Frequently Asked Questions
Here are some of the most popular questions we have been asked:
What is a seamount?
Seamounts are literally undersea mountains. They are features of elevated seafloor topography that are usually isolated and cone-shaped. Seamounts are often volcanic in origin and are usually composed of a hard substrate. Over geological time seamounts sink and erode to become less regular. The topography of seamounts can be complex and within any seamount one may find terraces, canyons, pinnacles, crevices and craters. Oceanic islands are seamounts that have breached sea level.
3 main types of submarine rise are formally recognized (1) seamount – an isolated elevation rising 1000m (1km) or more from the seafloor and of limited extent across the summit (2) knoll – an isolated elevation rising less than 1000m from the seafloor and of limited extent across the summit and (3) pinnacle – a smaller pillar-like elevation off the seafloor. However, there is no biological reason not to count smaller features and as such CenSeam classed features smaller than 1km as seamounts - therefore enabling us to collect as much information as possible.
How many seamounts are there?
The bathymetry of our oceans is resolved at a scale and detail unimaginable by early pioneers. Yet despite advances in ocean mapping technologies we are still unable to answer seemingly simple questions such as how many seamounts are there? The most recent and robust work has been completed by Yesson et al. (2011) which has used the highest resolution seafloor bathymetry available to estimate 33,400 seamounts, and 138,400 knolls.
Why are seamounts important?
Seamounts are found throughout the world’s oceans and can sometimes supporting high biodiversity and unique biological communities. Seamounts can be highly productive ecosystems, acting as feeding grounds for fishes, marine mammals, and seabirds. They are targeted for resource extraction such as fisheries and, in the future, mining, but are ecologically vulnerable to such exploitation.
However, at a global scale our knowledge of their biodiversity has improved but relatively few (< 300) seamounts have been studied in any detail. It is this which was the motivation for the CenSeam programme.
Where are seamounts found?
Seamounts are found in all ocean basins of the world, with their distribution varying in both space and time. Nearly half of the worlds seamounts are found in the Pacific Ocean. The rest are mostly found in the Atlantic and Indian Oceans, and overall more are found in the southern hemisphere.
What was CenSeam?
CenSeam is the Census of Marine Life field programme on seamounts (or undersea mountains). CenSeam aimed to (1) synthesize and analyze existing data (2) co-ordinate and expand existing and planned research (3) communicate the findings through public education and outreach and (4) identify priority areas for research, and foster scientific expeditions to these regions.
To help focus seamount research efforts we identified two overarching priority themes:
(1) What factors drive community composition and diversity on seamounts, including any differences between seamounts and other habitat types?
Or, put more simply are seamounts the same or different to other seamounts, and other deep-sea habitats?
(2) What are the impacts of human activities on seamount community structure and function?
What was the Census of Marine Life?
The international Census of Marine Life culminated in 2010 after a decade of exploration and research on the diversity, distribution, and abundance of life in the oceans – past, present, and future. More than 2,700 scientists in 80+ countries collaborated to study and synthesize information on marine biodiversity at an unprecedented scope and scale from microbes to whales in all ocean realms. In addition to discovering and describing more than 1,200 new species, the Census documented oceans richer in diversity, more connected through distribution and movements of animals, and more impacted by humans.
Who are seamount scientists?
Seamounts are of interest to biologists, geologists, physicists, chemists, and even economists. CenSeam has focused on the biology and ecology of seamounts but to fully understand seamount ecosystems it is imperative to examine all aspects of the system and take a cross-disciplinary approach.
How do scientists sample seamounts?
Studying seamounts is not easy. Whilst seamounts have been sampled since the 19th Century it is only in the last few decades that technologies have been developed to sample seamounts in sufficient detail. To date sampling is still biased towards the top 500m.
It is first necessary to map where the seamounts are. Satellite altimetry can be used to locate their position and general bathymetry. To obtain more detailed bathymetric information multi-beam acoustic mapping surveys are conducted. Multi-beam uses sound waves to produce detailed maps of the seafloor. Multi-beam can also be used to determine the composition of the seamounts e.g. hard or soft sediments.
Camera surveys should be carried out where possible to provide a general overview of community structure. Cameras can be mounted on tows, in Remotely Operated Vehicles (ROVs), Autonomous Underwater Vehicles (AUVs) and Submersibles.
However, to assess species and types of animals present it is also necessary to collect samples. Different methods are used to target different types of biodiversity. Often a combination of grabs and sleds and trawls are used for seamount surveys.
Samples are sorted and identified as much as possible at sea. However, after a voyage the work is far from over. Specimens must be identified, or described for the first time which can take months/years.
One of the aims of our Standardisation working group was to make recommendations for standard sampling practices, and a book will be published in 2011.
What lives on seamounts?
Seamounts can display high levels of biodiversity. A single seamount survey can return hundreds of species, many new to science and analyzing the samples can be a time consuming task. To date the most dominant organisms found on the hard substrates of seamounts are suspension feeders (animals that rely on water to deliver oxygen and food whilst removing waste and preventing burial by sediments) e.g. corals as well as animals like brittlestars.
Soft sediments can also accumulate on seamounts and the dominant organisms occurring here are the polychaetes (a type of worm). Other animals that live in the sediments might include oligochaetes (another type of worm) and gastropod molluscs (shelled animals).
Seamounts also provide habitats and spawning grounds for larger animals, including numerous fish. Some species including black oreo and black cardinalfish occur more often on seamounts than above the adjacent slopes and seafloor. Nearly 80 species of fish and shellfish are commercially harvested from seamounts and include rock lobster, mackeral, deep-sea red king crab, red snapper, several tuna species, orange roughy and perch.
What about hydrothermal vents?
Seamounts generally have a volcanic origin and therefore can be associated with hydrothermal venting. The communities that live on vents are specially adapted to face the challenges of this seemingly inhospitable environment. The Census of Marine Life programme ChEss (Biogeography of chemosynthetic ecosystems) focussed on these systems.
ChEss was a global study of the distribution, abundance and diversity of species in deep-water hydrothermal vents, cold seeps and other chemosynthetic ecosystems for the Census of Marine Life initiative. Directed from the National Oceanography Centre, Southampton, in the United Kingdom, ChEss aimed to improve our knowledge of the biogeography of chemosynthetic ecosystems and the processes driving them.
Do you have another question? If you do, please send us an email and we will endeavour to answer your question (and will also post the answer here).