The Porcupine Abyssal Plain (PAP) is located in international waters, adjacent to the

Irish Irish may refer to: Common meanings * Someone or something of, from, or related to: ** Ireland, an island situated off the north-western coast of continental Europe ***Éire, Irish language name for the isle ** Northern Ireland, a constituent unit ...

continental margin. The PAP lies beyond the

Porcupine Bank Porcupine Bank is an area of the Irish shelf, on the fringes of the Atlantic Ocean approximately west of Ireland. The relatively raised area of seabed, 200 m below sea level at its highest, lies between the deep-water Porcupine Seabight and Roc ...

's deepest point and is southwest of it. It has a muddy

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

, with scattered abyssal hills that covers an area approximately half the size of Europe's landmass. Its depth ranges from to .

Characteristics

The Porcupine Abyssal Plain is a vast, relatively level stretch of seabed with a depth range of . It has a muddy floor in the abyssopelagic zone and scattered rocky abyssal hills that rise into the

bathypelagic zone The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypelagi ...

forming seamounts and knolls. The water at this depth is relatively stable and moving slowly towards the south and southeast. There is a downward flow of organic detritus derived from primary production in the upper layers of ocean that settles on the sea floor.

Fauna

A large number of marine invertebrates inhabit the abyssal plain. About 90% by number and biomass of the macrobenthos are sea cucumbers and some of the commonest species are '' Oneirophanta mutabilis'', '' Pseudostichopus villosus'' and '' Psychropotes longicauda''. These animals are increasing in number as more

phytodetritus In oceanography, phytodetritus is the organic particulate matter resulting from phytoplankton and other organic material in surface waters falling to the seabed. This process takes place almost continuously as a "marine snow" of descending particles ...

falls to the seabed. Each species is found to feed on a slightly different portion. Another sea cucumber, '' Amperima rosea'', saw a great leap in its abundance in the years 1995 and 1996, increasing from two or three individuals per hectare to more than six thousand. Before 1995 it took about two and a half years for the sea cucumbers to churn up the surface layers of the sediment but since 1996 this process takes only about six weeks. The

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

is profoundly changed by the reworking and consequent aeration of the seabed surface layers. The starfish '' Psilaster andromeda'' which feeds mainly on molluscs is present on the abyssal plain,. The detritivore starfish '' Hyphalaster inermis'' and '' Styracaster chuni'', both of which feed by ingesting mud, are also common. There are a number of species of sea anemone present, also

sea spider Sea spiders are marine arthropods of the order Pantopoda ( ‘all feet’), belonging to the class Pycnogonida, hence they are also called pycnogonids (; named after ''Pycnogonum'', the type genus; with the suffix '). They are cosmopolitan, fou ...

tunicate A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time ...

s and dumbo octopuses (''

Grimpoteuthis ''Grimpoteuthis'' is a genus of pelagic umbrella octopuses known as the dumbo octopuses. The name "dumbo" originates from their resemblance to the title character of Disney's 1941 film ''Dumbo'', having a prominent ear-like fin which extends from ...

'' spp). The ecosystem is also home to the

xenophyophores Xenophyophorea is a clade of foraminiferans. Members of this class are multinucleate unicellular organisms found on the ocean floor throughout the world's oceans, at depths of . They are a kind of foraminiferan that extract minerals from their s ...

'' Occultammina'', '' Reticulammina'', and '' Galeathammina''.

Porcupine Abyssal Plain Observatory

The observatory is multidisciplinary and moored, and was deployed early on 7 October 2002 at 49° N and -16° 30' W. It is coordinated by the

National Oceanography Centre The National Oceanography Centre (NOC) is a marine science research and technology institution based on two sites in Southampton and Liverpool, United Kingdom. It is the UK’s largest institution for integrated sea level science, coastal and ...

and provides time-series datasets used for monitoring and analysing the

effects of climate change The effects of climate change impact the physical environment, ecosystems and human societies. The environmental effects of climate change are broad and far-reaching. They affect the water cycle, oceans, sea and land ice ( glaciers), sea le ...

on the deep Atlantic Ocean and its ecosystems. A full-depth mooring was established in 2012, with autonomous sensors to measure ocean temperature, salinity,

chlorophyll fluorescence Chlorophyll fluorescence is light re-emitted by chlorophyll molecules during return from excited to non-excited states. It is used as an indicator of photosynthetic energy conversion in plants, algae and bacteria Bacteria (; singular: b ...

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

and nitrate. A 2010 collaboration between the

Natural Environment Research Council The Natural Environment Research Council (NERC) is a British research council that supports research, training and knowledge transfer activities in the environmental sciences. History NERC began in 1965 when several environmental (mainly geog ...

and the United Kingdom Met Office has led to simultaneous monitoring of the ocean and atmosphere. The datasets are open access and available in near real time. They are uploaded to

MyOcean MyOcean is a series of projects granted by the European Commission within the GMES Program (Framework Programmes for Research and Technological Development, Seventh Framework Program), whose objective is to define and to set up a concerted and inte ...

and other websites daily for use in modelling activities. The datasets can be combined to show short-term variations on a daily or seasonal basis and longer term trends. The consequences of storms and other events can also be monitored.

References

External links

Photo
{{coord missing, Ireland Abyssal plains Landforms of the Atlantic Ocean