Oceanic Productivity: Zones, Factors & Relationships

1. Warm-Up • Name the three different types of animals you will find in the ocean • Nekton, benthos, plankton • What three factors are used to divide the ocean into its zones? • Sunlight, depth, distance from shore

2. Oceanic Productivity Chapter 15, Section 3

3. Primary Productivity • Primary Productivity – the production of organic compounds from inorganic substances through photosynthesis or chemosynthesis • Photosynthesis – the use of light energy to convert water and carbon dioxide into energy-rich glucose molecules • Chemosynthesis – the process by which certain microorganisms create organic molecules from inorganic nutrients using chemical energy • Two factors influence a region’s photosynthetic productivity: the availability of nutrients and the amount of solar radiation, or sunlight

4. Productivity in Polar Oceans • Polar regions experience continuous darkness for about three months of winter and continuous illumination for about three months of during summer • Productivity of phytoplankton, mostly single-celled algae, peaks in May • As soon as the phytoplankton develop, zooplankton come in to eat them • In summer, melting ice creates a low-salinity, low-density region on the surface that will not readily mix with the deeper waters; helping the phytoplankton to continue producing • The availability of solar energy is what limits photosynthetic productivity in polar areas

5. Productivity in Polar Oceans

6. Productivity in Tropical Oceans • Productivity is low in tropical regions of the open ocean • Light penetrates much deeper into tropical oceans than in temperate and polar waters • Solar energy is available year-round • A permanent thermocline prevents mixing between surface waters and nutrient-rich deeper waters; it is a barrier that cuts off the supply of nutrients from deeper waters • Productivity in tropical regions is limited by the lack of nutrients

7. Water Layers in the Tropics

8. 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: productivity is low, due to the low angle of the sun and shallower sunlight penetration • Spring: phytoplankton bloom due to an increase in nutrients and sunlight, nutrient supply is in greater demand and limits production • Summer: nutrients depleted from spring “bloom” are not able to be replenished from deep waters due to a sharp thermocline, phytoplankton population will remain low • Fall: nutrients return to the surface, as the summer thermocline breaks down, and another “bloom” of phytoplankton occurs (short-lived due to decreasing sunlight)

9. Productivity in Temperate Oceans

10. Comparing Productivities

11. Oceanic Feeding Relationships • As producers make food available to the consuming animals of the ocean, energy passes from one feeding population to the next • Trophic Level – a nourishment level in a food chain; plant and algae → herbivores → carnivores • The transfer of energy between trophic levels is very inefficient • Food Chain – sequence of organisms through which energy is transferred, starting with the primary producer • Food Web – 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

12. Ecosystem Energy Flow

13. Food Chain Vs. Food Web

14. Assignment • Read Chapter 15, Section 3 (pg. 433-437) • Do Section 15.3 Assessment #1-6 (pg. 437)