|
-- P l a n k t o n --
click on the question number for the answer |
||
| Q 1. | ||
| What are diatoms? |
||
| Q 2. | ||
| What sea animals live in shells of cellulose? |
||
| Q 3. | ||
| What are krill? |
||
| Q 4. | ||
| Is it possible that man will ever eat plankton? |
||
| Q 5. | ||
| What sea creature has never been positively classified? |
||
| Q 6. | ||
| What is meant by "plankton" and "nekton"? |
||
| Q 7. | ||
| What are dinoflagellates? |
||
| Q 8. | ||
| Do marine forms having free-floating larvae have an advantage over those that do not? |
||
| Q 9. | ||
| What is plankton? |
||
| Q 10. | ||
| Why are cold water plankton forms generally larger than the warm water forms? |
||
| Q 11. | ||
| On a recent trip to Europe, I observed what appeared to be an illusion of rain of the surface of the sea, although it was not actually raining. What phenomenon could have caused this? |
||
| Q 12. | ||
| What exactly is meant by plankton? |
||
| Q 13. | ||
| What is krill? |
||
| Q 14. | ||
| I am conducting research on plankton and its uses. Could you tell me where I might obtain information? |
||
| Q 15. | ||
| I have read that the blue whale, largest animal on earth, feeds entirely on krill. Just what is krill? |
||
| Q 16. | ||
| Could you explain the technique of "chlorophyll count" in seawater? |
||
| Q 17. | ||
| What is the deep-scattering layer? |
||
| Q 18. | ||
| Harvesting of krill is discussed in the September-October, 1977 issue of Sea Frontiers. Has there been any progress toward management of this resource, so that it will not be overexploited? |
||
| Q 19. | ||
| Can you provide information on the proper care and feeding of plankton in an aquarium? Also, where can one obtain live plankton? |
||
| Q 20. | ||
| In reviewing literature about red tides, I note that in some cases dinoflagellates are referred to as animals and in other cases they are called plants. Which is correct? |
||
| Q 21. | ||
| I have read that the dinoflagellate Noctiluca is luminescent and produces a so-called cold light in its body from an enzymatic reaction. Has any research been done toward possibly using this same type of substance in lighting systems for man? |
||
| Q 22. | ||
| Is it possible to keep live krill in an aquarium? |
||
| Q 23. | ||
| I want to try to raise larval marine fishes in my aquarium. Where can I obtain information on how to grow rotifers to feed newly hatched fishes? |
||
| Q 24. | ||
| Can humans obtain nourishment from the tiny, drifting sea animals called zooplankton? |
||
| Q 25. | ||
| In Science News, October 11, 1980, it was stated that German scientists were studying fluoride contamination in krill in Antarctica. What were the results of this study? |
||
| Q 26. | ||
| Do any animals other than whales eat krill in the Antarctic? |
||
| Q&A 1. | What are diatoms? |
||
| These are single-celled, microscopic, and strangely-formed plants of marine and fresh waters of the world. In appearance they are highly variable, and they may either grow singly or form long chains or clumps of individuals. Some elongate diatoms have slits or "raphae" along their sides. These slits are the sites for a continuous streaming movement of the body protoplasm, which sends the diatom gliding about like a miniature tank on a flat surface. Diatoms are also remarkable for being encased in a shell of silica, one half of which fits over the other like the cover of a box. These shells have formed great deposits in the sea over vast periods of time, and are responsible for the formation of diatomaceous earth, which is used in filtering processes and as a binder in the manufacture of dynamite. |
|||
| go back to Questions |
|||
| Q&A 2. | What sea animals live in shells of cellulose? |
||
| These are the strange microscopic dinoflagellates, which stand at the borderline between the plant and animal kingdoms. Because the bodies of some of them contain chlorophyll with which they manufacture their food, these particular ones, and all of them in general, are frequently considered to be true plants. On the other hand, dinoflagellates are capable of swimming freely through the water in the manner of single-celled animals by means of tiny tail-like appendages which protrude between the cellulose plates of their skeletons. |
|||
| go back to Questions |
|||
| Q&A 3. | What are krill? |
||
| This is the whaler's term applied to the swarms of tiny shrimp-like crustaceans which form the food of whalebone whales. Krill (or euphausids, as they are known by biologists) average about an inch or two in length. They are scooped out of the water and strained through the plates of baleen or whalebone attached to the whale's upper jaw. Since the whale's gullet is so narrow that it would choke on a fair-sized fish, it must consume enormous quantities of krill and other small sea animals in order to nourish its tremendous bulk. |
