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.