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Lecture 5: Life in Marine Environment I - Coggle Diagram
Lecture 5: Life in Marine Environment I
Key Physical Drivers of Marine Ecosystem
Light
Light penetration determines photosynthesis zones (euphotic zone) and influences species distribution.
Temperature
Forms thermocline (transition layer between warm surface water and cold deep water).
Vertical temperature gradients affect nutrient mixing and species habitats.
Ocean Currents (Great Ocean Conveyor)
Driven by differences in salinity (haline forcing) and temperature (thermal forcing).
Cold, salty water sinks in polar regions (e.g., North Atlantic), creating deep-water currents.
Warm surface currents flow toward poles, completing the global loop.
Impact
Distributes nutrients and oxygen, sustaining marine life.
Transports heat, regulating global climate.
Mixed Layer Depth
Latitudinal Differences
Tropics
Shallow mixed layer due to strong solar heating and stable stratification.
Temperate Zones
Seasonal variation; deeper mixing in winter due to storms/cooling.
Polar Regions
Deep mixing from strong winds and low surface temperatures.
consequence
Affects nutrient availability (e.g., upwelling in deeper mixed layers fuels productivity).
Influences phytoplankton blooms and food web dynamics.
Why Mixed Layer Depth Varies by Latitude
Tropics
Intense solar radiation → Warm surface layer → Stable stratification → Shallow mixing.
Low nutrient supply to surface waters, limiting productivity except in upwelling zones. (coastal regions)
Temperate
Seasonal cooling/wind → Deeper mixing in winter (Ekmen's Transport) → Nutrients brought to surface → Spring phytoplankton blooms.
Polar Regions
Low temperatures + strong winds → Deep mixing → High nutrient availability → Supports krill and fish populations.
Insights from the World Heat-Map
Biodiversity Hotspots
Coastal zones, coral reefs, and upwelling areas show high species richness.
Anthropogenic Impacts
Overfishing, pollution, and warming reduce biodiversity in tropical and polar regions.
Climate Change Effects
Shifts in species distributions (e.g., poleward migration) due to warming and acidification.
Marine Biodiversity
Drivers of Biodiversity
Physical factors (light, temperature, currents) create diverse habitats (e.g., coral reefs, hydrothermal vents).
Nutrient availability and vertical stratification influence productivity and species richness.
Threats
Climate Change: Warming, acidification, and deoxygenation disrupt ecosystems.
Human Activities: Overfishing, habitat destruction, and pollution accelerate biodiversity loss.
Global Significance
Marine ecosystems provide 50% of Earth’s oxygen and support 3 billion people as a primary protein source.
Biodiversity ensures resilience against environmental changes (e.g., carbon sequestration via blue carbon ecosystems).