In News:

A recent study published in Science Advances has offered fresh insights into the timing and duration of the Ocean Anoxic Event 1a (OAE 1a).

What is OAE 1a?

• Definition: A period during the Cretaceous Period (~119.5 million years ago) when Earth's oceans became oxygen-depleted (anoxic), causing significant disruption in marine ecosystems.
• Cause: Triggered by massive volcanic eruptions that released large amounts of CO?, leading to global warming and depletion of oxygen in oceans. This caused the formation of anoxic marine basins.
• Impact: The depletion of oxygen led to the extinction of marine species, especially plankton, and the formation of black shales (organic carbon-rich layers).

Anoxic Marine Basins:

• Characteristics: These are bodies of water with extremely low or absent oxygen, allowing certain microbes and fungi to thrive, while most aerobic organisms perish.
• Significance: Anoxic basins contribute to carbon sequestration by slowing down the decay of organic material, helping in the reduction of atmospheric CO? levels. Examples include the Black Sea, Cariaco Basin, and Orca Basin.

Recent Study Findings (Published in Science Advances):

• Timing: OAE 1a began approximately 119.5 million years ago and lasted for about 1.1 million years, with a long recovery period for ocean ecosystems.
• Methodology: The study used isotopic analysis of volcanic tuffs from Japan's Hokkaido Island to pinpoint the timing of the event.
• Volcanic Eruptions: The study confirmed that volcanic eruptions, particularly from the Ontong Java Nui complex, released CO?, triggering oceanic oxygen depletion.
• Relevance to Modern Climate Change: The study draws parallels between past volcanic CO? emissions and current human-induced warming, warning that rapid modern warming could cause similar disruptions in marine ecosystems and potentially lead to a Holocene extinction.

Holocene Extinction:

• Definition: The ongoing Sixth Mass Extinction, primarily driven by human activities like overexploitation, habitat loss, pollution, climate change, and invasive species.
• Impact: Current extinction rates are 1,000-10,000 times higher than natural rates, with severe consequences for biodiversity and ecosystem services.

Key Mass Extinction Events:

• Permian Extinction (~250 million years ago): Linked to volcanic activity, global warming, and ocean anoxia, leading to the extinction of over 95% of species.
• Cretaceous Extinction (66 million years ago): Caused by an asteroid impact, exacerbated by volcanic eruptions, leading to the extinction of non-avian dinosaurs.
• Holocene Extinction: Caused by human activities, with long-term implications for biodiversity and ecosystem services.

Efforts to Mitigate Extinction:

• Climate Action: Limiting global warming to 1.5°C as per the Paris Agreement.
• Biodiversity Conservation: The 30X30 Initiative, aiming to conserve 30% of lands and oceans globally by 2030.
• Sustainable Practices: Encouraging sustainable resource management to reduce habitat destruction, pollution, and overexploitation.