Phytoplankton mortality in a changing thermal seascape

Abstract

Phytoplankton growth generates half of the atmosphere's oxygen through photosynthesis, thus providing the energy that fuels pelagic food chains and playing key roles in biogeochemical cycles of oxygen, carbon and nutrient elements. Predicting spatiotemporal distributions of phytoplankton biomass and community composition heavily relies on experimental studies that document how environmental conditions influence net population growth rates, the difference between cell division rate and the death rate. Although the environmental controls on phytoplankton growth are well studied, the factors governing cell death rates remain unclear.Death rates in natural phytoplankton communities range from <0.01 to >1 day −1 (Marbá et al., 2007). Studies that have calculated death rates from measurements of cell lysis (Agustí & Duarte, 2000;Agustí et al., 1998) include contributions to death due to biotic factors such as viral infection as well as abiotic stress-induced physiological death. The death rate due to physiological stress is typically

Experimental evolution of environmental tolerance, acclimation, and physiological plasticity in a randomly fluctuating environment

“…Nevertheless, our detailed measurement of tolerance surfaces across a broad combination of acclimation and assay salinities still allowed us to detect evolutionary responses that would probably have gone unnoticed using simpler approaches. Partitioning of apparent death and growth rates confirmed that in phytoplankton, mortality becomes proportional to the abiotic stress when it exceeds the upper tolerance limit (as found with thermal stress in a diatom; Baker and Geider 2021 ). On the other hand, we were constrained to use a rather crude population growth model, assuming exponential growth to estimate a net per capita growth rate over 3 days.…”

Disentangling the effects of microalgal diversity and thermal history on freshwater phototrophic biofilms facing heat stress: A thermal dose approach

“…Such increased tolerance has been observed in marine copepods: a 4°C increase during development enables better thermal tolerance (Sasaki & Dam, 2019). Similarly, phytoplankton communities acclimated to thermal conditions above their optimum exhibited a better tolerance to heat stress (Baker & Geider, 2021). In our study, the relationship between acclimation temperature and tolerance of photosynthetic activity of synthetic microalgal communities was nonlinear, with an increase in tolerance four times higher when acclimation temperature increased from 20°C to 25°C than from 15°C to 20°C.…”

Compound hot temperature and high chlorophyll extreme events in global lakes

“…This can be expected given the strong temperature dependence of algal growth (Yvon-Durocher et al 2015). This may be particularly evident for some phytoplankton species that have ecophysiological adaptations that allow them to dominate aquatic systems under extended periods of warm and irregular temperatures (Jöhnk et al 2008, Duan et al 2009, Zhang et al 2016, Rasconi et al 2017, Baker and Geider 2021, as occurs during lake heatwaves. In some lakes, we calculated an LMF < 1, which indicates a negative dependence between the drivers of lake heatwaves and high chlorophyll extremes-i.e.…”