|||
| go back to Questions |
|||
| Q&A 4. | Is it possible that man will ever eat plankton? |
||
| The myriad of floating and drifting life in the upper layers of the ocean, mostly of very small size and collectively called "plankton", has been found to be rich in food material and if properly prepared, fit for human consumption. The main problem involved is concentrating this plankton in large amounts and separating the inedible from the edible parts. Fishes at the present time do this more efficiently than man can, and by eating the flesh of ocean fish, we indirectly get the benefit of the plankton. In the book "Kon-Tiki", the explorers tell how they strained plankton from the sea and found it bitter at first, but quite palatable after certain undesirable organisms were removed from it. During the last war German scientists also experimented with plankton as a possible source of food, though without particular success. One possible way of preparing plankton would be to press it into compact "planktonburgers", which could be fried and eaten on bread. |
|||
| go back to Questions |
|||
| Q&A 5. | What sea creature has never been positively classified? |
||
| Planktosphaera, a transparent, spherical animal about half an inch long, is occasionally brought up in plankton pets from deep ocean waters. Although this creature has been known for some fifty years, scientists have been unable to assign it to any known group of animals, although in form and structure it hints at relationship with several. It is possible that Planktosphaera may be a larval Crincid, or sea lily (a deep-sea animal related to the starfish), but this has not been established conclusively as yet. |
|||
| go back to Questions |
|||
| Q&A 6. | What is meant by "plankton" and "nekton"? |
||
| "Plankton" is Greek for "wanderer" and refers collectively to all drifting or floating sea life or that which swims so slowly that is virtually at the mercy of the wind and tide. Floating seaweeds, jelly fish, microscopic organisms, and many larval or very tiny fish are included under the name of plankton. "Nekton", also from the Greek, means "swimming", and refers to all marine animals that are able to migrate freely, such as most fish, whales, squids, etc. |
|||
| go back to Questions |
|||
| Q&A 7. | What are dinoflagellates? |
||
| Dinoflagellates are remarkable microscopic creatures found in both fresh and salt water, and have characteristics of both animals and plants, moving about freely like the former and manufacturing their food by means of chlorophyll like the latter. Actually, they are considered to be more closely related to plants by biologists, but they remain very animal-like in certain respects. One species of dinoflagellate (Gymnodinium) is believed to be responsible for the condition known as "Red Tide," while another (Noctiluca) produces phosphorescence, or "burning of the sea" at night. |
|||
| go back to Questions |
|||
| Q&A 8. | Do marine forms having free-floating larvae have an advantage over those that do not? St. Augustine, Florida |
||
| The free floating (non-pelagic) forms produce eggs with large yolk sacs upon which the young embryos feed until ready to hatch. They also feed on eggs that are not fertilized. The floating (pelagic) type larvae is divided into two groups, one which feeds entirely upon plankton and takes advantage of the ocean currents as a means of dispersal. The other feeds upon large yolky eggs and is entirely independent of the plankton as a source of food. It therefore has a much better chance of reaching the adult stage. Both forms have their advantages, except that the non-floating types are not able to take advantage of large-scale water movements, and also the large size of the eggs restricts the number that can be produced. The non-floating forms are thus not able to take advantage of large scale food increases to the extent that the free-floating forms can. |
|||
| go back to Questions |
|||
| Q&A 9. | What is plankton? Washington, D.C. |
||
| Plankton is a term of Greek origin used to describe all the various aquatic plants and animals, both marine and freshwater, which have little motility of their own. They are dependent principally on the tides and currents to transport them from place to place. While some animals classified as plankton have a certain ability to swim, such as some larval fish and certain jellyfishes, this matters little against the powers of oceanic tides and currents. The term nekton is used to describe animals, such as fish and squid, which are not planktonic and have the ability to swim. |
|||
| go back to Questions |
|||
