Abstract
A long-term time series of plankton and benthic records in the North Sea indicates an increase in decapods and a decline in their prey species that include bivalves and flatfish recruits. Here, we show that in the southern North Sea the proportion of decapods to bivalves doubled following a temperature-driven, abrupt ecosystem shift during the 1980s. Analysis of decapod larvae in the plankton reveals a greater presence and spatial extent of warm-water species where the increase in decapods is greatest. These changes paralleled the arrival of new species such as the warm-water swimming crab Polybius henslowii now found in the southern North Sea. We suggest that climate-induced changes among North Sea decapods have played an important role in the trophic amplification of a climate signal and in the development of the new North Sea dynamic regime.
Highlights
Several studies have described pronounced and sustained responses of marine ecosystems to climate warming (Intergovernmental Panel on Climate Change WGII 2007)
Changes in the North Sea after the ecosystem shift include an increase in phytoplankton, a change in the composition and abundance of the holozooplankton, increases in the frequency of jellyfishes and in the abundance of decapod and echinoderm larvae, and a decrease in bivalve larvae and flatfish recruits (Kirby & Beaugrand 2009)
To compare changes in decapod and bivalve larvae in the plankton, and the plankton with the benthos, we interpolated the data from 54 507 continuous plankton recorder (CPR) samples, after applying the transformation log10(x þ 1), on a 18 latitude by 18 longitude grid over the spatial domain 3.58 W–9.58 E and 50.58 N– 60.58 N using an inversesquared distance method with a 250 km search radius (Beaugrand et al 2000)
Summary
A long-term time series of plankton and benthic records in the North Sea indicates an increase in decapods and a decline in their prey species that include bivalves and flatfish recruits. Analysis of decapod larvae in the plankton reveals a greater presence and spatial extent of warm-water species where the increase in decapods is greatest. These changes paralleled the arrival of new species such as the warm-water swimming crab Polybius henslowii found in the southern North Sea. We suggest that climate-induced changes among North Sea decapods have played an important role in the trophic amplification of a climate signal and in the development of the new North Sea dynamic regime
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