Coarse-scale horizontal patchiness and vertical migration of zooplankton in Gulf Stream warm-core ring 82-H

摘要: Abstract A 1-m 2 MOCNESS with 20 nets was used to make a series of tows in Gulf Stream meander/ring 82-H (September/October 1982) including two 0–100 m undulating “towyos”. One towyo, made at dusk the core (of Sargasso Sea/Gulf origin) permitted study effect diel migration on spatial variability copepod and euphausiid species abundance, composition region low physical variability. The other towyo taken across front outer edge (a mixture Stream, Shelf Slope Water), allowed comparison same biological properties strong sharp transition occurred ring after sunset as dielly migrating euphausiids moved into surface waters. similar, but less extreme change took place because smaller proportion these migrated. All migrants also entered waters living deeper water column during day arriving later than those shallower. Enright 's (1977, Limnology Oceanography , 22 856–872) hypothesis for metabolic advantages available through vertical does not account observed behavior copepods this time place. Estimated swimming speeds (typically 50–200 h −1 ) were similar spite large differences body size between groups. Variations substantially larger where proportions changed radically concert changes water-mass properties. There samples from which equaled front. Hydrographic stronger due euphausiids. Streamers originated within frontal spiraled could provide colonizers many present formation.