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Chapter 6

Chapter 6. Aquatic Biodiversity. 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?

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Chapter 6

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  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. There are four major types of organisms in aquatic systems: • Plankton are free-floating, weakly swimming, generally one-celled organisms. • There are three major types of plankton: • phytoplankton (plant plankton) • zooplankton (animal plankton) they may be single-celled protozoa to large invertebrates such as jellyfish • ultraplankton that are no more than 2 micrometers wide and are photosynthetic bacteria. • Ultraplankton may be responsible for as much as 70% of the primary productivity near the ocean surface.

  12. There are four major types of organisms in aquatic systems: • Nekton is a second group of organisms. • These are fish, turtles and whales • Benthos are bottom dwellers • barnacles, oysters, worms, lobsters and crabs • Decomposers • These organisms break down organic matter into simple nutrients for use by producers.

  13. Three layers of aquatic life zones • Surface • Middle • Bottom • Factors that determine types and numbers of producers: • Temperature • sunlight availability • dissolved oxygen • nutrient availability

  14. Biological Zones in the Open Sea:Light Rules • The open sea is divided into three vertical zones based primarily on penetration of light. • Low average primary productivity and NPP occurs, but oceans are so large they make the largest contribution to NPP overall.

  15. Open Sea • Euphotic zone: brightly lit surface layer. • Nutrient levels low, dissolved O2 high, photosynthetic activity. • Large, fast-swimming predatory fish like swordfish, shark and bluefin tuna live in this zone.

  16. Open Sea • Bathyal zone: dimly lit middle layer. • No producers are in this zone (No photosynthetic activity) • Zooplankton and smaller fish live in this zone and migrate to euphotic zone to feed at night

  17. Open Sea • Abyssal zone: dark bottom layer. • Very cold, little dissolved O2. • The nutrients on the ocean floor support about 98% of species living in the ocean. • Organisms in this area are deposit feeders, or filter feeders. • Hydrothermal vents are present in some areas with specialized bacteria that feed on chemical nutrients and are food for other organisms

  18. Effects of Human Activities on Marine Systems • About 40% of the world population lives along coasts. • Over half of US population lives with 62 miles of the coast.

  19. 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

  20. 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

  21. Euphotic Zone • Euphotic zone describes the upper layer where sunlight can penetrate. • Clouding or excessive algal growth reduces depth of euphotic zone. • Dissolved oxygen levels are higher near the surface due to photosynthesis in this area • Conversely, O2 levels are lower in deeper, dark layers due to aerobic respiration and because less O2 gas dissolves in deeper and colder water.

  22. Nutrients • Open oceans tend to have limited amounts of nitrates, phosphates, iron, and other nutrients that limit productivity. • Conversely, shallow waters are generally well supplied with nutrients for growth. • Deep dwelling species depend on animal and plant material that die/ sink to bottom. • Large fish are vulnerable to overfishing depletion.

  23. Saltwater Life Zones • Oceans have two major life zones: • the coastal zone • the open sea

  24. The Coastal Zone: Where Most of the Action Is • The coastal zone interacts with the land so, it is greatly affected by human activities. • The coastal zone extends from the high-tide mark on land to the edge of the continental shelf. • Ecosystems in coastal zones have a high net primary productivity per unit area. • They constitute 10% of the oceans and contain 90% of all marine species. • There is ample sunlight and nutrients flow from land and wind/currents

  25. The Coastal Zone • Estuaries and coastal wetlands are subject to tidal rhythms, runoff from land, and seawater that mixes with freshwater and nutrients from rivers and streams. • Mangrove forest swamps grow in sheltered regions of tropical coasts. • They collect mud and anaerobic sediment.

  26. The Coastal Zone: • Coastal wetlands/ estuaries make nutrients available due to constant stirring of bottom sediment. • These areas filter toxic pollutants, excess plant nutrients, reduce storm damage and provide nursery sites for aquatic species. • Humans are destroying/degrading these ecosystems • 1/3 have already been lost.

  27. The Coastal Zone Figure 6-5

  28. 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

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

  30. 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

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

  32. Fig. 6-6, p. 130

  33. 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

  34. 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

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

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

  37. 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.

  38. 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.

  39. 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

  40. 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

  41. 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

  42. 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

  43. 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

  44. Barrier Islands • The islands help protect the mainland, estuaries, and coastal wetlands from heavy storm damage. • Sand is constantly shifting due to winds and parallel currents along the islands. • Undisturbed beaches have one or more rows of sand dunes on them. Grass roots hold the sand in place and the dune is a first line of defense against storms. It is safer to build behind the second set of dunes if any building occurs.

  45. Barrier Islands • People want to live on these islands, but they are subject to damage. • In spite of this, almost one-fourth of barrier islands are developed. • Developers want to build on the islands and do not consider the protective services that the dunes provide. • Large storms can and have swept away or severely damaged seaside buildings.

  46. Barrier Islands • Governments often provide funds for rebuilding and insurance at fairly low rates for building on the dunes. • Some people think that persons building in such risky places should accept all responsibility for repair or replacement due to storm damage.

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

  48. 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

  49. Coral Reefs • Coral reefs in shallow coastal zones of tropical and subtropical oceans support a very diverse, complex ecosystem. • They grow slowly and are vulnerable to damage. • They thrive in clear, warm, fairly shallow water with a high salinity. • The ideal water temperature is between 18-30oC and will bleach if the water warms above this by so much as 1oC.

  50. Coral Reefs • Severe storms, freshwater floods, and invasions of predatory fish adversely affect the reefs. • They have survived natural disturbances for a long geologic history. • The greatest threats today are due to sediment runoff and other human activities. • Coral reef systems may not have enough time to adapt to these rapidly changing conditions.

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