PICOPHYTOPLANKTON LINEAGES DISPLAY CLEAR NICHE PARTITIONING BUT OVERALL POSITIVE RESPONSE TO FUTURE OCEAN WARMING

ADAM C MARTINY; FLOMBAUM, P

Congreso; Aquatic Sciences Meeting; 2017

ASLO

Climate models predict that rising CO2 in the atmosphere and associated ocean warming lead to declines in global ocean photosynthetic biomass and activity. This decline is in large part driven by an expansion of ocean regions dominated by picophytoplankton including picoeukaryotic phytoplankton, Synechococcus, and Prochlorococcus. However, each lineage harbor extensive intraspecific diversity that could control the response to future ocean changes not currently captured by climate models. An alternative approach implicitly embracing this intraspecific diversity is to design realized niche envelope models and quantitatively predict future ocean phytoplankton biomass based on current abundances of diverse populations along gradients of light, temperature, and nutrients. Using a global dataset to calibrate a niche model, we project the global biogeography of the very abundant but little studied picoeukaryotic phytoplankton. We then combined this niche model with similar models for Prochlorococcus and Synechococcus. We find that cell size differences between lineages parallel a latitudinal niche partitioning but a shared overall biomass increase along a positive temperature gradient between 25 and 30°C. As consequence, future ocean conditions could lead to 24% higher total phytoplankton biomass in low latitude oligotrophic gyres. Combined, our niche models describe through 86,599 observations the global biogeography of key phytoplankton lineages across unique environments and suggest a previously unrecognized biological response to climate change. Future increases in biomass could have widespread ramifications for global carbon cycling and marine life in the ocean.