Aquatic Biodiversity: Types and Human Impact on Saltwater and Freshwater Life Zones

1. Chapter 6 Aquatic Biodiversity

2. Chapter Overview Questions • What are the basic types of aquatic life zones and what factors influence the kinds of life they contain? • What are the major types of saltwater life zones, and how do human activities affect them? • What are the major types of freshwater life zones, and how do human activities affect them?

3. Updates Online The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles. • InfoTrac: Down the bayou: a marine biologist, a community, and the resolve to preserve an ocean's bounty. Taylor Sisk. Earth Island Journal, Autumn 2006 v21 i3 p27(6). • InfoTrac: A scourge of the '70s returns to Great Lakes. The Christian Science Monitor, March 30, 2006 p14. • InfoTrac: The fate of the ocean. Julia Whitty. Mother Jones, March-April 2006 v31 i2 p32(15). • National Oceanic and Atmospheric Administration: Fisheries • Amazon Conservation Association: Amazon Rivers Project

4. 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

5. Fig. 6-1a, p. 126

6. Fig. 6-1b, p. 126

7. 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.

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

9. Ocean hemisphere Land–ocean hemisphere Fig. 6-2, p. 127

10. AQUATIC ENVIRONMENTS Figure 6-3

11. 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).

12. 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. • Bathyal zone (mid layer, dim light) • Abyssal zone (lower layer, no light from the sun, but many creatures use bioluminescence)

13. SALTWATER LIFE ZONES • The oceans that occupy most of the earth’s surface provide many ecological and economic services. Figure 6-4

14. Natural Capital Marine Ecosystems Economic Services Ecological Services Climate moderation Food CO2 absorption Animal and pet feed Nutrient cycling Pharmaceuticals Waste treatment Harbors and transportation routes Reduced storm impact (mangroves, barrier islands, coastal wetlands) Coastal habitats for humans Recreation Habitats and nursery areas Employment Genetic resources and biodiversity Oil and natural gas Minerals Scientific information Building materials Fig. 6-4, p. 129

15. 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.

16. The Coastal Zone Figure 6-5

17. High tide Sun Open Sea Coastal Zone Sea level Low tide Photosynthesis Euphotic Zone Estuarine Zone Continental shelf Bathyal Zone Twilight Abyssal Zone Darkness Fig. 6-5, p. 130

18. Marine Ecosystems • Scientists estimate that marine systems provide $21 trillion in goods and services per year – 70% more than terrestrial ecosystems. Figure 6-4

19. Fig. 6-6, p. 130

20. 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

21. Herring gulls Peregrine falcon Snowy Egret Cordgrass Short-billed Dowitcher Marsh Periwinkle Phytoplankton Smelt Zooplankton and small crustaceans Soft-shelled clam Clamworm Bacteria Producer to primary consumer Primary to secondary consumer Secondary to higher-level consumer All consumers and producers to decomposers Fig. 6-7a, p. 131

22. Fig. 6-7b, p. 131

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

25. 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.

26. Rocky and Sandy Shores: Living with the Tides • Organisms experiencing daily low and high tides have evolved a number of ways to survive under harsh and changing conditions. • Gravitational pull by moon and sun causes tides. • Intertidal Zone: area of shoreline between low and high tides.

27. 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

28. Rocky Shore Beach Hermit crab Sea star Shore crab High tide Periwinkle Sea urchin Anemone Mussel Low tide Sculpin Barnacles Kelp Sea lettuce Monterey flatworm Nudibranch Fig. 6-9, p. 132

29. Barrier Beach Beach flea Peanut worm Tiger Beetle Blue crab Clam Dwarf Olive High tide Sandpiper Ghost Shrimp Low tide Silversides Mole Shrimp White sand macoma Moon snail Sand dollar Fig. 6-9, p. 132

