Phytoplankton adapt to changing ocean environments

Andrew J. Irwin; Zoe V. Finkel; Frank E. Müller-Karger; Luis Troccoli Ghinaglia

doi:10.1073/pnas.1414752112

Edited by David M. Karl, University of Hawaii, Honolulu, HI, and approved March 27, 2015 (received for review August 1, 2014)

Significance

Most ecosystem models used to predict changes in community composition with climate change assume species’ responses to environmental conditions are genetically fixed on the century scale, but this hypothesis has not been tested. Using an oceanographic time series with directional environmental changes, we show here that many phytoplankton species are able to track, on average, modest changes in temperature and irradiance, but not decreases in limiting nutrient concentrations, on decadal timescales. This result suggests that models that use genetically fixed traits may not provide reasonable projections for changes in biological communities in response to climate change over decadal to longer timescales.

Abstract

Model projections indicate that climate change may dramatically restructure phytoplankton communities, with cascading consequences for marine food webs. It is currently not known whether evolutionary change is likely to be able to keep pace with the rate of climate change. For simplicity, and in the absence of evidence to the contrary, most model projections assume species have fixed environmental preferences and will not adapt to changing environmental conditions on the century scale. Using 15 y of observations from Station CARIACO (Carbon Retention in a Colored Ocean), we show that most of the dominant species from a marine phytoplankton community were able to adapt their realized niches to track average increases in water temperature and irradiance, but the majority of species exhibited a fixed niche for nitrate. We do not know the extent of this adaptive capacity, so we cannot conclude that phytoplankton will be able to adapt to the changes anticipated over the next century, but community ecosystem models can no longer assume that phytoplankton cannot adapt.

Footnotes

↵¹To whom correspondence should be addressed. Email: airwin{at}mta.ca.

Author contributions: A.J.I. and Z.V.F. designed research; A.J.I. and Z.V.F. performed research; F.E.M.-K. and L.T.G. collected data; A.J.I. and Z.V.F. analyzed data; and A.J.I., Z.V.F., F.E.M.-K., and L.T.G. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.