filtering 1 1 of water. During a moderate-size coccolithophorid bloom, the concentration of PIC 

 would increase by three or more orders of magnitude. 



The coccolithophorid E. huxleii has been reported as one of the dominant phytoplankton 

 within the study site. However, only calcified cells can be positively identified as E. huxleii 

 using conventional microscopy techniques (light and electron microscopy) so that this species, 

 which has both motile and non-motile naked life stages, may be far more abundant then 

 previously assessed. The abundance of the coccolithophorids will be assessed by conventional 

 microscopy, which uses polarized light to detect calcified cells. Both naked and calcified cells 

 will be detected by immunostaining with E. huxleii cell surface antibodies, and using HPLC to 

 monitor the concentration of the pigment 19' hexanoloxyfucoxanthin that is characteristic of 

 coccolithophorids. 



STRENGTHS AND LIMITATIONS OF PROPOSED RESEARCH 



The PIC pool, comprised mainly of CaC0 3 , is an important component of the total carbon 

 pool. The process of biocalcification, which leads to PIC accumulation, is an important 

 biogeochemical pathway within the carbon cycling. In contrast with other phytoplankton growth 

 that results in the production of POC and drawdown in pC0 2 , coccolithophore growth can cause 

 a significant drawdown of alkalinity and relative increase in pC0 2 . The influence of a 

 coccolithophorid bloom on air-sea exchange of C0 2 has been recently documented in the 

 Sargasso Sea near Bermuda (U.S. JGOFS Bermuda Atlantic Time- series Study, 310° 50' N, 640° 

 10') where a short-term increase in surface PC0 2 of 30 fatm reduced the net annual air- to-sea 

 flux of C0 2 by approximately 25%. Direct measurements of PIC during the OMP field year will 

 help obtain a complete carbon characterization of the carbon cycle at the study site. While major 

 blooms of coccolithophores have not been reported for the study area, sampling has been limited 

 and E. huxleii is a dominant species in the phytoplankton assemblages (most abundant identified 

 species in offshore shelf region) throughout the year. Blooming conditions could become 

 favorable, as they did in February 1992 at the BATS site. The process of calcification is poorly 

 understood biochemically and it is therefore essential to complement the field studies with 

 laboratory experiments in order to identify the environmental conditions favorable to calcification. 



Since OMP sampling will be limited to seasonal cruises, a transient increase in the 

 abundance of coccolithophores could easily be missed. However, their effect on the chemistry 

 of seawater could persist for several months and modify the annual net transfer of atmospheric 

 C0 2 into the surface waters. 



STATUS OF RESEARCH 



All of the proposed measurements can be accomplished using equipment available in 

 OASD. The proposed field work will complement laboratory studies already underway on the 



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