Abstract

A seasonal flux study of silicoflagellates and Actiniscus was conducted at subarctic Pacific Station PAPA (50N, 145W; water depth 4200 m) during September, 1982 through August, 1984 using PARFLUX high resolution time series sediment traps deployed at 1000 m and 3800 m depths. The time series sediment trap samples were collected for 4 to 16-day periods depending on the samples; most of the samples were collected for 14 to 16-day periods. From a depth of 3800 m, a total of 47 samples represents a nearly two-year continuous record of the fluxes of silicoflagellate and Actiniscus taxa. An additional 12 samples from 1000 m represent a 6-month period, providing synchronized time series samples with the deeper depth which is essential to understand particle sinking processes.Seven silicoflagellate taxa, several variants of silicoflagellates, and Actiniscus pentasterias (Ehrenberg) group were examined. A total of more than 32 × 103 specimens were identified to species level and counted in this study. Distephanus speculum (Ehrenberg) and Dictyocha mandrai Ling are the dominant taxa, generally contributing >75% of the flux assemblages. Considerable intra-annual and interannual flux variability was observed with the range of total silicoflagellate flux varying from 5 × 103 to 700 × 103 skeletons m−2day−1 during the two years. Seasonal flux patterns of D. speculum and its closely related taxa are internally consistent and they conform with the productivity signals shown by diatom, total mass, or opal fluxes. The seasonal flux pattern of D. mandrai exhibits its own unique late fall/early winter signals with most of the cumulative flux concentrated during this season in year 1.The sinking mechanism of silicoflagellates is large aggregates which sink faster than discrete specimens. Silicoflagellates generally sink faster than marine snow mediated diatom assemblages. The larger influence of fecal material may be responsible for the observed faster sinking speeds than those of diatoms. No significant dissolution of silicoflagellate assemblages occurs in the water column due to innate protection and to accelerated sinking. Most of the silicoflagellates supplied to the sea floor are subsequently dissolved, and only 1% of the total supply is preserved in the surface sediments, with considerably altered assemblages.

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