Fishing and climate change are harming UK marine life, according to a report by the Department for the Environment, Food and Rural Affairs (Defra).
Over-fishing is putting some species under stress
The report blames industrial activities, pollution, acidification and warming waters for the decline in certain sea species.
However, it does state that much of the open ocean is not affected by pollution and some contaminants are decreasing.
Environment Minister Elliot Morley says the problem requires a "new approach".
"Today's report suggests that asking new questions of our marine environment require a new approach," he stated. "This new approach will hopefully give us the answers we are looking for and help us plan for the long term.
"But what I can say with some certainty is that we are having an adverse effect on our marine life and climate change is certainly evident in our seas."
Charting Progress: An Integrated Assessment Of The State Of UK Seas provides the first integrated assessment, across the entire UK Continental Shelf, of how humans are affecting marine ecosystems.
Declining fish stocks
The report's main findings, which cover the Scottish and English coasts as far south as Flamborough Head, include:
- Fish stocks are declining. Although the region continues to be one of the most productive fisheries in the UK, species like cod are on the brink of collapse
- Sea surface temperatures have been rising since the 1970s, while surface salinity has been decreasing
- Warm water species of plankton are increasing, while cold water species are decreasing.
As well as being a major source of food for fish, plankton play an important role in the "biological pump", a process that takes carbon from the atmosphere dissolved in the top layers of the ocean down into deep-sea sediments.
Without the pump, the concentration of carbon dioxide in the atmosphere would be much higher.
The Continuous Plankton Recorder survey has been monitoring near surface plankton in the North Atlantic and North Sea for the past 70 years.
Chief Scientific Adviser at Defra, Howard Dalton, said: "The threat of climate change is becoming more certain. The Continuous Plankton Recorder is one of the most valuable long-term datasets monitoring these tiny organisms in our seas.
"The shift in plankton species is surprisingly large compared to movements of plants or birds on land.
"By understanding the movement of plankton, we are much better able to handle our fish resources."
In response to the report, Defra intends to do further research into the UK's marine environment.
As part of this initiative, it will set up a Marine Data & Information partnership and a Marine Climate Change Impacts Partnership, which "will help develop a better understanding of how climate change affects the marine environment", and help establish a more "holistic" management approach to marine ecosystems.
Wildlife advisory group English Nature said it "welcomes this step towards tackling the two most serious threats facing the sea: overexploitation of some marine species and the impacts of climate change".
Dr Dan Laffoley, the head of marine conservation at English Nature, said: "We back Defra's recommendation to make better use of information about our coasts and seas by pooling the expertise of all UK bodies which deal with the marine environment.
"This is the only way to gain a better understanding of the size of the problems we face. Then we can take informed action to safeguard our seas."