The chemistry, biology, and vertical flux of particulate matter from the upper 1500 m of the Panama Basin

TitleThe chemistry, biology, and vertical flux of particulate matter from the upper 1500 m of the Panama Basin
Publication TypeJournal Article
Year of Publication1980
AuthorsBishop, J. K. B., R. W. Collier, D. R. Ketten, and J. M. Edmond
JournalDeep Sea Research Part A
Date PublishedAugust 1980
Call NumberDRK8277
Keywordsbiogeochemical cycles, biological productivity, Panama Basin, vertical flux

Particulate matter divided into < 1-, 1- to 53-, and > 53-μm size fractions was obtained using the Large Volume in situ Filtration System (LVFS) modified to collect four samples per deployment. Samples collected to 1500 m at 0°45′N, 86°10′W were analyzed for major and minor element, organism (species assemblage and population densities), and large particle size distributions. Vertical fluxes of fecal matter, fecal pellets, Foraminifera, and diatoms were calculated from size distribution data and two settling models. Estimates of the vertical mass, organic carbon, carbonate, and opal fluxes were compared with mean particle collection rates by sediment traps deployed at 2500 m for 234 days commencing at the time of LVFS sampling. The productivity of the surface layer at this station is controlled by the north-south position of the Equatorial Front, which separates low productivity Tropical Surface Water (TSW) from a mixture of warm Subtropical Surface Water (SSW) and cool, nutrient-rich water upwelled along the Peruvian coast. At the time of LVFS sampling the front was south of the station, with the lower productivity TSW dominating the surface water. Particle distributions and fluxes indicated lower than average productivity and highly efficient zooplankton grazing. Variability in productivity at the station was indicated by weekly sea surface temperature data and was manifested by an anomalous centrate diatom maximum centered at 400 m and by the indication that the particle flux through 1500 m was 1/40th of the rates particles were collected by the sediment traps at 2500 m. The depth of the nitrite maximum corresponded to that of strongest rate of decrease of the organic carbon flux. Fluxes of particulate opal and carbonate decreased markedly in the upper water column although it was supersaturated with respect to calcite. The occurrence of fecal pellets devoid of birefringent material in the water column indicates that the carbonate dissolution was biologically mediated. Calculations indicate that the strong carbonate dissolution in the upper waters at this station is not representative of “average” ocean conditions and is probably a local or rare phenomenon.