Massive Dieoff of Algae 250 MYA: Poisonous Upheaval at PT Junction

Physorg
At the junction of the Permian and Triassic periods around 250 million years ago, the algae of the world appear to have been killed off by massive amounts of hydrogen sulfide. Massive volcanic activity triggered an enormous release of toxic gases as well as large quantities of CO2. The ocean's ecosystems were overturned, as only 1 in 10 ocean species survived. Massive quantities of dead algae, animals, and vegetation descended onto a dark and suddenly anaerobic seafloor, and were buried by large masses of ash and other sediment. In other words, a perfect environment for the formation of oil and other hydrocarbons. So, what happened to them?

The mass extinction at the end of the Permian period almost cleared the planet of life 250 million years ago. Only one in ten species in the ocean survived. Two-thirds of reptiles and amphibians disappeared. Even plants and insects suffered major losses. But in this near-perfect strike, the first "pin" to topple may have been algae, according to researchers studying molecular fossils from this time.

The Permian-Triassic, or P-T, extinction event happened long before dinosaurs had even appeared on the scene. Often called the Great Dying, it was the most dramatic pruning of the tree of life that we have on record. "It was not only the largest, but also the most enigmatic mass extinction of all time," says Roger Summons from MIT.

Unlike the dinosaur die-off, there's no credible evidence of an asteroid impact to blame for the P-T extinction. Instead, scientists have been forced to sort through a number of factors: The formation of the supercontinent Pangaea reduced shallow marine habitats; slower ocean circulation deprived the deep ocean of oxygen; and one of the largest volcanic eruptions in history caused a spike in carbon dioxide that would have greatly warmed the planet.
On top of all that, hydrogen sulfide – a lethal gas that smells of rotten eggs – may have poisoned the ocean and the atmosphere. Summons and his colleagues are leading proponents of this theory, having discovered molecular evidence for a substantial proliferation of bacteria that rely on hydrogen sulfide for their metabolism. _Physorg

More fascinating detail at the link above.

The Earth is about 4.5 billion years old. Photosynthetic organisms have been converting sunlight, CO2, and water into carbohydrates and lipids for about 3.5 billion years. And yet, most of the oil and gas that humans have accessed, originated roughly 200 million years or fewer ago.

Certainly CO2 levels were far higher in earlier periods of geologic history. Uncountable numbers of photosynthetic organisms lived and died to make and keep the planet's atmosphere oxygen rich and CO2 poor (currently 0.04% of atmosphere is CO2 vs over 20% O2).

It is highly likely that other less prominent dieoffs, accompanied by massive volcanism, occurred throughout the long geologic history of the planet. Each time CO2 concentrations shot up, Earth's photosynthetic arsenal massed itself to meet the challenge, and restore the oxygen heavy balance of the planet's gases.

Over and over again, massive volumes of plankton and vegetation were buried in deep anaerobic conditions, leading to unimaginable volumes of hydrocarbon generation. And almost all of that occurring in parts and depths of the Earth's crust which humans have not yet explored with any care.