What is the importance of the color "black" in the novel, Wilder Girls?

Black often symbolizes death or rot, and the people, animals, and plants on Raxter Island turn black when they begin to die. This is true of the famous irises that grow abundantly, of the crabs that live along the shore, and of the people. Byatt's hands are turning black as she makes her way outside the visitor center after inhaling the poison gas, but once the parasite is out of her body, she does not die.