Vertical distribution and active carbon transport by pelagic decapods in the North Pacific Subtropical Gyre

Abstract

Pelagic decapods were sampled during August 2011 in the central North Pacific Subtropical Gyre (NPSG). Depth-stratified samples using a MOCNESS-10 (10 m2 Multiple Opening/Closing Net and Environmental Sensing System) were collected at two stations to the west and north of the Hawaiian island of Oahu: Station Kahe: 21°20.6′N-158°16.4′W and Station ALOHA: 22°45′N-158°00′W. Total decapod abundance and biomass were 4.3 ind. m-2 and 0.71 gDW m-2. While 40 decapod taxa were identified, only 22 species were sampled sufficiently to study quantitatively their vertical migrations. All species were classified into three migration groups: Full migrators (6 species); partial migrators (13 species); and non-migrators (3 species). Using measured local temperature profiles along with decapod densities and published models of respiration, excretion and mortality as well as gut fullness data, the individual and total active downward carbon flux was calculated. Active carbon flux of migrating decapods ranged from 383 to 625 μgC m-2 day-1. This active flux was equal to 4.8-7.8% of passive flux at the mean nighttime residence depth of ∼711 m), 2.1-3.4% of passive flux at the mean daytime residence depth (∼262 m), and 1.5-2.4% of passive flux at the base of the euphotic zone (∼173 m). Mortality flux accounted for ∼70% of total active flux, followed by gut flux-∼18%.