If current climate trends follow historical precedent, ocean ecosystems will be in state of flux for next 10,000 years, according to Scripps Oceanography researchers
If history’s closest analog is any indication, the look of the oceans will change drastically in the future as the coming greenhouse world alters marine food webs and gives certain species advantages over others.
Scripps Institution of Oceanography, UC San Diego, paleobiologist Richard Norris and colleagues show that the ancient greenhouse world had few large reefs, a poorly oxygenated ocean, tropical surface waters like a hot tub, and food webs that did not sustain the abundance of large sharks, whales, seabirds, and seals of the modern ocean. Aspects of this greenhouse ocean could reappear in the future if greenhouse gases continue to rise at current accelerating rates.
The researchers base their projections on what is known about the “greenhouse world” of 50 million years ago when levels of greenhouse gases in the atmosphere were much higher than those that have been present during human history. Their review article appears in an Aug. 2 special edition of the journal Science titled “Natural Systems in Changing Climates.”
For the past million years, atmospheric CO2 concentrations have never exceeded 280 parts per million, but industrialization, forest clearing, agriculture, and other human activities have rapidly increased concentrations of CO2 and other gases known to create a “greenhouse” effect that traps heat in the atmosphere. For several days in May 2013, CO2 levels exceeded 400 parts per million for the first time in human history and that milestone could be left well behind in the next decades. At its current pace, Earth could recreate the CO2 content of the atmosphere in the greenhouse world in just 80 years.
In the greenhouse world, fossils indicate that CO2 concentrations reached 800-1,000 parts per million. Tropical ocean temperatures reached 35º C (95º F), and the polar oceans reached 12°C (53°F)—similar to current ocean temperatures offshore San Francisco. There were no polar ice sheets. Scientists have identified a “reef gap” between 42 and 57 million years ago in which complex coral reefs largely disappeared and the seabed was dominated by piles of pebble-like single-celled organisms called foraminifera.
“The ‘rainforests-of-the-sea’ reefs were replaced by the ‘gravel parking lots’ of the greenhouse world,” said Norris.
The greenhouse world was also marked by differences in the ocean food web with large parts of the tropical and subtropical ocean ecosystems supported by minute picoplankton instead of the larger diatoms typically found in highly productive ecosystems today. Indeed, large marine animals—sharks, tunas, whales, seals, even seabirds—mostly became abundant when algae became large enough to support top predators in the cold oceans of recent geologic times.
“The tiny algae of the greenhouse world were just too small to support big animals,” said Norris. “It’s like trying to keep lions happy on mice instead of antelope; lions can’t get by on only tiny snacks.”
Within the greenhouse world, there were rapid warming events that resemble our projected future. One well-studied event is known as the Paleocene-Eocene Thermal Maximum (PETM) 56 million years ago, which serves as a guide to predicting what may happen under current climate trends.
That event lasted about 200,000 years and warmed the earth by 5-9° C (9-16° F) with massive migrations of animals and plants and shifts in climate zones. Notably, despite the disruption to Earth’s ecosystems, the extinction of species was remarkably light, other than a mass extinction in the rapidly warming deep ocean.
“In many respects the PETM warmed the world more than we project for future climate change, so it should come as some comfort that extinctions were mostly limited to the deep sea,” said Norris. “Unfortunately, the PETM also shows that ecological disruption can last tens of thousands of years.”
The Latest on: Marine Food Web
- Climate change is totally reshaping ocean communitieson December 2, 2019 at 6:20 am
While one degree Celsius may not seem like a big change, for those fish and other marine organisms already at their maximum temperature tolerance the shift is enough to alter their chances of success ...
- Scientists used loudspeakers to make dead coral reefs sound healthy. Fish flocked to them.on December 1, 2019 at 6:45 am
Simpson, a marine biology professor at the University of Exeter and a senior author of the ... The new fish populations included species from all parts of the food web, such as scavengers, herbivores ...
- Scientists Are Using Speakers to Revive Damaged Coral Reefs By Luring Fish Back With Healthy Reef Soundson November 30, 2019 at 7:04 am
Photo by Harry Harding / University of Bristol Fish biologist Dr Mark Meekan, of the Australian Institute of Marine Science added: “Of course ... The researchers said that the diversity included ...
- Toxic Coastal Fog Linked To Dangerously High Levels Of Mercury In Mountain Lionson November 29, 2019 at 11:23 am
Marine fog appears to be responsible for elevated levels of mercury in coastal terrestrial food webs, and it’s trickling all the way to the top, according to new research published this week in ...
- Sounds of the past give new hope for coral reef restorationon November 29, 2019 at 2:03 am
Australian Institute of Marine Science fish biologist Dr Mark Meekan added ... This diversity included species from all sections of the food web - herbivores, detritivores, planktivores and predatory ...
- International Team of Scientists Complete Largest Global Assessment of Ocean Warming Impactson November 28, 2019 at 9:24 am
While one degree Celsius may not seem like a big change, for those fish and other marine organisms already at their maximum temperature tolerance the shift is enough to alter their chances of success ...
- How the Suez Canal will continue to change Mediterranean Seaon November 28, 2019 at 3:51 am
“Along the Levantine coast, you find in general more Lessepsian species than native,” Stelios Katsanevakis, professor of marine ecology at the University of the Aegean, told Al-Monitor. “This has ...
- Wikifactory and Thought For Food Challenge: Solutions to Sustainably Feed the Worldon November 28, 2019 at 12:02 am
There are many ongoing efforts to use 3D printing for the purposes of increasing sustainability in the world, from marine applications and reducing plastic ... and a data visualization web API for ...
- High Level of Mercury Found in Pumas Linked to Coastal Fogon November 27, 2019 at 7:52 pm
Coastal fog has been implicated as the likely culprit. The study entitled "Marine fog inputs appear to increase methylmercury bioaccumulation in a coastal terrestrial food web” conducted by scientists ...
- Study traces atmospheric source of super-toxic methylmercury in terrestrial food webon November 26, 2019 at 11:16 am
Marine fog brings more than cooler temperatures to coastal areas ... the study is the first to trace the atmospheric source of super-toxic methylmercury in the terrestrial food web up to a top ...
via Google News and Bing News