1. Ocean Water and Ocean Life
Oceanography

2. Composition of Seawater
One of the most obvious differences between pure water and seawater is the salty taste.

3. Composition of Seawater
The dissolved substances include sodium chloride, other salts, metals, and dissolved gases.

4. Composition of Seawater
Every known naturally occurring element is found dissolved, at least trace amounts, in seawater.

5. Composition of Seawater
The salt content makes it unsuitable for drinking or irrigation, but many parts of the ocean are full of life adapted to this environment.

6. Salinity The total amount of solid material dissolved in water.
The ratio of the mass of dissolved substances to the mass of the water sample.

7. Salinity
Because the proportion of dissolved substances in seawater is such a small number, oceanographers typically express salinity in parts per thousand.

8. Salinity
What is the salinity of seawater?
3.5%
35‰

9. Salinity
Most of the salt in seawater is sodium chloride, common table salt.

10. Sources of Sea Salts
Chemical weathering of rocks on the continents is one source of elements found in seawater.

11. Sources of Sea Salts
These dissolved materials reach oceans through runoff from rivers and streams at an estimated rate of more than 2.3 billion metric tons per year.

12. Sources of Sea Salts
The second major source of elements found in seawater is from the Earth’s interior.

13. Sources of Sea Salts
These dissolved materials come from volcanic eruptions 4 billion years ago.

14. Sources of Sea Salts
Certain elements—particularly chlorine, bromine, sulfur, and boron—exist in much greater quantities than could be explained by weathering of rocks alone.

15. Processes Affecting Salinity
Because the ocean is well mixed, the relative concentrations of the major components in seawater are essentially constant.

16. Processes Affecting Salinity
Some of the different processes that affect the amount of water include precipitation, runoff from land, iceberg melting, and sea ice melting.

17. Processes Affecting Salinity
Other processes, evaporation and formation of sea ice, remove large amounts of fresh water.

18. Processes Affecting Salinity
Variation in ocean surface temperature and surface salinity

19. Ocean Temperature Variation
The ocean’s surface water temperature varies with the amount of solar radiation received, which is primarily a function of latitude.

20. Temp Variation with Depth
If you lowered a thermometer from the surface of the ocean into deeper water, what temperature pattern do you think you would find?
Warmer water on top.

21. Temp Variation with Depth
At a depth of about 1000 meters, the temperature remains just a few degrees above freezing and is relatively constant below this level.

22. Temp Variation with Depth
Thermocline—layer of ocean water between about 300 and 1000 meters, where there is a rapid change of temperature with depth.

23. Temp Variations with Depth
The thermocline is a very important structure in the ocean since it creates a vertical barrier to many types of life.

24. Temp Variation with Depth
Low Latitude vs High Latitude

25. Ocean Density Variation
Density is a property of matter defined as the mass per unit volume.

26. Ocean Density Variation
Density is an important property of ocean water because it determines the water’s vertical position in the ocean.

27. Ocean Density Variation
Density differences cause large areas of ocean water to sink or float.

28. Factors Affecting Density
Seawater density is influenced by two main factors: salinity and temperature.

29. Factors Affecting Density
An increase in salinity adds dissolved substances and results in an increase in seawater density.

30. Factors Affecting Density
An increase in temperature results in a decrease in seawater density.

31. Factors Affecting Density
Temperature has the greatest influence on surface seawater density.

32. Factors Affecting Density
Temperature vs. density

33. Density Variation with Depth
Temperature and salinity—and the resulting density—vary with depth.

34. Density Variation with Depth
Pynocline is the layer of ocean water between 300 and 1000 meters where there is a rapid change in density with depth.

