1. Chapter 8
Aquatic Biodiversity

2. Core Case Study: Why Should We Care About Coral Reefs?
Coral reefs form in clear, warm coastal waters of the tropics and subtropics.
Formed by massive colonies of polyps.
Figure 6-1

3. Core Case Study: Why Should We Care About Coral Reefs?
Help moderate atmospheric temperature by removing CO2 from the atmosphere.
Act as natural barriers that help protect 14% of the world’s coastlines from erosion by battering waves and storms.
Provide habitats for a variety of marine organisms.

4. AQUATIC ENVIRONMENTS
Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface
Figure 6-2

5. AQUATIC ENVIRONMENTS
Figure 6-3

6. What Kinds of Organisms Live in Aquatic Life Zones?
Aquatic systems contain floating, drifting, swimming, bottom-dwelling, and decomposer organisms.
Plankton: important group of weakly swimming, free-floating biota.
Phytoplankton (plant), Zooplankton (animal), Ultraplankton (photosynthetic bacteria)
Necton: fish, turtles, whales.
Benthos: bottom dwellers (barnacles, oysters).
Decomposers: breakdown organic compounds (mostly bacteria).

7. Life in Layers
Life in most aquatic systems is found in surface, middle, and bottom layers.
Temperature, access to sunlight for photosynthesis, dissolved oxygen content, nutrient availability changes with depth.
Euphotic zone (upper layer in deep water habitats): sunlight can penetrate.

8. The Coastal Zone
Figure 6-5

9. The Coastal Zone: Where Most of the Action Is
The coastal zone: the warm, nutrient-rich, shallow water that extends from the high-tide mark on land to the gently sloping, shallow edge of the continental shelf.
The coastal zone makes up less than 10% of the world’s ocean area but contains 90% of all marine species.
Provides numerous ecological and economic services.
Subject to human disturbance.

10. Estuaries and Coastal Wetlands: Centers of Productivity
Estuaries include river mouths, inlets, bays, sounds, salt marshes in temperate zones and mangrove forests in tropical zones.
Figure 6-7

11. Figure 6.6
Natural capital degradation: view of an estuary taken from space. The photo shows the sediment plume at the mouth of Madagascar’s Betsiboka River as it flows through the estuary and into the Mozambique Channel. Because of its topography, heavy rainfall, and the clearing of forests for agriculture, Madagascar is the world’s most eroded country.
Fig. 6-6, p. 130

12. Figure 6.7
Natural capital: some components and interactions in a salt marsh ecosystem in a temperate area such as the United States. When these organisms die, decomposers break down their organic matter into minerals used by plants. Colored arrows indicate transfers of matter and energy between consumers (herbivores), secondary or higher-level consumers (carnivores), and decomposers. Organisms are not drawn to scale. The photo below shows a salt marsh in Peru.
Fig. 6-7b, p. 131

13. Mangrove Forests
Are found along about 70% of gently sloping sandy and silty coastlines in tropical and subtropical regions.
Figure 6-8

14. Estuaries and Coastal Wetlands: Centers of Productivity
Estuaries and coastal marshes provide ecological and economic services.
Filter toxic pollutants, excess plant nutrients, sediments, and other pollutants.
Reduce storm damage by absorbing waves and storing excess water produced by storms and tsunamis.
Provide food, habitats and nursery sites for many aquatic species.

15. Rocky and Sandy Shores: Living with the Tides
Organisms in intertidal zone develop specialized niches to deal with daily changes in:
Temperature
Salinity
Wave action
Figure 6-9

16. Barrier Islands
Low, narrow, sandy islands that form offshore from a coastline.
Primary and secondary dunes on gently sloping sandy barrier beaches protect land from erosion by the sea.
Figure 6-10

17. Threats to Coral Reefs: Increasing Stresses
Biologically diverse and productive coral reefs are being stressed by human activities.
Figure 6-11

18. Biological Zones in the Open Sea: Light Rules
Euphotic zone: brightly lit surface layer.
Nutrient levels low, dissolved O2 high, photosynthetic activity.
Bathyal zone: dimly lit middle layer.
No photosynthetic activity, zooplankton and fish live there and migrate to euphotic zone to feed at night.
Abyssal zone: dark bottom layer.
Very cold, little dissolved O2.

19. Lakes: Water-Filled Depressions
Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of:
Littoral zone (near shore, shallow, with rooted plants).
Limnetic zone (open, offshore area, sunlit).
Profundal zone (deep, open water, too dark for photosynthesis).
Benthic zone (bottom of lake, nourished by dead matter).

20. Lakes: Water-Filled Depressions
Figure 6-15

21. Effects of Plant Nutrients on Lakes: Too Much of a Good Thing
Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support.
Figure 6-16

22. Effects of Plant Nutrients on Lakes: Too Much of a Good Thing
Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support.
Oligotrophic (poorly nourished) lake: Usually newly formed lake with small supply of plant nutrient input.
Eutrophic (well nourished) lake: Over time, sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth.

23. Effects of Plant Nutrients on Lakes: Too Much of a Good Thing
Cultural eutrophication:
Human inputs of nutrients from the atmosphere and urban and agricultural areas can accelerate the eutrophication process.

24. Freshwater Streams and Rivers: From the Mountains to the Oceans
Water flowing from mountains to the sea creates different aquatic conditions and habitats.
Figure 6-17

25. Case Study: Dams, Wetlands, Hurricanes, and New Orleans
Dams and levees have been built to control water flows in New Orleans.
Reduction in natural flow has destroyed natural wetlands.
Causes city to lie below sea-level (up to 3 meters).
Global sea levels have risen almost 0.3 meters since 1900.

26. Freshwater Inland Wetlands: Vital Sponges
Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats.
Figure 6-18

27. Impacts of Human Activities on Freshwater Systems
Dams, cities, farmlands, and filled-in wetlands alter and degrade freshwater habitats.
Dams, diversions and canals have fragmented about 40% of the world’s 237 large rivers.
Flood control levees and dikes alter and destroy aquatic habitats.
Cities and farmlands add pollutants and excess plant nutrients to streams and rivers.
Many inland wetlands have been drained or filled for agriculture or (sub)urban development.