National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2001

Long-term studies of particulate flux on and near the Juan de Fuca Ridge

Tennant, D.A., E.T. Baker, A.J. Paulson, R.A. Feely, and G. Lebon

NOAA Tech. Memo. ERL PMEL-118, NTIS: PB2001-106334, NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, 87 pp (2001)

Sequentially sampling sediment traps were deployed in the region of the Cleft segment of the Juan de Fuca Ridge from 1984 to 1991 to gain a better understanding of the vertical flux of particles from hydrothermal plumes. Most traps collected ten sequential subsamples spanning a total deployment time of nearly a year. Data from four of the moorings (V18, V24, V26, and V43) were binned and averaged by trap depth to estimate the mean total flux from above and below the hydrothermal plume. Total flux in traps above 2100 m was 25.6 ± 44.6 mg m−2 day−1; below 2100 m the mean flux was 30.4 ± 37.1 mg m−2 day−1. The flux of hydrothermal particles enriched in Fe, Mn, P, V, S, and Cu at North Cleft moorings near Monolith and Pipe Organ vents showed a greater increase as a function of depth than did the total flux. Flux of these elements was 2 to 5 times greater below the plume than above but their combined flux was not great enough to account for the total flux increase at the bottommost traps. A combination of hydrothermal input and resuspended sediments may account for the near-bottom flux increase. Total and elemental fluxes generally increased at all depths during the spring and fall surface plankton blooms. Typical fluxes during non-bloom periods were 10 to 25 mg m−2 day−1, while peak fluxes during blooms were generally 40 to 150 mg m−2 day−1. Al, Si, P, Fe, and Mn fluxes increased by factors of 3 to 9 during bloom periods. Microscopic examination of trap samples indicated that organic aggregates were a common constituent. We suggest that organic aggregates produced in the euphotic zone account for the increase in hydrothermal sedimentation following surface blooms because these aggregates scavenge hydrothermal particles from the plume during the vertical descent and transport them to the seafloor.

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