Particulate organic carbon export fluxes estimated from <sup>234</sup>Th/<sup>238</sup>U disequilibria in the Xiamen Bay

CHEN Min; HUANG Yi-pu; QIU Yu-sheng

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CHEN Min, HUANG Yi-pu, QIU Yu-sheng. Particulate organic carbon export fluxes estimated from 234Th/238U disequilibria in the Xiamen Bay[J]. Haiyang Xuebao, 2002, 24(2): 66-76.

Citation:

CHEN Min, HUANG Yi-pu, QIU Yu-sheng. Particulate organic carbon export fluxes estimated from ²³⁴Th/²³⁸U disequilibria in the Xiamen Bay[J]. Haiyang Xuebao, 2002, 24(2): 66-76.

CHEN Min, HUANG Yi-pu, QIU Yu-sheng. Particulate organic carbon export fluxes estimated from 234Th/238U disequilibria in the Xiamen Bay[J]. Haiyang Xuebao, 2002, 24(2): 66-76.

Citation:

CHEN Min, HUANG Yi-pu, QIU Yu-sheng. Particulate organic carbon export fluxes estimated from ²³⁴Th/²³⁸U disequilibria in the Xiamen Bay[J]. Haiyang Xuebao, 2002, 24(2): 66-76.

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Particulate organic carbon export fluxes estimated from ²³⁴Th/²³⁸U disequilibria in the Xiamen Bay

Department of Oceanography, Xiamen Univeristy, Xiamen 361005, China

Received Date: 2001-04-03
Rev Recd Date: 2001-07-23

Abstract

Abstract

The daily variations of Chl.a,POC,primary production and ²³⁴Th/²³⁸U disequilibria in the Xiamen Bay were studied.POC concentration in the study area ranged from 14.4 to 34.6 mmol/m³,with an average concentration of 21.6 mmol/m³.The contributions of living organic carbon(phytoplankton) and organic detritus were estimated to be about 8%-26% and 74%-92% of the total POC,respectively.The profiles of POC showed a gradually decrease with the depth,and its temporal variation showed that the POC concentrations in daytime are higher than those in nighttime.Both features suggested that POC is closely related to biological processes in the Xiamen Bay.The primary production in the study area varied up to 5-folds in 1 d,which was consistent with that of the biomass.Primary production also decreased with the depth,was coincident with the patterns of Chl.a and POC.In the meantime,we studied the effect of incubation time on the determination of primary production.The primary production calculated from short-time incubation(2 h) is higher than that from long-time incubation(24 h),indicating some of the new fixed carbon are preferentially respired and then excreted.Based on the particulate ²³⁴Th export fluxes from ²³⁴Th/²³⁸U disequilibria and the POC/P_Th,ratios in particles,the Pox-export flux from euphotic zone is estimated to be 16.0 mmol/(m²·d),in which the export fluxes of living organic carbon and detrital organic carbon are 2.7 and 13,3 mmol(m²·d),respectively.The ratio between POC export flux and primary production,referred as ThE ratio,is 0.31.Both POC export fluxes and ThE ratios are consistent with the prediction value from relation formula presented by Aksnes and Wassmann in 1993,but not with other models.The residence time of POC in the euphotic zone was estimated to be 11 d,indicating a rapid regeneration rate of POC in study sea area.
- POC export flux,
- primary production,
- ²³⁴Th/²³⁸U disequilibria,
- ThE ratio

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