We’ve had a new treat on the Central Coast in the past few years–glowing blue waves!!! The glow is caused by wave action that disturbs millions of microalgae called dinoflagellates, causing them to glow, or bioluminesce. A dinoflagellate is a type of phytoplankton. Dinoflagellates can move through the water using two whiplike flagella. Most dinoflagellates can photosynthesize and make their own food. Some of them can also ingest other organisms. They generally favor warmer waters.
When nutrients and sunlight are plentiful, phytoplankton species “bloom”. Plankton blooms are normal, healthy events that occur every spring. Nutrients brought up by wave action during winter storms combine with lengthening daylight hours to fuel spring blooms. They are a critical part of the marine food web, providing a food source for microscopic invertebrate larvae, which in turn feed small bait fish, which in turn feed larger predators. Migrating birds and mammals in polar waters depend on these blooms for healthy breeding seasons. All along the west coasts of North and South America blooms support some of the most productive fisheries in the world. Ultimately, all marine animals depend on a healthy phytoplankton population to survive.
When the blue glow made an appearance in our waters in 2017, there was also a visible reddish tint to the coastal waters, indicating an active plankton bloom. Sometimes called a “red tide”, blooms are unrelated to tides and are not always red. A water sample was collected during the bloom for viewing using the microscope at the Morro Bay Museum of Natural History. The culprit was identified by Dr. Peter Franks at Scripps Institution of Oceanography as Lingulodineum polyedra, a bioluminescent dinoflagellate common in southern California waters. Bioluminescence is common in our area, but the bright blue version characteristic of Lingulodineum polyedra is a recent treat. Since then, it has reappeared every year and has recently been seen in Monterey. As water temperatures gradually creep up, we will likely see more dinoflagellate species make their way north.
Bioluminescence is rare among land organisms (fireflies are one of the few). However, researchers at Monterey Bay Aquarium Research Institute estimate that over 75% of species in the deep sea, including fish, worms, shrimp, jellies and plankton, are bioluminescent. It is not known exactly why bioluminescence is so common in the deep sea, especially since it requires energy to produce. It is probably useful for confusing a predator or attracting a mate or a meal.
Plankton blooms aren’t always good. They can occur anywhere that large loads of nutrients such as fertilizer runoff and sewage spills empty into ocean waters. When they harm the ecosystem, they are called “harmful algal blooms”. Most are dominated by a single species of phytoplankton. Some species produce a toxin that can accumulate in marine organisms and lead to toxic shellfish poisoning. Harmful algal blooms can result in “dead zones”, as uneaten plankton decay and the oxygen concentration of the water goes down. Low oxygen levels can adversely affect fish and invertebrates. A famous dead zone is in the Gulf of Mexico, at the Mississippi River delta, where 40% of the nation’s farmland drains. Dead zones can have severe economic impacts if local beaches are littered with dead fish and local fishers have to travel greater distances to find healthy fish populations.