Physiological responses of &amp;lt;i&amp;gt;Skeletonema costatum&amp;lt;/i&amp;gt; to the interactions of seawater acidification and the combination of photoperiod and temperature

Hangxiao Li,Juntian Xu,Jing Ma,Futian Li,Tianpeng Xu

doi:10.5194/bg-18-1439-2021

Physiological responses of &lt;i&gt;Skeletonema costatum&lt;/i&gt; to the interactions of seawater acidification and the combination of photoperiod and temperature

Hangxiao Li, Juntian Xu + Show 3 more

Open Access

https://doi.org/10.5194/bg-18-1439-2021

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Journal: Biogeosciences (Online)	Publication Date: Feb 24, 2021
Citations: 21	License type: CC BY 4.0

Affiliation: Jiangsu Ocean University

Abstract

Abstract. Ocean acidification (OA), which is a major environmental change caused by increasing atmospheric CO2, has considerable influences on marine phytoplankton. But few studies have investigated interactions of OA and seasonal changes in temperature and photoperiod on marine diatoms. In the present study, a marine diatom Skeletonema costatum was cultured under two different CO2 levels (LC, 400 µatm; HC, 1000 µatm) and three different combinations of temperature and photoperiod length (8:16 L:D with 5 ∘C, 12:12 L:D with 15 ∘C, 16:8 L:D with 25 ∘C), simulating different seasons in typical temperate oceans, to investigate the combined effects of these factors. The results showed that specific growth rate of S. costatum increased with increasing temperature and day length. However, OA showed contrasting effects on growth and photosynthesis under different combinations of temperature and day length: while positive effects of OA were observed under spring and autumn conditions, it significantly decreased growth (11 %) and photosynthesis (21 %) in winter. In addition, OA alleviated the negative effect of low temperature and short day length on the abundance of RbcL and key photosystem II (PSII) proteins (D1 and D2). These data indicated that future ocean acidification may show differential effects on diatoms in different clusters of other factors.

Highlights

Ocean acidification (OA) is one of major environmental changes caused by increasing atmospheric CO2, which has directly increased from 280 ppm in the preindustrial era to higher than 400 ppm at present (Friedlingstein et al, 2019)
We investigate the physiological performance of marine diatom Skeletonema costatum under two different CO2 levels and three combinations of temperature and photoperiod, which simulated different seasons in typical temperate oceans
The growth rate of S. costatum ranged from 0.47 ± 0.01 to 3.22 ± 0.08 d−1 under different treatments and increased significantly with increasing temperature and day length (P < 0.05) regardless of the pCO2 level (Fig. 1)

Summary

Introduction

Ocean acidification (OA) is one of major environmental changes caused by increasing atmospheric CO2, which has directly increased from 280 ppm in the preindustrial era to higher than 400 ppm at present (Friedlingstein et al, 2019). It has been suggested that calcifying organisms, such as coral reefs and coccolithophores, are vulnerable to OA due to the decreased calcification at elevated CO2 (Albright et al, 2016). Diatoms are ubiquitous photosynthetic phytoplankton which account for about 20 % of global primary productivity and play a crucial role in the global cycling of carbon and silicon (Falkowski et al, 2004). To overcome the limited aqueous CO2 concentration in seawater, they have developed CO2-concentrating mechanisms (CCMs) (Spalding, 2007). Decreased photosynthetic affinity for dissolved inorganic carbon (DIC) and activity of CCM-related enzymes are generally found under increased CO2 conditions (Raven and Beardall, 2014). For phytoplankton assemblages, elevated CO2 could lead to increases in chlorophyll a concentrations and the abundance of diatoms (Johnson et al, 2013).

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