Well first of all, the prey of the blue crab would decrease in population and the predators would increase in population. As a result the whole food chain would be thrown off. organisms which have the same diet, live in the same territory as the blue crab would also be affected because an increase in the blue crab population would mean a decrease in the natural resources that those blue crab exploit. if the blue crabs were able to keep a steady or exponential population growth, barring the natural resources around them lend way for population growth the blue crabs would eventually hit their carrying capicty. One they reach and begin going beyond this capacity the Blue Crabs would have to outcompete their selves for dwindling natural resources, mates, food, etc. Eventually the population would decrease because of this interspecies competeion as a result overexplotiation of natural resources. Things could in the entire ecosystem could return close to normal considering the no other species went extinct as a result of Blue crab population growth or no enviromental changes occured a sa result of this growth.