Ecology

    Dinoflagellates are considered to be important primary producers in the oceans. They are unicellular microscopic algae that have economic significance in the oceans. About 90% of the plankton are marine, but  they are also commonly found in freshwater lakes, rivers, and bogs. Dinoflagellates thought to be among the most primitive eukaryotic organisms (Speer and Waggoner 2002, Olney 2003).

Ecological Classification:

   Dinoflagellates are capable of using many different metabolic strategies. Because of this, they have been very difficult to classify, and often, they have been misclassified (Taylor 1987). About half of the known dinoflagellate species are autotrophic. This means that they are capable of synthesizing organic material from inorganic compounds. Most of the autotrophic species are contain chloroplasts which allow them to photosynthesize. Other Dinoflagellates are heterotrophic; they rely on other organisms for their organic material needs. Hetertrophic dinoflagellates can be herbivorous or carnivorous, depending on the species. These organisms eat algae, eggs, marine plankton larvae, and other dinoflagellates (Olney 2003). A third metabolic strategy used by dinoflagellates is mixotrophy. Mixotrophic species are able to be autotrophic or heterotrophic depending on the environmental conditions. Some examples of mixotrophic dinoflagellates include: Akashiwo sanguinea, Ceratium furca, Gyrodinium uncatenum, Gyrodinium galatheanum, and Prorocentrum minium. P. minium consumes nano and microciliate prey, and competes with macrozooplankton for food (Smalley 2001). Still other dionflagellates are parasitic. These forms are capable of heterotrophy and mixotrophy. Amoebophrya ceratii infects other free living dinoflagellates and affects their
capability to reproduce (Smalley 2001). Dinoflagellates also occur as symbionts with corals. These zooxanthellae are important primary producers in the coral reef ecosystem (Benfield 2003, Olney 2003). 

Bioluminescence:

    Dinoflagellates belong to the Division of Pyrrhophyta, and known as "fire plants" because they glow in the dark. The dinoflagellate produce flashes light when the compound luciferin is oxidized by the enzyme luciferase in the company of ATP and oxygen (Speer and Waggoner 2002).

Figure 1. Dinoflagellate Bioluminesence (Image Quest 3D 2001)

    Bioluminescence is usually triggered by mechanical stimulation. One hypothesis as to why dinoflagellates bioluminesce is that it is an anti-predator mechanism - or burglar alarm response- which attracts larger predators to eat the smaller predators that are posing a threat to the dinoflagellate. This light mechanism was first seen in the genus Noctiluca (Speer and Waggoner 2002).

Red Tides & Nutrients:

    Red Tides are algal blooms of high density and produce discolored waters. Red Tides are caused by temperature and light changes and are associated with the abundance of nutrients such as  nitrates and phosphates. Upwelling may be one means by which nutrient levels become elevated in the water.  These nutrients are also carried from the land to the sea by rivers and drainage (Speer and Waggoner 2002).

     Some algal blooms produce neurotoxins that are poisonous to other marine organisms and even to humans (Cavanihac 2001) If humans consume poisoned seafood, especially shellfish, serious illness or death are possible (Speer and Waggoner 2002).   

Figure 2. Dramatic image of a red tide in California (Anderson 2002)

Bacterial Interaction:

    Bacteriology is Dr. Bob Belas passion. He believes it is important to study dinoflagellates because of harmful algal blooms like red tides which is caused by Pfiesteria piscicida. He did research on dinoflagellates and their interaction with bacteria. He found each bacteria has input on a dinoflagellate’s physiology and toxigenesis. They may enhance dinoflagellate’s metabolism or metabolic processes. In his sample, 36 culturable & non-culturable bacterial groups were identified with Pfiesteria piscicida (Belas 2001).

    Dr. Belas found that the bacteria present have positive affects on a dinoflagellate’s growth. Dr. Belas and his team discovered a technique for creating a bacteria free, axenic, dinoflagellate culture. This is a growth curve that contrasts a pure axenic dinoflagellate culture and a bacterial/dinoflagellate culture. Notice the dinoflagellate growth was higher in the presence of bacteria. Belas also speculates that the dinoflagellate growth is closely associated with their ability to capture prey (Belas 2001).  

Figure 3. Axenic and bacterized growth of dinoflagellates in culture (Belas 2001)

 Phytoplankton & Carbon Cycling:

    Carbon is lost through the marine food web when phytoplankton and zooplankton die and sink to the sediments.  Carbon dioxide is also lost through when it is broken down photosynthesis and when it is released via respiration into the dissolved organic reservoirs. Finally, some carbon dioxide is lost when it is released into the air and then back into the ocean (Behrenfeld 2002).

 Page created by: Kim Morris

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