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What really lies beneath?

26 July 2013

Humans have long had a great fascination with the sea. The mystery of our oceans has inspired scientific investigation since the 3rd century BC. But even after many centuries of study, Bhavani Narayanaswamy asks, how much do we really know about what lies beneath?

The way Earth's vast oceans support human life is so complex we are only just beginning to understand it. They regulate our climate and weather systems, absorb carbon dioxide from our atmosphere, supply half of our oxygen and are fundamental to primary productivity - the base of the world's marine food chain. Our oceans provide us with roughly 20 per cent of the animal protein eaten around the world, support industries from fisheries and aquaculture, to oil and gas, sport and transport, and provide us with recreational, cultural and spiritual services which are so fundamental to us we are barely aware of them.

Yet despite our intertwined existence, the marine environment continues to puzzle us.
We have been exploring the oceans for centuries, trying to understand the diversity of marine life and how the marine ecosystem works - initially out of curiosity but increasingly so we can harness and manage our critical marine resources responsibly.

In 1872, the UK government converted HMS Challenger into a survey ship for a 130,000 km journey to investigate marine life. This four-year mission identified 4417 new marine species from as far down as 5km. This was a massive step forward in our understanding of the sea, but it would take decades of technological advances for us to discover, let alone investigate, the numerous complex habitats such as trenches, including the Marianas which is around 11km deep, or seamounts of which more than 30,000 are thought to exist, or hydrothermal vents where super-heated water is released from the Earth's crust.

Despite our intertwined existence, the marine environment continues to puzzle us.

With every new study it becomes clear that our current knowledge of marine life is merely a drop in the ocean.

In 2000, a ten-year global Census of Marine Life was launched to formally assess the diversity, distribution and abundance of marine life. The census catalogued life forms from whales to microbes, discovering over 6000 potential new species. In 2011, NERC funded a three-year research project to assess the seafloor biodiversity of some of the world's least-studied marine habitats - seamounts in the south-west Indian Ocean. This ongoing project has already revealed such a rich array of life at these features that two have been proposed to the Convention on Biological Diversity for designation as Ecologically or Biologically Marine Significant Areas.

As well as discovering new species, research projects are increasingly highlighting the complex interaction of human activity and the marine environment. From resource extraction to fishing and waste disposal, human activities are undoubtedly having an impact on the oceans. There is even evidence of human impact as far out at as the Indian Ocean seamounts, particularly from the fishing industry, and this in an area we have only just started to explore.

Across these and other marine areas there is clear evidence of habitat destruction, an increase in harmful algal blooms, changing nutrient contents in seawater and even the introduction of invasive 'alien' species.

Maintaining the biodiversity of life in all its forms is fundamental to the health of our planet. Its importance is recognised by European leaders, and the Marine Framework Strategy Directive aims to ensure European seas achieve and maintain good environmental health. But to maintain that status we need to understand the current state of our seas.

Fishing trawler

Fishing trawler.

Without a complete picture of the marine environment we can't be sure we fully understand the impact we are having and the long-term consequences for our oceans. Quantifying impact on an environment we know relatively little about is a major challenge. European seas have been exploited in one way or another for centuries, so working out a baseline picture of what marine environments were like before human impact is difficult.

But with more and more industries such as mining turning to the oceans for future operations, it is a challenge we must address.

Marine biodiversity and ecosystem function is at the very heart of much of the research we do at the Scottish Association for Marine Science (SAMS), with projects investigating the relationship of diversity and function in organisms ranging from microbes to mammals. Evidence from SAMS' projects is used by UK government advisors to help us achieve 'Good Environmental Status' for our seas, to determine the best locations for Marine Protected Areas, and to feed into the EU-led Marine Strategy Framework Directive. Our knowledge is also contributing to the first UN World Ocean Assessment, which aims to provide sound scientific evidence for the global management of our oceans and seas. Such assessments are critical to ensure the security of our seas and sustain the life forms (many still undiscovered) within them.

So the answer to the question 'what really lies beneath?' is 'more than we know'!

The oceans are vast areas, with many species undiscovered and the lives of many known species still a mystery to us. Different marine habitats will respond differently to human impact, yet despite the work done to assess marine life globally, we don't fully understand the links between marine life and human activity in any single habitat. A step-by-step approach, concentrating on individual regions or habitats, may give us the best chance of tackling the massive challenge of protecting our oceans. It will take an army of trained scientists but it also calls for widespread appreciation of the need to understand the links between marine life and human activity for sustaining our seas.


More information
Dr Bhavani Narayanaswamy is an expert in deep-water ecology at the Scottish Association for Marine Science. Email: Bhavani.Narayanaswamy@sams.ac.uk


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