San Francisco Bay Area Salt Ponds

Colors of the Salt Ponds

The salt ponds of the San Francisco Bay appear like some checker-board artwork, their chartreuse to orange-red hues shimmering at the edge of the estuary.

The dramatic palette of salt pond colors reflects a complex interaction of plants, animals and salinity.  Colors range from pale green to a deep coral pink.   Microorganisms create these colors, changing their own hues in response to increasing salinity.

-- Low to mid-salinity: Green algae lends the water a green cast.

-- Increased salinity: Dunaliella algae proliferates and turns the ponds a lighter shade of green.

-- Mid- to high salinity: High salt concentrations actually cause the Dunaliella to produce a red pigment.   Salt-loving, or halophilic, bacteria, also contribute red tints and purplish-red hues in brines.

-- Brine shrimp: Millions of tiny brine shrimp in mid-salinity ponds add an orange cast to the water.

-- Weather: When wind creates choppy conditions, the colors appear murkier.   Heavy rain can dilute the brine, causing the colors to shift toward the hues found in lower-salinity ponds or even turn the water clear.

Brine Shrimp ~ Sea Monkeys

Brine Shrimp or Sea Monkeys are reddish in color and are feed upon the algae in the salt ponds - which would otherwise prevent the salt from crystalizing.  Their eggs float to the surface where a skimmer can collect them.  They are dehydrated, canned and sold as very expensive tropical fish food. In their first stage of development, Artemia do not feed but consume their own energy reserves stored in the cyst.  Wild brine shrimp eat microscopic planktonic algae in the salt ponds.  Devoid of algae, the salt can crystalize under the natural heat of the sun, which can take up to seven years.

Artemia is a genus of aquatic crustaceans also known as brine shrimp or sea monkeys.  The first historical record of the existence of Artemia dates back to the first half of the 10th century AD from Lake Urmia, Iran, with an example called an "aquatic dog."   Artemia populations are found worldwide, typically in inland saltwater lakes, but occasionally in oceans. Artemia are able to avoid cohabiting with most types of predators, such as fish, by their ability to live in waters of very high salinity (up to 25%)!

The ability of the Artemia to produce dormant eggs, known as cysts, has led to extensive use of Artemia in aquaculture.  The cysts can be dehydrated and stored indefinitely and hatched on demand, to provide a convenient form of live feed for larval fish and crustaceans.  Nauplii of the brine shrimp Artemia constitute the most widely used food item, and over 2,000 metric tons (2,200 short tons) of dry Artemia cysts are marketed worldwide annually with most of the cysts being harvested from the Great Salt Lake in Utah.   In addition, the resilience of Artemia makes them ideal animals for running biological toxicity assays and it has become a model organism used to test the toxicity of chemicals. Breeds of Artemia are sold as novelty gifts under the marketing name Sea-Monkeys.

The brine shrimp Artemia comprises a group of seven to nine species very likely to have diverged from an ancestral form living in the Mediterranean area about 5.5 million years ago.

The total length is usually about 8–10 millimeters for the adult male and 10–12 mm for the female.

Brine shrimp can tolerate many levels of salinity from 25% to 250% with an optimal range of 60%–100%

Female brine shrimp can produce eggs that hatch almost immediately.  The eggs, also known as cysts, are metabolically inactive and can remain in total stasis for two years while in dry oxygen-free conditions, even at temperatures below freezing.  This characteristic is called cryptobiosis, meaning "hidden life".  While in cryptobiosis, brine shrimp eggs can survive temperatures of liquid air (−310 °F) and a small percentage can survive above boiling temperature (221 °F) for up to two hours.  Once placed in briny (salt) water, the eggs hatch within a few hours.  The nauplius larvae are less than 0.4 mm in length when they first hatch.

From cysts, brine shrimp nauplii can readily be used to feed tropical fish and crustacean larvae just after a one-day incubation. Instar I (the nauplii that just hatched and with large yolk reserves in their body) and instar II nauplii (the nauplii after first moult and with functional digestive tracts) are more widely used in aquaculture, because they are rich in nutrients, and small, which makes them suitable for feeding fish and crustacean larvae live or after drying.