The Fram Strait plays a crucial role in regulating the heat and sea-ice dynamics in the Arctic. The marine biota of this Arctic gateway is experiencing significant changes with increasing advection of Atlantic species. The footprint of this “Atlantification” of marine diversity is based largely on fragmented observations of species occurrences representing different parts of the plankton community. Multi-decadal investigations on how regional climate change facilitates the invasion of Atlantic species and affects the ecology of the resident species are lacking. Here we use planktonic foraminifera as a proxy for recent changes in the pelagic community in the Fram Strait in three dimensions. Our analysis is based on 51 species-resolved stratified population profiles collected during seven surveys between 1985 and 2015.
The analysis of the data reveals ongoing shift towards an Atlantic component, occurring independently of changes in local environmental conditions, thus reflecting higher production of the Atlantic species in their “source” region. At the same time, the ongoing extensive sea-ice export from the Arctic proper and associated cooling in the Fram Strait negatively affected the resident species T. quinqueloba that showed declining density and habitat shoaling. Since the resident N. pachyderma persists, the planktonic foraminifera community shifts to a new state, where the thriving cold-adapted resident is confronted with increasing advection of Atlantic expatriates. Our results show that both remote forcing of the Atlantic invaders and local climatic changes acting on the resident species induce rapid response of community structure as well as vertical distribution of planktonic foraminifera in the Fram Strait. When the strong summer export of Arctic sea-ice will decrease, the Arctic gateway will likely experience rapid restructuring of the pelagic community even in the absence of further warming. Such a large change in the gateway region will likely propagate into the Arctic proper.
Biologist working on microbial ecology and evolution. Studied Environmental Sciences at the University of Urbino and did his Master in Biology at the University of Bologna. In 2016 he joined the Arctrain PhD program at the University of Bremen. Currently, he is working as a Postdoctoral researcher at Smith College where he is applying a single-cell omics approach to explore population genomics in eukaryotic microbes.