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Climate change: impacts on our vision for a healthy and biologically diverse marine ecosystem

© Niall Benvie (rspb-images.com)As the marine ecosystem is highly interconnected through predator-prey relations, the direct impacts of ocean climate change have 'knock-on' effects through the food chain. For example, recent warmer conditions and associated shifts in plankton abundance and geographical distribution have led to reduced availability of prey fish for some seabirds, which has been strongly linked to recent poor breeding success and reduced survival rates.

The bold text indicates new information for the 2007-2008 report.


  WHAT IS ALREADY HAPPENINGWHAT COULD HAPPEN
Plankton
FRS; SAHFOS
  • A 1,000-km northward shift of warmer-water plankton, with a similar retreat of colder-water plankton, has been observed in the north-east Atlantic over the past 50 years, as the seas around the UK have become warmer.
  • In the North Sea, the population of the previously dominant and important cold-water zooplankton species Calanus finmarchicus has declined in biomass by 70% since the 1960s.
  • The seasonal timing of plankton production has altered in response to recent climate changes. Some species are occurring up to four to six weeks earlier than 20 years ago, affecting predators, including fish.

Continued increase in sea temperature, due to climate change and associated changes such as ocean acidification, are likely to exert major influences on plankton abundance and geographical distributions, with implications for primary production and climate control.

Fish
Cefas; FRS; MBA
  • Abundances of warm-water fish species (e.g. red mullet, John Dory, triggerfish) have increased in UK waters during recent decades, while many cold-water species have experienced declines.
  • There has been a notable influx of snake pipefish to UK waters since 2004, and research is under way to explain this.
  • Poor 'recruitment' of juvenile cod may be associated with a climate-related shift in the composition of zooplankton, but also by a reduction of the adult, parental population by fishing.
  • In some parts of the southern North Sea, cold-water species, such as cod and eelpout, have been shown to experience metabolic stress during warm years, as evidenced by slower growth rates and difficulties in supplying oxygen to body tissues.
  • Climate change will have far-reaching impacts on the dynamics of fish populations; however, current knowledge of underlying mechanisms is limited.
  • Much less is understood about the possible future impacts of climate change on non-commercial fish species, compared to those targeted by fisheries.
Marine mammals
Sea Watch Foundation; SMRU; University of Aberdeen
  • The impact of climate change on marine mammals (i.e. seals and cetaceans) remains poorly understood.
  • Range shifts have been observed in a number of cetacean species, but at present it is not possible to differentiate between short-term responses to regional resource variability and longer-term ones driven by climate change.
  • Marine mammals may suffer impacts from changes affecting the food chain that supports them.
Seabirds
CEH; JNCC
  • Poor breeding success and reduced survival of black-legged kittiwakes in recent years have been strongly linked to warmer winters and changes to their fish prey populations (e.g. smaller, less-nutritious sand eels, increased snake pipefish abundance). Other seabird species may have been similarly affected.
  • Some species will have difficulties in adapting to changing prey availability.
  • Long-term climate change will result in a northwards shift in the range of some species and consequently a decline in UK population size.
  • Anticipated sea-level rise and a greater number of more severe storms may reduce available breeding habitat for shoreline-nesting species (e.g. terns) and wash away nests.
Non-native species
FRS; SAHFOS; University of Cambridge
  • Future temperature increases could enable more species to invade and become established, replacing current native species.
Intertidal species
MBA; SAMS
  • Some warm-water invertebrates and algae show continued increases in abundance and have extended their ranges around northern Scotland and eastwards along the English Channel over the last 20 years.
  • The warm-water seaweed Bifurcaria bifurcata has established a new range boundary at Portland Headland in the last five years, 150 km east of previous records.
  • Cold-water species (e.g. the acorn barnacle and dabberlocks alga) have continued to decrease in abundance throughout the period 2001-2007.
  • Projected changes in sea level and storms may have important indirect impacts, as more sea defences are required. These act as artificial rocky shores allowing intertidal species to unnaturally extend their range.
  • Continued extension and retraction of ranges within the UK, with rising temperatures of southern and northern species respectively.
  • Some new species will become established, whilst others will disappear from our shores.
Seabed ecology
FRS; Liverpool University
  • Climatic processes influence the abundance and species composition of seabed communities, directly affecting the availability of food for bottom-feeding fish.
  • Localised effects of fishing, causing habitat modification, and of contaminants are also important and make it difficult to fully assess the scale of the influence of climate change.
  • Changes to sea temperature and/or food supply are likely to continue to alter the ecological structure of the seabed.
Coastal Habitats
University of Cambridge; University of Southampton
  • Coastal habitats are being lost around the UK. In England, it is estimated that at least 40-100 hectares of saltmarsh is being lost every year; projects are under way to estimate rates of loss in other regions.
  • Coastal habitat loss will be accelerated by sea-level rise.