Coccolithophore export production during the 1997–1998 El Nin˜o event in Santa Barbara Basin (California).
Articolo
Data di Pubblicazione:
2005
Citazione:
Coccolithophore export production during the 1997–1998 El Nin˜o event in Santa Barbara Basin (California). / B. De Bernardi, P. Ziveri, E. Erba, R. C. Thunell. - In: MARINE MICROPALEONTOLOGY. - ISSN 0377-8398. - 55:1-2(2005), pp. 107-125.
Abstract:
The response of coccolithophore export production to non-El Nin˜o and El Nin˜o conditions was monitored during a two
year period (26 March 1996–3 April 1998) in the centre of the Santa Barbara Basin (34814V N; 120802V W), California
borderland. During the 1997–1998 El Nin˜o the seasonal cycle of the surface water conditions was altered by the presence
of a relatively warm, low-nutrient and low-salinity water mass. Throughout the studied period, the total mass flux is
dominated by lithogenic components with terrigenous input being highest during El Nin˜o period. Although the annual
biogenic sediment fluxes were largely dominated by silica, with diatoms as the major contributor to the opal flux, the
coccolith flux was high during the entire studied period. During winter 1998 carbonate fluxes were unusually high for this
time of the year. Moreover, a strong positive correlation between organic carbon and opal flux indicates that siliceous
phytoplankton production is the most important factor controlling organic carbon flux in the Santa Barbara Basin. A
positive correlation between carbonate and organic carbon fluxes existed indeed during the final phase of El Nin˜o, when
the correlation between organic carbon and opal fluxes is poor. The sinking coccolithophore assemblage was dominated by
Emiliania huxleyi, followed by Florisphaera profunda, Umbilicosphaera sibogae, Gephyrocapsa oceanica, Helicosphaera
carteri, Gephyrocapsa muellerae and Calcidiscus leptoporus. The intensification of El Nin˜o 1997–1998 conditions altered
the typical hydrographic structure of the Santa Barbara Basin weakening the spring upwelling as reflected by reduced
diatom fluxes. In contrast, the coccolith flux was relatively high during El Nin˜o, particularly for the tropical species G.
oceanica, that showed a pronounced increase in its flux when the spring upwelling was reduced under El Nin˜o conditions.
In addition, we have found that this species has a strong correlation with nitrite, phosphate and iron availability in surface
water.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
coccolithophores; phytoplankton; sediment trap; Santa Barbara Basin; El Nin˜o Southern oscillation
Elenco autori:
B. De Bernardi, P. Ziveri, E. Erba, R. C. Thunell
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