Evolution in temperature-dependent phytoplankton traits revealed from a sediment archive: do reaction norms tell the whole story?

Abstract

The high evolutionary potential of phytoplankton species allows them to rapidly adapt to global warming. Adaptations may occur in temperature-dependent traits, such as growth rate, cell size and life cycle processes. Using resurrection experiments with resting stages from living sediment archives, it is possible to investigate whether adaptation occurred. For this study, we revived resting cysts of the spring bloom dinoflagellate from recent and 100-year-old sediment layers from the Gulf of Finland, and compared temperature-dependent traits of recent and historic strains along a temperature gradient. We detected no changes in growth rates and cell sizes but a significant difference between recent and historic strains regarding resting cyst formation. The encystment rate of recent strains was significantly lower compared with historic strains which we interpret as an indication of adaptation to higher and more rapidly increasing spring temperatures. Low encystment rates may allow for bloom formation even if the threshold temperature inducing a loss of actively growing cells through resting cyst formation is exceeded. Our findings reveal that phenotypic responses of phytoplankton to changing temperature conditions may include hidden traits such as life cycle processes and their regulation mechanisms. This study emphasizes the potential of living sediment archives to investigate plankton responses and adaptation to global warming.

How to analyse plant phenotypic plasticity in response to a changing climate

“…Finally, although not a plant example, growth rates of phytoplankton show a strong threshold relationship with temperature (Fig. d), where growth rate drastically declines beyond a critical temperature (Hinners et al ., ).…”

“…The GAM is a highly flexible model for complex reaction norm shapes (e.g. Hinners et al, 2017). Each population-level reaction norm shape is modelled along with three different scenarios of variation in the individual reaction norms, which are represented by different functions of each of the random effects separately (the three rows of Fig.…”

Rapid thermal adaptation in a marine diatom reveals constraints and trade‐offs

“…() found that after 1 year of experimental adaptation to elevated temperature (26.3°C), the marine coccolithophore Emiliania huxleyi evolved a higher population growth rate, smaller cell diameter and lower particulate organic and inorganic carbon content compared to cold (15°C)‐adapted populations. Hinners, Kremp, and Hense () found that 100‐year‐old resurrected strains of the marine dinoflagellate Apocalathium malmogiense did not differ in cell size or in its thermal reaction norm for growth compared to current strains, but that it did form resting cysts at a higher rate.…”

Temperature responses in a subarctic springtail from two geothermally warmed habitats

“…Although the difference is small, it is remarkably similar, both in character and degree, to latitudinal and altitudinal variation shown by other insect species over hundreds of kilometers (Bateman, 1967;Fujiyama and Harada, 1996;Liefting et al, 2009;Kutcherov et al, 2015), including the soil-dwelling springtail Folsomia candida (Stam et al, 1996). A taxonomically and conceptually distant but essentially similar example has recently come from phytoplankton studies: modern-day dinoflagellate strains, which experience seawater warming, show slightly faster growth rates, also at higher temperatures only, than strains revived from century-old sediments (Hinners et al, 2017). In all these cases, organisms from warmer thermal environments develop and/or grow slightly faster at higher temperatures relative to their colder-climate counterparts and reaction norms intersect around the lowest used experimental temperatures.…”