Ocean Water and Ocean Life

Salinity◦ total amount of solid material

dissolved in water◦ Expressed in parts per thousand◦ Mostly sodium chloride

Sources of Sea Salt◦ Chemical weathering of rocks on

the continents◦ The Earth’s Interior

Decrease Salinity◦ Precipitation◦ Sea ice melting◦ Icebergs melting◦ Runoff from land

Increase Salinity◦ Evaporation◦ Formation of sea ice

Surface water temperature varies with the amount of solar radiation received

Thermocline is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of temperature with depth

Density is defined as mass per unit volume

Seawater density is influenced by two main factors: ◦Salinity◦temperature

Pycnocline is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of density with depth

3 main zones – surface zone, transition zone, and deep zone

Surface Zone◦ Shallow (300 to 450 meters)◦ Zone of mixing◦ Sun-warmed zone

Transition ZoneBetween surface layer and deep zoneThermocline and pycnocline

Deep ZoneSunlight never reaches this zoneTemperatures are just a few degrees above freezingConstant high-density water

Marine organisms can be classified according to where they live and how they move.

Planktonall organisms—algae(Phytoplankton),

animals(Zooplankton), and bacteria—that drift with ocean currents.

Nektonanimals capable of moving independently

of the ocean currents (swimming, etc)Benthos

organisms living on or in the ocean bottom

Three factors are used to divide the ocean into distinct marine life zones:the availability of sunlightthe distance from shorethe water depth.

Availability of SunlightThe photic zone is the upper part of the ocean into

which sunlight penetrates.

Intertidal Zone◦ strip of land where the land

and ocean meet and overlap Neritic Zone

◦ extends from the low-tide line out to the shelf break

Oceanic Zone◦ beyond the continental shelf

Zone where seawater seeps into the ocean floor through cracks in the crust.water temperatures of 100oC or higher support

communities of organisms found nowhere else in the world

Primary productivity is the production of organic compounds from inorganic substances through photosynthesis or chemosynthesis

Polar OceansPhotosynthesis limited by low solar energy

Tropical OceansProductivity limited by lack of nutrients

Temperate OceansSunlight and nutrient supply controls

productivity