Most of the Southern Ocean outside of the narrow Antarctic continental shelf is more than 3000m deep. This poses a real challenge for scientists studying the assemblages of animals living on the seabed. Dr Dave Bowden, a benthic ecologist at NIWA, explains how marine biologists are beginning to unveil the mysteries of this deep ocean, particularly the relatively unknown sector between New Zealand and the Ross Sea. New high resolution deepsea cameras have revealed amazing sights, including ‘meadows’ of a new species of stalked crinoid (relatives of sea stars) in habitats only previously seen in the fossil record.
It’s a common myth that the oceans surrounding Antarctica hold the most diverse array of animals on earth, but they are home to a collection of species found nowhere else. Dr Dave Bowden then explains how a unique assemblage of animals evolved on the seabed of Antarctica’s continental shelf. This uniqueness is a product of isolation in a very cold environment over 20-30 million years, with ice shelves advancing and retreating.
One of the greatest threats to the ocean is also one of the most insidious because chances are it’s so mundane you don’t even notice it. Look around you right now: how much plastic do you see? The ocean is downstream from all of us so no matter where we live, so we can all help address the issue of plastic pollution in the ocean. Each year a huge amount of plastic eventually makes it into coastal waters and harms ocean life. Many animals such as seabirds, sea turtles, dolphins, and whales die every year from plastic entanglement or starvation because they fill up their stomachs on plastic they mistake for food. Take action for the oceans and prevent plastic from harming ocean wildlife!
Reduce plastic use . Help stop plastic pollution at its source! As consumers, we each have the power to reduce demand. And if you encourage family and friends to do the same, the more the more good we can do to keep the ocean clean and safe. Here are a few disposable plastic products everyone can reduce in our daily lives:
Plastic water bottles. Invest in a reusable water bottle, and filter water if necessary. Help the ocean and save money; it’s a win-win for you and the blue. On average, Americans now use 4 plastic water bottles a day—the highest ever recorded! Let’s turn the tide against wasteful plastic consumption.
Plastic bags. People use nearly 1 trillion plastic bags each year, and unfortunately, many of those end up ingested by sea turtles that mistake plastic for jellyfish. Remember to bring a reusable bag for food (including vegetables) and other shopping and save a life!
Straws, cups to-go, food containers, and utensils. Bring your own reusable products like mugs when you get coffee and take a pass on the plastic utensils when you get take-out food. And if you must have a straw, there a number affordable options!
Be aware of packaging. Pay attention to how much incidental plastic that comes with what you buy—your candy, headphones, pens, etc., all come in plastic packaging. Strive to cut down on your daily plastic consumption and reward corporations that package responsibly!
- Hold a ‘Switch for the Sea’ contest! Ask friends and family to switch one of their disposable plastic habits for a sustainable, ocean-friendly one: such as bringing reusable food containers from home when eating out for your ‘doggie bag.’
- Organize an aquatic clean-up! Head out to your nearest and dearest body of water with some friends and pick up all the trash you find. You’ll be surprised at how much of it is plastic.
- Ban the bag in your town (or country!). Many communities around the world are banning plastic bags from being used at their stores. Learn how to start a campaign to stop plastic bags use in your town!
Submarine canyons are steep-sided submarine valleys cut into the continental slope. They are considered to be the main pathways for sediment transport between the shelf (ca. 200 m depth), and the abyss (reaching depths over 4000 m). Unfortunately, in addition to that sediment, they also tend to funnel our human garbage and pollutants into the deep sea…
Submarine canyons occur worldwide, along all ocean margins. A recent study by Peter Harris and Tanya Whiteway counted at least 5849 of them! This work was based on a global bathymetric dataset of the oceans (ETOPO1) that is reasonably detailed. However, in some places we have much more detailed seabed maps, and we see that the better the maps, the more canyons we find. So there is still a lot to discover in the near future!
