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Expedition JC237, part of the UK’s CLASS programme, aims to carry out a whole series of important observations to help close these knowledge gaps. The deep sea is vast and challenging to investigate, hence the number of studies that have provided repeated observations from a single area, tracking how the environment and its inhabitants change over space AND time, are extremely limited. On JC237, we will visit two areas that are key for this type of long-term research: the Whittard Canyon on the Celtic Margin, and the Porcupine Abyssal Plain Sustained Observatory.
At both locations, we will use the latest robotic, sensor and sampling technologies to characterise the faunal communities and their spatial distribution, map the bathymetry and sediment type in unprecedented detail, and capture the fine-scale characteristics of the bottom water and currents. This will allow us to create detailed habitat maps, quantify biodiversity, and study the environmental factors that influence the biodiversity patterns. Comparing our new observations with results from previous investigations in our study areas will give us insight into the pace and extent of changes in deep seafloor ecosystems.
As we learn more about how the ocean environment will change in the future, we will also be able to predict better what effect that will have on the seabed fauna, and hence where and which conservation actions need to be taken to preserve this unique environment.
Submarine canyons, which can be found on all of the World’s continental margins, form the main connection between the continental shelves and the deep sea. Their complex terrain and associated unique current regimes create a variety of environmental niches that can host a highly diverse seabed fauna. Submarine canyons are dynamic environments: seabed currents and tides get amplified locally, regular flank collapses erode the canyon walls, and large volumes of sediment can be flushed down the canyon paths. The latter unfortunately don’t only transport sediment to the deep sea, but also pollutants and increasing amounts of litter. Canyon ecosystems have adapted, and even thrive, thanks to these dynamic processes.
However, submarine canyons, and their interfluves (the areas between the canyon branches), also make for rich fishing grounds. Bottom trawling activities can cause major disturbance, both by mechanical abrasion of the seabed, and through the excess sediment plumes they create. This may push canyon communities beyond their limits. Understanding the natural dynamics of submarine canyon systems, and how the ecosystem is adapted to, or relies on this, will enable us to assess how human activities interfere with these processes, and what their impacts really are.
Whittard Canyon is a large submarine canyon system on the Celtic Margin, located over 300 km from shore, and ranging from 200 m to more than 4000 m water depth. It has multiple branches that cut deeply into the continental margin. Previous research has shown that it hosts a wide variety of habitats, including spectacular cliffs covered in cold-water corals, clams or oysters. The team from NOC developed a series of new techniques to map out those vertical habitats in unprecedented detail. Whittard Canyon hosts highly amplified internal tides, forming partly standing waves in places, and recent research as part of the CLASS project has shown that it is prone to regular sediment flows that can have speeds and volumes similar to those observed in submarine canyons much closer to shore, that are directly linked to river systems on land. So far, the sources and triggers for these sediment flows still are an enigma.
In 2015, a large expedition took place in the Whittard, Canyon, as part of the ERC-funded CODEMAP project. The data collected during that expedition form the basis for the JC237 repeat visits. You can find a series of informative videos on the CODEMAP2015 YouTube playlist.
Part of the Whittard Canyon system (the Explorer and Dangaard Canyon side-branches) is designated as The Canyons Marine Conservation Zone (MCZ), and on 13 June 2022, a series of new Byelaws came into force prohibiting bottom contact fisheries in the area, in order to protect habitats such as cold-water coral reefs, coral gardens and seapen and burrowing megafauna. Our JC237 expedition provides the unique opportunity to document the seabed status at the start of this protection, creating the necessary baseline information for future monitoring of the area.
The Porcupine Abyssal Plain is one of only two sites globally where deep-sea floor biological communities have been studied for periods longer than 30 years. Our first visit to the site was in June 1985 and our most recent in May this year. Interest in the area was first sparked by our discovery that seasons are felt on the deep-sea floor – the main food source, known as phytodetritus, is produced in the surface ocean bloom of phytoplankton in spring and arrives on the seafloor 3 miles down (4850 m water depth) in late May each year. We then discovered that the animal community living on the abyssal plain responds to this food source, and also appeared to be changing unexpectedly over the years. We called that change the ‘Amperima Event’, after a small sea cucumber, Amperima rosea, that became 100 times more common in just a few years. Such a dynamic biological response was not previously expected in deep-sea animals. Today, we think changes in the biological communities of the Porcupine Abyssal Plain, are linked to changes in their food supply, and that those changes may be related to long-term climate cycles – but we need more evidence to be sure.
Over three decades and around 40 visits to observe the site, we have learned a great deal about the Porcupine Abyssal Plain, including more about how this food source varies with climate, what happens to it as it sinks, and how animals at the seabed respond. For those interested in the detail and the breadth of the science it is covered in three special issues of research journals:
For the present research cruise, we will focus on the abundance and distribution of the megabenthos, the largest of the invertebrate animals living on the abyssal plain. At this site, various species of sea cucumber and sea anemone make up most of the community, along with various worms (polychaetes, echiurans, sipunculids), sea squirts, starfish, brittle stars, squat lobsters, and deep-sea lobsters. We will photograph large areas of the seafloor from the AUV Autosub5 to study the ecology of these organisms and use the ROV Isis to photograph and collect some particular species for more detailed study.
Additional information on the Porcupine Abyssal Plain Sustained Observatory can be found on the associated project website, blog site, and social media (@PAP_observatory)