Phenology of Phytoplankton: a Potential Ecological Indicator for Climate Change in the Oceans
Platt, Trevor; Sathyendranath, Shubha; Racault, Marie-Fanny; Land, Peter
Plymouth Marine Laboratory, UNITED KINGDOM
The seasonality of marine phytoplankton, as characterized by a suite of objective metrics, is the strongest signal in the annual cycle of variation in the phytoplankton abundance. The phase of this signal is commonly referred to as the phytoplankton phenology, and it is subject to fluctuations between years. In assessing the phase of phytoplankton seasonality, the clearest marker is the timing of events in the Spring phytoplankton bloom (timing of bloom onset or of bloom maximum). Bloom timing has been shown to have an important influence on larval survival in gadoid fish. Under the Sverdrup hypothesis, bloom initiation is related closely to stratification in the water column, and secondarily to sea surface temperature. Remote sensing offers an ideal tool to assess phytoplankton phenology on regional scales. Here, we illustrate the combined us of ocean colour and AVHRR data to diagnose and interpret inter-annual changes in phytoplankton phenology, and elucidate possible longer-term variations consequent on climate change.