If you hit $0 Avail. funds for trading, your account will go into a margin call and Ameritrade will force you to sell positions or deposit money. I'm going to assume your Account Balance isn't -8.1k because you would have hit a margin call long before your account went negative unless this all happened overnight.
Sadly, these peaceful animals may not survive into the next century. Ape conservationists say time is running out, as there are only about 720 mountain gorillas left in the world, and the majority of gorilla populations are plummeting.
All three gorilla subspecies are listed as endangered by the U.S. Fish and Wildlife Service and by the Convention on International Trade for Endangered Species. There are currently about 50,000 western lowland gorillas living in the wild in West Central Africa. This gorilla is also the type most often seen in zoos. The eastern lowland gorilla population has declined significantly in recent decades. An estimated 5,000-15,000 lived in the eastern Congolese rainforest around 1960. Today only about 2,500 remain in the wild, and only a few dozen live in the world's zoos.