ISSN:
1432-1793
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Patterns of phytoplankton carbon (C) metabolism were examined in å combined laboratory and field study to assess the influence of light conditions on 14C assimilation into photosynthetic end-products. Laboratory studies with three species representing distinct size classes and taxonomic groups tested the influence of “low light” on patterns of C flow. Prorocentrum mariae-lebouriae (dinoflagellate) and Ditylum brightwellii (diatom) showed decreased movement of photoassimilated 14C into protein following a shift to “low light” 14C assimilation into lipids and photosynthetic pigments increased in “low light” and was paralleled by increased chl a per cell. The proportion of 14C fixed into protein returned to the pre-shift level upon return to initial light conditions. Monochrysis lutheri (chrysophyte) did not show this pattern of reduced % 14C → protein. Incubations of 12 and 24 h demonstrated significant rearrangements in labeling patterns at night, wherein 14C flow into protein in darkness was favored. % 14C → protein at night was lower for M. lutheri than for the other species, suggesting some interspecific differences in the “low light” response. Measurements of 14C assimilation in phytoplankton assemblages from Chesapeake Bay demonstrated movement of a higher proportion of photo-assimilated C into protein in samples collected in the surface mixed layer than in those below the pycnocline. In comparison, phytoplankton collected below the pycnocline fixed a higher proportion of 14C into lipids, photosynthetic pigments, and low molecular weight metabolites, as was observed in “low light” laboratory cultures. A comparison of 12- and 24-h incubations for measuring patterns of C flow into photosynthetic end-products confirmed the inadequacy of short-term measurements, as significant changes in 14C allocation occurred in the dark phase of the photocycle. Together, these results suggest that 14C assimilation into photosynthetic end-products can be a useful measure of adaptive state in changing light conditions, but point out some difficulties in applying this approach in situ.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00392883
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