(Henry 2001) Dinoflagellates
Dinoflagellates, which are sometimes referred to as algae, are microscopic, unicellular, and flagellated organisms. They are found in water that can be anywhere from 1°C to 35°C. They are found both in salt water and fresh water. They are distributed throughout the water based on the temperature on which they can survive. Because of this, they are used by humans as an indicator of changes in weather (Poulsen 2002). The structure of dinoflagellates is fairly simple. They have two flagella, one transverse and one longitudinal. The transverse flagella goes around the organism in a groove called the cingulum, while the longitudinal flagella is positioned perpendicular to the transverse one. The longitudinal flagella cause them to swim in a spiral motion (Speer and Waggoner 2002). There are over 2,000 species of dinoflagellates that are known today. Their phylogeny has been difficult to determine because of a lack of knowledge of distinguishing characteristics between the individual species (Taylor, 1987).
Because the dinoflagellates are flagellated, they swim up and down in the water column depending on the amount of light that is available (Langlois and Smith n.d.). The reason for the vertical migration is because the dinoflagellates possess pigments, such as chlorophyll a and c, as well as other accessory pigments, that react with a certain wavelength of light. During the day, the dinoflagellates are at the surface absorbing light so that they can perform photosynthesis, while at night, they are deeper gaining nutrients from upwelling (Speer and Waggoner 2002) . The dinoflagellates have the ability to store the products of photosynthesis as lipids and polysaccharides. They can then use these reserves when conditions become unfavorable (Taylor, 1987).
Dinoflagellate are ecologically important because of their integral role in the marine and freshwater food webs. The study dinoflagellates is important not only because they are one of the main sources for primary productivity in the ocean, but because they can also be very harmful to organisms in their own environment as well as humans. Dinoflagellates produce toxins that can be fatal to animals and eventually humans. When found concentrations, the community is called a bloom. A certain bloom, characterized by a reddish water, is called a red tide. When this phenomenon occurs, the toxins produced by the dinoflagellates are introduced into many species including shellfish, which can cause paralytic shellfish poisoning (PSP). If the shellfish are consumed by humans, neurological effects that could eventually lead to death are a possibility (MacRae 1994).
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