Effects of the diatom-Emiliana huxleyi succession on photosynthesis, calcification and carbon metabolism by size-fractioned phytoplankton

Abstract

Changes in species composition, photosynthesis, calcification and size-fractionated carbon metabolism by natural phytoplankton assemblages were monitored in three mesocosms under different nutrient conditions during May 1993 . In the 3 enclosures, the decline of the diatom-dominated assemblages was followed by the development of a bloom of the coccolithophorid Emiliania huxleyi . Highest growth of E. huxleyi was observed in the mesocosm with a high N : P ratio, suggesting this species is a good competitor at low phosphate concentrations . The transition from diatom-to E. huxleyi-dominated assemblages brought about a sharp reduction of the phytoplankton standing stock and carbon-specific photosynthetic rate . The relative contribution of the smaller size fraction to total photosynthesis increased as the succession progressed . Calcification rate and E. huxleyi cell-specific calcite production were highest during the early stages of development of the E. huxleyi bloom . Distinct changes in the patterns of 14 C allocation into biomolecules were noticed during the diatom-E. huxleyi succession . The diatom-dominated assemblage showed high relative 14C incorporation into low molecular weight metabolites (LMWM), whereas proteins and, specially, lipids accounted for the largest proportion of carbon incorporation in the E. huxleyi bloom . The patterns of photoassimilated carbon metabolism proved to be strongly dependent on cellular size, as protein relative synthesis was significantly higher in the smaller than in the larger size fraction, irrespective of the nutrient regime and the successional stage. These results are discussed in relation to the ecological and physiological features of small phytoplankton .

The hydrography and biology of a bloom of the coccolithophorid Emiliania huxleyi in the northern North Sea

“…The average value of integrated photosynthesis at the bloom stations was 1:1 š 0:1 mg C m 2 d 1 compared with 3:2 š 1:3 mg C m 2 d 1 in stations located outside the bloom area. A decrease in primary productivity associated with the occurrence of E. huxleyi blooms has been found previously in both mesocosm (Marañón et al, 1996) and open ocean studies (Balch et al, 1991;Van der Wal et al, 1995). The changes in the photosynthesis to chlorophyll a ratio across the transect between stations 27 and 31 could suggest that photosynthetic efficiency was higher within the E. huxleyi bloom.…”

Role of Saharan dust on phytoplankton dynamics in the northeastern Mediterranean

“…Eker-Develi et al (2006) reported that nitrate was more favorable for this species under laboratory conditions. In many investigations it has been reported that E. huxleyi is a good competitor at low phosphate concentrations (Egg & Heimdal 1994, Townsend et al 1994, Vanbleijswijk et al 1994, Marañón et al 1996. In the present investigation, the study area was generally arid during the stratification period.…”

Biogeochemical study of a coccolithophore bloom in the northern Bay of Biscay (NE Atlantic Ocean) in June 2004

“…The SEM observations (not shown) revealed that coccolithophores were present, mainly E. huxleyi and other species like Gephyrocapsa oceanica at lower densities, as well as less abundant and probably old population of diatoms. In mesocosms, the transition from a diatom-dominated to a coccolithophore-dominated assemblage led to a reduction of biomass and of productivity (Marañon et al, 1996). The patterns of remotely sensed variables (Fig.…”