Dynamics of oxygen production / consumption in Dunaliella salina, Thalassiosira weissflogii and Heterocapsa triquetra circulating within a simulated upper mixed layer

S BARBIERI, ELENA; VIRGINIA ESTELA VILLAFAÑE; WALTER HELBLING, E

INVESTIGACIONES MARINAS CICIMAR

Año: 2006 vol. 34 p. 97 - 108

0186-5102

Oxygen production / consumption dynamics in three phytoplankton species (20-25 μm in effective diameter),Dunaliella salina (Chlorophyceae), Thalassiosira weissflogii (Bacillariophyceae) and Heterocapsa triquetra(Dinophyceae), was experimentally determined when cells circulated within a simulated upper mixed layer (UML).Samples were exposed to three radiation treatments receiving: a) full solar radiation (PAB, 280-700 nm), b) PAR+UV-A(PA, 320-700 nm), and c) only PAR (P, 400-700 nm). Two pathways were simulated (as if the cells started to circulatefrom the surface or from the bottom of the UML): 1) downward circulation (i.e., from 100% to 9% irradiance and backto 100%), and 2) upward circulation (i.e., from 9% to 100% irradiance and back to 9%). There were no significant differencesamong radiation treatments (p < 0.05) and photosynthetic inhibition was only due to PAR. We found importantinter-specific differences in O2 rates when cells circulated within the simulated UML, D. salina was affected by bothhigh and low irradiances whereas T. weissflogii was only inhibited by high irradiances. On the other hand, H. triquetrashowed the least variability and it benefited by fluctuating radiation regimes. We also determined differences in the depthintegrated O2 production when species performed a complete rotation within the simulated UML, with the highest valuesin H. triquetra and the lowest in D. salina. Our findings suggest that the different pathways of the cells circulating in thewater column should be considered at the time to assess primary productivity in areas exposed to changing meteorologicalconditions throughout the year, and hence with variable UMLs.