ES 106 2006 May 3 Physics of sea water Composition A Salinity 1 parts per thousand permil sea water is 35 permil 2 salt from dissolved mineral material and volcanic gases 3 dissolved matter removed by a organisms secreting hard parts and b chemical precipitation B variations in salinity due to variations in water 1 additional water from a precipitation b melting ice c runoff 2 water removed by a evaporation b formation of sea ice polar sea salinity varies seasonally 3 variation from 33 permil to 38 permil although some marginal areas a to 42 permil Persian Gulf or b 10 permil Baltic II Temperature A Varies from equator to pole and from top to bottom B Variation with depth 1 in low latitudes it is warm at top by sun energy 2 declines sharply at about 300 m to 1000 m the thermocline 3 below about 1000 m constant to sea floor about 2o C 4 in high latitudes cold and constant from surface to sea floor 5 mid latitudes may have seasonal thermoclines C change in temperature over time would affect stability of life in the sea III Density A Affected by salinity and temperature 1 temperature has inverse relation to density 2 salinity has direct relation to density 3 because sea water salinity varies only slightly temperature has a greater affect on density of sea water B density zones with depth pycnocline is change in density with depth 1 surface mixed zone 2 a to 300 meters b depth varies with latitude and season 2 intermediate transition zone 18 includes thermocline and pycnocline 3 high density zone 80 a below 1000 m in mid latitudes b somewhat more shallow in equatorial seas c all high latitude sea water is high density I IV desalinization of sea water A Expensive 1 minor source of drinking water 2 unlikely source of agricultural water B Processes 1 distillation 2 membrane processes use semi permeable membranes 3 freezing chemical catalyst demineralization V Ocean life A Basis of sea life is algae photosynthesis 1 need sunlight 2 provides food and oxygen for other organisms B classifications 1 plankton float a phytoplankton plants algae etc b zooplankton consumers animals c most of Biosphere is plankton 2 nekton swim a confined by environment constrains of 1 temperature 2 salinity 3 depth 4 density of water 5 food sources b fish 1 most abundant near shore in cold water 2 some migrate between rivers and sea for reproduction 3 benthos organisms a live on the bottom surface of it or beneath bottom surface b seaweed and kelp live in shallow zones c deep sea home to organisms that do not need light C distribution zones controlled by 1 availability of sunlight a photic zone affected by clarity depth season time latitude b euphotic good light 1 photosynthesis to about 100 m 2 light to avoid predators to perhaps 1000 m c aphotic zone no light 2 distance from shore a intertidal zone emergent from sea at times b neritic zone 1 continental shelf from intertidal zone to shelf break at beginning of continental slope 2 may be photic to bottom 3 abundant nutrients from land runoff c oceanic zone open waters with less nutrients available 3 water depth a pelagic zone open ocean of any depth b distinct differences of nekton to benthos organisms c distinct differences from photic to aphotic d abyssal organisms are benthos and aphotic 1 high pressure of sea water due to depth 2 low temperature except at hydrothermal vents VI ocean productivity A primary from photosynthesis 1 available nutrients 2 solar radiation a seasonal b latitude control B variation by latitude 1 polar seas lack thermocline and pycnocline constant supply of nutrients due to continual mixing control due to sunlight variation a diatoms flourish in spring b copepods and krill increase after feeding on diatoms 2 tropical seas a deep sunlight penetration b permanent thermocline prevents much mixing with deeper water c nutrients depleted in surface water resulting in low biologic productivity 3 temperate seas mid latitude significant seasonal variations a winter low productivity 1 low sunlight is control 2 nutrient levels high due to mixing b spring more sunlight 1 bloom of phytoplankton 2 nutrient level plummets used up c Summer thermocline prevents mixing nutrients stay low d Fall 1 cooling allows thermocline to break down 2 nutrient levels increase allow fall phytoplankton bloom VII ocean food relationships A trophic levels amount of food energy consumed at a certain feeding stage 1 plants consumed by herbivores planktonic and larger 2 herbivores consumed by carnivores planktonic and larger B transfer efficiency 1 2 sun energy absorbed by algae becomes algae structure 2 remainder of energy used for its life processes 3 10 to herbivores to primary carnivores to top carnivores C specific web example herring of Atlantic 1 Newfoundland herring eat copepods with diatom food 2 North Sea herring more complex
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