Red Tides

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Posted by Merry on April 25, 2020 at 10:47:14:

They're back!

[Using an old microscope, I was able to get these images from samples from Redondo Beach. ID’s are tentative and based on morphology.]

Patches of red or brownish-colored water, such as what Phil has been seeing off Palos Verdes, may be due to a population explosion of dinoflagellates, unique and diverse members of the phytoplankton. Some dinoflagellates are responsible for the blue bioluminescence (currently) seen as waves break along the beach. Although dinoflagellates produce neurotoxins and are responsible for several types of shellfish poisoning, the vast majority of “red tides” along the California coast are produced by nontoxic species. However, even a bloom of non-toxic dinoflagellates can be harmful to marine life due to oxygen depletion or by physically clogging the gills of fish.

We tend to think of all phytoplankton as simple single-celled algae, but dinoflagellates are uniquely complex. Roughly half of the species contain photosynthetic pigments, such as chloroplasts, and derive their energy solely through photosynthesis. Some of these types live symbiotically in the tissues of a wide variety of marine invertebrates.

The non-photosynthetic dinoflagellates are grazers or are parasitic. They prey on other components of the plankton such as diatoms, protists, or even other dinoflagellates. Some have a specialized organ used to sting, while others use a feeding veil to snare other plankton. Using a directional eye spot (a light antennae) and two flagella, they migrate within the water column to take advantage of nutrients and ultimately aggregate in dense patches.

Dinoflagellate size is measured in microns.

Red tide at Redondo Beach in 2009
Red tide along a current line

Red tide inshore Redondo Beach

The scientific names of some dinoflagellates have changed since I made the video:


Tripos muelleri


Tripos furca
Tripos furca, formerly Ceratium furca

Protoperidinium sp.

Dinophysis - three species
Dinophysis, three species

Gymnodinium sp?
Gymnodinium sp (?)

Cochlodinium sp.

Tripos sp? and Prorocentrum
Ceratium or Tripos fusus (?) bottom, Prorocentrum micans top

Lingulodinium polyedrum (possibly)
Lingulodinium polyedrum (?)

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