“We see more and more toxic algae blooms in lakes and in shallow marine environments that are related to increases in temperature and changes in plant communities which are leading to increases in nutrient contributions to freshwater habitats. So, a lot of parallels to today. The volcanism was a source of CO2 in the past, but we know that the rate of CO2 input seen back then was similar to the speed of CO2 increases today because of anthropogenic effects. Tracy Frank, University of Connecticut
The worst extinction event in earth history was the Permian extinction, or if you prefer, the great dying that occurred 252 million years ago. The event caused the loss of 57% of biological families, 83 % of genera, and equally high percentages of terrestrial and marine species. The event also wiped out most insects, according to Wiki.
Humankind has jump-started a sixth mass extinction, also referred to as the Anthropocene extinction event. The current event that we are in the midst of has similarities to the end-Permian with the death of fungi, bacteria, plants, and animals at the hands of humans.
A team of researchers dug deep into the fossil records and reported the findings in the journal Nature Communications. In their study abstract, they introduce the topic this way, “Harmful algal and bacterial blooms linked to deforestation, soil loss, and global warming are increasingly frequent in lakes and rivers. We demonstrate that climate changes and deforestation can drive recurrent microbial blooms, inhibiting the recovery of freshwater ecosystems for hundreds of millennia.”
From the press release in UCONN Today:
In a healthy ecosystem, microscopic algae and cyanobacteria provide oxygen to aquatic animals as a waste product of their photosynthesis. But when their numbers get out of control, these microbes deplete free oxygen, and even release toxins into the water. By studying the fossil, sediment, and chemical records of rocks near Sydney, Australia, the researchers discovered that several pulses of bloom events had occurred soon after the first volcanic rumblings of the end-Permian mass extinction. Once the bottom-feeder animals, or “detritivores,” were killed off, there was no one left to keep the microbes in check. The freshwater systems then seethed with algae and bacteria, delaying the recovery of animals for perhaps millions of years.
Frank and Fielding study sediment, and Frank explains their contribution to the work, which was performed while both were at the University of Nebraska–Lincoln, was in gleaning details about the conditions of the environment, and the resulting toxic soup, from the layers of sediment.
The three main ingredients for the toxic soup are accelerated greenhouse gas emissions, high temperatures, and abundant nutrients. The volcanic eruptions provided the first two, while sudden deforestation caused the third. When the trees were wiped out, the soils bled into the rivers and lakes, providing all the nutrients that the microbes would need. When the researchers compared the fossil records of different warming-related mass extinctions, the team found extremely similar fossil records. This implicates deadly microbial blooms as repeat offenders of freshwater extinctions during extreme warming events.
One of the researchers who arrived at the University of Connecticut, Chris Fielding, pointed to the end-Permian as the parallel to what we see today with freshwater blooms of algae and subsequent dead zones in marine environments.
“The other big parallel is that the increase in temperature at the end of the Permian coincided with massive increases in forest fires. One of the things that that destroyed whole ecosystems was fire, and we’re seeing that right now in places like California. One wonders what the longer-term consequences of events like that as they are becoming more and more widespread.”
Many actions can slow this process down, reducing CO2 emissions and preventing agricultural runoff from entering saltwater and freshwater habitats.
_____________________________________
