Jeremy enters the bowels of Lighthouse Cave, San Salvador, Bahamas.
As you sail into the night, a magical iridescent glow amidst the waves surrounds your boat. What is the origin of these mysterious lights? These glimmering lights are produced by bioluminescent dinoflagellates agitated by the wake of the ship. Dinoflagellates are small unicellular phytoplankton mostly found in the surface water of tropical or subtropical oceans. With diverse qualities both physical and chemical characteristics of dinoflagellates are found to vary. Some are found to be photosynthetic and containing chlorophyll while others are carnivores, parasites, or symbionts. Only about 30% of marine dinoflagellates are bioluminescent (access science). Bioluminescence is the ability of an organism to produce itês own light. Bioluminescence is a beautiful natural phenomenon, that is but one of the extraordinary adaptations of the marine creatures being explored.
Dinoflagellates are thought to have been around for millions of years. These free-floating marine creatures are known to vary in size and shape. Dinoflagellates generally, have two small tails called flagella, which they use to propel themselves through their marine environment. Some have shells made of chiton, while others live without this adaptation for protection. Species of dinoflagellates have been seen with the following characteristics horns, spins, wings, and thick cellulose plates resembling armor (Encarta). Although, there are species of this phytoplankton living in freshwater, dinoflagellates are prevalently found in tropical oceanic waters. They can also reproduce sexually or asexually depending on the particular organism.
Generally the life of a dinoflagellate is spent free-living in surface waters or symbiotically within an invertebrate marine organism. In the case of where reproduction of particular dinoflagellates at its highest, a condition referred to as –Red Tide,” describing the color the water turns as a result of the enormous density. Dinoflagellates with chlorophyll make their own food through photosynthesis. It is said that those without chlorophyll trap their food. Although these creatures are small they are not invisible to the eyes of predators such as crusteans. bioluminescent dinoflagellates, light up when they are being hunted to both distract their predators and to attract more larger creatures to prey on its own predator.
Bioluminescence is the ability of an organism to chemically create its own light. Not all dinoflagellates are bioluminescent but those that are, radiate a blue-green light when the water around them is disturbed by a marine animal or boat. The flow must be generally strong, such that waves on windy day, generally will not affect bioluminescent dinoflagellates. In this case, turbulent water has been shown to reduce reproduction rates of dinoflagellates and causing them even to change shape (Scripps). The light created by bioluminescence is not absorbed and radiated but actually created within the organism itself. Dinoflagellates are not the only marine creatures capable of bioluminescence but the means of luminescence is found to be chemically similar. It is initiated by the reaction of the substance luciferin and the enzyme luciferase in the presence of oxygen creates a light energy (Hutchinson and Hawkins 184). This is similar to when a glow stick is bent and shaken. This occurs within cells called photocytes or organs in some creatures called photophores (Prager and Earle 204). The light is emitted from small cortical locations in organelles called scintillons (access science) Luminescence is generally regulated by a rhythmic cycle of day and night.
For many years, bioluminescent dinoflagellates puzzled boaters as they created dazzling lights in the wake of their boats. There are also myths of –milky seas” where entire seas are illuminated in the night. This not proven but is usually contributed to a type of bacteria that continuously lights up, in contrast to the luminescence of dinoflagellates. Scientists from the National Science Foundation have concluded that bioluminescent dinoflagellates thrive best in calm conditions, in contrast to other planktonic algae, which prefer turbulent conditions. This most likely results from their extreme flow sensitivity that triggers their luminescence (Scripps). The dinoflagellates are not the only marine creatures with the bioluminescent adaptation. Other organisms that have species exhibiting this characteristic are squid, jellyfish, starfish, flashlight fish, and certain bacteria. It can be used to provide counter-illumination, as a signal, to lure prey, and distract predators (Hutchinson and Hawkins 184).
Dinoflagellates, a part of the phytoplankton family serves mostly as a source of food for larger marine organisms. From the phylum Dinoflagellata, there is thought to be around 130 known genera and 2000 species (Encarta). The contributions therefore, to other marine life, are varied by its genus and species. For example, while genus Noctiluca are phosphorescent when disturbed, the genus Symbiodinium generally lives symbiotically with corals and clams (Pernetta 224). Some are even known to build up skeleton like structures for other marine organisms. One of the most well known symbiotic relationships of a dinoflagellate exists with the coral reef. The zooxanthellae algae lives within the coral polyp, photosynthesizing food for both themselves and the coral, but also receiving a protected home (Davidson 16) Without the zooxanthellae algae the coral itself would not be as beautiful, for it is the zooxanthellae that give color to the coral polyps.
