Marine and Coastal Systems - Key Concepts and Notes

Marine and Coastal Systems Notes

Housekeeping

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Presentation Outline

  • Structure and Functions of Oceans
    • Topics include ocean bathymetry, ocean water composition, ocean life zones, and surface and deep currents.
  • Ocean Resources
    • Discussion on coral reefs, estuaries, salt marshes, mangrove forests, and their ecosystem services.
    • Exploration of stressors on oceans.
  • Fisheries and Marine Reserves
    • Current pressures on marine fisheries, impact of industrial fishing practices, fisheries management, and historical examples such as the Atlantic Cod Fishery.
    • Importance of marine reserves and protected areas for conservation.

Structure and Functions of Oceans

  • Ocean Coverage and Depth:
    • Oceans cover ~71% of Earth’s surface; mean depth of ~3.8 km.
    • NASA budget for ocean research significantly less than comparative agencies (NOAA).
  • Importance of Oceans:
    • Interactions with atmosphere, geosphere, biosphere.
    • Influences climate and supports biodiversity & ecosystems.
    • Resource provider (food, employment) and transportation mode.
Ocean Bathymetry
  • Refers to the topography of the ocean floor, influenced by geological processes:
    • Divergence, convergence, subduction, and volcanism.
  • Major structures:
    • Continental Shelf, Slope, Trench, Abyssal Plain.
Ocean Composition
  • Physical Composition of Ocean Water:
    • 96.5% water, 2.5% dissolved salts (e.g., NaCl), nutrients (nitrogen, phosphorus), and dissolved gases (O2).
    • Critical reservoir for atmospheric CO2.
Stratification of Ocean Water
  • Ocean water vertical structure (thermocline, halocline, pycnocline):
    • Surface (warm and stir from wind), Deep (cold, dense).
    • Temperature and salinity affect density:
    • Higher temperature = lower density.
    • Higher salinity = higher density.
Ocean Life Zones
  • Distinct zones based on light penetration and depth:
    • Photic Zone: well-lit top layer (supports most life).
    • Aphotic Zone: lack of light.
    • Pelagic Zone: open water habitats.
    • Benthic Zone: ocean floor habitats.
    • Zones: Littoral (shore), Neritic (coastal), Oceanic (open sea).
Marine Biodiversity
  • Organisms categorized into:
    • Planktonic: depend on currents (e.g., phytoplankton).
    • Nektonic: free-swimming organisms.
    • Benthic: organisms on the sea floor.
  • Hydrothermal vent ecosystems depend on chemosynthetic bacteria (no photosynthesis).

Ocean Resources

  • Types of Marine Habitats:
    • Coral reefs (biodiverse, endangered): 25% of marine species.
    • Estuaries (critical for aquatic life).
    • Mangroves and salt marshes (critical habitats, ~70% lost).
  • Threats to Ocean Resources:
    • Overfishing, habitat loss, pollution, and climate change leading to biodiversity loss.
    • Coral Reefs:
    • Sensitive to temperature/light; coral bleaching and diseases as threats.
    • Estuaries:
    • Pollution, habitat alteration, overfishing threats; vital for nutrient cycling.

Ocean Pollution and its Effects

  • Pollutants:
    • Land-based sources: ~80% of ocean pollution.
    • Plastics (microplastics), chemicals (mercury) harmful to marine life.
  • Nutrient Runoff:
    • Causes algal blooms (eutrophication), leading to dead zones.
    • Noise Pollution:
    • Disrupts marine life communication and navigation.

Fisheries and Marine Reserves

  • Fisheries Status:
    • Overfishing affecting food security (90% of marine fish stocks overexploited).
    • Aquaculture importance and issues of sustainability.
Impacts of Industrial Fishing
  • Industrial practices causing ecosystem damage:
    • Longlining, drift netting, bottom trawling leading to bycatch and habitat destruction.
  • Bycatch:
    • Significant unintentional capture of non-target species, harming biodiversity.
Modern Fisheries Management Strategies
  • Sustainable Management:
    • Defined by Maximum Sustainable Yield (MSY).
    • Precautionary and ecosystem-based management approaches.
    • Involves cooperation with stakeholders.
  • Marine Reserves:
    • Areas where fishing is prohibited or restricted to encourage population recovery.
    • Increase in the effectiveness with larger reserves
The Atlantic Cod Collapse
  • Factors include overfishing and poor management practices.
  • Closed fisheries maintained till stocks recover but show slow signs of recovery.

Conclusion

  • Oceans are crucial for global biodiversity and human activity.
  • Pressures due to climate change, pollution, and overfishing necessitate urgent action for conservation and sustainable management.