Temperatures above thermal optimum reduce cell growth and silica production while increasing cell volume and protein con
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PRIMARY RESEARCH PAPER
Temperatures above thermal optimum reduce cell growth and silica production while increasing cell volume and protein content in the diatom Thalassiosira pseudonana Cristin E. Sheehan . Kirralee G. Baker . Daniel A. Nielsen . Katherina Petrou
Received: 30 June 2020 / Revised: 9 August 2020 / Accepted: 5 September 2020 Ó Springer Nature Switzerland AG 2020
Abstract Temperature plays a fundamental role in determining phytoplankton community structure, distribution, and abundance. With climate models predicting increases in ocean surface temperatures of up to 3.2°C by 2100, there is a genuine need to acquire data on the phenotypic plasticity, and thus performance, of phytoplankton in relation to temperature. We investigated the effects of temperature (14–28°C) on the growth, morphology, productivity, silicification and macromolecular composition of the marine diatom Thalassiosira pseudonana. Optimum growth rate and maximum P:R ratio were obtained around 21°C. Cell volume and chlorophyll a increased with temperature, as did lipids and proteins. One of the strongest temperature-induced shifts was the higher silicification rates at low temperature. Our results reveal temperature-driven responses in physiological, morphological and biochemical traits in T. pseudonana; whereby at supra-optimal temperatures cells grew slower, were larger, had higher chlorophyll and protein content but reduced silicification, while those
Handling editor: Sofie Spatharis C. E. Sheehan D. A. Nielsen K. Petrou (&) School of Life Sciences, University of Technology Sydney, Sydney, NSW, Australia e-mail: [email protected] K. G. Baker School of Life Sciences, University of Essex, Wivenhoe Park, UK
exposed to sub-optimal temperatures were smaller, heavily silicified with lower lipid and chlorophyll content. If these conserved across species, our findings indicate that as oceans warm, we may see shifts in diatom phenotypes and community structure, with potential biogeochemical consequences of higher remineralisation and declines in carbon and silicon export to the ocean interior. Keywords Phenotypic traits Thermal performance curves Climate change Diatoms Silicification Macromolecules
Introduction Temperature defines the biogeographical boundaries and distribution of major groups of phytoplankton (Longhurst, 2010), but with ocean temperatures predicted to warm between 1.2 and 3.2°C by 2100 (Meehl et al., 2007; Gattuso et al., 2015), changes to phytoplankton biogeography are expected. As temperature zones shift due to climate change, we are seeing the displacement of local or regional species by species that are better suited to the new environmental conditions (Burrows et al., 2014; Barton et al., 2016). While spatial changes in ocean temperature could lead to altered species distributions, temporal changes could affect the timing of spring blooms (Edwards &
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Hydrobiologia
Richardson, 2004; Gao et al., 2012). To gain insight into how species dist
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