An unexplored realm

The deep-ocean margin extends from the edge of the 200 metre deep continental shelf to a depth of around 4 000 metres where the ocean basin begins. Europe’s deep ocean margins cover an area of 3 million km2 and run for some 15 000 km, from the Arctic in the north to the Mediterranean in the south, and from the Atlantic in the west to the Black Sea in the east.

Yet this vast area remains largely unexplored and poorly understood. What we do know is that the deep ocean is a major carbon sink, and as such it influences the processes behind climate change. It also harbours unique, as yet largely untapped, genetic resources.

The aim of HERMES is to study this underwater world before it is irreparably changed or damaged by climate change and human activities. The project has a particular focus on ‘biodiversity hotspots’, locations where the environmental conditions contrive to enable large numbers of species, both known and unknown, to thrive.

The 50 project partners come from universities, government laboratories, non-governmental organisations, research institutes and private companies located in 18 countries. They include experts in marine biology, geology, oceanography, biogeochemistry, microbiology, geophysics, modelling and the socio-economic sciences.

With most of Europe’s deep ocean margins lying within its 200 nautical mile Exclusive Economic Zone (EEZ), the project has particularly urgency. States have exclusive rights over the marine resources inside this area, and activities such as bottom trawling, hydrocarbon exploration and extraction and deep-sea mining are at an all time high. If policy makers are to successfully oversee the sustainable management of Europe’s valuable marine resources, information from HERMES will be vital, as it is the first project to integrate research from many disciplines in a wide range of environments.

Diving down into the depths

In the first half of the project alone, the HERMES partners embarked on some 80 expeditions around the European margin, including the Nordic slope off the coast of Scandinavia, the Porcupine-Rockall area in the Atlantic, the eastern and western Mediterranean and the Black Sea.

The team used remotely operated vehicles, tethered to the mother ship and fitted with cameras to peer into this hidden world. Specially adapted tools attached to these vehicles enabled the scientists to collect data on biodiversity hotspots such as cold seeps, where hydrocarbon- rich fluids seep out of the seabed, cold-water coral mounds and reefs, canyons, and anoxic areas, where the sea water is low in oxygen. As information is gathered, it is archived and made available using the pan-European GIS (geographic information system).

Uncovering a hidden world

One of the project’s most important findings highlights the link between biodiversity and ecosystem functioning. The scientists demonstrated that ecosystem functioning in the deep sea is exponentially linked to the number of species living there. In other words, if species are lost due to human activities or other causes, the consequences for these ecosystems could be dire.

Another finding has implications for the fishing industry. Fishermen often catch species other than those targeted; this ‘by-catch’ is discarded. Many of these by-catch species live over a wide depth range. As modern fishing gears reach down to depths of 2 000 metres, it is now having major impacts on deep-water ecosystems.

Other discoveries highlight how much we still have to learn about our continent’s ocean margins. In the central Mediterranean, a ‘hanging garden’ of coral was discovered growing downwards from a reef, whilst a very rich deep water coral reef was found lying southeast of Scotland’s Outer Hebrides islands. In the apparently barren deep Black Sea novel microbial communities have been discovered that may lead to new medicines.

Surveys of undersea canyons in the northwest Mediterranean are revealing how a type of seasonal current called Dense Shelf Water Cascading (DSWC) moves vast amounts of water and sediment to the deep ocean, reshaping the ocean floor and bringing with it oxygen and nutrients that recharge this hidden world and maintain significant shrimp fisheries. The HERMES team is concerned that climate change could reduce the frequency and intensity of this phenomenon, thereby affecting deep-sea ecosystems and the organisms that live there.

Elsewhere, scientists exploring the depths of the Tyrrhenian Sea were horrified by the amount of rubbish caught up in the coral there.

Spreading the word

The project’s partners are working hard to transform their findings into policy advice for those responsible for managing Europe’s deep sea environments and resources. For example, its Science Policy Panel brings together HERMES scientists and participants with representatives of key European agencies, industry and non-governmental organisations. Through this and other means, the HERMES team is helping to make sure that the people at the top know what is going on at the bottom of the sea.