Ocean depths no haven from global catastrophes
There may be nowhere for life to hide from the effects of climate change or asteroids hitting the Earth, according to research presented by a Southampton marine biologist at the BA Festival of Science.
Presenting the Charles Lyell Award Lecture at the BA Festival, Dr Jon Copley of the University of Southampton is sharing a first-hand account of recent discoveries on the ocean floor, where "islands" of exotic deep-sea life thrive around volcanic vents and other seabed features that were unknown 30 years ago.
Scientists used to think these "islands" on the ocean floor acted as air-raid shelters for some species during global catastrophes. Carpets of mussels and swarms of shrimp thrive in these seemingly hostile environments, nourished by minerals seeping from the Earth's crust. This food source is independent of the world above and anything that disrupts it—such as an asteroid slamming into the Earth and blotting out the Sun.
But Dr Copley and his colleagues have discovered seasons in the sex lives of these shrimp and mussels on the seafloor. Despite living in the dark ocean depths, these species still follow the seasonal cycles of the sunlit world above, breeding in late autumn and hatching their offspring in early spring.
The inhabitants of these "islands" on the ocean floor have plenty of food all year round as adults, thanks to life-sustaining minerals seeping from the Earth's crust. But their offspring grow up away from these havens, feeding on whatever sinks from sunlit surface waters. So the animals time the release of their offspring to coincide with a spring bloom in microscopic plant life growing at the surface. This link to the sunlit world above has been overlooked, according to Dr Copley.
"I used to think these deep-sea communities would be safe from whatever havoc happens up here," says Copley. "But finding seasonality down there shows that life beneath the waves is far more connected than we realised. Like nineteenth-century naturalists, we are enjoying a golden age of discovery as we visit these previously-unexplored "islands" in the abyss – and we are gaining new insights into the patterns of life throughout the oceans as we do so."
Dr Copley warned that as climate change alters the pattern of life in surface waters, these newly-discovered connections could carry its effects to the remote corners of the ocean depths – although researchers have no evidence yet of impacts down there from climate change.
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