The interactive effects of elevated temperature and nutrient concentrations on the physiological responses of Ulva linza
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23RD INTERNATIONAL SEAWEED SYMPOSIUM, JEJU
The interactive effects of elevated temperature and nutrient concentrations on the physiological responses of Ulva linza Linnaeus (Ulvales, Chlorophyta) Jee Eun Lee 1 & Jin Woo Kang 2 Received: 29 June 2019 / Revised and accepted: 29 December 2019 # Springer Nature B.V. 2020
Abstract We tested the interactive effects of increased temperature and nutrient (ammonium, NH4+) levels on physiological properties such as photosynthetic rates, NH4+ uptake rates, relative growth rates, chlorophyll fluorescence, and tissue nutrient contents in Ulva linza Linnaeus. The experiments were conducted at four temperatures (LT, low temperature (15 °C); MT, medium temperature (20 °C); CT, control temperature (25 °C); and HT, high temperature (30 °C)) and three NH4+ concentrations (LN, low nutrient (4 μM); MN, medium nutrient (60 μM); and HN, high nutrient (120 μM)). The interaction between temperature and NH4+ levels influenced the photosynthetic rates, NH4+ uptake rates, relative growth rates, photosynthetic efficiency, tissue nitrogen contents, and C:N ratios in algal tissues. Temperature strongly affected the photosynthetic rates, NH4+ uptake rates, and photosynthetic efficiency. Nutrient enrichment increased the photosynthetic rates, nutrient uptake rates, relative growth rates, photosynthetic efficiency, tissue nitrogen contents, and tissue C:N ratios. Our study results could help understand the physiological responses of U. linza under future ocean environmental conditions such as ocean warming and eutrophication. Keywords Ammonium (NH4+) . Temperature . Ulva linza . Physiological responses
Introduction Atmospheric CO2 concentration has increased from 280 ppm in the pre-industrial era to the current level of 400 ppm because of anthropogenic activities following the Industrial Revolution (IPCC 2014). Many studies predict CO2 concentrations will double their current levels by the year 2100 (Roleda et al. 2012; IPCC 2014). According to the IPCC report (2014), global average temperature will increase by 0.6 to 2.0 °C, based on projections of the climate change model. If no effort is made to curb CO2 emissions, then global average temperature will increase by 2.6 to 4.8 °C (IPCC 2014). In addition, seawater temperatures could increase from 1.9 to 5.8 °C by the end of the twenty-first century under elevated CO2 conditions (IPCC 2014). * Jin Woo Kang [email protected] 1
Seaweed Research Center, National Institute of Fisheries Science, Haenam 59002, Republic of Korea
2
Project Management Division, East Sea Branch, Korea Fisheries Resources Agency, Pohang 37601, Republic of Korea
Seawater temperature is an important factor for macroalgae survival, growth, reproduction, morphology, and metabolism (Lüning and Neushul 1978; Davison 1991; Wernberg et al. 2010; Rothäusler et al. 2011; Martínez et al. 2012). Temperature change could influence the activity of enzymes including photosynthetic C and N assimilation, ribulose-1,5bisphosphate carboxylase oxygenase (Rubisco) activity, and nitrate redu
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