M. Pahlow et al., IMPACT OF CELL-SHAPE AND CHAIN FORMATION ON NUTRIENT ACQUISITION BY MARINE DIATOMS, Limnology and oceanography, 42(8), 1997, pp. 1660-1672
Diatoms have evolved a multitude of morphologies, including highly elo
ngated cells and cell chains. Elongation and chain formation have many
possible functions, such as grazing protection or effects on sinking.
Here, a model of diffusive and advective nutrient transport is used t
o predict impacts of cell shape and chain length on potential nutrient
supply and uptake in a turbulent environment. Rigid, contiguous, prol
ate spheroids thereby represent the shapes of simple chains and solita
ry cells. Ar scales larger than a few centimeters, turbulent water mot
ions produce a more or less homogeneous nutrient distribution. At the
much smaller scale of diatom cells, however, turbulence creates a roug
hly linear shear and nutrients can locally become strongly depleted be
cause of nutrient uptake by phytoplankton cells. The potential diffusi
ve nutrient supply is greater for elongated than for spherically shape
d cells of similar volume but lower for chains than for solitary cells
. Although the relative increase in nutrient transport due to turbulen
ce is greater for chains, single cells still enjoy a greater total nut
rient supply in turbulent environments, Only chains with specialized s
tructures, such as spaces between the cells, can overcome this disadva
ntage and even obtain a higher nutrient supply than do solitary cells.
The model results are compared to laboratory measurements of nutrient
uptake under turbulent conditions and to effects of sinking.