Seasonal and interannual variation of coccolithophore fluxes and species composition in sediment traps north of Gran Canaria (29 deg N 15 deg W)


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csprengel [ at ] awi-bremerhaven.de

Abstract

Coccolithophore flux variations in sediment traps of the time-series station ESTOC (European Station for Time-series in the Ocean, Canary Islands),located 60 nautical miles north of Gran Canaria, were recorded from April 1993 to December 1996. The 20 cup particle traps were deployed at 1000 and 3000 m belowsea surface, and sampling intervals ranged from eight days to three weeks.Coccolith and coccosphere fluxes at both trap depths were characterized by a strong seasonality. At 1000 m, maximum coccolith fluxes were reachedduring spring from March to April 1995 and from February to March 1996. Highest coccolith fluxes of 4538e6 coccoliths m-2 d-1 occurred at thebeginning of March 1996, whereas lowest values of 19.8e6 coccoliths m-2 d-1 were recorded in June 1994. Total coccosphere fluxes were constantly lowduring most of the investigated time interval and showed only high values during the main sedimentation phases from January to March 1995 (up to 6.2e6spheres m-2 d-1) and in March 1996 (36.4e6 spheres m-2 d-1).At 3000 m water depth, the sedimentation pattern was rather similar to the pattern observed at 1000 m. Maximum coccolith and coccosphere fluxes werealso reached during spring time in February 1994 (8200e6 and 15.6e6 m-2 d-1, respectively) and in March 1996 (8114e6 and 32.3e6 m-2 d-1,respectively). However, total coccolith flux peaks at 3000 m were about 2-4 times higher compared to the upper traps, probably due to horizontal advectionfrom phytoplankton material from north of the study site. This effect also influenced the coccolith-CaCO3 flux estimates. Mean calculated coccolith-CaCO3fluxes ranged between 3.9 mg m-2 d-1 for the upper traps (1995/1996) and 9.9 mg m-2 d-1 for the lower traps (1996). Coccoliths contributed for about8-78% of the measured total CaCO3 fluxes (<1 mm fraction), with a mean contribution of 33.4% in the upper, and 41.4% in the lower traps.The coccolithophore assemblages were dominated by Emiliania huxleyi, Florisphaera profunda, and Gephyrocapsa ericsonii during the entire samplingperiod, whereas all other species together generally contributed less than 40% to the total assemblages. Variability of species compositions at either trapdepth was very low, indicating similar seasonal flux patterns of the different species.



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ISI/Scopus peer-reviewed
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Eprint ID
4757
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Sprengel, C. , Baumann, K. H. and Neuer, S. (2000): Seasonal and interannual variation of coccolithophore fluxes and species composition in sediment traps north of Gran Canaria (29 deg N 15 deg W) , Marine Micropaleontology, 39 , pp. 157-178 .


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