Photoperiod mediates the differential physiological responses of smaller Thalassiosira pseudonana and larger Thalassiosi
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Photoperiod mediates the differential physiological responses of smaller Thalassiosira pseudonana and larger Thalassiosira punctigera to temperature changes Ge Xu 1 & Jihua Liu 1 & Bokun Chen 1 & Gang Li 2,3 Received: 19 January 2020 / Revised and accepted: 4 May 2020 # Springer Nature B.V. 2020
Abstract Global warming is altering both phytoplankton-experienced temperature and light-exposure duration through shifting their niches from low to high latitudes. We explored the growth, physiology, and compositions of a smaller Thalassiosira pseudonana and a larger Thalassiosira punctigera, temperate marine centric diatoms, in responses to a matrix of temperatures (12, 15, 18, and 21 °C) and photoperiods (light:dark cycles of 4:20, 8:16, 16:8, and 24:0). Both T. pseudonana and T. punctigera grew faster under medium temperature and longer photoperiod, under the expected optimal instantaneous light intensity. The biovolumebased pigments content of T. pseudonana responded largely to temperature, while that of T. punctigera responded more to photoperiod duration than to temperature. In T. pseudonana, shortest photoperiod enhanced cellular protein content and alleviated their temperature dependency. Continuous growth light reduced the photosynthetic capacity of T. pseudonana at the lowest temperature and reduced that of T. punctigera across temperatures. Moreover, we found the increasing temperature linearly increased the dark respiration rate (Rd) and molar ratio of carbon to nitrogen (C:N) of T. pseudonana but decreased that of T. punctigera, with the scattered effects of photoperiod. Our results demonstrated that responses of diatoms Thalassiosira across photoperiods and temperatures vary with species and possibly with cell size, suggesting that the poleward shift of the niches of phytoplankton in nature might cause a change in community structure. Keywords Photoperiod . Temperature . Growth . Pigments . Dark respiration . RubisCO activity . Cell size . Diatoms Thalassiosira
Introduction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10811-020-02149-6) contains supplementary material, which is available to authorized users. * Jihua Liu [email protected] * Gang Li [email protected] 1
Institute of Marine Science and Technology, Shandong University, No. 72, Binhai Road, Jimo District, Qingdao 266237, Shandong, China
2
Key Laboratory of Tropical Marine Bio-resources and Ecology & Key Laboratory of Science and Technology on Operational Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510530, China
3
Southern Marine Science and Engineering Guangdong Laboratory, No. 164, Xingangxi Road, Guangzhou 510301, Guangdong, China
Global warming is increasing the temperature in surface ocean (Fischetti 2013; Gattuso et al. 2015) where phytoplankton cells dwell to obtain light energy to drive photosynthesis. Meanwhile, ocean warming is forcing temperate phytoplankton to shift their distributions poleward (Hallegraeff 2010; Thomas et
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