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African Journal of Marine Science

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Phytoplankton models and life history strategies

HC Eilertsen, T Wyatt

Abstract


Phytoplankton models generally do not consider the initial phases of seed stocks and deal only with the vegetative growth phase, ignoring life history strategies. Some quantitatively important diatoms, such as species of
Chaetoceros and Skeletonema, have special strategies with respect to the timing of the planktonic phase that cannot be explained purely on the basis of environmental clues. In Norwegian waters and elsewhere, the first
Chaetoceros bloom of the growth season usually starts in mid March, initiated by C. socialis. Other Chaetoceros species appear in the water column later. Species of dinoflagellates like Alexandrium also bloom at
certain times of the year. In many cases, phytoplankton inocula originate from resuspension of bottom-dwelling spores or cysts rather than from residual planktonic vegetative cells, and it is probable that, in some species, inoculation events are controlled by endogenous biological clocks. The sequential appearance of different Chaetoceros species may be related to day-length-regulated germination of spores. Most Chaetoceros species have few generations, but they appear at opportunistic times in the plankton. In contrast, Skelelonema costatum and Scrippsiella trochoidea appear at any time of the year. Some modelling results can be improved by including the dynamics of phytoplankton seed stocks in the sediments.



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