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.
1 Eastern lowland gorilla (Gorilla gorilla graueri) is slightly larger in size weighing up to 220 kg (484 lb) and darker in coloration than the western lowland gorilla. They live in the rainforests of central Africa.  Mountain gorilla (Gorilla gorilla beringei) is the largest and rarest of all three subspecies. Adult males may weigh over 227 kg (500 lb.) They are found at high elevations of the Virunga Volcano range that separates Zaire from Rwanda and Uganda.