Notes for Standard 4, Objective 2 –Oceans
Analyze the physical and biological dynamics of the oceans.
Physical—nonliving or abiotic
Biological—living or biotic
Dynamics—change or motion
The physical dynamics of the oceans are things like waves, tides, and currents.
Tides in the ocean are caused by the pull of gravity from the moon.
Waves are usually caused by wind blowing on the ocean far out at sea.
Surface currents are also caused by wind.
Deep currents are caused by cold, salty water that sinks and moves along the bottom of
the ocean. When the deep currents reach land the current is forced up, bringing up
nutrients from the bottom of the ocean. These areas where the deep currents rise up are
called upwellings. The nutrients in the upwelling make the algae grow. The algae
provide food for plankton, which are food for fish.
The physical dynamics of the ocean have major effects on the of biological dynamics
the ocean. El Nino is a good example of this idea.
During an El Nino, warm surface waters from the Western Pacific move east toward the
coast of South America. The warm waters block the nutrient-rich upwelling currents near
the coast of South America. This effects the ocean food chain and has economic impacts
for fishermen. The change in ocean temperature also changes weather patterns all over
the world.
Salinity=Saltiness
High salinity occurs in dry, warm regions where a lot of ocean water evaporates, leaving
the salt behind. High salinity also occurs in cold regions where ice forms. When ice
forms, the salt is left behind in the water, making the ocean extra salty. Where a river
runs into the ocean the salinity is decreased.
In most ocean ecosytems energy comes from the sun as light. The energy is captured by
phytoplankton--tiny plantlike organisms in the ocean such as algae. The plants change
the light energy into food (chemical) energy. Zooplankton are little animals that eat the
algae. Larger animals such as fish feed on the zooplankton. The energy eventually
leaves the ecosystem as heat from all the bodies of the animals and plants.
Ocean levels can gradually change over long periods of time (geologic time) depending
on the earth’s average temperature. During warm periods sea levels rise because of two
reasons. 1.Warm water expands. 2. Glaciers on land melt. During ice ages sea levels
drop because of two main reasons. 1.Cold water contracts. 2. Water freezes on the land
to form glaciers instead of running back into the ocean. Right now, sea levels are rising
due to global warming.