35. Ocean Layering
The ocean like Earth’s interior is layered according to density.

36. Ocean Layering
Oceanographers generally recognize a three-layered structure in most parts of the open ocean.

37. Ocean Layering Three layers: A shallow surface mixed zone.
A transition zone.
A deep zone.

38. Surface Zone
Solar energy is received here, and it is here that the water temperatures are the warmest.

39. Surface Zone
Mixed zone is the area of the surface created by the mixing of water by waves, currents, and tides.

40. Surface Zone
Usually extends to about 300 meters.

41. Transition Zone
Below the sun-warmed zone of mixing, the temperature falls abruptly with depth.

42. Transition Zone
Distinct layer existing between the warm surface layer above and deep zone of cold water below.

43. Transition Zone
This zone includes the thermocline and the pycnocline.

44. Deep Zone
Below the transition zone.
Sunlight never reaches this zone.

45. Deep Zone
Water temperatures are just a few degrees above freezing.

46. Deep Zone
Water density in this zone remains constant and high.

47. Ocean Layering
In high latitudes, the three-layered structure doesn’t exist.

48. Ocean Layering
The three layers do not exist because there is no rapid change of temperature or density with depth.

49. Ocean Layering
Good vertical mixing is able to happen in the high latitudes.

50. Ocean Layering
Cold high-density water forms at the surface, sinks, and initiates deep-ocean currents.

51. The Diversity of Ocean Life
A wide variety of organisms inhabit the marine environment.

52. The Diversity of Ocean Life
Marine biologists have identified over 250,000 marine species, and is constantly increasing as new organisms are
discovered.

53. The Diversity of Ocean Life
Most marine organisms live within the sunlit surface waters.
The strong sunlight supports photosynthesis for marine algae.

54. The Diversity of Ocean Life
Algae either directly or indirectly provide food for the majority of organisms.

55. Classification of Marine Organisms
Marine organisms can be classified according to where they live and how they move.

56. Classification of Marine Organisms
Marine organisms can be classified as either plankton (floaters) or nekton (swimmers), and all others are benthos, bottom dwellers.

57. Plankton
Plankton include all organisms—algae, animals, and bacteria—that drift with the ocean currents.

58. Plankton
Just because plankton drift does not mean they are unable to swim.
Many plankton can swim but either move very weakly or move only vertically.

59. Plankton
Among plankton, the algae that undergo photosynthesis are called phytoplankton.
Animal plankton are called zooplankton.

60. Plankton
Zooplankton include the larval stages of many marine organisms such as fish, sea stars, lobsters, and crabs.

61. Nekton
Nekton include all animals capable of moving independently of the ocean currents, by
swimming or other
means of
propulsion.

62. Nekton
Nekton are able to determine their location in the ocean and in many cases complete long migrations.

63. Nekton
Nekton include most adult fish and squid, marine mammals, and marine reptiles.

64. Nekton
Fish may appear to exist everywhere in the oceans, but they are more abundant near continents and in colder waters.

65. Nekton
Some fish, salmon, swim upstream in fresh water rivers to spawn.
Many eels do just the opposite, grow to maturity in fresh water and then swimming to breed in the deep ocean.

66. Benthos
The term benthos describes organisms living on or in the ocean bottom.

67. Benthos
The shallow coastal floor, where most benthos are found, contains a wide variety of physical conditions and nutrient levels.

68. Benthos
Shallow coastal areas are the only locations where marine algae, seaweeds, are found attached to the bottom.

69. Benthos
Throughout most of the deeper parts of the seafloor, animals live in perpetual darkness, where photosynthesis cannot occur.

70. Benthos
In these areas the organisms must survive on each other or whatever nutrients fall from the productive surface waters.

71. Benthos
The deep-sea bottom is an environment of coldness, stillness, and darkness.
Under these conditions, life progresses slowly.

72. Benthos
Organisms that live in the deep sea usually are widely distributed because physical conditions vary little on the deep-ocean floor.

73. Marine Life Zones
The distribution of marine organisms is affected by the chemistry, physics, and geology of the oceans.

74. Marine Life Zones
Three factors are used to divide the ocean into marine life zones: the availability of sunlight, the distance from shore, and the water depth.

75. Availability of Sunlight
The upper part of the ocean into which sunlight penetrates is called the photic zone.

76. Availability of Sunlight
The clarity of seawater is affected by many factors, such as the amount of plankton, suspended sediments, and decaying organic particles in the water.

77. Availability of Sunlight
The euphotic zone is the portion of the photic zone near the surface where light is strong enough for photosynthesis to occur.

78. Availability of Sunlight
In the euphotic zone, phytoplankton use sunlight to produce food and become the basis of most oceanic food webs.

79. Availability of Sunlight
Although photosynthesis cannot occur much below 100 meters, there is enough light for animals to avoid predators, find, food, recognize their species, and locate mates.

