NEUTRAL CARBOHYDRATE GEOCHEMISTRY OF PARTICULATE MATERIAL IN THE CENTRAL EQUATORIAL PACIFIC

Neutral carbohydrate compositions were determined for particulate samp les from plankton net tows, shallow floating sediment traps, mid-depth and deep moored sediment traps, and sediment cores collected along a north-south transect in the central equatorial Pacific Ocean during th e U.S. JGOFS EqPac program. Total neutral carbohydrate depth profiles and patterns along the transect follow essentially the same trends as bulk and organic carbon (OC) fluxes-attenuating with depth, high near the equator and decreasing poleward. OC-normalized total aldose (TCH2O ) yields along the transect and with depth do not show any consistent patterns. Relative to a planktonic source, neutral carbohydrate compos itions in sediment trap and sediment core samples reflect preferential loss of ribose and storage carbohydrates rich in glucose, and prefere ntial preservation of structural carbohydrates rich in rhamnose, xylos e, fucose, and mannose. There is also evidence for an intermediately l abile component rich in galactose. It appears that compositional signa tures of neutral carbohydrates in sediments are more dependent upon th eir planktonic source than on any particular diagenetic pathway. Relat ive to other types of organic matter, neutral carbohydrates are better preserved in calcareous oozes from 12 degrees S to 5 degrees N than i n red clays at 9 degrees N based on OC-normalized TCH2O yields, due to either differing sources or sorption characteristics. Weight per cent glucose generally decreases with increased degradation of organic mat erial in the central equatorial Pacific region. Based on weight per ce nt glucose, comparisons of samples between Survey I (El Nino) and Surv ey II (non-El Nino) indicate that during Survey I, organic material in the epipelagic zone in the northern hemisphere may have undergone mor e degradation than organic material in the southern hemisphere. Copyri ght (C) 1996 Elsevier Science Ltd.