Analysis of total suspended matter in the Caribbean Sea

Abstract

Toted suspended matter (TSM) in the Caribbean was determined quantitatively by means of filtration through prepared 0.45 pm membrane filters. The new filtration technique employed enabled gravimetric precision to within 6 pg/1, which represents considerable improvement over previous methods. The mean surface concentration of TSM in the Caribbean is 172 pg/1, while the TSM below the photic zone (200 m) is 38 pg/1. Since the concentration within 500 m of the bottom averages only 36 pg/1, there is apparantly no gravimetrically-detectable nepheloid layer in the Caribbean. The bulk of the matter is introduced to the Caribbean through the passages of the Lesser Antilles, probably as discharge from the Amazon and Orinoco Rivers. The generally low productivity of the Caribbean results in an unusually high ratio of mineral matter over planktonic detritus. A broad TSM high extends northward from the South American coast, apparantly related to northward advection at the confluence of the westerly Caribbean Current and an eastward-flowing coastal counter current. Subsurface advection and diffusion studies support the conclusion that particulate material distribution may be accounted for by transport from the sills, with resuspension in the deep basins being a minor contributor. Light-scattering profiles taken at several stations in the central and eastern Caribbean do not indicate the presence of a permanent nepheloid layer.