RADIOLARIAN SEDIMENTARY IMPRINT IN ATLANTIC EQUATORIAL SEDIMENTS - COMPARISON WITH THE YEARLY FLUX AT 853 M

Radiolarian specific compositions in a series of 20 sediment trap samp les covering an entire year (1.3.1989 to 16.3.1990, collected at 853 m ) were compared with bottom (0-1 cm) materials from the same site (eas tern equatorial Atlantic: 01 degrees 47.5'N, 11 degrees 07.6'W). Data on mean sediment accumulation rates at the site of the mooring (1.59 g /cm(2)/kyr), mean radiolarian flux at 853 m (28,446 shells/m(2)/day), and abundance in the 0-1 cm bottom layer (48,258 shells/g) suggest tha t approximately 95% of the radiolarians produced are lost to the fossi l record. Sediment trap sample-to-sample correlations (based on relati ve abundances of 40 radiolarian species present at levels greater than or equal to 1% in at least one sample, mean value, r=0.886) did not d iffer significantly from correlations between each water column sample and surface sediments (mean r=0.878). Similarities between the flux a nd the sediments were not associated with time of year and with period s of enhanced radiolarian output. Two taxa had lower, and nine tars ha d higher percentage contributions in the sediments than in any one sed iment trap sample, and a few of the abundant species had averages up t o 7 times higher in either the water column or the sediments. These di ssimilar percentage loadings are attributed to selective dissolution, lateral subsurface and deep advection of shells from higher-latitude a reas, and identification biases. As opposed to species-level inventori es, family-level databases (including shells identified to family only ) differed significantly between the water column and the sediments. S pumellaria (especially Spongodiscidae) were more abundant in the sedim ents (35%) than in the water column (19%), while Nassellaria showed th e opposite trend (64% and 80%, respectively). It is suggested that eas e of identification of spongodiscid fragments and fragility of juvenil e nassellarians are responsible for these differences.