3. • Picture courtesy NASDA/NASA
This is an image of global sea surface temperatures taken from Japan
National Space Development Agency's (NASDA) AMSR-E instrument
aboard NASA's Aqua spacecraft on August 27, 2003. The colors in this
false-color map represent temperatures of the ocean's surface waters,
ranging from a low of -2 C (28 F) in the darkest green areas to a high of
35 C (95 F) in the brightest yellow-white regions. Sea ice is shown as
white and land is dark gray.
4. Temperature
• Thermo-haline surface circulation: Thermohaline
circulation simply refers to global density-driven
circulation (convection) of the oceans.
5. Oceanic currents
• Trade winds cause circles near equator
• Westerly winds carry polar water towards equator
• Labrador current –very cold
• Equator currents slosh towards east after continetal heating
• Gulf currents –very warm
6. • The flow of cold, saline surface water (blue)
downward and toward the equator can only
be clearly recognized in the Atlantic. Warm
surface water (red) flows in the opposite
direction,
7. Factors affecting: Oceanic
currents
• Another key factor that influences ocean
currents is the density of seawater. Both
temperature and salinity contribute to
seawater density, thus local changes in
temperature and the magnitude of
freshwater inputs from rivers and streams
can alter near shore ocean currents.
8. Marine upwelling
• Winds near the peninsula
push warm water away from
the surface allowing deep,
cool, nutrient-rich water to
rise, bringing nourishment to
plankton, the basis of the
oceanic food web. This
process of upwelling is
essential to the ocean oasis.
• Remains of dead,
decomposing organisms sink
to the ocean bottom making
these deep, cold waters rich
in nutrients. However, it is in
the upper, sunlit layers of the
ocean that phytoplankton
(very small drifting plants) are
able to utilize these nutrients.
10. Temp. Tolerance
• Eurythermic species
• Stenothermic species
• There are many different ecosystems within the ocean depending on
conditions such as the water temperature, the amount of sunlight that filters
through the water, and the amount of nutrients.
• Sunlight breaks through the top layer of ocean water. It can make its way as
deep as 200 meters (656 feet).
• Almost all marine life (about 90%) lives within this top, sunlit layer of the ocean.
• The temperature of ocean water varies depending on its location. Water
near the polar regions is colder than water near the equator. Water that is
deep in the ocean is colder than water that is near the ocean surface.
• Many animals and other organisms can only survive at certain temperatures.
• Others are able to survive at wide range of temperatures and can live in
more places in the ocean.
11. Temperature tolerance and
Migration
• Because cold-blooded fish live within a small temperature range
(stenothermic).
• Many fish try to stay within what is called their thermal optimum —
not too warm, not too cold — just right. This thermal optimum varies
for different species.
• Water temperature is a key factor for fly fishermen who chase
striped bass and other game fish along the Atlantic seaboard.
• In spring, as the ocean starts to warm, the first arrivals from the south
will be striped bass and bluefish, followed later by bonito and little
tunny (false albacore).
• This pattern reverses itself as the water starts to cool in the fall, when
the albies and bonito generally head south first. Looking in more
detail at the stripers, their spring migration may be more closely tied
to the northward migration of prey, such as herring, which in turn
are probably influenced by warming water and spawning urges.
13. Antarctic creatures
• About 200 species have been
discovered. These include midges,
mites and tardigrades.
• Krill are found in huge swarms which
cover hundreds of kilometers in the
waters around Antarctica.
• Many of the fish that live in
Antarctica have 'antifreeze' in their
bodies to stop their body fluids from
freezing. Seaweeds, sponges,
corals, worms, sea anemones and
sea spiders are just some of the
creatures to be found on the bottom
of the Antarctic oceans.
17. Global
warming
affecting
(changes in)
oceanic
temperature
• Courtesy NOAA
Three-dimensional view of projected surface air
temperature and ocean warming due to greenhouse
gases as calculated by a low-resolution GFDL coupled
ocean-atmosphere climate model.
18. LIGHT
• The visible light spectrum is the section of the electromagnetic
radiation spectrum that is visible to the human eye. It ranges in
wavelength from approximately 400 nm to 700 nm and is also
known as the optical spectrum of light.
