1. Ocean Water & Ocean Life

2. Objectives
Identify the units used to express the salinity of ocean water.
List the sources of salt in ocean water.
Recognize the factors that affect the density of ocean water.
Compare and contrast the three main zones of the open ocean.

3. Vocabulary – (5 words 10 minutes)
Salinity
Thermocline
Density
Pycnocline
Mixed zone

4. Essential Questions
What units are used to express the salinity of ocean water?
What are the sources of salt in ocean water?
What factors affect the density of ocean water?
What are the three main zones of the open ocean?

5. Salinity Sources of Sea Salt
total amount of solid material dissolved in water.
oceanographers typically express salinity in parts per thousands.
Most of the salt in seawater is sodium chloride, common table salt.
Sources of Sea Salt
*Chemical weathering of rocks on the continents is one source of elements found in seawater.
*The second major source of elements found in seawater is from Earth’s interior.

6. The Composition of Seawater

7. Processes Affecting Salinity
Processes that decrease salinity:
Precipitation
Sea ice melting
Icebergs melting
Run off from land
Processes that increase salinity:
Evaporation
Formation of sea ice

8. Natural Processes Affecting Salinity

9. Which processes decrease the salinity of water
Which processes decrease the salinity of water? Which processes increase the salinity of water?
Decrease: precipitation, runoff from land, icebergs melting, sea ice melting.
Increase: evaporation, formation of sea ice.

10. Ocean Temperature Variation
The ocean’s surface water temperature varies with the amount of solar radiation received, which is primarily a function of latitude.
Temperature Variation w/ Depth
The thermocline is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of temperature with depth.
The thermocline is a very important structure because it creates a barrier to marine life.

11. At which latitudes is sea surface highest? Why?
Sea surface temperature is highest at the equator and low latitudes because these areas receive the most solar radiation at the highest angle of incidence.

12. Why is the thermocline absent in the high latitudes?
The thermocline is absent in the high latitudes because the temperature of surface water is closer to the temperature of deeper water.

13. Ocean Density Variation
Density is defined as mass per unit volume. It can be thought of as a measure of how heavy something is for its size.
Factors Affecting Seawater Density
Seawater density is influenced by two main factors: salinity and temperature.
Density Variation with Depth
The pycnocline is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of density with depth.

14. What is the difference between the low-latitude graph and the high-latitude graph? Why does this difference occur?
Pycnocline is not present in high latitude waters. This occurs because density and temperature do not vary with depth.

15. Ocean Layering
Oceanographers generally recognize a three-layered structure in most parts of the open ocean:
a shallow surface mixed zone,
a transition zone,
a deep zone.

16. Surface Zone Transition Zone Deep Zone
Shallow (extends to meters)
Zone of mixing
Sun-warmed zone
Transition Zone
Between surface layer and deep zone
Thermocline and pycnocline
Deep Zone
Sunlight never reaches this zone.
Temperatures are just a few degrees above freezing.
Constant high-density water

17. Ocean Zones

18. What units are used to express the salinity of ocean water?
Salinity is represented by parts per thousand.

19. What are the sources of salt in ocean water?
Chemical weathering of rocks on continents and Earth’s interior

20. What factors affect the density of ocean water?
Temperature and salinity affect the density of water.

21. What are the three main zones of the open ocean?
The three main zones of the open ocean are surface mixed zone, transition zone, and deep zone.

22. The Diversity of Ocean Life

23. Objectives Recognize how marine organisms can be classified.
Differentiate between plankton and nekton.
Describe the area of the ocean in which most benthic organisms live.
List the factors used to divide the ocean into marine zones.

24. Vocabulary Plankton Phytoplankton Zooplankton Nekton Benthos
Photic zone
Intertidal zone
Neritic zone
Oceanic zone
Pelagic zone
Benthic zone
Abyssal zone

25. Essential Questions How can marine organisms be classified?
What is the difference between plankton and nekton?
In which area do most benthos live?
What factors are used to divide the ocean into marine life zones?

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

27. Plankton
Plankton include all organisms—algae, animals, and bacteria—that drift with ocean currents.
Phytoplankton are algal plankton, which are the most important community of primary producers in the ocean.
Zooplankton are animal plankton.