80. Availability of Sunlight
Below the photic zone is the aphotic zone where there is no sunlight.

81. Distance from Shore
The area where the land and ocean meet and overlap is called the intertidal zone.

82. Distance from Shore
The intertidal zone, where the land is alternatively covered and uncovered due to the tides, is a harsh place to live.

83. Distance from Shore
The intertidal zone has crashing waves, periodic drying out, and rapid changes in temperature, salinity, and oxygen concentrations.

84. Distance from Shore
Seaward from the low-tide line is the neritic zone.
Covers the gently continental shelf.

85. Distance from Shore
Although the neritic zone covers only about 5% of the world ocean, it is rich in both biomass and number of species.

86. Distance from Shore Many organisms find the neritic zone ideal.
Photosynthesis occurs readily, nutrients wash in from the land, and the bottom provides shelter and habitat.

87. Distance from Shore
The neritic zone is so rich that it supports 90% of the world’s commercial fisheries.

88. Distance from Shore
Beyond the continental shelf is the oceanic zone, where the deep ocean is.

89. Distance from Shore
The oceanic zone, due to the great depths, have lower nutrient concentrations, which results in smaller populations.

90. Water Depth
Open ocean of any depth is called the pelagic zone, where animals swim or float freely.

91. Water Depth
The photic part of the pelagic zone is home to phytoplankton, zooplankton, and nekton, such as tuna, sea turtles, and dolphin.

92. Water Depth
The aphotic part of the pelagic zone has giant squid and other species adapted to life in deep water.

93. Water Depth
The benthic zone is home to many benthos, giant kelp, sponges, crabs, sea anemones, sea stars, and marine worms.

94. Water Depth
The benthic zone includes any sea-bottom surface regardless of its distance from shore.

95. Water Depth The abyssal zone is a subdivision of the benthic zone.
Includes the deep-ocean floor, such as the abyssal plain.

96. Water Depth
The abyssal zone is characterized by extremely high water pressure, consistently low temperatures, no sunlight, and sparse food.

97. Water Depth
Some food, tiny decaying particles, in the abyssal zone constantly “rains” down.
Other food arrives as whole carcasses of organisms that sink from the surface.

98. Water Depth
Some organisms that are in the abyssal zone include: filter-feeders, brittle stars, burrowing worms, grenadier, tripodfish, and hagfish.

99. Hydrothermal Vents
Among the most unusual seafloor discoveries in the past 30 years, have been the hydrothermal vents.

100. Hydrothermal Vents
At some vents water temperature of 100 °C or lower support communities of organisms found nowhere else in the world.

101. Hydrothermal Vents
Hundreds of new species have been discovered surrounding these deep-sea habitats.

102. Hydrothermal Vents
Chemicals from the vents become food for bacteria, which produce sugars and other foods that enable many organisms to live in this environment.

103. Oceanic Productivity
Like other ecosystems on Earth, organisms in the marine environment are interconnected through the web of food production and consumption.

104. Oceanic Productivity
Why are some regions of the ocean teeming with life, while others seem barren?

105. Primary Productivity
The production of organic compounds through photosynthesis or chemosynthesis.

106. Chemosynthesis
The process in which certain microorganisms create organic molecules from inorganic nutrients using chemical energy.

107. Chemosynthesis
Bacteria in hydrothermal vents use hydrogen sulfide as an energy source.
Acting as producers, these bacteria support these communities.

108. Photosynthesis
The use of light energy to convert water and carbon dioxide into energy-rich glucose molecules.

109. Photosynthesis
Two factors influence a region’s photosynthetic productivity: the availability of nutrients and the amount of solar radiation, or sunlight.

110. Primary Producers
Marine producers include phytoplankton, larger algae such as seaweeds, and bacteria.

111. Primary Productivity
Primary producers need nutrients such as nitrogen, phosphorus, and iron.
The most abundant marine life exists where there are ample nutrients and good sunlight.

112. Primary Producers
Oceanic productivity, varies dramatically because of the uneven distribution of nutrients throughout the photosynthetic zone and the availability of solar energy due to seasonal changes.

113. Productivity in Polar Oceans
Polar regions experience continuous darkness for about three months of winter and continuous illumination for about three months of summer

114. Productivity in Polar Oceans
Productivity of phytoplankton peaks during May.
During May the sun rises high enough to penetrate deep into the water.

