SALINITY. Dissolved in the ocean water are ions which account for 3.47% of the weight of seawater.
Bio. Significance. The density effect of changing salinity is most pronounced in the constantly low-temperature waters of the high latitudes. Here, during winter months when ice is forming, surface waters become salty enough to make them sink to the deep-ocean floor. They carry with them the oxygen needed by the animal populations of the deep ocean. Throughout the oceans, organisms must cope with any osmotic regulatory problems created by differences in the salinity of their body fluids and the salinity of the ocean.
LIGHT TRANSMISSION. Sixty-five percent of the solar radiation hitting the ocean surface is infrared. It is virtually all absorbed and converted to heat in the top 10 cm of the ocean. The visible wavelengths penetrate deepest. Of the total solar radiation that strikes the ocean surface, 55% is absorbed in the top 1 m, 80% is absorbed in the top 10 m, and less than 0.5% penetrates below 100 m.
Bio. Significance. Light provides the energy for photosynthesis. Energy is then transmitted in a chemical form through food chains. The heating of surface waters produces a density stratification that is permanent at low latitudes. This pycnocline prevents nutrient-rich deep water from mixing with sunlit surface water. Throughout much of the open ocean, this barrier is a major factor in limiting productivity.
SOUND TRANSMISSION. Ocean water transmits sound better than most fluids. The speed of sound increases with increasing temperature.
Bio. Significance. Many animals produce sounds. Fish generate sound with their swimbladders, crustaceans make clipping sounds, and mammals emit a variety of sounds.
CURRENTS. Mass movement of water in the
oceans is of two basic types. Horizontal ocean currents are driven
by the prevailing wind systems. This circulation in large ocean
basins takes the form of large rotating gyres. They rotate clockwise
in the Northern Hemisphere and counterclockwise in the Southern
Hemsiphere.
Deep-ocean circulation is driven by the sinking of dense water
in the high latitudes where there is no density stratification
separating the surface water from the deep water.
Bio. Significance. Many marine animal
migrations are designed so that pelagic eggs can be spawned into
the ocean at a location that assures they will be carried to a
place where appropriate food will be available when they hatch.
Upwelling of nutrient-rich deeper water to the sunlit surface
produces local areas of prolific biological productivity. Upwelling
occurs when surface currents flow past one another or a landmass
with a particular orientation.
Life in the deep ocean depends on the oxygen carried by sinking
high-latitude water masses.
WAVES. Energy is transmitted across the ocean by waves which may be driven by wind (swell and surf) or the gravitational attraction between the earth, sun, and moon (tides).
Bio. Significance. Wind-generated waves
are responsible for the mixing of the surface layer of ocean water
so that nutrients can be returned to the sunlight surface waters
instead of droppingin an uninterrupted fall through the photosynthetic
zone. The continual release of energy by these waves in the surf
zone has been a major factor in determining the life forms that
have evolved in the nearshore and intertidal benthic communities.
The tides ebb and flow, alternately covering and exposing portions
of the shore. The zonation of intertidal life forms has resulted
from the varying degrees to which benthos have adapted to exposure
during low tide.
PHYSICAL STATES. Water is the only substance
that occurs as a gas, liquid, and
solid within the temperature range found at the earth's surface.
Bio. Significance: As a gaseous component
of the atmosphere, water helps transfer
heat from warm low latitudes to cold high latitudes. As a liquid,
water runs across the
continents dissolving minerals from the rocks and carrying them
to the oceans. It is this
form of water that accounts for over 85% of the mass of most marine
organisms and serves
as the medium in which the chemical reactions that support life
occur. Liquid water also
contributes to heat transfer through ocean currents. Solid water
(Ice), during the winter
season at the higher latitudes increases surface salinity and
makes possible the sinking of
dense surface water. This water is the only source of oxygen for
the deep ocean.
SOLVENT PROPERTY. Water can dissolve more substances than any other common liquid.
Bio. Significance. Ocean water carries
dissolved within it the nutrients and oxygen required
by marine organisms. This has produced the "saltiness"
of the ocean.
HEAT CAPACITY. The quanity of heat required
to change the temperature of 1 gram of a
substance 1 Degree Celsius. Water has the highest heat capacity
of all common liquids.
Bio. Significance. It is this property
that makes water an important moderator of climate.
It accounts for the narrow range of temperature found at any location
in the ocean. Because
water can gain or lose a tremendous amount of heat without changing
its temperature it acts
as an insulator for marine life.
LATENT HEAT OF MELTING. The quantity
of heat gained or lost per gram by a substance
changing from a solid to a liquid or from a liquid to a solid
without a change in temperature.
The latent heat of melting for water is 80 cal, the highest of
all common substances.
Bio. Significance. When ice forms, most
of the heat energy lost is released to the
heat-deficient atmosphere. When ice melts, the energy gained by
the water is manifested
as molecular energy of the liquid water. This prevents the high-latitude
ocean from
becoming much warmer or colder than the freezing point of seawater.
LATENT HEAT OF VAPORIZATION. The quantity
of heat gained or lost per gram
by a substance changing from a liquid to a gas or from a gas to
a liquid without a change
in temperature.
Bio. Significance. A great amount of
excess heat energy is removed from the low-latitude
ocean by evaporation and released through precipitation into the
atmosphere at heat-deficient
higher latitudes. This property contributes greatly to the fact
that the polar regions do not get
increasingly colder and the equatorial region does not get increasingly
hotter.
SURFACE TENSION. Highest of all common
liquids. Cohesive attraction of hydrogen
bonds causes a "skin" one molecule thick to form on
a water surface and helps to make
capillarity possible.
Bio. Significance. Some organisms use
this "skin" as a walking surface. Others hang
from its undersurface.
DENSITY. Mass per unit of volume. Density
is increased by increasing salinity and
pressure and decreasing temperature.
Bio. Significance. Plankton that stay
near the surface through bouyancy and frictional
resistance to sinking are greatly influenced by the effect of
temperature on density.
In low-density warm water, plankton must be smaller or more ornate,
thereby increasing
the ratio of surface area to unit of body mass, in order to reduce
their rate of sinking.