Diatoms Are Encased in Petri-Plate-Like Cases (Valves) Made of Translucent

Diatoms are encased in petri-plate-like cases (valves) made of translucent hydrated silica whose thickness can be varied. The material used to store excess calories can also be varied. At certain times, diatoms store excess calories in the form of the liquid polysaccharide, laminarin, and at other times as oil. The following are data concerning the density (specific gravity) of various components of diatoms, and of their environment.
Specific Gravities of Materials Relevant to Diatoms
$$\begin{array} { | l | c | } \hline \text { Material } & \begin{array} { c } \text { Specific Gravity } \\\left( \mathrm { kg } / \mathrm { m } ^ { \mathbf { 3 } } \right) \end{array} \\\hline \text { Pure water } & 1000 \\\hline \text { Seawater } & 1026 \\\hline \text { Hydrated silica } & 2250 \\\hline \text { Liquid laminarin } & 1500 \\\hline \text { Diatom oil } & 910 \\\hline\end{array}$$
-Water's density and, consequently, its buoyancy decrease at warmer temperatures. Based on this consideration, and using data from the table above, at which time of year should one expect diatoms to be storing excess calories mostly as oil?

A) mid-winter
B) early spring
C) late summer
D) late autumn

Correct Answer:

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