Plankton And The Open Sea (1962)

for lives they must adjust to the alternating and air as man on the other hand intertie of in the open sea to study Shore Waters he must depend upon ships to carry to collect and analyze seawater he must have Nets to strain living things from the sea Ure the success of a marine Expedition there must be crew members to operate the ship guiding his ship to the right place at the right [Music] time some studies require only short trips to gather materials for later examination others involve Journeys lasting as long as a year and a half and covering the distance around the world [Music] [Music] [Music] on a long Voyage the ship serves as the floating laboratory the scientists aboard study samples of water and of living organisms while the ship travels from one collecting location to another a sample of water brought on board with a bucket appears surprisingly clear and transparent but an occasional jellyfish May remind us that these Waters support animal life what do these animals of the Open Sea feed upon living as they do in a vast expanse of water that covers almost 34 of our planet for only about a quarter of our Earth is dry land we know that on land green plants are the basic source of food for all animal life but where are the Green Pastures of the Open Seas what is it that converts the sun's energy into food for the abundance animal life we find here to study the ocean systematically scientists must have the constant cooperation of captain and crew to sample a particular spot they must stop the ship samples of water must be made at carefully recorded locations and depths a collecting device called a nanson bottle is used to collect samples of sea water when the bottle is at a predetermined depth a weight is dropped to it this causes the bottle to turn over record the temperature of the water and at the same time fill and close taking a water sample which can be analyzed for chemical composition for collecting plants and animals in larger quantities a net is used instead of a nansen bottle once the ship is moving again the net is lowered into the sea such a net can be towed at a predetermined depth thus it strains out suspended plant and animal life and accumulates it in a detachable bucket at the narrow end of the net [Applause] such a collection can be studied while still alive or preserved for study at a later [Applause] time before the invention of the microscope even the best observers could not know as we do now that the base of the Marine economy is the floating invisible green Plankton of the sunlit surface waters these Plankton range in size from microscopic forms to those just visible to the uned eye the best known members of the plant Plankton are the datom one- celled greenish Brown plants enclosed in transparent shells of silica countless millions of these dats float in the lit upper layers of water and are eaten by several kinds of minute herbivores in the sea some datom live joined together in long chains others exist as separate individuals individuals that assume a vast number of different shapes some have shells drawn out into long fine projections that increase surface area and help to keep the datom from sinking though datom are endlessly varied in shape they are all alike in containing the green pigment chlorophyll and in carrying on photosynthesis datom are not the only green organisms that serve as primary food producers in the Marine economy they share this role with many smaller but even more numerous green flagellates propelled by whip-like flagella the flagellates move like animals living among the plant Plankton and feeding upon them are many kinds of animal Plankton common among the one cell animals are the radiolarians other one celled animals are the foraminifer despite their elaborate skeletons these are related to the familiar freshwater amibas not all plantonic animals are Unis cellular almost every important group of animals from fish downward are represented in the Plankton by adults or laral forms or both especially carnivorous are the jellyfishes and comb jellies also notable among mult M cellular animal Plankton is the Slender and transparent Arrow worm during certain Seasons Arrow worms are exceptionally abundant and at such times form the principal food of some fishes common and easily recognized Are embryonic snails and ciliated laral forms of snails called villagers however the most important animal Plankton are crustaceans among crustations the tiny copap pods are the most numerous occupying a niche comparable to that of abundant Plante eating insects on land copap pods feed on the basic food producers the datom and flagellates converting these microscopic forms into food large enough to be eaten by many small carnivores and even by fishes other common larel St ages are those of analid worms and of crabs and other Crustaceans none are strong enough to swim against sea currents and they drift about like the smaller Plankton fish eggs are abundant in plankton the eggs hatch and in time the laral fishes may leave the Plankton though some return to feed planktonic young of such animals as seaw worms and sea urchins descend to the ocean floor as they mature there they become bottom dwelling adults as we can see by looking at the digestive tract of a crustation green Plankton is the major food in turn small crustations may be eaten by small fishes small fishes are eaten by larger fishes ever since the first toe net was pulled behind a boat men have put to Sea to study Plankton organisms and their role in the natural economy of the [Applause] sea scientists have also been analyzing the sea water itself and the conditions under which sea waterer best supports plankton in cold Waters they find the greater concentration of Plankton than in warm Waters seawater samples from cold Waters show a higher content of dissolved oxygen carbon dioxide and of phosphates and nitrates all of which are important for the growth of plant Plankton samples of sea water collected in nanson bottles are analyzed for oxygen content by the Winkler method which involves titration the technician begins with a bottle containing a known measured amount of water to this he adds an analytic reagent and iodine the result is a yellow precipitate then while a Mixer keeps the solution uniform he adds starch yielding a blue color finally another reagent is added slowly the amount of reagent required to turn the solution colorless again is a measure of oxygen content while the nanson bottle is underwater the water temperature is recorded on board a scientist reads the thermometer such temperature readings are compared with data on ox oxygen content and Plankton density over large areas of the sea in this way we have found out that the higher the oxygen content the greater the concentration of certain Plankton samples taken in nanson bottles Also may be analyzed for phosphorus content and the solution is allowed to stand it gradually becomes blue in color a portion of the resulting blue solution is then put in a container called an absorption chamber the chamber is inserted in a spectr photometer and the light it absorbs is measured at certain wavelengths thus the concentration of phosphorus can be measured in this way measuring samples from various depths scientists have determined that phosphates are concentrated in deep Waters they are less concentrated at the surface where Plankton use phosphates and other minerals analysis is carried on while a ship cruises to other locations when the ship is stopped technicians lower their sampling apparatus samples from the Bottom of the Sea contain living animals if the depth permits sunlight to penetrate plants also are found it has been shown that animal Plankton respond to light during daylight most move downward at night they move up toward the surface again but a floating laboratory does have limitations some samples are preserved for later study in Laboratories where more extensive equipment and more time for examination of specimens is available thus a ship heads back to Port Laden with samples for later study in a laboratory on land a biologist sets out to determine the quantity of Plankton per volume of collected sample first he carefully measures sample volume he filters the Plankton from the sample then he determines the decrease in total volume of the sample after their removal he records these data finally he assembles the Plankton filtered from the [Music] sample he examines them under a microscope and sorts them into groups of similar forms from such analyses of kind and quantity scientists can learn about the distribution of Plankton species over the oceans of the world of the dependence of one kind of Plankton upon other kinds and of the amount of food available at the base of marine food chains as human population increase our interest in the unexploited pastures of the Seas grows sharper and more urgent as a result Marine Expeditions are becoming more frequent and more promising in what they can reveal of Plankton and the Open Sea