Biological invasion drives ecosystem state and metabolism across tipping points

Abstract

Abrupt regime shifts of complex ecosystems between alternative stable states are widespread in nature. Yet, our mechanistic understanding of disturbance-shift-ecosystem functioning relationships remains poor, and it is further unclear whether biotic disturbances can drive such shifts. Using a 5-year pond experiment, we demonstrate that invasion by the red swamp crayfish (Procambarus clarkii) drove a regime shift from a clear-water, macrophyte-dominated, to a turbid, phytoplankton-dominated state. The regime shift was associated with increased water temperature due to increased water turbidity enhanced light absorption, and with a seasonal switch of ecosystem metabolism from hetero-to autotrophy due to decreased respiration in summer, despite constant gross primary production. Reducing crayfish population densities by 44 % failed to move ecosystems back towards their initial state and functioning. Our results stress that biotic disturbances may have hardly-reversible consequences on the biophysical and biogeochemical processes that support ecosystem functioning.