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This programme examines some of the properties of water that are relevant to the study of natural environments. The following topics are discussed: 1. Variations of density with temperature and the... production of layers of water of differing density (themocline); 2. Water as a supporting medium for organisms; 3. Light Penetration through water; 4. Dissolved oxygen in water; 5. Wave action. Taking part in the programme are Dr. R.C.I.Wilson and Dr. M.E. Varley.
Metadata describing this Open University video programme
Item code: S2-3; 01
First transmission date: 01-07-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:23:58
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Producer: Penny Crompton
Contributors: Peggy Varley; Chris Wilson
Publisher: BBC Open University
Keyword(s): Dissolved oxygen; Light penetration; Temperature; Water density variations; Water 'layers'; Water organisms; Wave action
Footage description: Chris Wilson introduces the progranme. The programme will examine some of the properties of water. Wilson uses a glass tank filled with water to demonstrate the significance of the fact that water is most dense at 4 C. He points out the thermocline between the hot and cold layers of water in the tank and explains that these occur in natural bodies of water. Wilson simulates wind and wave conditions in his tank. Peggy Varley picks up a jelly fish and places it in a jar of sea water. She explains tne importance of specific gravity of sea water bang greater than air for many organisms which live in the sea. Film sequence shows lobster walking along the sea floor. P. Varley holds a live lobster in the air to contrast the movements. The lobster cannot walk without the support of sea water. Chris Wilson with the tank which has wind and waves simulated. He adds Potassium permanganate to the water so that currents in the water can be observed. He points out the movement and shows that despite currents and wind conditions, the thermocline will survive in natural conditions. Wilson explains how the thermocline is sometimes broken down naturally. P. Varley with a graph which records the temperature of water at any given depth, (depth vs light absorbtion from the sun). Chris Wilson with the apparatus for measuring the amount of light which penetrates water at various depths. He explains the apparatus and then does the experiment. Peggy Varley plots the figures from this experiment on her graph. The results were achieved with a red filter over the light source Chris Wilson repeats the experiment, this time using a blue filter over the light source. Peggy Varley plots the readings on her graph. The two curves are compared. Red light is absorbed faster than blue light. Peggy Varley discusses what significance these findings have for living organisms. She holds up some red and some green seaweed. The red seaweed is found in much deeper waters than the green. Varley with apparatus which measures the amount of dissolved oxygen in water. She does an experiment which shows the effect of bacterial growth in water on its oxygen content. Varley with a map of the Thames between London and Gravesend. She indicates the results of oxygen surveys which have been carried out along the river. Dissolved oxygen content drops as the river flows past London. Away from London the dissolved oxygen content increases again. Varley discusses the causes for this drop in oxygen content. Varley places sample population figures for roach, stickleback, and sprat fish along the Thames. She correlates fish population figures with oxygen content figure. Chris Wilson uses a wave tank to examine the effect of orbital motion of water particles on the water's surface. A series of neutral boyancy balls in the water show the orbital motion of the water particles. Wilson shows 2 photographs of the same beach - one taken in winter, the other in summer. Summer beach in made up of sand while the winter beach is filled with boulders. Wilson uses the water tank to try to explain the reasons for this difference. The amplitude of the waves determines whether the sand is built up or washed away from the shore line.
Master spool number: 6LT/70367
Production number: 00521_2146
Videofinder number: 1649
Available to public: no