Transient physical forcing of pulsed export of bioreactive material to the deep Sargasso Sea

• Published in: Deep-sea research. Part I, Oceanographic research papers Oceanographic research papers, 2003-10, Vol.50 (10-11), p.1157-1187
• Main Authors: CONTE, M. H, DICKEY, T. D, WEBER, J. C, JOHNSON, R. J, KNAP, A. H
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biology; Chemical reactions; Fundamental and applied biological sciences. Psychology; Marine; Oceans; Sea water ecosystems; Synecology
• ISSN: 0967-0637; 1879-0119
• DOI: 10.1016/s0967-0637(03)00141-9

Considerable attention has recently been focused on the role of eddies in affecting biogeochemical fluxes and budgets of the Sargasso Sea. In late November 1996, the Bermuda Testbed Mooring (BTM) and Bermuda Atlantic Time Series (BATS) shipboard sampling evidenced a fall phytoplankton bloom at the Bermuda time-series site which was strongly forced by the interplay between seasonal mixed layer destratification and perturbation of mixed layer dynamics due to passage of a warm mesoscale feature. The feature was characterized by clockwise current vector rotation from near the surface to about 200 m and a thick, warm, low salinity isothermal layer >180 m in depth. Nutrients, chlorophyll fluorescence and pigment profiles indicated high primary production stimulated by enhancement of nutrient entrainment and intermittent deep mixing down to the base of the feature's isothermal layer. Nearly coincident with the arrival of this productive feature at the BTM site, the Oceanic Flux Program (OFP) sediment traps recorded an abrupt, factor of 2.5 increase in mass flux at 3200 m depth. Even more dramatic was the observed increase in flux of labile bioreactive organic matter. Fluxes of primary phytoplankton-derived compounds increased by factors of 7-30, bacteria-derived compounds by 6-9, and early degradation products of sterols by a factor of 10. The covariation of early degradation products and bacteria-derived compounds with phytoplankton-derived compounds indicated that the settling phytoplankton bloom material contained elevated bacterial populations and was undergoing active degradation when it entered the 3200 m trap cup. [PUBLICATION ABSTRACT]