Chapter 8: Aquatic Biodiversity

Coral Reefs

Ecological & Economic Services

• Moderate atmospheric temperatures
• Act as natural barriers protecting coasts from erosion
• Provide habitats
• Support fishing and tourism businesses
• Provide jobs and building materials
• Studied and enjoyed

Degradation and Decline

• Coastal development
• Pollution
• Overfishing
• Warmer ocean temperatures leading to coral bleaching→ Kill algae and thus the polyps
• Increasing ocean acidity

What Is the General Nature of Aquatic Systems?

Most of the Earth Is Covered with Water

• Saltwater includes;
  • Atlantic
  • Pacific
  • Arctic
  • Indian
• Freshwater: Any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids.

Aquatic Life Zones

• Saltwater life zones (marine life zones): Oceans, estuaries, coastlands, shorelines, coral reefs, and mangrove forests.
• Freshwater life zones: Lakes, rivers, streams, and inland wetlands

Aquatic Species

• Plankton→ Free floating creatures
  • Phytoplankton: Primary producers for most aquatic food webs
  • Zooplankton: Primary and secondary consumers. Single-celled to large invertebrates like jellyfish
  • Ultraplankton: Tiny photosynthetic bacteria
• Nekton are strong swimmers
  • Fish, turtles, whales, etc.
• Benthos: Bottom dwellers
  • Oysters, sea stars, clams, lobsters, crabs, etc.
• Decomposers: Mostly bacteria

Key Factors That Determine Types & Numbers of Organisms

• Critical factors in the distribution of organisms
  • Temperature
  • Dissolved oxygen content
  • Availability of food
  • Availability of light and nutrients needed for photosynthesis in the eutrophic (photic) zone
• Turbidity: Degree of cloudiness in the water, inhibits photosynthesis

Why Are Marine Aquatic Systems Important?

Oceans Provide Vital Ecological and Economic Resources

• Reservoirs of diversity in three major life zones
  • Coastal zone: Warm, nutrient-rich, shallow. Shore to the edge of a continent shelf.
  • Open sea
  • Ocean bottom

Major Ecological and Economic Services Provided by Marine Systems

• Ecological Services
  • Climate moderation
  • CO2 absorption
  • Nutrient cycling
  • Waste treatment
  • Reduced storm impact (mangroves, barrier islands, coastal wetlands
  • Habitats and nursery areas
  • Genetic Resources and biodiversity
  • Scientific information
• Economic Services
  • Food
  • Animals and pet feed
  • Pharmaceuticals
  • Harbors and transportation routes
  • Coastal habitats for humans
  • Recreation
  • Employment
  • Oil and natural gas
  • Minerals
  • Building materials

Estuaries and Coastal Wetlands

• Estuaries/Coastal Wetlands: Where rivers meet the sea and seawater mixes with freshwater (ex. river mouths, inlets, bays, sounds, salt marshes, and mangrove forests.)
  • Very productive ecosystems→ high nutrient levels
• Seagrass Beds: Grow underwater in shallow areas, support a variety of marine species, stabilize shorelines, and reduce wave impact.
• Mangrove forests: Along tropical and subtropical coastlines, 69 different tree species grow in saltwater

Rocky and Sandy Shores Host Different Types of Organisms

• Intertidal zone: Rocky shores or sandy shores which have barrier beaches

Three Zones of the Ocean

1. Euphotic zone: Phytoplankton, nutrient level low, dissolved oxygen levels high.
2. Bathyal zone: Dimly lit, zooplankton and smaller fishes
3. Abyssal zone: Dark and cold, high levels of nutrients, little dissolved oxygen, deposit feeders, filter feeders

How Have Human Activities Affected Marine Ecosystems?

Major threats to marine systems

• Major threats to marine systems
• Coastal development
• Overfishing
• Use of fishing trawlers
• Runoff of nonpoint source pollution
• Point source pollution: Discharge pollutants at specific locations
• Habitat destruction
• Introduction of invasive species
• Climate change from human activities
• Pollution of coastal wetlands and estuaries

Why Are Freshwater Ecosystems Important?

Water Stands in Some Freshwater Systems and Flows in Others

• Standing (lentic) bodies of freshwater: Lakes, ponds, inland wetlant=ds
• Flowing (lotic) systems of freshwater: Streams and rivers
• Littoral zone: Near shore where rooted plants grow, high biodiversity,
  • Turtles, frogs, crayfish, and some fish
• Limnetic zone: Sunlight area away from shore, main photosynthetic zone, some larger fish
• Profundal zone: Deepwater too dark for photosynthesis, low oxygen levels, with some fish
• Benthic zone: Decomposers, detritus feeders, and some fish, nourished primarily by dead matter

Major Services Provided by Freshwater Systems

• Ecological Services:
  • Climate moderation
  • Nutrient cycling
  • Waste treatment
  • Flood control
  • Groundwater recharge
  • Habitats for many species
  • Genetic resources and biodiversity
  • Scientific information
• Economic Services:
  • Food
  • Drinking water
  • Irrigation water
  • Hydroelectricity
  • Transportation corridors
  • Recreation
  • Employment

Some Lakes Have More Nutrients Than Others

• Oligotrophic Lakes: Low levels of nutrients and low NPP with very clear water
• Eutrophic Lakes: High levels of nutrients and high NPP and murky water with high turbidity
• Mesotrophic Lakes: Commonly clear water lakes and ponds with beds of submerged aquatic plants and medium levels of nutrients
• Cultural Eutrophication: This occurs when sewage, detergents, fertilizers, and other nutrient sources are introduced into the ecosystem as a result of human water pollution, accelerating the aging process.

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