Question

What is the impact of human activities on the world's oceans?

Answer 1

Primarily, gross physical pollution and detrimental impact on marine ecologies.

Explanation:

"Turn the Tide on Plastic" is currently promoting awareness and furthering scientific research in this area WHILE competing in the round-the-world Volvo Ocean Race currently in Leg 4!
http://www.volvooceanrace.com/en/dashboard.html

Human refuse has been dumped into the seemingly endless oceans for so long that it is becoming apparent that the oceans are not, in fact, "endless"! Plastic is particularly prevalent due to its resistance to other weathering and degradation.

Over-fishing or habitat destruction stress or destroy marine ecologies in many parts of the world.