Blue-green algae are most common in wetlands and freshwater, but are abundant along the ocean shore. Dinoflagellates The majority of dinoflagellates are marine. They display characteristics of both plants and animals, containing photosynthetic pigments as well as actively propelling themselves through the water using a flagellum. They rapidly reproduce asexually, doubling their population with each division. This rapid reproduction in species that are red produces a phenomenon known as 'red tide'.
Red tides can cause serious illness and death on other life form - even humans.
When a person ingests shellfish containing saxitoxin, which they obtain through filter-feeding, a condition known as paralytic shellfish poisoning may occur, causing illness and in severe cases death. During summer months beaches may be closed due to red tide conditions. Another interesting occurrence caused by dinoflagellates is phosphorescence. When disturbed, dinoflagellates can create their own light, causing this bioluminescence. The larger species, such as sea lettuce, can form thin, light-green sheets in the shallows of temperate bays and inlets.