Evolution: plankton and the ocean/carbon cycle (Introduction)

by David Turell , Wednesday, October 02, 2019, 20:12 (1878 days ago) @ David Turell

An excellent article on the contribution of plankton to evolution and ocean's carbon cycle environment:

https://www.quantamagazine.org/how-jurassic-plankton-stole-control-of-the-oceans-chemis...

"... researchers largely take it for granted that ecological relationships are the primary force of evolution.

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"In the oceans, for example, ecological success was closely tied to the inanimate forces steering ocean chemistry until only about 170 million years ago.

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"Between the Ordovician period, about 485 million years ago, and the early Jurassic, about 170 million years ago, there was abundant volcanic activity, which led to the extinction of many, many marine species. During that time, organisms thrived or died mostly based on factors beyond their control...But since the middle of the Jurassic, that hasn’t really been the case.

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"That’s because layers of dead carbonate organisms on the seafloor can dissolve when the seawater pH starts to drop, and the released carbonate ions then raise the pH again. Places where there is an abundance of dead carbonate organisms have always acted as a buffer to stabilize the ocean’s chemistry. But before these calcifying plankton appeared, this carbonate buffer was restricted to shallow continental shelves. There simply wasn’t enough chalky floor space to buffer against the extreme changes in acidity from volcanoes or other geological events.

"Then the calcifying plankton took over. Nowadays, you’d be hard-pressed to find ocean waters less than 100 meters deep that don’t contain calcifying plankton. Despite their teeny size, they may account for nearly 12% of the total biomass in the oceans. And they’ve completely altered the way carbon moves around the planet. About 80% of the carbon-containing rocks on Earth are derived from the remains of these plankton and other marine calcifiers — even though by mass, these plankton may account for less than 0.2% of Earth’s carbon-containing life.

“'All of a sudden you have all these little teeny tiny carbonate organisms that together add up to this huge carbonate sink that draws a ton of calcium carbonate out of the ocean, and as is articulated nicely in the paper, changes the dynamics of where that carbonate is deposited,” said Rowan Martindale, a paleoecologist at the University of Texas, Austin. “And so it really fundamentally changes how the ocean buffering capacity works.”

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"And that’s exactly what he and his team saw — until 170 million years ago, when calcifying plankton became widespread. Then the organisms abruptly decoupled from fluctuations in the temperature and magnesium levels, and aragonite organisms began to dominate despite unfavorable conditions.

"The researchers weren’t able to demonstrate conclusively that the plankton caused this shift, but they argued that simply by existing — and dying — in such huge numbers in deeper waters, these creatures created a deep reserve of carbonate that could then dissolve to buffer ocean chemistry whenever environmental changes pushed seawater to become more acidic.

"As Eichenseer and his co-authors noted in the paper, the ocean’s calcium cycle wasn’t the only thing this explosion in calcifying plankton would have changed: Because of knock-on effects, virtually the entire marine ecosystem would have changed. Dying plankton drop toward the sea bottom in a steady rain; their decomposition is a process that depletes seawater of dissolved oxygen. But because calcifying plankton are relatively heavy, they sink into the depths before they fully decompose, leaving more oxygen in shallow waters. That change might have increased the range of organisms that could live along continental shelves and made them less vulnerable to other environmental changes.

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"Eichenseer also notes that the plankton didn’t exactly rewrite the laws of evolution — they just tipped the balance that made biotic interactions like competition and predation more important. “Earth’s life systems stabilized. And these environmental perturbations, they still happened, but life was prepared.'”

Comment: It seems to me if God is in charge, He introduced plankton to make this shift in ocean characteristics, allowing evolution to advance.