Marine and Estuary Ecosystems Lecture Notes

Overview of Estuaries

• Estuaries are areas where rivers meet the sea, mixing freshwater and saltwater.
  • Salinity Levels:
    • Freshwater: Less than 0.5% salinity
    • Ocean Water: Greater than 30% salinity
    • Estuaries: Salinity between 0.5% and 30%, but can exceed 30% due to evaporation in isolated ponds.
• Include both deep water habitats and wetlands (e.g., salt marshes and seagrass habitats).
• Highly productive ecosystems:
  • Home to organisms like oysters and seagrasses.
  • Provide nursery habitats for fish, crabs, and other seafood.
  • Important for birdwatching.

Estuaries in North Carolina

• Known as "sounds" (e.g., Albemarle Sound, Pamlico Sound).
• Located behind barrier islands that separate ocean water from river water.
• Major rivers flowing into sounds:
  • Tar-Pamlico River (Pamlico Sound)
  • Neuse River (Pamlico Sound)
  • Cape Fear River (further south)
  • Chowan River and Roanoke River (Albemarle Sound)
• Critical for fisheries economy:
  • Significant blue crab and oyster production.

Marine Environments

Tidal Zone

• Area between low and high tide.
  • Consists of sandy or rocky shores.
  • Organisms must adapt to wet and dry periods (e.g., sea stars, barnacles, crabs, algae).

Neuritic Zone

• Also known as the coastal zone.
  • Extends from the low tide line to the edge of the continental shelf (approx. 200 meters deep).
  • Always covered with water, supports photosynthetic organisms.
  • Common organisms: Fish, phytoplankton, kelp, turtles, jellyfish.

Pelagic Zone

• Open ocean zone beyond the continental shelf.
  • Largest habitat on Earth, divided based on light and depth:
  • Photic Zone:
    • Surface to about 200 meters deep with sufficient light for photosynthesis.
    • Dominated by phytoplankton, primary producers.
  • Benthic Zone:
    • 200 to 4,000 meters deep, little to no light.
      • Increased pressure and decreased oxygen levels.
      • Food chains based on detritus and organisms moving between zones.
  • Example organisms: Baffle swimming crab, vampire squid, anglerfish.
  • Abyssal Zone:
    • 4,000 to 6,000 meters deep, no light, very low oxygen, high pressure.
      • Food webs based on detritus and chemosynthesis at deep-sea vents.
  • Hadal Zone:
    • Below 6,000 meters.
  • Benthic Zone (Sediment):
    • Spans from continental shelf to abyssal zone.