Phenology
Phenology is the study of the timing of recurring natural phenomena (e.g. seasonal events). Due to the sensitivity of the physiological development of meroplankton to temperature, we have chosen echinoderm larvae as a representative indicator of phenological changes in shelf sea environments. The figure above shows the annual peak seasonal abundance 'centre of gravity index' of echinoderm larvae from 1958-2008 in the central North Sea (i.e., the peak in seasonal appearance). It is clear that there is a major trend towards an earlier seasonal peak. Since 1988 in particular, with the exception of 1996 (a negative NAO year), the seasonal development of echinoderm larvae has occurred much earlier than the long-term average. For example, in the 1990s the seasonal cycle occurred up to 4-5 weeks earlier than the long-term mean. This trend towards an earlier seasonal appearance of meroplanktonic larvae during the last decade is highly correlated with sea surface temperature. This trend continued in 2008 with the early seasonal appearance of echinoderm larvae.
Read more: Edwards, M. and Richardson, A.J., 2004. Impact of climate change on marine pelagic phenology and trophic mismatch. Nature, 430: 881-884.
Inter-annual variability in the peak seasonal development of echinoderm larvae (an indicator of plankton phenology) in the North Sea showing a movement from a July peak to presently a June peak. Warmer temperatures = earlier seasonal appearance, colder temperatures = late seasonal appearance.
