View of a red tide in the Santa Monica Bay from the Venice Pier, Venice, CA. Note the reddish-brown color of the water on the backside of the wave's curl. Photo: Heal the Bay. Enlarge image.
View of a red tide in the Santa Monica Bay from the Venice Pier, Venice, CA. If you look closely, you can see distinct clouds of the phytoplankton bloom in the smooth water ahead of the breaking wave. Photo: Heal the Bay. Enlarge image.
Lingulodinium polyedrum, a non-toxic red tide dinoflagellate species. Enlarge image.

About red tides
The name red tide is a bit of a misnomer as the color of the water is usually not red, and its occurrence is not associated with the tides. Nonetheless, red tides occur when there is a high concentration of phytoplankton in the water. The responsible organisms are mostly dinoflagellates, a small, single-celled phytoplankton that possess two flagella, or whiplike projections.

These organisms reproduce by fission where a single cell divides in half and then creates two new cells, and so on and so on as the population continues to grow exponentially. Under the right conditions (see “Causes of Red Tide” below) the phytoplankton can reproduce once a day creating massive population blooms. When this happens, the ocean water appears as a rusty-brownish color as the light reflects off the pigments in the cells of the numerous phytoplankton floating on the surface.and presto.red tide! During the peak of the red tide there can be tens or hundreds of thousands of dinoflagellates in one drop of water!

Although not all red tides are harmful to humans, they do significantly, yet temporarily, alter the ocean environment where they occur. During a phytoplankton bloom, the organisms grow quickly and significantly reduce the amount of sunlight that is able to penetrate to the ocean bottom. In addition, metabolic wastes (feces) build up from the zooplankton and fish that feed on the abundant phytoplankton. Bacteria then break down this matter using up much of the water's oxygen in the process. Overall, this produces a light and oxygen reduced environment in the local area of the red tide.

Causes of red tide
Red tides are unpredictable and the causes of them are not entirely known. However, red tides have been occurring more frequently. Some factors that may contribute to the blooms that produce red tides are: reduced water salinity; optimal light conditions; warm surface temperatures; transport of algae in ballast water of ships; and excessive nutrients. As for the nutrients, sewage and urban runoff can contribute a high level of phosphates and nitrates into the ocean environment. Burning of fossil fuels also contributes to the amount of nitrogen, and is considered the greatest source to the open ocean.

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. 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.

What does all this mean?
According to the State Environmental Specialist for the Shellfish Sanitation Unit with the Department of Health Services, there have been a lot of Lingulodinium polyedrum (formerly known as Gonyaulax polyedra) in southern California, a non-toxic red tide dinoflagellate species (see photo at the top of this article). 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, so be careful out there!

But do go and check it out-it as it is pretty amazing. And if you have the chance to visit the ocean at night, check out the bioluminescence that occurs in the waves. These dinoflagellates can take energy from a chemical reaction and convert it to light energy so that they produce an awesome blue-green light that looks like a fireworks show in the water. Happy exploring!