to catch fish. but, you know, i don't know if the sharks got the memo. >> reporter: because it's a natural predator, a reduced shark population impact the balance of nature. there will be enough work, scientists say, to keep researchers busy studying the effects of oil on sharks for decades. john zarrella, cnn, in the gulf of mexico. world leaders gather to talk about money and debt. president obama declares progress made at the g-20 summit in toronto. what does that mean for you and me? outside the meeting hall, protesters also clashed with police over a wide range of causes. why are they marching and what do they want? we'll have a firsthand view from the street. we created the tide "loads of hope" program, a free laundry service that provides clean clothes to families affected by disasters. [ woman ] it feels so good to be able to know that i've got clean clothes. you don't know how very basic essentials are until you have none. ♪ this is what gives us hope.