Abrupt shifts in 21st-century plankton communities.

B B Cael,Stephanie Henson,Stephanie Dutkiewicz

doi:10.1126/sciadv.abf8593

B B Cael, Stephanie Henson + Show 1 more

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https://doi.org/10.1126/sciadv.abf8593

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Abstract

Marine microbial communities sustain ocean food webs and mediate global elemental cycles. These communities will change with climate; these changes can be gradual or foreseeable but likely have much more substantial consequences when sudden and unpredictable. In a complex virtual marine microbial ecosystem, we find that climate change–driven shifts over the 21st century are often abrupt, large in amplitude and extent, and unpredictable using standard early warning signals. Phytoplankton with unique resource needs, especially fast-growing species such as diatoms, are more prone to abrupt shifts. Abrupt shifts in biomass, productivity, and community structure are concentrated in Atlantic and Pacific subtropics. Abrupt changes in environmental variables such as temperature and nutrients rarely precede these ecosystem shifts, indicating that rapid community restructuring can occur in response to gradual environmental changes, particularly in nutrient supply rate ratios.

Highlights

Phytoplankton are the foundation of global ocean ecosystems; they are responsible for about half of global primary production [1], and they mediate biogeochemical cycles and thereby regulate climate [2]
S4), given the limitations of the model, we do not focus on these. That most of these abrupt shifts occur in the latter half of the 21st century suggests that a less severe emission scenario would lead to substantially fewer abrupt shifts
Abrupt shifts are increasingly likely with lower silicate supply ratios, which are associated with increased rates of change in silica-limited diatom populations, which can have knock-on effects for the entire plankton community via changes in the extent to which diatoms compete for other resources

Summary

Introduction

Phytoplankton are the foundation of global ocean ecosystems; they are responsible for about half of global primary production [1], and they mediate biogeochemical cycles and thereby regulate climate [2]. Plankton community structure and function are the emergent result of numerous environmental factors including insolation, nutrient concentrations/supplies, temperature, carbon chemistry, and the fluid motions in which they are embedded [3]. Nonlinear changes, whether these are rapid community readjustments to gradual environmental change or commensurate responses to rapid environmental change, are intrinsically more difficult to characterize, predict, and plan for Both for climate policy and ecosystem management, the possibility of environmental changes triggering “tipping point” responses in ocean ecology and biogeochemistry is a substantial concern [10]. Abrupt shifts in plankton can result in wholesale shifts to an alternative ecosystem state, affecting food webs, elemental cycling, and even fisheries, such as after the North Pacific regime shifts in 1977 and 1989 [11]

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