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Chapter 13 Biological Productivity and Energy Transfer Essentials of Oceanography 7 th Edition.

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Presentation on theme: "Chapter 13 Biological Productivity and Energy Transfer Essentials of Oceanography 7 th Edition."— Presentation transcript:

1 Chapter 13 Biological Productivity and Energy Transfer Essentials of Oceanography 7 th Edition

2 Primary productivity Primary productivity is the amount of carbon (organic matter) produced by organisms Mostly through photosynthesis Energy source = solar radiation Also includes chemosynthesis Energy source = chemical reactions

3 Photosynthetic productivity Figure 13-1

4 Oceanic photosynthetic productivity Controlling factors affecting photosynthetic productivity: Availability of nutrients Nitrates Phosphates Iron Amount of sunlight Varies daily and seasonally Sunlight strong enough to support photosynthesis occurs only to a depth of 100 meters (euphotic zone)

5 Locations of maximum photosynthetic productivity Margins of the oceans Abundant supply of nutrients from land Water shallow enough for light to penetrate all the way to the sea floor Upwelling areas Currents hoist cool, nutrient-rich deep water to the sunlit surface

6 Coastal upwelling Figure 13-3

7 The electromagnetic spectrum and light penetration in seawater Figure 13-4

8 Water color and life in the ocean Ocean color is influenced by: The amount of turbidity from runoff The amount of photosynthetic pigment, which corresponds to the amount of productivity Yellow-green = highly productive water Found in coastal and upwelling areas (eutrophic) Clear indigo blue = low productivity water Found in the tropics and open ocean (oligotrophic)

9 Satellite view of world productivity Figure 13-6

10 Photosynthetic marine organisms: Plants Seed-bearing plants Eelgrass (Zostera) Surf grass (Phyllospadix) Figure 13-7 Surf grass

11 Photosynthetic marine organisms: Macroscopic algae Brown algae Sargassum (top left) Macrocystis (top right) Green algae Codium (bottom left) Red algae Lithothamnion (bottom right) Figure 13-8

12 Photosynthetic marine organisms: Microscopic algae Microscopic algae include: Golden algae Diatoms (silica test resembles a pillbox) Coccolithophores (calcite plates form a spherical test) Dinoflagellates Produce a test made of keratin Posses a whip-like flagella Bioluminescence Exist in great abundance, creating red tides (harmful algae blooms)

13 Dinoflagellates and red tides Figure 13C

14 Regional productivity Photosynthetic productivity varies due to: Amount of sunlight Availability of nutrients Thermocline (a layer of rapidly changing temperature) limits nutrient supply Examine three open ocean regions: 1. Polar oceans (>60° latitude) 2. Tropical oceans (<30° latitude) 3. Temperate oceans (30-60° latitude)

15 Productivity in polar oceans Sunlight peaks in summer Nutrients available nearly year-round (only weak seasonal thermocline develops) Productivity: Peaks in spring Limited by sunlight Figure 13-10a

16 Productivity in tropical oceans Sunlight strong year-round Nutrients limited by strong, permanent thermocline Productivity: Steady, low rate Limited by nutrients Exceptions: Upwelling areas Coral reefs Figure 13-11

17 Productivity in temperate oceans Sunlight varies seasonally Nutrients limited by thermocline Productivity: Spring bloom limited by nutrients Fall bloom limited by sunlight Figure 13-12

18 Productivity in tropical, temperate, and polar oceans Figure 13-13

19 Energy flow in marine ecosystems Categories of organisms: Producers Consumers Decomposers Figure 13-14

20 Biogeochemical cycling of matter Figure 13-16

21 Ecosystem energy flow and efficiency Energy is passed between trophic (feeding) levels Transfer efficiencies: Algae = 2% Other levels = 10% Figure 13-18

22 Comparison between a food chain and a food web Figure 13-19

23 Biomass pyramid At each step up the pyramid, there is/are: Larger organisms Fewer individuals A smaller total biomass Figure 13-20

24 Ecosystems and fisheries Fishery = fish caught from the ocean by commercial fishers Largest proportion of marine fish are taken from shallow shelf and coastal waters Figure 13-21

25 Fisheries and overfishing World total marine fish production has increased dramatically Overfishing occurs when adult fish are harvested faster than their natural rate of reproduction Figure 13-22

26 Fisheries and bycatch Some fishing practices produce large amounts of incidental catch (bycatch): Purse seine nets set for tuna can trap dolphins Driftnets (gill nets) take many unwanted species Figure Spotted dolphin

27 Fisheries management Fisheries management seeks to maintain a long- term fishery by: Assessing ecosystem health Determining fish stocks Analyzing fishing practices Enforcing catch limits Fisheries management does not regulate the number of fishing vessels Figure 13-25

28 End of Chapter 13 Essentials of Oceanography 7 th Edition


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