28. Plankton

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

30. Benthos
Benthos describes organisms living on or in the ocean bottom.

31. Marine Life Zones
Three factors are used to divide the ocean into distinct marine life zones: the availability of sunlight, the distance from shore, and the water depth.
Availability of Sunlight
The photic zone is the upper part of the ocean into which sunlight penetrates.

32. Distance From Shore
The intertidal zone is the strip of land where the land and ocean meet and overlap, or the zone between high and low tides.
The neritic zone is the marine-life zone that extends from the low-tide line out to the shelf break.
The oceanic zone is the marine-life zone beyond the continental shelf.

33. Marine Life Zones

34. Water Depth
The pelagic zone is open zone of any depth. Animals in this zone swim or float freely.
The benthic zone is the marine-life zone that includes any sea-bottom surface regardless of its distance from shore.
The abyssal zone is a subdivision of the benthic zone characterized by extremely high pressures, low temperatures, low oxygen, few nutrients, and no sunlight.

35. Hydrothermal Vents
Here seawater seeps into the ocean floor through cracks in the crust.
At some vents, water temperatures of 100oC or higher support communities of organisms found nowhere else in the world.

36. Hydrothermal Vents

37. Tubeworms found along Hydrothermal Vents

38. How can marine organisms be classified?
Marine organisms can be classified by where they live and how they move.

39. What is the difference between plankton and nekton?
Nekton are able to move independently of ocean currents. Plankton are not.

40. In which area do most benthos live?
Most benthos live on the shallow coastal ocean floor.

41. What factors are used to divide the ocean into marine life zones?
The factors dividing the marine life zone are: availability of sunlight, distance from shore, and water depth.

42. Oceanic Productivity

43. Objectives
List the factors that influence a region’s photosynthetic productivity.
Describe the transfer of energy from one trophic level to another.
Compare and contrast food webs and food chains.

44. Vocabulary Primary productivity Photosynthesis Chemosynthesis
Trophic level
Food chain
Food web

45. Essential Questions
What advantage do organisms in a food web have over those in a food chain?
What limits primary productivity in tropical oceans? Why?

46. Primary Productivity
Primary productivity is the production of organic compounds from inorganic substances through photosynthesis or chemosynthesis.
Photosynthesis is the use of light energy to convert water and carbon dioxide into energy-rich glucose molecules.
Chemosynthesis is the process by which certain microorganisms create organic molecules from inorganic nutrients using chemical energy.

47. Example of Productivity in the Barents Sea

48. Productivity in Polar Oceans
The low availability of solar energy limits photosynthetic productivity in polar areas.

49. Productivity in Tropical Oceans
Productivity in tropical regions is limited by the lack of nutrients.
Solar energy is available year-round but nutrients are trapped in deeper waters because the permanent thermocline prevents mixing between surface water and deeper water.

50. Productivity in Temperate Oceans
In temperate regions, which are found at mid- latitudes, a combination of these two limiting factors, sunlight and nutrient supply, controls productivity.
Winter
Low productivity
Days are short and sun angle is low.

51. Productivity in Temperate Oceans
Spring
Spring bloom of phytoplankton is quickly depleted.
Productivity is limited.
Summer
Strong thermocline develops so surface nutrients are not replaced from below.
Phytoplankton population remains relatively low.

52. Oceanic Feeding Relationships
Trophic Levels
A trophic level is a nourishment level in a food chain. Plant and algae producers constitute the lowest level, followed by herbivores and a series of carnivores at progressively higher levels.
Transfer Efficency
The transfer of energy between trophic levels is very inefficient.

53. Food Chains & Food Webs
A food chain is a sequence of organisms through which energy is transferred, starting with the primary producer.
A food web is a group of interrelated food chains.
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.

54. Food Chains & Food Webs

55. What advantage do organisms in a food web have over those in a food chain?
Organisms in a food web have alternative foods to eat if one of their food sources diminishes or disappears.

56. What limits primary productivity in tropical oceans? Why?
The availability of nutrients; solar energy is available year-round but nutrients are trapped in deeper waters because the permanent thermocline prevents mixing between surface water and deeper water.