HPLC analysis of chlorophyll a breakdown products to interpret microalgae dynamics in a shallow bay |
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Authors: | B Le Rouzic G Bertru L Brient |
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Institution: | (1) Laboratory d'Evolution des Systèmes Naturels et Modifiés, Université de Rennes I, Campus de Beaulieu, Avenue du Général Leclerc, 35042 Rennes Cedex, France |
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Abstract: | Phytoplankton production is determined by growth, senescence, sinking and zooplankton grazing. In an attempt to follow algal senescence and grazing, some authors have used HPLC fluorescence detection of chlorophyll a breakdown products. Laboratory grazing experiments have shown that copepods reduce chlorophyll a from diatoms leading to an increase in pheophytin a rather than pheophorbide a. However, field measurements only indicated a slight increase of pheopigment concentrations in summer. During this period, high heterotrophic activities (zooplankton and bacteria) seemed to be responsible for rapid pheopigment disappearance. On the other hand, highest chlorophyllide a levels appeared to be related to spring accumulation of nutrient-limited senescent algae. While increases in pheophytin a accounted for chlorophyll a consumption, changes in pheophorbide a concentrations could be linked to chlorophyllide a abundance. These results suggest that laboratory studies cannot be uncritically extrapolated to the field. |
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Keywords: | pheopigments chlorophyllide grazing senescence copepods diatoms |
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