Although dinoflagellates are productive members of their marine environment, particular species are shown to be quite dangerous. When the production of dinoflagellates is increased and conditions are right it may result in the discoloration of waters called –red tide.” The –red tide” is named describing the red color the water turns from the algae pigment. The main culprits are the two species of dinoflagellates called Gonayaulax and Gymnodinium, they are known to multiply when there is a abundance of nitrogen and phosphorous, warm temperature, and little competition (Svarney and Barnes-Svarney). They eat up the nitrogen and phosphorous creating an algae –bloom”, a surface carpet that absorbs oxygen and cuts off sunlight (Svarney and Barnes-Svarney). The result of these algae fish is death to surrounding marine life.
Of the approximate 5000 phytoplankton species, fewer than 80 are known to be toxic (NRC, 1999). Instead of –red tide” scientists use the term –harmful algal blooms” (HABs) to describe the hazardous circumstances. –Harmful algae blooms” not only threaten marine life, but in causing the paralytic poisoning of shellfish they have been known to also poison humans with their toxins. Another dinoflagellate is known to cause ciguatera, a poisoning humans can get from eating contaminated fish. It can lead to a debilitating illness characterized by pain and numbness in the arms, legs, joints, and bones, and also a reversal of temperature sensation (Prager and Earle 263). Ciguatera has been known to affect around 50,000 people a year (Prager and Earle 263).
Scientists have been studying bioluminescent dinoflagellates to help explain how all cells can be affected by flow. Although, scientists are still trying to figure out how dinoflagellates detect their fluid environment, they believe that there are similarities to those controlling responses in other cells(Scripps). In addition to these studies of dinoflagellates and flow, they are also exploring how dinoflagellates can be used as microscopic flow sensors. In the future, this kind of technique could be used to develop safer artificial hearts by making sure the shear of blood pumping is not too high or low(Scripps). Bioluminescent dinoflagellates are not only mysterious beautiful creatures of the ocean, they also are being studied by scientists to learn more about the relationships of all cells and of fluid shear.
Dinoflagellates are phytoplankton that are found mostly in tropical ocean waters. Because there are countless numbers of species their body structures vary in size and shape. One of the most allusive adaptations of particular dinoflagellates such as the Nauticus, is their bioluminescene. Bioluminescence is that chemical ability of an organism to create its own light. These bioluminescent creatures can be seen lit up when their fluid environment is disturbed by something such as a ship or dolphin. The physiological relationships of bioluminescence and dinoflagellates are being studied by scientists to further understand how cells are affected by their fluid environment, along with the complexities of flow. Dinoflagellates are one of the most spectacular marine organisms as they create a sea of stars and color our coral reefs. Therefore, although dinoflagellates are known to contribute to –harmful algal blooms” or –red tide,” they are one of the magnificent creatures that make our ocean so unique and beautiful.
Davidson, Osha G. The Enchanted Braid. New York: John Wiley & Sons, Inc., 1998.
Hutchinson, Stephen, and Lawrence E. Hawkins. Oceans. Buffalo: Firefly Books, 2005.
Pernetta, John. Guide to the Oceans. New York: Firefly Books, 2004.
Prager, Elllen J., and Sylvia A. Earle. The Oceans. New York: McGraw-Hill, 2000.
Svarney, Thomas E., and Patricia Barnes-Svarney. The Handy Ocean Answer Book. Farmington Hills: Visible Ink Press, 2002.
J. Woodland Hastings, "Bioluminescence", in AccessScience@McGraw-Hill, http://www.accessscience.com, DOI 10.1036/1097-8542.083200, last modified: July 23, 2004.
National Resource Council (NRC). 1999. From Monsoons to Microbes: Understanding the Oceanês Role in Human Health. Ocean Studies Board/National Academy Press, Washington, D.C.
Scripps Institution of Oceanography
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