; in revised form 26 January 1999; accepted 27 January 1999)
Abstract: Plankton biomass and indices of metabolism and growth [electron transport system (ETS), glutamate dehydrogenase (GDH) and aspartate transcarbamylase (ATC) 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 mm size classes. On the large-scale, zooplankton (>200 mm) enzymatic activities increased westward in the study section, where large cyanobacteria chains (Trichodesmium spp.) were observed. Parallel to it, an increase in medium calanoids (1-2 mm length) was observed towards the western part of the transect, whereas small calanoids (<1 mm) were dominant throughout the boundary area of the subtropical gyre. Microplankton ETS and mesoplankton ETS and ATC activities seemed to match the wave length of low frequency waves. Our results suggest that such waves are related to the observed enhancement of metabolic activity of micro- and mesoplankton. The large-scale and mesoscale variability observed give evidence of the inadequacy of assuming a steady-state picture of the euphotic zone of tropical and subtropical waters.