Global oceans could be in a more fragile state than previously apparent, new research published today suggests.
An international team involving Trinity College Dublin (TCD) has shown that current de-oxygenation levels are very similar to those that were implicated in one of the world’s largest ever mass extinctions.
The research published in international journal Nature Geosciences suggests that oceanic anoxia played an important role in ecosystem disruption and extinctions in marine environments during the Triassic–Jurassic mass extinction.
Sampling of the Carnduff cores, which were drilled in the Larne Basin, Northern Ireland
This was a major extinction event that occurred around 200 million years ago, and one of a series linked to the collapse of global ecosystems and extinction of species.
The international research team led by scientists from Royal Holloway in Britain, and involving scientists from Trinity College Dublin’s School of Natural Sciences and the Netherlands Utrecht University was able to link two key aspects associated with the Triassic–Jurassic mass extinction.
The team used chemical data from ancient mudstone deposits obtained from drill-cores in Northern Ireland and Germany.
The scientists say they discovered that pulses in de-oxygenation in shallow marine environments along the margins of the European continent at that time “directly coincided” with increased extinction levels in those places.
A core sample of ~201 million year old sediments obtained from the Carnduff-2 core, drilled in the Larne Basin (Northern Ireland), showing the shell of an animal that lived on the seabed shortly after the Triassic–Jurassic global mass extinction
The team also found that the global extent of extreme deoxygenation was rather limited, and similar to the present day.
“Scientists have long suspected that ocean de-oxygenation plays an important role in the disturbance of marine ecosystems, which can lead to the extinction of species in marine environments,” Micha Ruhl, assistant professor in Trinity’s School of Natural Sciences and a member of the research team, has said.
“The study of past time intervals of extreme environmental change shows this to be the case, which teaches us important lessons about potential tipping points in local, as well as global ecosystems in response to climatic forcing,”Ruhl said.
“Crucially however, the current findings show that even when the global extent of de-oxygenation is similar to the present day, the local development of anoxic conditions and subsequent locally increased extinction rates can cascade in widespread or global ecosystem collapse and extinctions,”he warned.
He said this can happen “even in areas where de-oxygenation did not occur”.
“It shows that global marine ecosystems become vulnerable, even when only local environments along the edges of the continents are disturbed,”he said.
“Understanding such processes is of paramount importance for assessing present day ecosystem stability, and associated food supply,”he said.
He said this was especially so “in a world where marine deoxygenation is projected to significantly increase in response to global warming and increased nutrient run-off from continents”.
This research was supported by a Natural Environment Research Council Doctoral Training Partnership award and the National Natural Science Foundation of China.
