|Utilité des mesures dimensionelles et des calculs de surface et biovolume du phytoplancton: comparaisons entre deux écosystèmes differents|
Kim, K.-T.; Travers, M. (1995). Utilité des mesures dimensionelles et des calculs de surface et biovolume du phytoplancton: comparaisons entre deux écosystèmes differents. Mar. Nat. 4: 43-71
In: Marine Nature. Marine Science Institute, Yeungnam University: Kyongsan. ISSN 1225-990X
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The quantitative assessment of phytoplankton generally is made by microscopic counting of organisms, or chlorophyll a measurement. However the meaning of this biomass indicator is too closely dependent on the highly variable volume of the ratio of chlorophyll to organic matter or carbon. It may be better to extend the advantages of microscopical examination of microalgae to the measurement of their cell dimensions. Then one can compute cell biovolume V (equivalent to true biomass), plasma volume VP ('useful' biomass) and simultaneously cell surface areas and S/V ratio, other parameters bound to phytoplankton productivity and metabolism. But do these additional data really justify the important expenditure of time required by measurements and calculations? This problem is examined comparatively on phytoplankton from sea and from a neighbouring lagoon, with variable but usually very low salinity, and hence a strong prevalence of freshwater species. Data are given regarding more than 300 taxa and phytoplankton estimates during two years. The size of lagoon microalgae is generally more varied and smaller than that of marine species, with a S/V ratio twice higher on an average. Because of larger size variations in the lagoon, the image of plankton evolution, as described by cell numbers, is more changed by the use of biovolumes in the lagoon than in the sea. Nevertheless cell volumes computations are useful also in the sea, as biomass estimates. With respect to V, the estimate of VP is only essential when diatoms participation is important, i.e. principally in the sea station here.