As big as it is, the ocean is nutrient-limited. If you wanted to investigate this, one reasonable approach would be to A) follow whale migrations in order to determine where most nutrients are located. B) observe Antarctic Ocean productivity from year to year to see if it changes. C) experimentally enrich some areas of the ocean and compare their productivity to that of untreated areas. D) compare nutrient concentrations between the photic zone and the benthic zone in various marine locations. E) contrast nutrient uptake by autotrophs in marine locations that are different temperatures.