Dunaliella species make up just 10 percent of the algae in the south arm when they used to be 90 percent, Belovsky says. Under a microscope the diatoms look like crystal pill boxes. Beautiful, but inedible to shrimp. Because of the limited food supply, adult shrimp can't reproduce well. There has been a five-fold reduction in survival from the hatchling to the juvenile stage compared to when Dunaliella was the dominant algae type in the early 1990s, Belovsky says.
Lower salinities invite more predators, too.
Belovsky found that insects like corixids, or waterboatmen, live where salinity is 4.5 percent, usually along the shore. They suck out the shrimps' insides and likely eat 2 percent of the population a month. They're just a soft fluffy bag of food. They don't have a shell to speak of and they don't swim very fast. They've got a lot of protein and they're high in fat.