115. Productivity in Polar Oceans
As soon as the phytoplankton develop zooplankton begin feeding on them.
The zooplankton biomass peaks in June and continues at a relatively high level until October darkness.

116. Productivity in Polar Oceans
Density and temperature vary little with depth in the polar regions and mixing occurs between surface and nutrient rich deeper waters.

117. Productivity in Polar Oceans
In the summer, melting ice creates a thin, low salinity layer that does not readily mix with the deeper waters.
This lack of mixing helps prevent phytoplankton being carried into the deeper darker waters.

118. Productivity in Polar Oceans
Because of the constant supply of nutrients rising from deeper waters below, high-latitude surface waters typically have high nutrient concentrations.

119. Productivity in Polar Oceans
The availability of solar energy is what limits photosynthetic productivity in polar areas.

120. Productivity in Polar Oceans

121. Productivity in Tropical Oceans
Productivity is low in tropical regions of the open ocean.
The sun is more directly overhead, so light penetrates deeper, and solar energy is available year-round.

122. Productivity in Tropical Oceans
Productivity is low because a permanent thermocline prevents mixing between surface waters and the nutrient-rich deeper waters.

123. Productivity in Tropical Oceans
Productivity in tropical regions is limited by the lack of nutrients.
These areas have so few organisms that they are considered biological deserts.

124. Temperate Oceans
Productivity is limited by available sunlight in polar regions and by nutrient supply in the tropics.

125. Temperate Oceans
In temperate regions, which are found at mid-latitudes, a combination of these two limiting factors, sunlight and nutrient supply, controls productivity.

126. Temperate Oceans Winter— productivity very low
nutrient concentration highest
solar energy limited
depth which photosynthesis can occur is shallow and phytoplankton do not grow much.

127. Temperate Oceans Spring—
Sun rises higher-greater depth for photosynthesis
Spring bloom of phytoplankton occurs with solar energy and nutrients.

128. Temperate Oceans Spring— seasonal thermocline develops
traps algae in euphotic zone.
productivity decreases sharply, due to depletion of nutrient source.

129. Temperate Oceans Summer—
Sun rises higher-surface waters continue to warm.
strong seasonal thermocline remains and phytoplankton population remains low.

130. Temperate Oceans Fall— solar radiation decreases
thermocline breaks down
nutrients return to the surface
rise in phytoplankton, but less dramatic than the spring.

131. Temperate Oceans Fall— rise in phytoplankton is short lived
sunlight becomes the limiting factor as winter approaches

132. Biomass Productivity

133. Oceanic Feeding Relationships
Marine algae, plants, and bacteria-like organisms are the main oceanic producers.
As producers make food available to the consumers, energy is passed from one population to the next.

134. Oceanic Feeding Relationships
Energy is “consumed” or “lost” at each level, so only a small percentage of the energy taken in at any level is passed on to the next level.

135. Oceanic Feeding Relationships
The producer’s biomass in the ocean is many times greater than the mass of the top consumers, such as sharks and whales.

136. Trophic Levels
Chemical energy stored in the mass of the ocean’s algae is transferred through feeding.

137. Trophic Levels Zooplankton are herbivores, so they eat algae.
The herbivores are then eaten by carnivores.
Smaller carnivores are eaten by another population of larger carnivores.

138. Trophic Levels
Each of the feeding stages is called a trophic level.

139. Transfer Efficiency
The transfer of energy between trophic levels is very inefficient.
The efficiencies of different algal species vary, but the average is only 2%.

140. Transfer Efficiency
Only 2 percent of the light energy absorbed by algae is ultimately changed into food and made available to herbivores.

141. Transfer Efficiency

142. Food Chains and Food Webs
A food chain is a sequence of organisms through which energy is transferred.

143. Food Chains and Food Webs
Food webs are all the feeding relationships between producers and the top consumers.

144. Food Chains and Food Webs
A herbivore eats the producer, then one or more carnivore eats the herbivore. And finally the top carnivore eats the carnivore below it.

145. Food Chains and Food Webs
Animals that feed through a food web rather than a food chain are more likely to survive because they have alternative foods to eat should one of their food sources diminish or disappear.

146. Food Chains and Food Webs