Toxic Diatoms


Phytoplankton are plants (usually tiny) that drift in aquatic environments. At the base of the aquatic food chain, these plants convert huge amounts of carbon dioxide into energy and release a major percentage of the world’s oxygen. A few species of phytoplankton produce toxins that can be harmful to some animals, including humans.

The NWFSC’s Harmful Algal Bloom Program studies the impacts that harmful algal bloom (HABs) and marine biotoxins have on fisheries, the local economy, public health and the ecosystem, focusing on Eastern Pacific marine waters from Alaska to Hawaii. With the aid of SEM and other advanced tools, scientists are now able to identify, track and forecast where and when these toxic blooms will occur, as well as give managers the early warnings needed to better protect shellfisheries and human health.

  • Toxic Diatoms

    Toxic Diatoms

    The long skinny diatoms are in the family Pseudo-nitzschia; under certain conditions these diatoms can produce toxins harmful to humans. Some shellfish, such as razor clams, become toxic if they eat a large number of these diatoms. If vertebrates including marine mammals and humans eat the toxic clams, the toxins can cause seizures, paralysis or even death. To prevent accidental human poisoning, marine waters are monitored, and when toxin levels are too high, beaches are closed for shellfish harvesting. Like the vast majority of diatoms, the two disc-shaped diatoms (family Thalassiosira) are harmless.

  • Diatom: Odontella

    Diatom: Odontella

    Diatoms are single celled plants with shells made of silica. They come in an amazing array of sizes and shapes. Some diatoms stick to things like rocks, plants and the walls of fish tanks. Odontella is one of thousands of marine diatoms that float as part of the plankton. Although they are invisible to the naked eye, diatoms and other plants in the sea convert huge amounts of carbon dioxde into oxygen, helping to regulate the planets climate.

  • Dinoflagellate: Ceratium

    Dinoflagellate: Ceratium

    Dinoflagellates are singled-celled organisms that occur in the phytoplankton. Several species produce toxins, and people become very ill if they eat shellfish that have been feeding on the toxic dinoflagellates. Many dinoflagellates are harmless, and some are responsible for the bioluminescence that can often be seen in Puget Sound waters. This is a harmless dinoflagellate in the genus Ceratium. Two diatoms are also present. The porous material underneath the phytoplankton is a membrane filter.