Ocean Warming and Acidification Study Notes

Heat Transfer: As atmospheric temperatures rise, heat is transferred to the oceans.
  - The ocean absorbs heat that is radiated back to the Earth by greenhouse gases.
  - It has been estimated that approximately 90% of the Earth's warming over the past 50 years occurred in the oceans.
  - The heat absorbed by oceans can remain for decades and may eventually be transferred back to the atmosphere.
  - The thermohaline circulation is responsible for distributing heat absorbed at the ocean surface to its depths and other regions of the Earth.

Oxygen Availability: Warmer water holds less dissolved oxygen, leading to respiratory stress or even suffocation in marine organisms.
Altered Migration and Reproduction:
- Changes in migratory routes and breeding seasons for marine species, particularly whales.
- Reproductive timing, often closely linked to temperature changes, can be disrupted, notably affecting fish populations.
Habitat Loss: Coral bleaching caused by increasing ocean temperatures leads to habitat degradation.
- As the ocean warms, shallow, sunlit waters, which are ideal habitats for algae and coral, may become deeper due to melting ice.
Toxic Algal Blooms: Warmer waters favor the proliferation of toxic blue-green algae.
- Elevated temperatures prevent the mixing of water layers, enabling these blooms to occur.
- These algal blooms can release toxins harmful to marine life and block sunlight, leading to hypoxia (low oxygen conditions).

Impact of Climate Change on Coral Ecosystems:
  - Coral reef ecosystems are significantly impacted by climate change through various mechanisms:
    - Warming Oceans: Leads to thermal stress and coral bleaching.
    - Sea Level Rise: Affects the structure and viability of coral reefs.
    - Changes in Storm Patterns: Stronger and more frequent storms can cause physical damage.
    - Sedimentation: Increased sedimentation can smother corals.
    - Infectious Disease: Higher temperatures may lead to increased susceptibility to diseases.
    - Altered Ocean Currents: Changes in currents can disrupt nutrient supply and connectivity between reef systems.
    - Ocean Acidification: Increased CO₂ levels lead to lower pH, impacting coral ability to form calcium carbonate skeletons.

Mutualistic Relationship:
- Coral reefs consist of a mutualistic partnership between corals and photosynthetic algae known as zooxanthellae.
- Zooxanthellae provide sugars to corals, while corals supply CO₂ and organic matter (detritus) essential for algae survival.
Temperature Tolerance: Zooxanthellae have a narrow temperature tolerance; when temperatures rise above optimal levels, they leave the reef.
Stress Response:
- Corals lose their color and become more susceptible to disease without their algal partners, which serve as their primary food source.
- Factors such as pollutants from runoff (sediments, pesticides, sunscreens) can also adversely affect the health of zooxanthellae.

Question: Describe one climate change-related threat to coral reef ecosystems and one threat to a marine species other than coral.