(a) Thalassiosira pseudonana and (b) Chaetoceros simplex, and two flagellate clones
(c) Emiliania huxleyi and (d) Isochrysis galbana.
(^) (After Nelson & Brand 1979.)
Six species of diatom strongly favored daytime division. One species of
dinoflagellate and six varied species of microflagellates had division maxima at night
(Fig. 3.12c & d). There are counter-examples in the literature of dark-period division
in diatoms (Eppley et al. 1971), but, on the whole, diatoms are diurnal dividers, while
other forms divide at night. There are cycles in many other physiological parameters
which parallel those of division.
Effects of Nutrient Availability
(^) The organic matter of a typical phytoplankton assemblage in the sea has the following
elemental composition in terms of atoms (or moles) relative to phosphorus:
(^) These numbers are known as the Redfield ratios after A.C. Redfield, who first
measured them carefully in 1934 (see Redfield et al. 1963). Oxygen and hydrogen are
also present in organic material, but clearly are never limiting in the marine
environment. Carbon as carbonate (about 2 mM) is not limiting, either, although