Opposite phenological responses of zooplankton to climate along a latitudinal gradient through the European Shelf

Abstract

Abstract Zooplankton phenological shifts may affect energy transfer through pelagic food web and up to fisheries, but few studies have compared zooplankton phenology across a wide latitudinal range of water temperatures. We examined the phenological variations of zooplankton at four sites along a latitudinal gradient from the Bay of Biscay [Bilbao and Urdaibai (BU)], the English Channel (Plymouth; L4), and the North Sea [Stonehaven (SH)] from 1999 to 2013. Zooplankton taxa showed interannual phenological variations that were opposite in direction between the southernmost BU and the northernmost SH sites. The East Atlantic pattern was the climate teleconnection best related to zooplankton phenological variations. Among local variables , salinity at BU was best related to phenological changes at BU as opposed to those at SH. Locally, chlorophyll a was most relevant at SH and temperature at L4. While we did see some imprints of temperature in causing expected directions of phenology shifts, i.e. towards earlier appearance of spring taxa and later appearance of autumn taxa in warm years, these patterns were by no means clear-cut. The dominant role of temperature in driving phenological variation suggested by some studies seems to be obscured by biotic and climatic controls acting differently along our environmental gradient.