Electromagnetic spectrum
19. Fate of light in aquatic systems:
• Reflection - prevented
from entering water by air-
water surface interface
• Scattering - suspended
particles reflect light at a
massive array of angles
• Absorption - diminution of
light by transformation into
heat energy
20. Visible light penetration
• Visible light penetrates
into the ocean, but
once past the sea
surface, light is rapidly
weakened by
scattering and
absorption (coastal
water). The more
particles that are in the
water, the more the
light is scattered. This
means that light travels
farther in clear water
(open ocean).
21. Light: Oceanic Zonation
• 45% of red and 2% of
blue light is absorbed
for every meter of
depth.
• Euphotic zone (00 to
200 m)
• Disphotic zone (200 to
1000 m)
• Aphotic zone (1000 to
4000 m)
• Abyssal zone more than
4000 m.
22.
23. Photic zone animals
• he dark backs and
light undersides of
• these near-surface
fish help them match
• their environment in
the open ocean. To
• a predator looking
from above, their dark
• backs seem to blend
into the dark depths.
• From the side, their
lighter sides blend
• with the sunlit water
24.
25. Deep sea animals
• Several organisms living in ocean depths have
red coloration. Their red color effectively
makes them “disappear” in the inky darkness,
because no red wavelengths are present.
• Many deep sea organisms are able to
produce their own light, called
bioluminescence. Some animals, like the
viperfish, possess bioluminescent organs on
their bellies. As they migrate upwards to find
food in shallower depths, where some visible
light does penetrate, the bioluminescent
organs on their bellies brighten.
26.
27.
28. Many bristlemouth species, such as the "spark angle -mouth"
above, are also bathypelagic ambush predators which can
swallow prey larger than themselves.
29. Light: Vertical migration
• Figure 1. Vertical distribution of the sardine
(Sardina pilchardus) in the Thracian Sea. The dots
show the observed average depths, and the solid
line shows the predicted average depth of the
distribution according to a cosine function model
based on the time of day.
30. • Plankton at the sea surface is
consumed by vertically migrating
midwater fishes and squids. The
daily migrations of these midwater
species take them to the surface at
night to feed, and to depths below
500 meters during the day. This
helps them avoid predators by
keeping them in constant darkness.
However, these vertical migrators
decend on the bottom during
daytime (downward migrations),
are available to bottom dweller
wreckfish to consume them. This
vertical migration completes a
transfer of energy from sunlit
surface layers to the dark depths
where wreckfish dwell
31. • Marine zooplankton perform daily
excursions (i.e., vertical migrations) up
and down in the water column, with
changing levels of light triggering these
daily migrations. For example, the
classic pattern consists of zooplankton
residing deep in the water column
during the day when light levels are
high. They ascend at dusk to the
surface waters where they graze on
phytoplankton at night.
32. • Red flabby whale fish make nightly
vertical migrations into the lower
mesopelagic zone to feed on
copepods.
34. Oxygen
• Oxygen is a very important gas in the ocean
because of its role in biological processes.
Marine plants such as phytoplankton ,
seaweed, and other types of algae produce
organic matter from carbon dioxide and
nutrients through photosynthesis , the process
that produces oxygen.
• The upper 10 to 50 meters (33 to 164 feet) of
the ocean can be highly supersaturated with
oxygen owing to photosynthesis.
35. Factors governing DO
• Atmospheric pressure, temperature and the rates of
photosynthesis and decomposition.
• Oxygen is produced during photosynthesis and consumed
during respiration and decomposition (compensation
depth). The latter processes occur throughout the day and
night, while the former occurs only during the day. For this
reason, dissolved oxygen levels are often lowest just before
dawn before photosynthesis resumes.
• Since the concentration of oxygen in our atmosphere is about
21%, and only a fraction of 1% in water, oxygen seeks
equilibrium by dissolving into water. This diffusion is increased
by any turbulent flow over riffles in the creek, or by wind-driven
waves both of which increase the surface area through which
the diffusion can occur.
• The other major control of DO concentration is water
temperature. Cold water can hold more dissolved gas than
warm water.
36. Relationship between
temperature and DO
• Oxygen has
limited solubility
in water, usually
ranging from 6
to 14 mg L -1
• Oxygen
solubility varies
inversely with
salinity, water
temperature
and
atmospheric
and hydrostatic
pressure.
