Dissolved oxygen is an integral part of marine life used by all organisms for respiration. Water samples from the N. Atlantic and Caribbean were collected using a hydrocast during a SEA oceanographic cruise measuring dissolved oxygen and chlorophyll-a concentrations. Chlorophyll maximums correlated with increasing DO concentrations.  Primary production was greatest at a depth similar in all locations. The connection between dissolved oxygen and chlorophyll-a helps determine the location of production in the ocean.