Aquatic Life Zones

Aquatic Life Zones

Saltwater and freshwater aquatic life zones cover 75% of the

Earth’s surface

Aquatic Life Zones: The Basics

temperature dissolved oxygen

content availability of food availability of light

and nutrients necessary for photosynthesis.

The key factors determining biodiversity in aquatic systems are

Most of the Earth Is Covered with Water

Aquatic life zones• Saltwater: marine • Oceans and estuaries• Coastlands and shorelines• Coral reefs• Mangrove forests

• Freshwater• Lakes• Rivers and streams• Inland wetlands

Aquatic Trophic Structure

Plankton Floats• Phytoplankton• Zooplankton• Nanoplankton

Nekton Swims Benthos Bottom Decomposers

Distribution of Marine Life Temperature Dissolved oxygen Availability of food

Availability of light and nutrients needed for photosynthesis • Euphotic - light• Disphotic - twilight• Aphotic - dark

Importance of Marine Aquatic Systems

Irreplaceable reservoirs of biodiversity

Provide major ecological and economic services.

Marine Ecological and Economic Resources

Reservoirs of diversity in three major life zones• Coastal zone• Usually high NPP

• Open sea• Ocean bottom

Highly Productive Coastal Zones Estuaries and coastal wetlands • River mouths, Inlets, Bays,

Sounds, Salt marshes• Mangrove forests• High NPP• Nutrients, Light• O2 can be limited

Seagrass Beds• Support a variety of marine

species, stabilize shorelines, reduce wave impact

• High NPP• Nutrients, Light, O2

Intertidal Zones High NPP• Nutrients• Dissolved O2

• Light Rocky & Sandy shores• barrier beaches

Organisms must adapt to deal with daily salinity and moisture changes

Coral Reefs

Extremely high NPP• Marine equivalent of

tropical rain forests• Habitats for one-

fourth of all marine species

Tropical• Temperature• Light• Nutrients• O2

Pelagic and Benthic Zones

Pelagic = Open Ocean Vertically Stratified• Light & Nutrients• Euphotic zone

• Plankton & Nekton• Bathyal zone

• Deposit feeders• Filter feeders

• Abyssal zone:• Deposition of CaCO3

• Upwellings NPP is variable

Freshwater Ecosystems

Freshwater ecosystems provide major ecological and economic services and are irreplaceable reservoirs of biodiversity.

Lentic and Lotic Systems

Standing (lentic) bodies of freshwater• Lakes• Ponds• Inland wetlands

Flowing (lotic) systems of freshwater• Streams• Rivers

Lentic Systems Formation of lakes• Geologically short-lived

Four zones based on depth and distance from shore• Littoral zone• Limnetic zone• Profundal zone• Benthic zone

Lentic Nutrient Levels Oligotrophic lakes• Low levels of nutrients and

low NPP Eutrophic lakes• High levels of nutrients and

high NPP Mesotrophic lakes• Intermediate

Cultural eutrophication leads to hypereutrophic lakes

Freshwater Streams and Rivers Carry Water from the Mountains to the Oceans

Watershed, drainage basin• Surface water runoff• Groundwater storage

Three aquatic life zones • Channel• Riparian• Floodplain

Marshes Swamps Prairie potholes Floodplains Arctic tundra in summer

Intense Nutrient Cycling and Storage

High NPP

Freshwater Inland Wetlands

What impacts aquatic life zones?

Marine Agriculture Logging Mining Waste Disposal Dams Overfishing Plastic Melting ice caps and

glaciers

Fresh water Agriculture Logging Mining Waste Disposal Dams Diversions Groundwater withdrawal