- Author: Chris M. Webb
Some of you, especially those who commute between Ventura and Santa Barbara Counties, may have noticed murky, red tinted ocean water along the coast. This abnormal looking sea water is due to a natural event called a “red tide.” The event has been ongoing in the waters off Ventura County for several weeks, with a shorter but still significant and noticeable event more recent off Santa Barbara County.
What are red tides? Why do they happen? And how do they impact our environment?
Today, Carrie Culver, our Ventura and Santa Barbara County UCCE Sea Grant Marine Advisor shares some of her knowledge with us.
Red tides are made up of microscopic, single cell plants known as phytoplankton. These tiny plants are the basis of the bottom of the ocean food web. Phytoplankton have pigments that capture sunlight used for growth and reproduction. Red tides occur when these plants reproduce extremely rapidly resulting in a large ‘blooms’ of phytoplankton.
Because phytoplankton blooms can reach concentrations of millions of cells per gallon of water, the water itself can change color. The color of the water varies depending on the types of phytoplankton species present. The blooms can produce hues of bright red, brown, burgundy, yellow and anything in-between. Some blooms produce no visible changes.
Blooms can last from a few days to several months. The length of time depends on a variety of variables including: available nutrients, sunlight, water temperature, changes in wind or surf conditions, competition with other species, and grazing by zooplankton and small fish.
Depending on the type of phytoplankton, the blooms may or may not be toxic. Luckily our current red tide is not toxic. It consists of three organisms; mainly Lingulodinium polyedrum in combination with species of Prorocentrum and Ceratium. While these organisms do not produce toxins, they still can impact people and marine life due to the changes in the chemical composition of the water. People swimming through a non-toxic bloom have reported irritation of the eyes, mouth, and throat, as well as cold and flu-like symptoms. The water can also become depleted of oxygen leading to fish kills and deaths of other marine life.
How do you know whether a red tide is toxic or not? You can’t tell just by looking at the water. You need to refer to the experts, including the California Department of Public Health (CDPH). This agency works with dedicated volunteers from other agencies, universities and public and private groups to routinely monitor our coast and shellfish for the presence of these blooms. You can obtain the collected data from CDPH’s toll-free Biotoxin Information Line at 1-800-553-4133. That line can also be used to request a copy of the monthly monitoring newsletter or to get further information on phytoplankton blooms.