Deepwater is full of nutrients that are released from the decomposition of organic matter (carcasses, feces, etc.). How do these nutrients re-enter surface waters

Upwelling

Explanation:

Upwelling is the process through which cold water gets to ascends from the bottom, providing nutrients to the superficial stratum.

Upwelling is an ascending displacement of marine currents. The phenomenon can also occur in lakes or freshwater dams.

Wind blowing over the coast can cause surface water to move out to sea. This motion is complemented by a slow ascension of cold water coming from the bottom forward to the coast. This currents movement is known as upwelling.

Upwelling water is extremely cold and rich in nutrients, which result from remineralization, by bacterial action, of organic matter that accumulates in the deepest stratum of the water body.

The contact of minerals with photosynthesizing organisms in superficial layers produces a significantly high primary productivity.