Trends in Marine Plankton Biodiversity over the 21st Century under Different Climate Change Scenarios
Creators: name: Li, Xinhang
Publisher: name: ETH Zurich
Year: 2023
Subjects: subject: marine biodiversity, plankton biogeography, climate change
subject: info:eu-repo/classification/ddc/500
subject: Natural sciences
subject: FOS: Natural sciences

description: Marine plankton are at the base of the marine food webs. They perform essential ecological functions such as biological carbon sequestration and food provision to higher trophic levels. However, they are subject to anthropogenic climate change, and the impacts of different climate change scenarios on marine plankton biodiversity and habitat are poorly quantified. In this study, we use an ensemble of species distribution models to project habitat suitability index for a total of 843 marine plankton species (326 phytoplankton and 517 zooplankton) under three climate change scenarios (RCP2.6, RCP4.5 and RCP8.5) from 2012-2100. The differences in plankton biodiversity among the three RCPs are substantial. In RCP2.6, compared to the baseline (2012-2031), the global mean relative increase in plankton species richness by the end of the 21st century (2081-2100) is only 1.6%. This relative change increases to 3.4% in RCP4.5 and further to 8.0% in RCP8.5. From RCP2.6 to RCP8.5, there is a remarkable expansion of species richness change hotspots. In RCP8.5, the species richness change hotspots will cover three fourths of the global surface ocean from 60°N to 60°S by the end of the 21st century. The majority of plankton species (85%) will shift poleward in the future in response to ocean warming. Furthermore, there is a significant acceleration of poleward shift, from 3.76 km/dec in RCP2.6 to 19.95 km/dec in RCP8.5. The Arctic Ocean is the ocean basin that will experience the highest level of species turnover in plankton assemblages under all RCP scenarios, which indicates a high sensitivity to climate change in this region. Species turnover in the Arctic Ocean amounts to 0.45 in RCP8.5, which means that nearly half of the species in plankton assemblages will be replaced by the end of the 21st century. Phytoplankton and zooplankton are different in their biodiversity responses to ocean warming in the tropics: Phytoplankton species richness will increase under all RCP scenarios, by contrast, zooplankton species richness will slightly decrease in RCP8.5, and slightly increase in RCP4.5 and RCP2.6. Additionally, the dissimilarity of phytoplankton assemblage composition between baseline and future is driven by both turnover and nestedness, whereas the dissimilarity of zooplankton assemblage composition between baseline and future is primarily driven by species turnover. Overall, limiting global warming below 1.5°C can avoid the significant expansion of plankton richness change hotspots under RCP8.5 compared to RCP2.6, constrain the speed of poleward habitat shift below one fifth of that in RCP8.5, and keep the species turnover in the Arctic Ocean at about half of that in RCP8.5. Potential negative impacts on ocean carbon cycles and ecosystem services caused by marine plankton biodiversity change and habitat shift can be avoided if collaborative efforts are made to limit global warming below 1.5 °C.