Climate variability and multi-decadal diatom abundance in the Northeast Atlantic

Diatoms are important contributors to marine primary production and the ocean carbon cycle. In the North Atlantic and its adjacent seas primary production is driven by diatoms that transfer a significant part of the produced energy to higher trophic levels and carbon to the deep ocean. Anthropogenic warming and climate variability will likely have important consequences for the productivity and spatial dynamics of these eukaryotic phytoplankton. Using multidecadal diatom abundance data (>60 years) for the Northeast Atlantic and the North Sea, we show significant spatial and temporal correlations over these scales between diatoms and climate variability. A general multidecadal trend is established where climate warming is increasing diatom populations in northerly systems but decreasing populations in more southerly systems. We discover major phase shifts in diatom abundance synchronous with multi-decadal trends in Atlantic climate variability that occurred after the mid-1990s. Long term variability in temperature and wind patterns impacts diatom populations in the Northeast Atlantic, with warming leading to increased abundance in cold oceanic regions and decreased abundance in warm regions, according to an analysis of 60-years of continuous plankton recorder observations.