Radiolarian sedimentary imprint in Atlantic Equatorial Sediemnts: Comparison with the yearly flux at 853 m.

BOLTOVSKOY, D.; ALDER V.A.; ABELMANN, A.

MARINE MICROPALEONTOLOGY

Elsevier Science Publishers

Año: 1993 vol. 23 p. 1 - 12

0377-8398

Radiolarian specific compositions in a series of 20 sediment trap samples 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 (eastern equatorial Atlantic: 01°47.5'N, 11°07.6'W). Data on mean sediment accumulation rates at the site of the mooring (1.59 g/cm¨/ky), mean radiolarian flux at 883 m (28,446 shells/m¨/day), and abundance in the 0-1 cm bottom layer (48,258 shells/g) suggest that approx. 95% of the radiolarians produced are lost to the fossil record. Sediment trap sample-to-sample correlations (based on relative abundances of 40 radiolarian species present at levels ·1% in at least one sample, mean value, r=0.886) did not differ significantly from correlations between each water-column sample and surface sediments (mean r=0.878). Similarities between the flux and the sediments were not associated with time of year and with periods of enhanced radiolarian output. Two taxa had lower, and nine taxa had higher percentage contributions in the sediments than in any one sediment trap sample, and a few of the abundant species had averages up to 7 times higher in either the water-column or the sediments. These dissimilar percentage loadings are attributed to selective dissolution, lateral subsurface and deep advection of shells from higher-latitude areas, and identification biases. As opposed to species-level inventories, family-level databases (including shells identified to family only) differed significantly between the water-column and the sediments. Spumellaria (especially Spongodiscidae) were more abundant in the sediments (35%) than in the water-column (19%), while Nassellaria showed the opposite trend (64% and 80%, respectively). It is suggested that ease of identification of spongodiscid fragments and fragility of juvenile nassellarians are responsible for these differences.