Changing marine environment'The seas around Scotland have warmed by 1˚C over the last 20 years. Warmer seas have prompted changes in composition, abundance and distribution of a number of marine species including plankton, fish, sea birds, whales, mammals, dolphins and porpoises.
Warm water fish such as red mullet, sardines and anchovies have been caught off Scotland's coast since 1995. Some plankton species, which form the basis of the marine food web, have migrated north by up to 10 degrees latitude (about 700 miles). Changes in plankton distribution and abundance have serious consequences not only for the marine ecosystem but for the ability of the oceans to absorb carbon dioxide and ultimately regulate the Earth's climate.'
SEPA state of the Environment report 2006
Seabirds like puffins, guillemots and kittiwakes nest in huge numbers round the coast of Scotland. In recent years there has been a run of very poor breeding seasons, especially in 2004 and 2005.
In these years seabird colonies produced very few young. Some species didn’t lay eggs while in others the young died before they could leave the colony. The most important cause was lack of food for both adults and young, especially the usually common sand eel, which is the preferred food for many of these species.
Both seabirds and sand eels populations have been studied for about 40 years in the North Sea, because of concerns that industrial fishing of sand eels, for agricultural fertiliser and as a fuel for power stations, would damage sea bird populations and commercial fisheries. While the fishing had affected seabird populations in the past, the 2004 and 2005 problems could not be caused by fishing as the fishing is now strictly controlled.
A complex story unfolded. The shallow North Sea is heating up quickly, by between 1˚C to 2˚C in 30 years. Slower warming is occurring in deeper Atlantic water to the west of Scotland. This warming is changing the timing and distribution of the tiny plants (the phytoplankton) and the small animals that feed on them (the zooplankton) that form the base of the North Sea food-web.
This leads to changes in size and distribution in sand eels. If there are not enough sand eels in the waters near the sea bird colonies, then they will have a poor breeding season, or even disastrous ones like 2004 and 2005.
Since 2005 Scotland’s seabirds have had some better breeding years but the changes in fish distribution, caused by warming seas, have lead to poor breeding success in most. Declines in breeding numbers of most species since 2000 have occurred in most seabird species, especially on the east coast, with 55% fewer kittiwakes and 25% reduction in Arctic terns. These declines are especially worrying as seabirds are long lived and it takes years of poor breeding success to affect the numbers of breeding adults.
Photo credit: mrpattersonsir (hi Ben!)
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