Phytoplankton feed on the nutrients brought up by this type of deep cold water current

A water column is a form of precipitation which brings nutrients like nitrogen, carbon dioxide, iron and phosphorus. As phytoplankton create their own food source throw photosynthesis by converting sunlight into energy, a better word than feed on the nutrients, is absorb, as they do not gain energy from the nutrients, but the necessary nutrients allow for the phytoplankton to photosynthesize.

That is true tge cactus as a structural adaptation to its envirinment has it leaves reduced to spines. but this doesnt mean it cant produce food it produces food because of the presence of chlorophyll in its stem