How deep sea creatures survived the killer asteroid

Cardiff University researchers answer the key question.

by Madeleine Banfield

Researchers at Cardiff University have continued to make a significant contribution to scientific discoveries. A new study has shed light on the mysterious survival of deep sea creatures after an asteroid collision resulted in a mass extinction 65 million years ago.

Many scientists believe that an asteroid collided with the Mexican Yucatan peninsula around 65 million years ago. The impact caused many different catastrophic events to occur, for example the excess amount of debris blocked out the sunlight, whilst the rise of greenhouse emissions similarly increased the temperature of the Earth. This starved the planet of natural resources, whilst earthquakes and tsunamis also contributed to making an inhospitable environment to survive. Additionally, there was an increase in Sulphur Trioxide (SO3) in the atmosphere. This caused acid rain which dramatically impacted water sources, like rivers and lakes, and oceans, especially in the Epipelagic Zone. These hostile factors resulted in the mass extinction of dinosaurs, invertebrates, large marine animals and also microscopic organisms.

It was believed that this collision cut off food supplies for many different animals. Subsequently, scientists were extremely puzzled because of the continued survival of animals in the deep sea. This study, which was led by PhD student Heather Birch from the School of Earth and Ocean Sciences, provides answers to some long sought after questions.

The composition of shell fossils, which were found in drilling cores from the South Atlantic Ocean floor, were analysed during this research project. The findings provided information to examine the movement of organic matter from the surface of the sea to the sea bed after the collision.

This research enlightened the otherwise murky understanding of this subject, and Heather Birch explains that their research has exposed ‘some types of photosynthesising organisms, such as algae and bacteria, were living in the aftermath of the asteroid strike’.

This revelation suggests that the asteroid did not destroy all potential life lines. Indeed, algae and bacteria offered a constant, if not slow, food supply to the sea creatures that were situated near the ocean bed. This study has helped to answer how these sea creatures continued to exist during this destructive period.

Additionally, this study has also suggested that it only took 1.7 million years for the food supply to return to its normal state. This is surprising as it is half of the time that was previously estimated, suggesting the capability that the Earth has to adapt to difficult climates and physical phenomena.

The survival of deep sea creatures has consistently puzzled scientists because the asteroid caused chaotic upheaval to many ecosystems. The findings, as Heather Birch affirms, answer ‘one of the outstanding questions that still remained regarding this period of history’. This research has offered vital clarity, and the paper can be read fully in the April publication of the Geology journal.

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