30. 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

31. Primary Dune Secondary Dune Bay or Lagoon Ocean Beach Trough Back Dune No direct passage or building No direct passage or building Limited recreation and walkways Most suitable for development Intensive recreation, no building Intensive recreation Grasses or shrubs Bay shore No filling Taller shrubs Taller shrubs and trees Fig. 6-10, p. 133

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

33. Gray reef shark Green sea turtle Sea nettle Fairy basslet Blue tangs Parrot fish Sergeant major Brittle star Hard corals Algae Banded coral shrimp Phytoplankton Symbiotic algae Coney Zooplankton Blackcap basslet Sponges Moray eel Bacteria Producer to primary consumer Primary to secondary consumer Secondary to higher-level consumer All consumer and producers to decomposers Fig. 6-11, p. 134

34. Natural Capital Degradation Coral Reefs Ocean warming Soil erosion Algae growth from fertilizer runoff Mangrove destruction Bleaching Rising sea levels Increased UV exposure Damage from anchors Damage from fishing and diving Fig. 6-12, p. 135

35. 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, “marine snow” of nutrients, little dissolved O2.

36. Effects of Human Activities on Marine Systems: Red Alert • Human activities are destroying or degrading many ecological and economic services provided by the world’s coastal areas. Figure 6-13

37. Natural Capital Degradation Marine Ecosystems Half of coastal wetlands lost to agriculture and urban development Over one-third of mangrove forests lost to agriculture, development, and aquaculture shrimp farms Beaches eroding because of coastal development and rising sea level Ocean bottom habitats degraded by dredging and trawler fishing At least 20% of coral reefs severely damaged and 30–50% more threatened Fig. 6-13, p. 136

38. FRESHWATER LIFE ZONES • Freshwater life zones include: • Standing (lentic) water such as lakes, ponds, and inland wetlands. • Flowing (lotic) systems such as streams and rivers. Figure 6-14

39. Natural Capital Natural Capital Freshwater Systems Ecological Services Economic Services Climate moderation Nutrient cycling Waste treatment Flood control Groundwater recharge Habitats for many species Genetic resources and biodiversity Scientific information Food Drinking water Irrigation water Hydroelectricity Transportation corridors Recreation Employment Fig. 6-14, p. 136

40. 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).

41. Lakes: Water-Filled Depressions • During summer and winter in deep temperate zone lakes the become stratified into temperature layers and will overturn. • This equalizes the temperature at all depths. • Oxygen is brought from the surface to the lake bottom and nutrients from the bottom are brought to the top. • What causes this overturning?

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

43. Sunlight Painted turtle Green frog Blue-winged teal Muskrat Pond snail Littoral zone Limnetic zone Diving beetle Plankton Profundal zone Benthic zone Northern pike Yellow perch Bloodworms Fig. 6-15, p. 137

44. 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

45. Natural Eutrophication • 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.

46. Human-Caused Eutrophication • Cultural eutrophication: • Human inputs of nutrients from the atmosphere and urban and agricultural areas can accelerate the eutrophication process. • Sewage • Fertilizers • Nitrates from smog • Sediments

47. Human-Caused Eutrophication (Nitrogen may be in the form of either Urea or Ammonium Nitrate – or both) Algae Bloom due to Cultural Eutrophication Components of Fertilizer

48. Lake Stratification • Lakes in the temperate zone become stratified (layered) during the summer. • Surface water is warmed by the sun, while deep water remains cool. • Since warm water is less dense than cold water, the warm water stays on the top and does not mix with the cooler water below.

49. Lake Stratification • Upper layer = “epilimnion” • Lower layer = “hypolimnion” • Boundary between layers = “thermocline” Notice the rapid temperature drop at the thermocline!

50. Lake Stratification • Since the epilimnion is in contact with the atmosphere, and it is continually stirred up by waves and wind, it has a higher oxygen content than the hypolimnion (even though cold water has a greater ability to hold dissolved oxygen). • Since dead organisms (fish, leaves, logs, etc.) and their wastes tend to sink, the hypolimnion has a higher level of nutrients than the epilimnion.