Some of the canyons that have been mapped are directly connected to a river system on land (e.g. the Mississippi Canyon or the Congo Canyon). Others do cut right into the shelf, but are not necessarily connected to a river. They may be following the course of a deep-seated fault in the geology (e.g. Nazaré Canyon offshore Portugal), or may catch the currents and sediments at the end of a Bay (e.g. Cap de Creus Canyon in the Mediterranean Sea).
Finally, there are also canyons that do not cut the shelf, but are formed deeper on the continental slope, sometimes as the result of repeated submarine slides cutting upslope into the continental margin sediments (e.g. canyons in the Rockall Trough, NE Atlantic).
Canyons are formed by a combination of the erosive and abrasive forces of sediment flows, and of slope failures such as submarine landslides occurring on the canyon flanks. The first process tends to make canyons deeper, while the second one makes them wider. The origin of the sediment flows could be anything from flooding in the feeding river (bringing a lot of material into the ocean) to the activity of storms on the shelf, which stir up al lot of sediment. Many canyons used to be much more active during the ice-ages, when the sea level was lower than today, and the shoreline with its river mouths was much closer to the shelf edge.
Because of the steep topography and the regular occurrence of erosive currents and submarine landslides, submarine canyons contain habitat types that are often rare along the smoother and more homogeneous continental slope. For example, in some places we find rock outcrops which form a solid anchoring point for a variety of sessile fauna that catch their food through filtering of the passing waters.
Figure 1: Stylasterid coral on the flanks of Whittard Canyon (©National Oceanography Centre, Southampton, UK)
In addition, the steep shape of the canyon tends to affect local current patterns, often pushing deeper, nutrient-rich waters to the sea surface (so-called ‘upwelling’). Once there, the nutrients stimulate extra primary production or plankton growth, which in turn is the basis for a rich food chain. On the other hand, the occasional downslope sediment flows that transport material from the shelf to the deep sea also bring fresh organic matter from the shallower to the deeper waters. This supports a richer fauna also in the deeper parts of some canyons, compared to the average continental slope.
Overall, canyons are often found to be areas with increased regional biodiversity and increased biological growth. This is a result of all the different habitat types that can be found so closely together and of the specific processes that bring nutrients to the sea surface, and organic matter to the bottom of the canyons. It makes submarine canyons very important locations when considering environmental conservation in the deep sea!
Unfortunately, still far too little is known about submarine canyons, about the exact way those current and sediment transport processes work, and about the enormous variety in biological life forms, species and ecosystems that occur. Again owing to their complex shape, marine research in submarine canyons has always been quite difficult. The steep walls cannot easily be sampled or photographed with traditional, drop-down equipment. It is only since the technological development of deep-water robotic vehicles that we can now slowly begin to ‘look around’ in submarine canyons, and can start to understand how they work.
This sometimes requires researchers to think outside the box and turn well-established methods on their head! Which is exactly what Veerle Huvenne and her colleagues did a few years back in the Whittard Canyon. They used ISIS, a Remotely Operated Vehicle (or ROV) to survey the steep canyon flanks. Instead of deploying the multibeam echosounder (the typical piece of acoustic equipment to make seabed maps) in its traditional down-ward pointing orientation, they placed it in a forward-looking position, and used that to make a series of maps of one of the steep canyon walls. To their surprise, they found that the wall was (a) not just steep, but actually overhanging, which is something you’d never be able to see from the sea surface, and (b) covered with a rich hanging cold-water coral habitat, including corals, sponges, fish, bivalves,…
Figure 3: Mapping the steep or overhanging walls of submarine canyons leads to the discovery of rich hanging ecosystems which were entirely unknown until a few years ago! (after Huvenne et al. (2011, PLoS One)).
