Joint effects of naphthalene and microcystin-LR on physiological responses and toxin bioaccumulation of Landoltia punctata

Zhu

et al. 2023

Toxicol Ind Health

To meet the strict requirements of reducing sulfur emissions, an increasing number of commercial ships have installed exhaust gas cleaning systems (EGCSs). However, wash water produced during the cleaning process is discharged back to the marine environment. We investigated the effects of closed-loop scrubber (natrium-alkali method) wash water on three trophic species . Severe toxic effects were found when Dunaliella salina, Mysidopsis bahia, and Mugilogobius chulae were exposed to 0.63–6.25, 0.63–10, and 1.25–20% concentrations of wash water, respectively. The 50% effective concentration in 96 h (EC50-96 h) for D. salina was 2.48%, and the corresponding total polycyclic aromatic hydrocarbons (PAHs) and heavy metals were 22.81 and 23.67 μg L−1. The 50% lethal concentration in 7 d (LC50-7 d) values for M. bahia and M. chulae were 3.57% and 20.50%, respectively. The lowest observed effect concentration (LOEC) values for M. bahia and M. chulae were 1.25% and 2.5%, respectively, and the corresponding total PAHs and heavy metals were 11.50 and 11.93 and 22.99 and 23.86 μg L−1. M. bahia’s body weight was negatively correlated with the amount of wash water. Low concentrations of wash water (0–5%) had no significant effect on the reproduction of M. bahia. Although concentrations of 16 PAHs and 8 heavy metals are known, different compounds might react with each other and form more unknown toxic substances, and the measured toxicity comes from synergistic effects between various pollutants. Therefore, future work is needed to clarify other more toxic contaminants in wash water. We highly recommend that wash water be treated before being discharged to the marine environment.

Section: Discussioncontrasting

confidence: 72%

Toxic effects of ship exhaust gas closed-loop scrubber wash water

Zhu

et al. 2023

Toxicol Ind Health

“…We suspected that naphthalene (NAP), Cr, Ni, Cu and Zn played a vital role for the inhibition effect on D. salina. It has been reported that there was signi cant inhibition for Landoltia punctata at NAP concentration low to 10 µg L −1 [47] , hence, the concentration of NAP was 898.02 µg L −1 in our study, which was 90 times higher than that. In addition, Zaki et al [48] investigated the single toxicity (i.e., EC 50 ) of heavy metals on the growth of Pseudokirchneriella subcapitata were 200 µg L −1 for Cr, 55 µg L −1 for Ni, 48 µg L −1 for Cu, and 80 µg L −1 for Zn, respectively.…”

Section: Algae Growth Inhibitionmentioning

confidence: 48%

Toxic Effects on Dunaliella salina, Mysidopsis bahia, and Mugilogobius chulae from Ship Exhaust Gas Closed-loop Scrubber Wash Water

Zhu

et al. 2022

Preprint

To meet the strict requirements of reducing sulfur emission, more and more commercial ships have installed exhaust gas cleaning systems (EGCSs). However, wash water produced during cleaning process is discharged back to the marine environment. We investigated effects of the closed-loop scrubber (natrium-alkali method) wash water on three trophic species. Severe toxic effects were found when Dunaliella salina, Mysidopsis bahia and Mugilogobius chulae were exposed to 0.63-6.25, 0.63-10 and 1.25-20% concentrations of wash water, respectively. EC50-96 h of D. salina was 2.48%, corresponding to total polycyclic aromatic hydrocarbons (PAHs) or heavy metals were 22.81, 23.67 µg L−1. LC50-7 d of M. bahia and M. chulae were 3.57 and 20.50%. The LOEC of M. bahia and M. chulae were 1.25% and 2.5%, corresponding to total PAHs and heavy metals were 11.50, 11.93 and 22.99, 23.86 µg L−1. M. bahia’s body weight was negatively correlated with concentrations of wash water. Although wash water contained high concentrations of PAHs (e.g., naphthalene) and heavy metals (e.g., Cr, Ni, Cu and Zn), none of the single pollutant could explain the high toxicity of wash water. The measured toxicity might arise from synergistic effects among several contaminants or from other more toxic contaminants we know very little about. We highly recommend that wash water should be treated prior to being discharged to the marine environment.

“…The transcript encoding GBSS was not significantly different under nitrogen starvation conditions. Yang et al [ 18 ] found that under the treatment of different concentrations of pollutants, the starch synthase of duckweed was also affected to different degrees, which ultimately affected the accumulation of starch. Zhu et al [ 46 ] found by RNA-seq that maleic hydrazide treatment might affect the expression of transcripts of some key enzymes in the starch biosynthesis pathway.…”

Section: Metabolism Pathway Of Duckweed Starchmentioning

confidence: 99%

“…This showed that the coordination of carbon metabolism and nitrogen metabolism plays an important role in the detoxification mechanism of duckweed. Yang et al [ 18 ] showed that the starch content of La. punctata increased to 29.8% (DW) under the joint stress of Naphtalene (NAP) and MC-LR, which suggested that this phenomenon might be related to the destruction of starch degrading enzymes.…”

Section: Pathways To Promote the Accumulation Of Duckweed Starchmentioning

confidence: 99%

“…Duckweed can be converted to bioethanol with a conversion efficiency of 94.7% of the starch in duckweed [ 15 ] and a theoretical yield of ethanol about eight times that of corn [ 16 ]. Additionally, duckweed can remove pollutants from wastewater through enrichment and can combine water pollution control with bioenergy production [ 17 , 18 , 19 ]. Therefore, duckweed is a promising strategic new non-food biomaterial that might solve the feedstock problem faced during the development of the biofuel industry [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Duckweed Is a Promising Feedstock of Biofuels: Advantages and Approaches

2022

IJMS

Self Cite

With the growing scarcity of traditional sources of energy and the accompanying acute environmental challenges, biofuels based on biomass are favored as the most promising alternative. As one of the core raw materials for biomass energy, research on its production methods and synthesis mechanisms is emerging. In recent years, duckweed has been used as a high-quality new biomass feedstock for its advantages, including fast biomass accumulation, high starch content, high biomass conversion efficiency, and sewage remediation. This study provides a systematic review of the growth characteristics, starch metabolism pathways, and methods to improve starch accumulation in the new energy plant, duckweed. The study also presents a prospect that might be used as a reference for the development of duckweed as a new energy-providing plant.