CHAPTER 8

• Coral reefs


  Among world's oldest, most diverse, and most productive ecosystems
• Coral reefs


  • Form in clear, warm coastal waters in tropical areas
  • Tiny animals (polyps) and single-celled algae have a mutualistic relationship
  • Polyps secrete calcium carbonate shells, which become coral reefs
• Coral reefs


  Provide important ecological and economic services
• Ecological and economic services of coral reefs

  • Natural barrier to protect coastlines
  • Habitat, food, or spawning grounds for one-quarter to one-third of ocean's organisms
• Coral reefs are vulnerable to

  • Soil runoff
  • Climate change increasing ocean temperature
  • Increasing ocean acidity
• Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth's surface
• Factors determining aquatic biodiversity

  • Temperature
  • Dissolved oxygen content
  • Availability of food
  • Access to light and nutrients necessary for photosynthesis
• Global ocean areas


  • Atlantic
  • Pacific
  • Arctic
  • Indian
  • Southern
• Saltwater life zones (marine life zones)

  • Oceans
  • Estuaries
  • Coasts
  • Coral reefs
  • Mangrove forests
• Freshwater life zones


  • Lakes
  • Rivers
  • Streams
  • Inland wetlands
• Plankton


  Drifting aquatic microorganisms
• Types of plankton


  • Phytoplankton
  • Ultraplankton
  • Zooplankton
• Phytoplankton


  • Many types of algae
  • Primary producers for most aquatic food webs
• Ultraplankton


  • Photosynthetic
  • Smaller than photoplankton
• Zooplankton


  • Secondary consumers
  • Range from single-celled to large invertebrates like jellyfish
• Types of aquatic organisms

  • Plankton
  • Nekton
  • Benthos
  • Decomposers
• Nekton


  Strong swimmers—fish, turtles, and whales
• Benthos


  Bottom dwellers—oysters, sea stars, clams, lobsters, and crabs
• Decomposers


  Mostly bacteria
• Key factors in the types and numbers of aquatic organisms

  • Temperature
  • Dissolved oxygen content
  • Availability of food
  • Availability of light and nutrients needed for photosynthesis
• Turbidity


  Degree of cloudiness in water
• Saltwater ecosystems provide major ecosystem and economic services and are irreplaceable reservoirs of biodiversity
• Ecosystem services of oceans

  • Produce more than half of oxygen we breathe
  • Provide most of the rain that sustains water supply
  • Seafood
  • Provide rain that sustains the water supply
• The earth's oceans are poorly understood and are a potential source of ecological and economic benefits
• Major life zones of oceans

  • Coastal zone
  • Open sea
  • Ocean bottom
• Coastal zone


  • Warm, nutrient rich, shallow water
  • Extends from land to edge of continental shelf
  • Makes up less than 10% of world's ocean area
  • Contains 90% of all marine species
• Estuaries


  Aquatic zone where river meets the sea
• Coastal wetlands


  • Coastal land covered with water all or part of the year
  • Include coastal marshes (salt marshes), mangrove forests, seagrass beds, and coral reefs
• Ecosystem services of coastal wetlands

  • Filter and absorb pollution
  • Food and habitats for aquatic and terrestrial species
  • Reduce coastal erosion
• Tides are caused by the gravitational pull of the sun and moon
• Intertidal zone


  • Area of shore between high and low tides
  • Organisms must survive with daily salinity and moisture changes
• Rocky shores


  Pounded by waves
• Barrier beaches (sandy shores)

  Most organisms burrow, dig, or tunnel in sand
• Barrier islands


  • Long, narrow, sandy islands
  • Parallel to coastlines
  • Protect against erosion
• Coral reefs are being destroyed and damaged worldwide
• Ocean acidification


  • Oceans absorb CO2
  • CO2 reacts with ocean water to form a weak acid that decreases levels of carbonate ions (CO32–) needed to form coral
• Vertical zones of the open sea

  • Euphotic zone
  • Bathyal zone
  • Abyssal zone
• Euphotic zone


  • Phytoplankton
  • Nutrient levels low
  • Dissolved oxygen levels high
  • Upwelling brings nutrients from below
• Bathyal zone


  • Dimly lit middle zone
  • Zooplankton and smaller fishes
• Abyssal zone


  • Dark and cold
  • High levels of nutrients
  • Little dissolved oxygen
  • Deposit feeders
  • Filter feeders