The nature of the Sea is to be eutrophic full of nutrients. The nutrients are what support the rich and abundant life in the Sea. They flow in with the water that comes from urban and agricultural runoff. The nutrients do not create a known health risk. Once in the Sea, some nutrients are continuously recycled, used by living creatures and then returned to the Sea when they die.
Some nutrients precipitate out.
But as with salts, evaporating water in a closed basin concentrates the nutrients which are left behind. The Salton Sea is like an underwater tropical rainforest. Little critters , microorganisms of many varieties, abound. Scientists have found completely new, previously unknown species as well as a vast number of known ones. They form the basis for the food chain, providing food for fish which in turn are food for birds.