| Q&A 10. | Why are cold water plankton forms generally larger than the warm water forms? Boston, Massachusetts |
||
| One theory advanced to account for this is that the increased density and viscosity of cold water enables large forms to keep afloat more successfully in cold water. The matter of overcoming the constant action of gravity is of tremendous importance to weak swimming animals such as small crustaceans. Another theory is that lowered temperatures lengthen the time required for the animals to reach sexual maturity. Hence in cold water forms the delay permits a longer growing period with resultant larger size at maturity. The oxygen consumption of certain non-locomotory warm water benthic species is higher than that of related cold water species and this may also have a bearing on the question. |
|||
| go back to Questions |
|||
| Q&A 11. | On a recent trip to Europe, I observed what appeared to be an illusion of rain of the surface of the sea, although it was not actually raining. What phenomenon could have caused this? New York City, New York |
||
| You may have observed a large number of small planktonic animals skipping about the surface of the water. One species of copepod, Anomalocera pattersoni, might well be called "the flying fish of the copepod world". They are very energetic and might easily give the illusion of rain. Norwegian fishermen welcome a "shower" of these animals as a good fishing indicator, since the summer herring feeds extensively upon them. |
|||
| go back to Questions |
|||
| Q&A 12. | What exactly is meant by plankton? Washington, D.C. |
||
| There is no exact definition, because the work is used to describe a good many forms of sea life which differ greatly but which it is convenient to group together. It includes all free-living plants or animals which are not strong swimmers but which drift about in the water at the mercy of currents. A newly hatched fish is part of the plankton but it is impossible to state the exact size at which it ceases to be planktonic because of its growing ability to swim. |
|||
| go back to Questions |
|||
| Q&A 13. | What is krill? New York City, New York |
||
| Most of the whales which are caught for commercial use feed on the planktonic animals which they strain from the sea water. Only a few species of whale, notably the sperm whale, catch larger prey. The plankton used by whales in the Antarctic is collectively known as krill. A shrimp-like euphausid forms a large fraction of this plankton, but young stages of certain other crustaceans may also form a fairly large fraction. |
|||
| go back to Questions |
|||
| Q&A 14. | I am conducting research on plankton and its uses. Could you tell me where I might obtain information? Tarrytown, New York |
||
| Plankton and its utilization is the subject of numerous scientific articles. You should attend a marine laboratory and take a summer course in the subject. For the time being it is suggested that you read The Sun, The Sea and Tomorrow, by Smith and Chapin (Scribners) which has a chapter on the subject in non-technical language. A more detailed account of plankton generally is The Open Sea-The World of Plankton, by Allister Hardy, published by Houghton-Mifflin. |
|||
| go back to Questions |
|||
| Q&A 15. | I have read that the blue whale, largest animal on earth, feeds entirely on krill. Just what is krill? New York City, New York |
||
| All of the baleen, or whalebone, whales feed almost exclusively on planktonic organisms. In the Antarctic, The plankton consumed by whales is known collectively as krill. A large part of this plankton is composed of small, shrimp-like animals known as euphausids, but other crustaceans are also present. Recent investigations have shown that even the baleen whales eat a small percentage of somewhat larger animals such as squids and fishes. |
|||
| go back to Questions |
|||
| Q&A 16. | Could you explain the technique of "chlorophyll count" in seawater? Palmerton, Pennsylvania |
||
| To measure the chlorophyll content in natural waters, a given quantity of water is filtered or centrifuged in order to extract the plankton. Then the residual plankton is ground and the chlorophyll pigment removed with acetone. The fluorescence of the pigment sample is then compared with that of a known quantity of chlorophyll. Based on this comparison, one can estimate the amount of chlorophyll contained in the original volume of water. From this, in turn, an estimate of the quantity of phytoplankton in the original sample can also be determined. |
|||
| go back to Questions |
|||
| Q&A 17. | What is the deep-scattering layer? Avon, Connecticut |
||
