CO2-induced pH reduction increases physiological toxicity of nano-TiO2 in the mussel Mytilus coruscus

Menghong Hu,Weiqun Lu,Daohui Lin,Yueyong Shang,Yimin Chen,Ke Ning,Yi Hu,Youji Wang,Xizhi Huang

doi:10.1038/srep40015

Menghong Hu, Weiqun Lu + Show 7 more

Open Access

https://doi.org/10.1038/srep40015

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Journal: Scientific Reports	Publication Date: Jan 5, 2017
Citations: 39	License type: open-access

Affiliation: Zhejiang University, Shanghai Ocean University

Abstract

The increasing usage of nanoparticles has caused their considerable release into the aquatic environment. Meanwhile, anthropogenic CO2 emissions have caused a reduction of seawater pH. However, their combined effects on marine species have not been experimentally evaluated. This study estimated the physiological toxicity of nano-TiO2 in the mussel Mytilus coruscus under high pCO2 (2500–2600 μatm). We found that respiration rate (RR), food absorption efficiency (AE), clearance rate (CR), scope for growth (SFG) and O:N ratio were significantly reduced by nano-TiO2, whereas faecal organic weight rate and ammonia excretion rate (ER) were increased under nano-TiO2 conditions. High pCO2 exerted lower effects on CR, RR, ER and O:N ratio than nano-TiO2. Despite this, significant interactions of CO2-induced pH change and nano-TiO2 were found in RR, ER and O:N ratio. PCA showed close relationships among most test parameters, i.e., RR, CR, AE, SFG and O:N ratio. The normal physiological responses were strongly correlated to a positive SFG with normal pH and no/low nano-TiO2 conditions. Our results indicate that physiological functions of M. coruscus are more severely impaired by the combination of nano-TiO2 and high pCO2.

Highlights

The increasing usage of nanoparticles has caused their considerable release into the aquatic environment
The purpose of this study was to assess the interactive effects of nano-TiO2 and high pressure of CO2 (pCO2) on M. coruscus by integrating key eco-physiological parameters, i.e., clearance rate, food absorption efficiency, organic rate in faeces, respiration rate, ammonia excretion rate, oxygen to nitrogen (O:N) ratio as well as scope for growth (SFG)
(30%) phases (Supplementary Figure 1A), which was consistent with the product information nano-TiO2 showed different sizes under scanning electron microscope (SEM) and transmission electron microscope (TEM), the morphology was typical of grinded particles, and some particles were agglomerated (Supplementary Figure 1B and C)

Summary

Introduction

The increasing usage of nanoparticles has caused their considerable release into the aquatic environment. As gill cells play important roles in food transport and respiration for mussels[23], there is a unique interest in expanding studies on nano-TiO2 toxicity in mussel’s feeding and physiology. Some studies show that CO2-induced pH reduction impacts bivalve physiology by changing extracellular acid–base balance[26,27], metabolic activities[28] and feeding[29,30]. A rise in pCO2 levels can induce changes in the extracellular acid–base balance that can produce metabolic disturbances, adversely affecting relevant biological processes, such www.nature.com/scientificreports/. Many marine calcifying organisms have exhibited negative responses to high pCO2, such as disorder in metabolic rates[26,28], reduction of food uptake[29,30] and alteration in calcification and development[33]. The extracellular alterations caused by exposure to elevated pCO2 are likely to affect processes such as energy partitioning and metabolism[32,34]

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