The majority of marine organisms are found in coastal regions, rather than the open ocean. which of the following best explains why?
ocean currents bring nutrient-rich water into coastal regions.
the shallow waters of coastal regions provide less oxygen.
salinity is usually much higher in coastal regions.
temperatures are cooler in coastal regions.

Majority of marine organisms are found in coastal regions because ocean currents bring nutrient-rich water into coastal regions. Marine coasts are environments that dynamically change through the process of weathering and change in sea levels. Coast lines mostly consist of continental shelves that contain relatively shallow waters of only 200 meter depths. These continental shelves extend approximately 68 kilometers from the shoreline. 

Since water is generally shallow, photosynthetic processes are possible for marine life which attracts more organisms to their primary food sources. Since the land is near shallow waters, discharges of nutrients from the soil are brought into the sea for the consumption of organisms. Aside from these reasons, periodic upwellings in the sea also provide cool and nutrient rich waters for different species.