Recently, in certain areas, Santa Monica Bay water looked like a bucket of liquid rust.

Suddenly and with no apparent cause, the normal bluish hue of our bay turned to a murky brownish-red body of dirty looking water.

The dramatic shift in the water’s color is due to the return of the red tide, which is actually a phenomenon where a reddish-colored plankton called dinoflagellates reproduces or “blooms” in great numbers.

The occurrence often happens in late summer/early fall when water is warmer.

“Red tides in Southern California seem to occur in the late summer or early fall when there’s been a long period of warm water followed by a cold water upwelling event,” says the Santa Monica environmental watch-group Heal the Bay on the organization’s Web site.

“This cold water is rich in nutrients and combined with the strong sunlight that at this time of year provides ideal conditions for a red tide (or other algae) bloom.”

The surge of red tide has been appearing all over Southern California waters recently, causing marine biologists and scientists to scratch their collective heads.

“These red tides are unpredictable,” said Scripps Institution of Oceanography professor Peter Franks.

“I’ve worked on them for years, and I still could not tell you whether we’re going to have one in a given year, when it will occur, or even what species it will be (we have two main species that cause local red tides).

“They tend to occur in the summer and early fall, though I’ve seen them in winter and spring,” he said.

The red tide can be cause for concern because in some cases the plankton contains domoic acid — a poison that enters into the food chain through smaller fish that feed on plankton and algae.

When the larger fish feed on these bait-fish and in turn larger animals eat them, including us, there can then be problems and complications.

Fortunately, not all red tides contain the poison, but there is no way to find out except testing the water or noticing a trend of sick animals.

A couple of years ago there were quite a few sick sea lions beaching themselves on Mothers Beach on Palawan Way and also on oceanside beaches.

The sea lions turn a pale, almost white color when they’ve been infected with the acid.

This year, as in the aforementioned instance, there has been an unusual number of sick sea lions, but it’s too soon to tell if these sicknesses were caused by this recent red tide or just a build up of domoic acids in their systems from the past.

“Domoic acid is a big problem,” says Long Beach Aquarium Marine biologist Stephanie Schmidt.

“I volunteer at a sea lion rescue facility and we’ve been seeing a lot of them coming in because of the acid.”

Although the red tide can sometimes contain toxins, for the most part, it’s believed that it isn’t usually very harmful to people, but can be an annoying irritant.

There is credible speculation that various forms of food poisoning can be traced to the red tides and there have been cases of skin irritation associated with them as well.

“While the brown foam, due to the decaying phytoplankton, is not harmful, some believe that swimming, boating, or breathing sea spray that is affected with red tide organisms can cause eye irritations, skin discomfort and sore throats,” said a Heal the Bay spokeperson.

In the daylight the red tide can make the water look unappealing and soiled, but come nightfall, the plankton produces a visual spectacle.

“The dinoflagellates are bioluminescent,” said Franks. “Each cell can create its own eerie blue light.

“It does this in a sudden flash, presumably to either warn away predators, or to attract visual predators to eat the organisms that are eating the dinoflagellates.”

Surfer Mathis Riley adds:

“I am actually a fan of red tide — yeah it stinks, looks nasty, and possibly gives you ear and throat infections, but red tide contains phosphorescence.

“One good night session, sticking your hand into the face of the wave and watching the trail of light race back into the glowing foam makes all those inconveniences worth it.

“Besides, the version we have in California is not that dangerous.”

As quickly as the so-called tide comes, is as fast and capriciously as it goes away.

The currents and winds are said to play a part in the unpredictability of the phenomenon, making them quite an illusive subject for our marine scientists to track and attempt to fully understand.