The Porcupine Abyssal Plain (PAP) is located in international waters, adjacent to the Irish continental margin. The PAP lies beyond the Porcupine Bank'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 bathypela ...

forming

seamount A seamount is a large submarine landform that rises from the ocean floor without reaching the water surface (sea level), and thus is not an island, islet, or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly a ...

s 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 Macrobenthos consists of the organisms that live at the bottom of a water columnJ.S. Link, C.A. Griswold, E.T. Methratta, J. Gunnard, Editors. 2006Documentation for the Energy Modeling and Analysis eXercise (EMAX). United States Department of ...

are

sea cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...

s and some of the commonest species are '' Oneirophanta mutabilis'', '' Pseudostichopus villosus'' and '' Psychropotes longicauda''. These animals are increasing in number as more phytodetritus 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) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

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 Detritivores (also known as detrivores, detritophages, detritus feeders or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...

starfish Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...

'' Hyphalaster inermis'' and '' Styracaster chuni'', both of which feed by ingesting mud, are also common. There are a number of species of

sea anemone Sea anemones ( ) are a group of predation, predatory marine invertebrates constituting the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemone ...

present, also

sea spider Sea spiders are marine arthropods of the class (biology), class Pycnogonida, hence they are also called pycnogonids (; named after ''Pycnogonum'', the type genus; with the suffix '). The class includes the only now-living order (biology), order P ...

tunicate Tunicates are marine invertebrates belonging to the subphylum Tunicata ( ). This grouping 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

octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...

es (''

Grimpoteuthis ''Grimpoteuthis'' is a genus of pelagic Cirrina, cirrate (finned) octopods known as the dumbo octopus. The name "dumbo" originates from their resemblance to the title character of Disney's 1941 film ''Dumbo'', having two prominent ear-like fi ...

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

xenophyophores Xenophyophorea is a clade of foraminiferans. Xenophyophores 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 surround ...

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

effects of climate change Effects of climate change are well documented and growing for Earth's natural environment and human societies. Changes to the climate system include an Instrumental temperature record, overall warming trend, Effects of climate change on the ...

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

salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...

chlorophyll fluorescence Chlorophyll fluorescence is light re-emitted by chlorophyll molecules during return from Excited state, excited to non-excited states. It is used as an indicator of photosynthetic energy conversion in plants, algae and bacteria. Excited chlorop ...

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

and

nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...

. A 2010 collaboration between the

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

and the United Kingdom Met Office has led to simultaneous monitoring of the ocean and atmosphere. The datasets are

open access Open access (OA) is a set of principles and a range of practices through which nominally copyrightable publications are delivered to readers free of access charges or other barriers. With open access strictly defined (according to the 2001 de ...

and available in near real time. They are uploaded to MyOcean 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