| The deep-scattering layer, or DSL, is a deep-ocean zone of concentrated pelagic animals which reflects sonar waves, creating false bottoms and hazy areas above the true bottom. It consists mainly of small shrimp-like crustaceans known as euphausids, or krill, and deep-water fishes such as lanternfishes and hatchetfishes. It is the gas bubbles trapped in the swim bladders of these fishes that scatter the sound waves and create the false returns. While the presence and movements of the DSL have been known for many years (the United States Navy became particularly interested in it during World War II when its presence interfered with submarine location with sonar), the exact composition and dynamics of the zone were investigated only recently in a project known as Ocean Acre. In this cross-section of the ocean, roughly 60 nautical miles square, off the coast of Bermuda, scientists from several institutions and the United States Navy concentrated their efforts. The project verified many previously documented facts about the zone, and identified many of the more abundant sound-scattering species (See "Ups and Downs of Deep-Scattering Layers in Oceans," Smithsonian, Vol. 7, No. 1, April, 1976). |
|||
| go back to Questions |
|||
| Q&A 18. | Harvesting of krill is discussed in the September-October, 1977 issue of Sea Frontiers. Has there been any progress toward management of this resource, so that it will not be overexploited? Yarmouth, Nova Scotia |
||
| Active experimental harvesting, product development, and biological/ecological research on the Antarctic krill resource are being carried out by many nations. These include the Soviet Union, Poland, Japan, West Germany, Chile, Norway, France, Taiwan, and the United Kingdom. The results of these efforts are contributing knowledge that will be necessary for proper management of the krill stocks when full-scale fishing begins. As a further effort to avoid ecological tragedy, the BIOMASS (Biological Investigation of Marine Antarctic Systems and Stocks) research program was adopted as an official objective by the United Nations Intergovernmental Oceanographic Commission last fall. BIOMASS is expected to begin in 1980. In addition, representatives of the 13 member nations of the Antarctic Treaty of 1959 met at Canberra, Australia this spring and agreed upon a draft convention for conservation of Antarctic biological resources. The agreement, if finalized, would provide for a commission that could set annual catch quotas for krill-a difficult task since the population dynamics of these crustaceans are not well studied as yet. Further talks are planned at Buenos Aires, Argentina, in July. |
|||
| go back to Questions |
|||
| Q&A 19. | Can you provide information on the proper care and feeding of plankton in an aquarium? Also, where can one obtain live plankton? Chicago, Illinois |
||
| The term plankton includes all free-living plants and animals which are not strong swimmers but which drift in the water at the mercy of currents. Keeping most species, either freshwater or marine, alive in an aquarium is difficult. Most plankters are ultrasensitive to water quality conditions, and many require specialized live food. The water must be kept clean and aerated, but the filtering systems generally available to the home aquarist tent to filter out the plankton as the water passes through the system. Nevertheless, there are some hardy species that can survive in an aquarium, Phytoplankton is easier to grow than zooplankton, since it requires less space and uses the nutrients present in the water. It does tend to settle out onto the bottom of the container, however, unless the water is kept circulating, and the nutrients must be replenished periodically. |
|||
| go back to Questions |
|||
| Q&A 20. | In reviewing literature about red tides, I note that in some cases dinoflagellates are referred to as animals and in other cases they are called plants. Which is correct? Columbus, Ohio |
||
| Most of the flagellates, dinoflagellates included, have been a taxonomic problem. One of the prime distinctions normally made between the organisms known as plants and those called animals is that the former are autotrophic (they "build" their own food from inorganic materials available in the environment) and the latter are heterotrophic (they ingest existing organic material). The flagellated organisms fall into a sort of gray area. Some can and do make their own food but, at times, or under certain conditions, these species will feed on other organisms. Thus, in one case, they are "plants" while, in the second, they are "animals." At the same time, some species of dinoflagellates are strictly heterotrophic (e.g., Noctiluca), while others are strictly autotrophic. As a result, many systematists assign all of these organisms to a third major kingdom, the Protista. In the five-kingdom model proposed by Robert Whittaker (Science, 1969, 163: 150-160), the Protista includes the dinoflagellates, golden algae, diatoms, photosynthetic flagellates, heterotrophic flagellates, amoebas, foraminiferans, parasitic sporozoans, and ciliates. |
