Global warming triggers abrupt regime shifts in island lake ecosystems in the Azores Archipelago

Abstract

Global warming significantly alters lake ecosystems worldwide. However, the effects of warming at aregional scale are often overlooked due to the scarcity of multidecadal to centennial regional studies.Here, we examined diatom sedimentary records from five lakes on São Miguel Island (Azoresarchipelago) over the last 170 years. Our analysis using hierarchical generalised additive modelsrevealed an abrupt shift in the island-wide diatom community around 1982 CE, when the NorthernHemisphere temperature exceeded 0.35 °C above the 20th-century mean. This community regimeshift resulted in a 27% loss in regional diatom diversity across the Island. Furthermore, previousanthropogenic impacts may have enhanced lakes’ rapid response to warming. These findingshighlight the vulnerability of freshwater island ecosystems to climate warming and emphasise theimportance of transitioning from local to regional assessments to preserve regional resilience andprevent irreversible damage to these essential freshwater resources and their biodiversity.