38. DO at different depths
• Surface is richest due
to surface diffusion
and photosynthesis
• Minimal zone where
respiration exceeds
the photosynthesis
• The deeper zone
retains oxygen due to
less respiration and
decomposition rate
39. Oxygen regime at depths
• Compensation depth is
the balance between
the photosynthesis of
phytoplankters and the
oxygen cosumed in
respiration of all
organisms and
decomposition.
40. Diurnal pattern of DO
• Diurnal pattern of
DO in sea shallows
control the
vertical migration
of zooplankters
and fish
41. Salinity
• Definition: Total amount of solid materials in
grams dissolved in one kilogram of sea water
when all the carbonate has been converted
to oxide, the bromine and iodine replaced by
chlorine and all organic matter completely
oxidized.
• It is calculated by Knudsen’s formula
• It is referred by ppt (part per thousand or % )
• Salinity is an ecological factor of considerable
importance, influencing the types of
organisms that live in a body of water.
42. • Marine waters are those of the ocean,
another term for which is euhaline seas. The
salinity of euhaline seas is 30 to 35. Brackish
seas or waters have salinity in the range of
0.5 to 29 and metahaline seas from 36 to 40
• On average, seawater in the world's oceans
has a salinity of about 35 ppt.
• Although the vast majority of seawater has
a salinity of between 31 ppt and 38 ppt,
seawater is not uniformly saline throughout
the world.
• Climate, weather, currents and seasons can
all have an affect on salinity.
43. Extremes of salinity
• Where mixing occurs with fresh water
runoff from river mouths or near melting
glaciers, seawater can be substantially
less saline.
• The most saline open sea is the Red Sea
(41 ppt), where high rates of evaporation,
low precipitation and river inflow, and
confined circulation result in unusually
salty water.
• The salinity in isolated bodies of water like,
the Dead Sea ranges between 300 and
400 ppt.
44. Conveyor belt
• The degree of salinity in oceans is a driver of the
world's ocean circulation, where density changes
due to both salinity changes and temperature
45. Salinity tolerance
• Euryhaline organisms are able to adapt to a wide range
of salinities. An example of a euryhaline fish is the molly
(Poecilia sp.) which can live in fresh, brackish, or salt
water. The European shore crab (Carcinus maenas) is an
example of a euryhaline invertebrate that can live in salt
and brackish water. Euryhaline organisms are commonly
found in habitats such as estuaries and tide pools where
the salinity changes regularly. However, some organisms
are euryhaline because their life cycle involves migration
between freshwater and marine environments, as is the
case with salmon and eels.
• The opposite of euryhaline organisms are stenohaline
ones, which can only survive within a narrow range of
salinities.
46. • Salinity tolerance leads to zonation in
estuarine plants and animals. Estuarine
organisms have different tolerances and
responses to salinity changes.
• Many bottom-dwelling animals, like
oysters and crabs, can tolerate some
change in salinity, but salinities outside an
acceptable range will negatively affect
their growth and reproduction, and
ultimately, their survival.
• Some groups of animals, such as the
echinoderms, which include animals such
as sea stars, brittle stars and sea
cucumbers, have very few species living
in estuaries because of their low
tolerance of reduced salinity.
50. pH
• pH is generally understood to be an
expression of acidity or the hydrogen
ion (H+) concentration in water. The
value is a negative (reciprocal)
logarithm, which means that acidity
increases as the value decreases and
that each unit change reflects a 10-
fold change(logarithmic).
51. • Normal pH values in sea water are
about 8.1 at the surface and decrease
to about 7.7 in deep water.
• Many shellfish and algae are more
sensitive than fish to large changes in
pH, so they need the sea’s relatively
stable pH environment to survive.
52. • pH balance is one of the biggest factors
in affecting marine life. The ocean
absorbs vast amounts of carbon dioxide
from the atmosphere, which reacts with
the water and produces carbonic acid.
This causes the water's natural pH
balance to lower to an increased acidic
level. This damages marine life because it
destroys the essential calcium in the
water that is needed to build their
internal and external skeletons.
53. • Shallow waters in subtropical regions
that hold considerable organic matter
often vary from pH 9.5 in the daytime
to pH 7.3 at night. Organisms living in
these waters are able to tolerate these
extremes
54. • As the carbon dioxide is absorbed, it
reacts with the ocean water to form
carbonic acid. This process is called
ocean acidification. Over time, this
acid causes the pH of the oceans to
decrease, making ocean water more
acidic.