Whose job is it to clear up all the rubbish floating in the oceans?

I was in the middle of giving a talk on the marine debris problem at a notable Californian marine research institute, when I drank the last of my water bottle, threw it onto the hall floor from the podium, and kept talking. There it sat, to the surprise of several members of the audience. One well-meaning citizen then picked it up and returned it to the lectern. “Why did you do that?” I asked. “It just seemed wrong to leave it there,” he replied. Individuals know that something is wrong when the oceans are filled with debris. It is time for governments to act on that knowledge. But sea debris comes from both land and sea sources and it’s hard to point to its exact origin and hence to get a polluter to take responsibility for cleaning it up