Diatoms produce oil, both to store chemical energy from photosynthesis and to increase buoyancy. When large coastal diatom blooms die and sink to the bottom, they can be buried under sediments and later compressed during rock formation, which squeezes out the oil, forming pools of oil under sections of impermeable rock. Relatively large, slow-growing cells with two flagella used for swimming. Red tides are not easy to predict, but seem to occur most often with calm water, stratification, and high nutrient concentrations. These characteristics make tropical areas near large population centers very vulnerable.
Red tides seem to be increasing, and there is a major research effort underway to find out why.
A kind of dinoflagellate is also responsible for outbreaks of ciguatera , a kind of fish poisoning that can cause paralysis in humans in the tropics. Mainly tropical, carry calcareous shells that contribute to sediments in shallow regions where they reach the sea floor before dissolving. Very common in subtropical waters. This group includes shrimp, crabs, and lobsters. Consider first the holoplankton, or permanent members of the plankton.