英语听力：自然百科 佛罗里达州的温泉（四）

The cormorant gives up for now. The bird has been foiled by the clarity of the water, the very thing that enables the manatee to thrive. The light through these waters helps plants flourish, and manatees are strict vegetarians. They can eat a hundred pounds a day and can weigh more than a ton and a half.

Despite all the advantages of Florida springs, manatees are still highly endangered. Boatpropellers have killed many of them. Only about 2,000 of these gentle creatures are left in Florida.

Following the manatee into the springs are saltwater fish. Mangrove snappers should not be able to survive in these fresh waters. But high calcium concentrations give the springs properties similar to saltwater, lucky for the snappers who can bask in these warm waters until winter lets up.

Snappers and manatees drift, suspended in time in a winterless world.

The water is teeming with fish, but the eagle has a problem. Being top predator means nothing if everyone can see you. Underwater, striped mullet harvest algae which grow on fields of eelgrass. If the mullets spot the eagle, they would dash for cover. The clear waters have once again foiled the predator. The eagle comes up empty-handed.

The smaller osprey is also disappointed. As long as the eagle is around, the osprey can't fish without fear of being robbed. Frustrated, he tries to chase the eagle away. Undeterred, the eagle sets out again and finally the osprey can catch a meal.

These two have found a way to overcome the challenge of hunting in these clear waters. There's another predator here too. When it shows up, everyone gets out of the way.