The Marine Environment

The Marine Environment - As noted before 71% of the Earths...

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As noted before 71% of the Earth’s surface is seawater Terrestrial organisms are situated on a series of islands However the marine environment is one interconnected body of water Differences in water temperatures and densities effect the movement of this water body ( thermohaline circulation ) and wind patterns effect the circulation of surface waters These in turn are effected by received sunlight radiation greatest at the equator, major seasonal differences at the poles (24 hrs in summer)
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Properties of seawater - recap Water consists of an oxygen atom and two hydrogen atoms This molecule is highly polar with a +ve end and a –ve end This polarity allows the water molecules to form weak bonds with other polar molecules Weak bonds formed between water molecules = HYDROGEN BONDS This gives water many of its properties…
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Properties of seawater - VISCOSITY Hydrogen bonds mean that there is a slight ‘stickiness’ between water molecules = VISCOSITY At the surface of the water, attraction of water molecules to each other is greater than to air, creating a “skin” = SURFACE TENSION Viscosity of water reduces the tendency of floating organisms (plankton) to sink – providing buoyancy This viscosity also increases DRAG – swimming organisms need adaptations to overcome this drag. So many organisms have a shape that is HYDRODYNAMIC (reduces drag) n.b. Viscosity increases as temperature decreases
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Properties of seawater – DENSITY/TEMPERATURE Usually density increases with decreasing temperature But the density of water decreases between 4 o C and freezing Due to formation of ice crystals (which occupy a larger volume than free water) Frozen water (ice) is even lighter (floats – 8% less dense than liquid water at same temperature) Without this ice would sink – aquatic environments would freeze from the bottom up, and aquatic life would be more difficult Marine species can survive in water underneath ice floes (e.g. Arctic Ocean)
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Properties of seawater – HEAT CAPACITY Temperature is a measure of the amount of kinetic energy (movement of molecules ) Due to hydrogen bonds, more energy needs to be added to water to make molecules move more = HIGH SPECIFIC HEAT CAPACITY Also more energy is needed to turn liquid into gas, or solid into liquid =HIGH LATENT HEAT OF VAPORIZATION etc This makes the aquatic environment more temperature stable (moderate) with less fluctuation than on land Also an important factor in climate (~movement of energy)
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Properties of seawater – SOLVENT The small size and polar nature of water makes it easy for it to interact with, come between and ‘dissolve’ substances = THE UNIVERSAL SOLVENT Substances held together by ionic bonds are especially susceptible to the dissolving action of water Therefore seawater contains many ions in solution (Na + , Cl - , K + , CO 3 - ) these ions are biologically essential But large molecules with no electrical charge don’t dissolve (e.g. oil) Also oxygen does not dissolve well in water – lower concentrations in seawater than in air
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The Marine Environment - As noted before 71% of the Earths...

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