Unit 4

4:12 a PHYSICAL PROPERTIES OF WATER 1.TEMPERATURE IS THE MOST IMPORTANT LIMITING FACTOR. A change in temperature can alter many other parameters Thus thermal pollution is a serious concern. Surface water is heated by the sun and changes seasonally. A narrow zone called the thermocline separates warm surface water from cool bottom water. Divers can feel temperature differences as they go through this zone. Whales use this zone for long distance communication. Most marine animals are ectothermic (cold-blooded). Warmer water temperature increase their metabolism.

However warm water hold less O 2 so they tolerate cold Water at extremes better than water that is too warm. Mammals and a few fishes are endothermic (cold-blooded) They can usually maintain a constant body temperature. But can suffer from hypothermia just as humans do. Pollution, illness and other environmental stresses alter their ability to keep warm and maintain enzyme functions.

4:12 B Sea Surface Temperature Evaporation and energy condensation provide to run the hydrologic cycle; this energy reduces the possibility of freezing in marine organisms’ tissue. Water also has high heat capacity that allows it to absorb or release large quantities of heat with little temperature change’ helps to moderate climate. 2.Salinity is the amount of dissolved solids in water Including ions of chloride, sodium, sulfate, magnesium, Calcium and potassium.

The first four ions Listed are remarkably Constant in seawater. If The chloride ion is measured Then the other ions can be Measured. Salinity can be measured by a hydrometer as specific gravity, or by conductivity or chlorinity. Units are in parts per thousand (ppt). Surface salinity is greatly influenced by temperature. High Temperatures cause increased evaporation rates and Increased salinity

4:12 C The halocline is a place where fluctuating surface salinity Is divided from the constant of deeper water. Stenohaline organisms can Not tolerate changes in salinity. Euryhaline organisms can adapt to most fluctuations Some properties of temperature are due to the unusual Nature of the water molecule.

4:12 C cont 3.Density is mass/volume It is affected by temperature and salinity. Water is 800 times more Dense than air. Sea water Is more dense than fresh. This density causes buoyancy. Above the freezing point, the density of water is 1g/cubic centimeter When water freezes, its density decreases because the volume Increases. Ex. Hose cracking when water freezes in it.

4:12 C cont. Ice has a density of.92 grams/cm 3 so it floats in water. Any object will float in water if the density is less than the density of water it is floating in. In order to reduce an object’s density, the volume can be increased

1.The pH is a logarithmic function of the per cent of hydrogen ions in a solution In sea water, the pH is closely associated with dissolved carbon dioxide and is usually between 7.5 – 8.5

4”13 A cont. CO 2 is a reactant in photosynthesis And a product of respiration. It dissolves easily in sea water And is stored in marine shells And sediments H 2 O + Co 2 = H 2 CO 3 Water + Carbon Dioxide makes carbonic acid. that lowers the pH.

4:13 A cont.H 2 CO 3 = HCO 3 +H Carbonic acid disassociates hydrogen which raises the pH These reactions change the pH of the water. The pH is expressed on a scale from 1 – 14. Each value is 10 fold increase the previous number.

Enzyme activities and the shapes of vital proteins require a stable pH. Since Mollusk’s shells are calcium carbonate, a decrease in pH could dissolve shells.

4:13 B Dissolved Gases Dissolved nitrogen is the most common gas in the ocean because it dissolves from the gas in the atmosphere where there is 78% Nitrogen gas can’t be used by organisms until it is attached to oxygen in a process called nitrogen fixation Nitrogen fixation occurs because blue-green algae convert nitrogen gas to a useable form that animals need for Building proteins and amino acids.

4:13 B cont 3. Dissolved oxygen primarily comes from photosynthesis of marine plants and algae. They produce well over 50% Of the total atmospheric Oxygen. Oxygen is not Oxygen gas is not very soluble so most of it diffuses Into the air. Marine animals need it for respiration. Below the thermocline there is very little oxygen

4:13 b cont. 4.Carbon dioxide is highly soluble in sea water which contains about 50 times more CO 2 than the atmosphere. It enters the water from the air as well as from respiration. However it can be depleted at the surface due to use By plants. It is also necessary for shell formation. Oceans remove and store carbon dioxide which remain relatively constant between 45 and 54 mL/L of sea water

The sun emits wavelengths of energy in the form of light. Light is only 1 wavelength segment on the electro-magnetic spectrum.

4:14 A cont Marine plants (autotrophs)) Make their own food by Photosynthesis. Heterotrophs can’t make make food so they eat plants. Marine food webs depend on light that is either Absorbed or reflected as it enters the water. About 65% of the light energy is absorbed in the first five Feet and can’t be used by autotrophs. Red light is absorbed first in most marine environments. Many marine bottom dwelling animals are red. Why?

4;14 A cont Blue light is transmitted best. Why does the sky and water look blue? Light is inversely proportional to depth. As you descend it gets darker. The lighted layer is called the photic zone: about 10% of the ocean. Dark layer is the aphotic zone: 90% of the ocean is dark.

4:14 B Turbidity Turbidity is the measure of suspended and dissolved Solids. The more sediment (solids), the less light Penetration and the poorer the visibility. Photosynthesis Is reduced by turbidity. The compensation zone is the depth where the rate of photosynthesis = rate of respiration. Oxygen production = carbon dioxide consumption

4:14 B cont. The zone’s depth depends on light/ turbidity raises the compensation zone. Turbidity can be measured with a secchi disk as visibility Divide the depth of the secchi disk line by the water’s depth. Turbidity is usually lower in areas of high productivity. Filter-feeders use some of the TSS (total suspended solids) for food.

4:15 A Pressure Pressure at sea level is the Weight of air (14.7 lbs/in 2 ). As you descend pressure results from the weight of the Water above you (hydrostatic pressure) as well as The air pressure. For every 33 feet = 1 atmosphere of pressure 14.7 lb/in 2 At 100 feet = 4 atmospheres of pressure 58.8 lb/in 2 The pressure in the Mariana Trench is 7 tons/ 2 This tremendous pressure lowers water’s freeing point without affecting the volume.

SCUBA tanks contain air under pressure so that the internal pressure inside the lungs equals the pressure on the external surfaces exerted by the water. 4:15 A Cont.

4:15 A When ascending, the air volume in your lungs expands. The lungs could be ruptured if you do not continuously exhale There is a limit to how much pressure a person can withstand. It varies due to experience but safe recreational diving stops at 130 ft.

4:15 B Molecular Arrangement of Water The shape of the water molecule gives it special properties that effect marine organisms. 1.Viscosity is the resistance to flow; it provides buoyancy for plankton while increasing the energy used by nekton to swim. 2.Surface tension is the attraction of surface water molecules. They provide limited support for insects & larvae 3.Water is the universal solvent. Many substances will dissolve in water which helps dilute the harmful waste products of animals.

Relationships of Parameters The properties of water are interconnected. their relationship to each other demonstrates how easily the delicate balance can be upset. By examining relationships, the effect that one parameter has on another can be predicted

4:15 B cont. A direct relationship is when two parameters both increases or decreases at the same time An inverse relationship is when 1 parameter increases while the other parameter decreases. Generally, as you descend, the ocean becomes colder, denser, saltier, and more pressure, less light and fewer gases.

That’s all Folks!