The Salt Pond Ecosystem

Salt Pond Colors - The palette of colors reflected in the salt pond system ranges from pale green to rich red and characterizes the three distinct ecosystems that occur in the salt ponds. These colorful ponds, which measure several hundred acres each, which are most visible from the air, provoke frequent comment and many theories about their origin and use, especially among airline passengers visiting the San Francisco Bay Area for the first time. Though often misunderstood, like the Golden Gate Bridge, the salt ponds are a unique marvel of San Francisco Bay.

Low Salinity Ponds - Ponds with low salinities support wildlife similar to those found in bay waters. Yet because they are sheltered from the tides and winds that whip up bay sediments and whitecaps, these ponds are relatively still and clear -- creating prime fishing areas for fishing birds, pelicans, gulls, terns, cormorants, diving ducks and other waterfowl. One species, the least tern, a threatened species, is notable for having adopted the salt ponds as training grounds for its young. Adult Least Terns have been tracked guiding their fledglings from their nests 20 miles away – at the former Alameda Naval Air Station – to the Hayward salt ponds near the San Mateo Bridge - where they teach them to fish in the calm, shallow-bottomed waters.

Mid Salinity Ponds - Midway through the salt making process, the brines are too salty for fish, and just salty enough for brine shrimp (Artemia franciscana) to thrive in abundance. Brine shrimp are tiny – just 10 millimeters long, but they are a huge part of the salt pond ecosystem. They multiply in salt ponds where salinity measures 8 to 19 percent. They devour algae and are consumed, in turn, by flocks of shorebirds, including the dainty sandpiper, the colorful avocet and graceful black-necked stilt. The lowly brine shrimp lays the foundation for the avian life most characteristic of the salt pond ecosystem.

Brine shrimp are so plentiful, in fact, they have spawned a second salt pond industry. These little crustaceans are prized fish food and supply aquarists the world over. Harvested by fishermen casting very fine nets, they are then dried, packaged and marketed internationally. Some may even end up as toys or dried “sea monkeys” that come alive when immersed in water.

High Salinity Brines - As the brines reach the near saturation point for salt, brine shrimp no longer reproduce. Consequently, their prey, the organisms lower on the food chain, multiply. These are halophilic bacteria, sometimes referred to as blue-green algae. The most dominant, Dunaliella, actually changes the color of its protoplasm. As the brines grow saltier, the algae darken and its orange hue transforms into a brilliant vermillion– coloring the brines the same vivid red. Without fish or brine shrimp at the bottom of the food chain, higher organisms do not frequent the high salinity ponds and crystallizers and the highly industrial nature of the salt production does not disturb or conflict with the abundance of wildlife in the majority of the salt-making system. The only animals found near the salt plant are casuals – visiting gulls or other birds that may roost for a while before seeking food elsewhere.

The Salt Pond Ecosystem
Associated Habitat
Protected Species
Restoration Project
Starting the Process
A History of Cooperation