Why Is It That Satellites, Using Wavelength Reflectance Technology, Detect

Why is it that satellites, using wavelength reflectance technology, detect variable levels of productivity across latitudes in the Earth's oceans, rather than an increase approaching the equator?

A) Temperatures at the equator often exceed those which are optimal for primary production.
B) Light at the equator is too constant and direct.
C) NPP in Earth's open oceans could differ due to variability in depth, nutrients, the presence of coral reefs, or by ocean currents.
D) Satellites detect differences by measuring the amount of water vapor emitted by transpiring producers, and this is a variable measurement in the oceans.