Satellites can be equipped with color scanners that can efficiently detect variation over very large areas. This image was produced from data collected by the Coastal Zone Color Scanner over the Gulf of Maine. The color red is a false color, indicating high concentrations of chlorophyll. Note the strong concentration over Georges Bank (GB), one of the most productive fishing grounds in the world (at least until overfishing occurred in recent decades).

While the color gives us very useful ideas of changes in chlorophyll concentrations, it must be calibrated by measurements made "on the ground." Many problems still prevent a universal calibration, including the problem of detecting chlorophyll at depth and the relationship of total chlorophyll, a measure of biomass, to productivity.

This diatom occurs in chains of cells, armed with spines. This diatom is not preferred by suspension feeding bivalve mollusks. Have you any ideas why the spines are present? Ah...me either.