Upwelling currents are caused by: 1.temperature differences between water masses
2.salinity differences between water masses
3.pressure differences between water masses
4.Ekman spiral

its the ekman spiral not pressure differences between water masses

Explanation:

Upwelling. Along some coasts, the Ekman spiral causes an upwelling of deeper water to replace the water that has moved offshore. The colder, deeper water is richer in nutrients. These upwelling areas contain some of the richest fishing grounds in the world.

kelp are large brown algae that live in cool, relatively shallow waters close to the shore. they grow in dense groupings much like a forest on land. these underwater towers of kelp provide food and shelter for thousands of fish, invertebrates, and marine mammal species.

e) all of the above