Marine phenology (CLIM 014) - Assessment published Sep 2008
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Climate change (Primary topic)
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CLIM 014
Key policy question: .
- Temperature increases in the ocean have caused many marine organisms in European seas to appear earlier in their seasonal cycles than in the past. For example, some species have moved forward in their seasonal cycle by 4-6 weeks.
- Changes in the timing of seasonal cycles have important consequences for the way organisms within an ecosystem interact and ultimately for the structure of marine food-webs at all trophic levels. The consequences include:
- increased vulnerability of North Sea cod stocks to over-fishing;
- decline in seabird populations.
- Marine species may be able to adapt genetically to changed conditions. However, with the current pace of climate warming this may be hampered because genetic changes require several reproductive cycles to occur.
Decapod abundance in the central North Sea 1950-2005
Note: Left: year vs
Edwards M. and Richardson A. J., 2004. Impact of climate change on marine pelagic phenology and trophic mismatch. Nature 430: 881884. (left and right) Hadley Centre (http://hadobs.metoffice.com/hadisst/data/download.html) (right)
In the North Sea, work on pelagic phenology has shown that plankton communities, including fish larvae, are very sensitive to regional climate warming with the response to warming varying between trophic levels and functional groups. However the ability and speed at which fish and planktonic communities adapt to climate warming is not yet known. In other European regional areas, long-term data on marine phenology changes are quite sparse. According to some preliminary studies, there has also been some phenological movement in certain copepod species in the Mediterranean Sea over the past decade (Juan-Carlos Molinero, pers. com.).
Due to the sensitivity of their physiological development to temperature, decapod larvae were selected as representative of phenological changes in shelf-sea environments (Lindley, 1987). The zooplankton growing season indicator shows the annual timing of peak seasonal abundance of decapod larvae from 1958-2005 in the central North Sea (Figure 1 left). A shift towards an earlier seasonal peak is clearly visible. In particular, since 1988, the seasonal development of decapod larvae has occurred much earlier than the long-term average (baseline mean: 1958-2005) - in the 1990s up to 4-5 weeks earlier than the long-term average This trend towards an earlier seasonal appearance of decapod larvae during the 1990s is highly correlated with sea surface temperature (Figure 1 right).
Projections of how individual species react to future climate change have not yet been made, but the empirical evidence suggests that it is very likely that phenological changes will continue to occur as climate warming continues to accelerate. It is currently much less certain to what degree genetic adaptations within species populations can cope with these changes and whether the current pace of climate warming is too fast for genetic adaptations to take place.
HadISST1 - Global sea ice and Sea Surface Temperature analyses
provided by Met Office Hadley Centre observations datasets
Continuous Plankton Recorder (CPR) survey
provided by Sir Alister Hardy Foundation for Ocean Science (SAHFOS)
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