Irish sea the Irish Sea

Environment[edit]

The most accessible and possibly the greatest wildlife resource of the Irish Sea lies in its estuaries: particularly the Dee Estuary, the Mersey Estuary, the Ribble Estuary, Morecambe Bay, the Solway Firth, the Firth of Clyde, Belfast Lough, Strangford Lough, Carlingford Lough, Dundalk Bay, Dublin Bay and Wexford Harbour. However, a lot of wildlife also depends on the cliffs, salt marshes and sand dunes of the adjoining shores, the seabed and the open sea itself.
The information on the invertebrates of the seabed of the Irish Sea is rather patchy because it is difficult to survey such a large area, where underwater visibility is often poor and information often depends upon looking at material brought up from the seabed in mechanical grabs. However, the groupings of animals present depend to a large extent on whether the seabed is composed of rock, boulders, gravel, sand, mud or even peat. In the soft sediments seven types of community have been provisionally identified, variously dominated by brittle-stars, sea urchins, worms, mussels, tellins, furrow-shells, and tower-shells.
Parts of the bed of the Irish Sea are very rich in wildlife. The seabed southwest of the Isle of Man is particularly noted for its rarities and diversity,^[24] as are the horse mussel beds of Strangford Lough. Scallops and queen scallops are found in more gravelly areas. In the estuaries, where the bed is more sandy or muddy, the number of species is smaller but the size of their populations is larger. Brown shrimp, cockles and edible mussels support local fisheries in Morecambe Bay and the Dee Estuary and the estuaries are also important as nurseries for flatfish, herring and sea bass. Muddy seabeds in deeper waters are home to populations of the Dublin Bay prawn, also known as "scampi".^[25]
The open sea is a complex habitat in its own right. It exists in three spatial dimensions and also varies over time and tide. For example, where freshwater flows into the Irish Sea in river estuaries its influence can extend far offshore as the freshwater is lighter and "floats" on top of the much larger body of salt water until wind and temperature changes mix it in. Similarly, warmer water is less dense and seawater warmed in the inter-tidal zone may "float" on the colder offshore water. The amount of light penetrating the seawater also varies with depth and turbidity. This leads to differing populations of plankton in different parts of the sea and varying communities of animals that feed on these populations. However, increasing seasonal storminess leads to greater mixing of water and tends to break down these divisions, which are more apparent when the weather is calm for long periods.
Plankton includes bacteria, plants (phytoplankton) and animals (zooplankton) that drift in the sea. Most are microscopic, but some, such as the various species of jellyfish and sea gooseberry, can be much bigger.
Diatoms and dinoflagellates dominate the phytoplankton. Although they are microscopic plants, diatoms have hard shells and dinoflagellates have little tails that propel them through the water. Phytoplankton populations in the Irish Sea have a spring "bloom" every April and May, when the seawater is generally at its greenest.
Crustaceans, especially copepods, dominate the zooplankton. However, many animals of the seabed, the open sea and the seashore spend their juvenile stages as part of the zooplankton. The whole plankton "soup" is vitally important, directly or indirectly, as a food source for most species in the Irish Sea, even the largest. The enormous basking shark, for example, lives entirely on plankton and the leatherback turtle's main food is jellyfish.
A colossal diversity of invertebrate species live in the Irish Sea and its surrounding coastline, ranging from flower-like fan-worms to predatory swimming crabs to large chameleon-like cuttlefish.^[25] Some of the most significant for other wildlife are the reef-building species like the inshore horse mussel of Strangford Lough and the inter-tidal honeycomb worm of Morecambe Bay, Cumbria and Lancashire. These build up large structures over many years and, in turn, provide surfaces, nooks and crannies where other marine animals and plants may become established and live out some or all of their lives.
There are quite regular records of live and stranded leatherback turtles in and around the Irish Sea. This species travels north to the waters off the British Isles every year following the swarms of jellyfish that form its prey. Loggerhead turtle, ridley sea turtle and green turtle are found very occasionally in the Irish Sea but are generally unwell or dead when discovered. They have strayed or been swept out of their natural range further south into colder waters.^[26][27]
The estuaries of the Irish Sea are of international importance for birds. They are vital feeding grounds on migration flyways for shorebirds travelling between the Arctic and Africa. Others depend on the milder climate as a refuge when continental Europe is in the grip of winter.^[25]
Twenty-one species of seabird are reported as regularly nesting on beaches or cliffs around the Irish Sea. Huge populations of the sea duck, common scoter, spend winters feeding in shallow waters off eastern Ireland, Lancashire and North Wales.^[25]
Whales, dolphins and porpoises all frequent the Irish Sea, but knowledge of how many there may be and where they go is somewhat sketchy. About a dozen species have been recorded since 1980, but only three are seen fairly often. These are the harbour porpoise, bottlenose dolphin and common dolphin. The more rarely seen species are minke whale, fin whale, sei whale, humpback whale, North Atlantic right whales^[28] which are now considered to be almost extinct in eastern North Atlantic, sperm whale, northern bottlenose whale, long-finned pilot whale, orca, white-beaked dolphin, striped dolphin and Risso's dolphin.^[25] In 2005, a plan to reintroduce grey whales by airlifting 50 of them from the Pacific Ocean to the Irish Sea was claimed to be logically and ethically feasible;^[29] it had not been implemented by 2013.
The common or harbour seal and the grey seal are both resident in the Irish Sea. Common seals breed in Strangford Lough, grey seals in southwest Wales and, in small numbers, on the Isle of Man. Grey seals haul out, but do not breed, off Hilbre and Walney islands, Merseyside, the Wirral, St Annes, Barrow-in-Furness Borough, and Cumbria.^[25]