Answer: a. dead organisms from the marine food web.
c. liberation through ATP hydrolysis in living organisms.
Upwelling is a wind driven motion of lower bottom nutrient rich and warmer water on the surface of the water body. This wind driven motion facilitates the movement of nutrients available for growth of primary producers like phytoplanktons growing on the surface of water body. The dead organisms from the marine food web get decomposed and the organic matter obtain after decomposition is a rich source of phosphorous. This phosphorous gets transferred to the upper layers of the water body by upwelling. In aquatic organisms ATP hydrolysis occurs which is a catabolic process that uses water to split the bonds present in the ATP molecule and hence, releases energy for functions performed by them along with a release in phosphate atom. This phosphate gets mixed with the water. Therefore, PO32 come from dead organisms from the marine food web and liberation through ATP hydrolysis in living organisms that circulates due to upwelling.
They build up Muscle Tissue :)
