Interactive effects of increasing atmospheric CO2 and copper exposure on the growth and photosynthesis in the young sporophytes of Sargassum fusiforme (Phaeophyta)

Highlights

  • Effects of Cu2+ and elevated atmospheric CO2 on young sporophytes of Sargassum fusiforme were investigated.
  • At elevated CO2, growth inhibition and pigment damage caused by Cu2+ remain at the same level.
  • Elevated CO2 alleviates the Cu-induced suppression on photosystem.
  • Elevated CO2 down-regulates the enzymatic antioxidant system against Cu2+.

Abstract

Little attention has been given to the combined effects of elevated atmospheric CO2-induced ocean acidification (OA) and heavy metal pollution on marine macroalgae at the young stage. This study investigated the mutual effects of copper (Cu) and elevated CO2 on the young sporophytes of brown macroalgae Sargassum fusiforme. A matrix of four copper concentrations, 0, 0.025, 0.075 and 0.15 mg‧L-1, and two levels of CO2 (ambient CO2: 400 μatm; elevated CO2: 1,000 μatm) were used. High concentration of copper exposure greatly depressed photosynthesis and growth of the young sporophytes of S. fusiforme by reducing the apparent photosynthetic efficiency (ɑ), maximum net photosynthetic oxygen evolution rate (Pmax), maximum photochemical quantum yield (Fv/Fm) and pigments content (Chl a and Car). While elevated CO2 alone had obscure impact on this alga. However, the inhibition of Cu stress on Fv/Fm was weakened by elevated CO2, which also decreased the light compensation point (Ic). Meanwhile, the Cu2+-induced ascent in the dark respiration rate (Rd) and superoxide dismutase (SOD) activity was mitigated under the growth with elevated CO2, suggesting an alleviated oxidative stress. Overall, we propose that, under CO2 enrichment condition, the young sporophytes of S. fusiforme may increase photosynthesis efficiency and synthesize less enzymatic antioxidants in face of increasing Cu stress.

Wen J. & Zou D., 2021. Interactive effects of increasing atmospheric CO2 and copper exposure on the growth and photosynthesis in the young sporophytes of Sargassum fusiforme (Phaeophyta). Chemosphere 269: 129397. doi: 10.1016/j.chemosphere.2020.129397. Article (subscription required).

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