Tham khảo tài liệu 'biomass and remote sensing of biomass part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | In Situ Primary Production Measurements as an Analytical Support to Remote Sensing - An Experimental Approach to Standardize the 14C Incorporation Technique 251 sample volumes also the final acid concentrations were very diverse among the studies. Although the 14C technique has now been used in more than 35 000 oceanographic experiments del Giorgio Williams 2005 from the review of the earlier and recent literature we evidenced that different methods are still used to stop the photosynthetic activity and that highly variable concentrations of HCl are added to remove the excess labelled bicarbonate which was not assimilated by the microalgae. In order to standardize this step of the 14C method we designed a series of experiments using both water samples and a mix culture of microalgal taxa which represent a coastal phytoplankton community. The first aim of our study was to define which HCl concentration with an equal volume among 1N 2N and 5N was sufficient both to remove the excess labelled bicarbonate and to kill the cells but without damaging their structures with a consequent loss of assimilated 14C. Secondly using both chlorophyll a red autofluorescence and motility of flagellates and diatoms as proxies of microalgal viability we tested if different acid concentrations were sufficient to stop the microalgal photosynthetic activity. 2. Materials and methods Water sampling On 18th October 2006 29th January 2007 and 4th September 2008 five litres of seawater was collected at 5 m depth by a Niskin bottle about 10 km far from the coast in the Gulf of Trieste northern Adriatic Sea Italy . In each cruise seawater temperature and chlorophyll a chl a were recorded by a Multiparameter Probe Ocean Seven 316 Idronaut. In laboratory the sampled water was immediately transferred to translucent polycarbonate carboy Nalgene and kept at in situ temperature 20 C in October 10 C in January 20 C in September and light conditions ranging from 100 to 200 umol .
