Large-Scale Niche Analysis of Phytoplankton Cell Shapes and Their Spatial Distribution in Transitional Water Ecosystems in the Framework of Global Warming

Climate change is a key driver of changes to abiotic niche dimensions such as water temperature in aquatic ecosystems. This study focuses on phytoplankton cell shapes in response to global warming. It quantifies spatial niche models of phytoplankton cell shape and applies these trends to current and future scenarios at the global scale. This study was carried out based on (1) six phytoplankton datasets accounting for 127,311 specimens, belonging to 306 taxa and 35 cell shape categories covering transitional aquatic ecosystems in the Northeast Atlantic, Mediterranean, Southwest Atlantic, Indian Ocean, and South Pacific, and (2) a unified dataset for all geographical areas including sea surface temperature, salinity, depth, primary production and coastal distance with data derived from GMEDs. Species distribution and niche models have been used to characterize the niches of 24 out of the 35 phytoplankton cell shapes and evaluate their current and future spatial distribution range. The predicted future scenario showed a reduction in the potential spatial distribution of four predominantly elongated shapes, representing 4.42% of all taxa in the datasets; we observed an increase for 15 simple cell shapes (67.51%) and no change for 5 shapes (23.03%). The results achieved suggest that phytoplankton taxa with simple body shapes will expand their distribution range in warmer coastal ecosystems.