|||
| go back to Questions |
|||
| Q&A 21. | I have read that the dinoflagellate Noctiluca is luminescent and produces a so-called cold light in its body from an enzymatic reaction. Has any research been done toward possibly using this same type of substance in lighting systems for man? Fort Eustis, Virginia |
||
| The reaction to which you refer involves a luminous material called luciferin which is accumulated by the dinoflagellate. To emit light, the animal triggers a chemical reaction in which the luciferin is oxidized by the enzyme luciferase (see "Luminous Creatures of the Sea," Sea Frontiers, Vol. 10, No. 3, July, 1964). Since heat is not emitted in the reaction, the light is called cold light. This biological method of producing cold light is referred to as bioluminescence. To produce light of a sufficient intensity to be useful to humans, large quantities of natural luciferin would be needed; therefore, it would not be commercially feasible to use this material. There are other chemical reactions, however, known as chemoluminescence, that do produce significant amounts of light, and they are used in the manufacture of light sticks or light wands. These devices are designed for underwater use or for use in situations in which incandescent, or hot light, is potentially hazardous (i.e., around gasoline or other volatile fluids). They are available in most dive shops and fishing supply stores. |
|||
| go back to Questions |
|||
| Q&A 22. | Is it possible to keep live krill in an aquarium? Don Mills, Ontario |
||
| Techniques for maintaining captive adult Euphausia superba (commonly called krill) in large flowing-seawater tanks were developed by the late Dr. Mary Alice McWhinnie of DePaul University. She also succeeded in rearing this small shrimp-like crustacean through the first three larval stages. Since krill are naturally found in Antarctic waters and are adapted to low temperatures, the seawater in the tank must be maintained below 39 Fahrenheit. A good flow-through system is necessary because it promotes feeding by krill by providing a continual supply of their food organisms - phytoplankton and small zooplankton. Attempts to keep E. superba in small recirculating aquariums, such as those generally available to the home aquarist, are usually unsuccessful due to lack of adequate temperature control and water movement. Some aquarium pumps and filters may even strain the plankton form the seawater. |
|||
| go back to Questions |
|||
| Q&A 23. | I want to try to raise larval marine fishes in my aquarium. Where can I obtain information on how to grow rotifers to feed newly hatched fishes? Bangor, Maine |
||
| Although among the smallest multicelled animals, rotifers have played a major role in the successful rearing of larval marine fishes. They fill the gap in sources of food between the time the fish larvae start to eat and when they are large enough to eat brine shrimp nauplii. Marine rotifers are available at aquarium stores under the name Ocean Plankton. Instructions for their culture have appeared in "The Mighty Rotifer," Freshwater and Marine Aquarium, August 1978 and "Grow Some Rotifers," Marine Aquarist, vol.8, no.4, 1977. Rotifer culture is the subject of a cooperative project currently being carried out by Dr. Terry Snell of the University of Tampa, Florida and Dr. Esther Lubzens of the Institute of Oceanographic Research in Haifa, Israel. |
|||
| go back to Questions |
|||
| Q&A 24. | Can humans obtain nourishment from the tiny, drifting sea animals called zooplankton? Stamford, Connecticut |
||
| Humans receive nourishment from zooplankton, indirectly, by consuming plankton-eating fishes. On their own, planktonic animals contain significant amounts of protein and vitamins, but most of them have mineralized parts that are indigestible and their internal salt concentration is high. Therefore, fresh zooplankton should be used only as an emergency food supplement, along with extra freshwater to rid the body of excess salt. In 1981, when IOF member Patrick Childress circumnavigated the globe single-handedly aboard Juggernaut, he experimented with fresh plankton as a possible emergency food supplement. Childress reported in Cruising World, September 1983, that zooplankton he netted off Ascension Island and tasted raw was "similar to a fish paste with a texture of wet peanut shells." Childress also tried rinsing zooplankton in freshwater to remove salt and boiling off excess water; he found that the cooked plankton tasted better, especially with a dash of Tabasco sauce. He cautioned, however, that net contents must be discarded when toxic organisms are present. Processed Antarctic krill - one form of zooplankton-is being marketed by a few countries. In general, however, considering the effort and expense necessary to harvest substantial zooplankton (concentrations vary with area and season) and to process it in a palatable manner, it may prove more efficient to let plankton-eating fishes do the harvesting. |