Further research into this method is currently ongoing within the CODEMAP project, while other examples of rich hanging deep-sea communities have recently been discovered in different canyons around the world. In terms of marine conservation, these vertical communities could be very important. By grace of their steep morphology, they somehow protect themselves from a lot of the potential human impacts in the deep ocean (at least from trawling fisheries, for example, which nowadays can take place to >1500 m water depth). This way they could act as nursing grounds for several species, and we hope one day they might also provide the larvae needed for the restoration and re-colonisation of other parts of the deep sea that already have been affected by human impacts. Still, steep bathymetry will not protect the rich biodiversity from all the perils caused by human exploitation of the deep ocean – the corals in Whittard Canyon will still feel the effects of ocean acidification, while entangled fishing lines and plastic bags, swept down the canyon by the occasional sediment flows, could be seen in between the coral framework. So it is very important we are careful with those vulnerable marine ecosystems, and that we try to protect them as much as possible.
Here’s an interview with Veerle Huvenne herself, speaking about her work in the Hermione project.
Harris, P., & Whiteway, T. (2011). Global distribution of large submarine canyons: Geomorphic differences between active and passive continental margins Marine Geology, 285 (1-4), 69-86 DOI: 10.1016/j.margeo.2011.05.008
Huvenne VA, Tyler PA, Masson DG, Fisher EH, Hauton C, Hühnerbach V, Le Bas TP, & Wolff GA (2011). A picture on the wall: innovative mapping reveals cold-water coral refuge in submarine canyon. PloS one, 6 (12) PMID: 22194903
Thanks and acknowledgements go out to Dr. Veerle Huvenne of NOC for taking the time to produce this blog post and informing us of this relatively undiscovered seabed habitat.
The miraculous journey of infant sea turtles as these tiny animals run the gauntlet of predators and harsh conditions. Then, in numbers, see how human behavior has made their tough lives even more challenging.
How long is the coastline of Australia? One estimate is that it’s about 12,500 km long. However the CIA world factbook puts the figure at more than double this, at over 25,700 km. How can there exist such different estimates for the same length of coastline? Well this is called the coastline paradox. Your estimate of how long the coastline is depends on the length of your measuring stick – the shorter the measuring stick the more detail you can capture and therefore the longer the coastline will be.
Fractals are typically self-similar patterns that show up everywhere around us in nature and biology. The term “fractal” was first used by mathematician Benoit Mandelbrot in 1975 and used it to extend the concept of theoretical fractional dimensions to geometric patterns in nature, including the seabed.
A hydrothermal vent is a fissure in a planet’s surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both geologically active and has large amounts of water on its surface and within its crust. Common land types include hot springs, fumaroles and geysers. Under the sea, hydrothermal vents may form features called black smokers. Relative to the majority of the deep sea, the areas around submarine hydrothermal vents are biologically more productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic archaea form the base of the food chain, supporting diverse organisms, including giant tube worms, clams, limpets and shrimp.
The Endeavour Mid-ocean Ridge is an exciting study location because it is a place where new volcanic seafloor is constantly created at the spreading boundary between the Juan de Fuca and Pacific plates. The region (approximately 300 km off the British Columbia coast), has been the site of intensive investigation for more than 20 years.The Ocean Networks Canada Observatory, comprising VENUS and NEPTUNE Canada cabled networks, supports transformative coastal to deep ocean research and technology. It enables real-time interactive experiments, focused on ocean health, ecosystems, resources, natural hazards, and marine conservation. The Observatory is a national facility led by the University of Victoria for a pan-Canadian consortium of universities and partners.
NEPTUNE Canada’s real-time monitoring capability will benefit both ongoing and new experiments. Continuous data gathered before, during and after events like earthquakes and intrusions will be recorded across a coordinated suite of instruments both at the hydrothermal vents on the seafloor and within moorings extending 250m up into the 2,200m water column. A network of seismometers here and at other sites will provide high resolution information on tectonic processes such as earthquakes and strain across the Juan de Fuca plate.
Some more footage of the Endeavour ridge hot vents acquired using the ROPOS ROV. See also the BBC news report about a recent British expedition to the Cayman Trough to the deepest undersea vents.