Why the Ocean Is an Extreme Environment

The ocean's extreme conditions challenge organism survival:

1. Pressure: ~1,000x sea level at Mariana Trench, affecting physiology.
2. Darkness: No sunlight beyond upper layers, hindering photosynthesis and vision.
3. Cold Temperatures: Near-freezing in deep water, slowing metabolism.
4. Salinity: 34–42 ppt; organisms must regulate internal salt/water balance.
5. Oxygen Levels: Low or anoxic zones in deep water challenge aerobic life.
6. Hydrothermal Vents: Extreme heat, pressure, chemical gradients host specialized communities.
7. Ocean Currents: Fast currents displace organisms, affect nutrient transport.

Human impacts (pollution, overfishing, habitat destruction, climate change) add further stress.