|||
| go back to Questions |
|||
| Q&A 25. | In Science News, October 11, 1980, it was stated that German scientists were studying fluoride contamination in krill in Antarctica. What were the results of this study? Kansas City, Missouri |
||
| The fluoride in krill (Euphausia superba) and certain other Antarctic animals is not a result of contamination. It is the result of the natural, active accumulation of fluoride by these animals. Fluoride is accumulated in high concentrations (greater than 3,00 parts per million) in the chitinous exoskeletons, or shells, of Antarctic krill. When the krill die, the fluoride rapidly moves out of the shell and into the muscle, thus prohibiting human consumption of products made from the tiny shrimp-like crustaceans. In experiments, the German scientists were able to reduce movement of fluoride into the flesh of freshly caught krill by immediately steaming them or by freezing them at -22 Fahrenheit. Why krill concentrate fluoride is not known, although there is some speculation that the fluoride serves to harden their shells. Whether animals higher in the Antarctic food chain acquire fluoride levels greater than the 1.4 parts per million in seawater by eating krill or by their own bioaccumulation is also no known at this time. Many marine animals, both in the Antarctic and elsewhere, accumulate fluoride above seawater concentration. It is generally found in their skeletal structures. |
|||
| go back to Questions |
|||
| Q&A 26. | Do any animals other than whales eat krill in the Antarctic? Halifax, Nova Scotia |
||
| Yes. In addition to the baleen whales, the large carnivores of the Antarctic region- seabirds, fishes, squids, and seals -eat krill. The shrimp-like crustaceans called krill, which eat phytoplankton and zooplankton, serve as a crucial link in the food web, as described by Stephen Nicol and William de la Mare in "Ecosystem management and the Antarctic krill," American Scientist, January-February 1993. Baleen whales depend entirely on krill for food. Crabeater seals and penguins also require krill in addition to the alternative fishes and squids that, in turn, eat krill. Bottom-living invertebrates also get nutrients from krill waste products. The tremendous ecological significance of krill drives researchers to study the effects of commercial fisheries for these animals in the Antarctic. Fishing for the most abundant krill species, Euphausia superba, grew rapidly in the late 1970s, and by 1981 annual catches peaked at 550,000 tons. The fishery declined by the mid-1980s because large markets for krill didn't develop as expected. Despite this, krill currently constitute the largest Antarctic fishing operation. Fishermen locate the two-inch krill easily in the upper layers of the ocean where the animals' dense swarms often make the surface look reddish-brown. In areas of high krill density, trawler catches amount to as much as 30 tons per hour. The 1981 Convention on the Conservation of Antarctic Marine Living Resources governs exploitation of Antarctic species (except mammals) by looking at the whole ecosystem. Debates take place, however, between fishing nations that want to ensure their harvesting rights and conservationists who suggest imposing fishing limits in South Shetland Island waters where large colonies of seabirds and seals depend on krill to survive. Researchers still don't have reliable estimates of Antarctic krill populations, which are distributed unevenly throughout an area of about 14 million square miles. They need to determine if there is just one great Antarctic stock of krill or if there are many small stocks that need individual management. Fishermen on factory shops process krill immediately to avoid spoilage. They market the small crustaceans as animal feed or as human food. The latter includes whole krill, peeled tail meat, and a paste or mince that can be used in other products. Krill paste serves as an enhancer in butter, cheese, sausages, and Siberian dumplings. Krill mince flavors soups, pie fillings, fish cakes, Scandinavian fish balls, mayonnaise, and salads. |
|||
| go back to Questions |
|||
|
|
|||
|
Rosenstiel School of Marine & Atmospheric Science Library
University of Miami, FL USA 4600 Rickenbacker Causeway, Miami, Florida 33149 Phone: 305 421 4060 Fax: 305 421 9306 E-mail: libcirc@rsmas.miami.edu |
 |
go to the top |
|