Climate change-related regime shifts have altered spatial synchrony of plankton dynamics in the North Sea.

Emma J Defriez,Lawrence W Sheppard,Daniel C Reuman,Philip C Reid

doi:10.1111/gcb.13229

Abstract

During the 1980s, the North Sea plankton community underwent a well-documented ecosystem regime shift, including both spatial changes (northward species range shifts) and temporal changes (increases in the total abundances of warmer water species). This regime shift has been attributed to climate change. Plankton provide a link between climate and higher trophic-level organisms, which can forage on large spatial and temporal scales. It is therefore important to understand not only whether climate change affects purely spatial or temporal aspects of plankton dynamics, but also whether it affects spatiotemporal aspects such as metapopulation synchrony. If plankton synchrony is altered, higher trophic-level feeding patterns may be modified. A second motivation for investigating changes in synchrony is that the possibility of such alterations has been examined for few organisms, in spite of the fact that synchrony is ubiquitous and of major importance in ecology. This study uses correlation coefficients and spectral analysis to investigate whether synchrony changed between the periods 1959-1980 and 1989-2010. Twenty-three plankton taxa, sea surface temperature (SST), and wind speed were examined. Results revealed that synchrony in SST and plankton was altered. Changes were idiosyncratic, and were not explained by changes in abundance. Changes in the synchrony of Calanus helgolandicus and Para-pseudocalanus spp appeared to be driven by changes in SST synchrony. This study is one of few to document alterations of synchrony and climate-change impacts on synchrony. We discuss why climate-change impacts on synchrony may well be more common and consequential than previously recognized.

Highlights

Population dynamics are influenced by climate fluctuations, and there is ever-growing evidence that global change-related alterations to climate fluctuations alter population dynamics
Nine of the 23 taxa and one of the two environmental variables we examined showed changes in synchrony over the regime shift, either in a distance category or in a frequency band or both
These results indicate that the climate change-driven North Sea regime shift of the 1980s, which was well documented in earlier work that only examined purely spatial or purely temporal aspects of plankton population dynamics (Reid et al, 2001; Beaugrand, 2004; Alheit et al, 2005; Lindley et al, 2010), affected spatiotemporal population patterns

Summary

Introduction

Population dynamics are influenced by climate fluctuations, and there is ever-growing evidence that global change-related alterations to climate fluctuations alter population dynamics. Garcıa-Carreras et al found links between changes in the spectral colors of climatic fluctuations and the spectral colors of population fluctuations (Garcıa-Carreras & Reuman, 2011). In the North Sea, several studies have demonstrated that a climate change-induced ecosystem regime shift occurred in the 1980s. The ecosystem shifted from a cooler to a warmer state (Beaugrand, 2004; Beaugrand & Iban~ez, 2004), altering relationships between species and large-scale climate variables such as the North Atlantic Oscillation (NAO) and Northern Hemisphere Temperature (NHT) (Reid et al, 2001; Beaugrand & Reid, 2003; Beaugrand, 2004, 2012; Lindley et al, 2010), and resulting in increases in phytoplankton biomass and shifts in community composition (Beaugrand, 2003). Changes similar to some of these have been detected in the North Pacific (Venrick et al, 1987; Hays et al, 2005). Reid et al (2016) showed recently that the 1980s regime shift formed part of a major change in the Earth’s biophysical systems triggered by the combined effects of anthropogenic warming and a volcanic eruption

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Conclusion