Risk assessment of excessive CO2 emission on

Science of the Total Environment 566–567 (2016) 1349–1354

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Risk assessment of excessive CO2 emission on diatom heavy metal consumption Fengjiao Liu, Shunxing Li ⁎, Fengying Zheng, Xuguang Huang a b

Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000, China College of Chemistry and Environment, Minnan Normal University, Zhangzhou, 363000, China

H I G H L I G H T S

G R A P H I C A L

A B S T R A C T

• Excessive CO2 in seawater may causes ocean acidification and desalination. • The relationships between Cu, Zn, and Cd were all positively correlated by desalination. • Significant effects of salinity on intracellular concentration of Cu and Cd • Cu and Cd in marine phytoplankton could be regulated by metal excretion. • Heavy metal consumption was affect by excessive CO2.

a r t i c l e

i n f o

Article history: Received 8 April 2016 Received in revised form 16 May 2016 Accepted 27 May 2016 Available online 2 June 2016 Editor: D. Barcelo Keywords: Climate change Acidification Desalination Heavy metal Diatom Seafood safety

a b s t r a c t Diatoms are the dominant group of phytoplankton in the modern ocean, accounting for approximately 40% of oceanic primary productivity and critical foundation of coastal food web. Rising dissolution of anthropogenic CO2 in seawater may directly/indirectly cause ocean acidification and desalination. However, little is known about dietary diatom-associated changes, especially for diatom heavy metal consumption sensitivity to these processes, which is important for seafood safety and nutrition assessment. Here we show some links between ocean acidification/desalination and heavy metal consumption by Thalassiosira weissflogii. Excitingly, under desalination stress, the relationships between Cu, Zn, and Cd were all positively correlated, especially between Cu and Zn (r = 0.989, total intracellular concentration) and between Zn and Cd (r = 0.962, single-cell intracellular concentration). Heavy metal consumption activity in decreasing order was acidification b acidification + desalination b desalination for Zn, acidification b desalination b acidification + desalination for Cu and Cd, i.e., heavy metal uptake (or release) were controlled by environmental stress. Our findings showed that heavy metal uptake (or release) was already responded to ongoing excessive CO2 emission-driven acidification and desalination, which was important for risk assessment of climate change on diatom heavy metal consumption, food web and then seafood safety in future oceans. © 2016 Elsevier B.V. All rights reserved.

1. Introduction ⁎ Corresponding author at: College of Chemistry and Environment, Minnan Normal University, Zhangzhou 363000, China. E-mail address: [email protected] (S. Li).

http://dx.doi.org/10.1016/j.scitotenv.2016.05.196 0048-9697/© 2016 Elsevier B.V. All rights reserved.

Diatoms are the dominant group of phytoplankton in the modern ocean, especially in well-mixed coastal upwelling regions (Chao et al., 2012; Ken et al., 2005), accounting for approximately 40% of

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oceanic primary productivity and critical foundation of coastal food web (Faksness et al., 2008; Rabosky and Sorhannus, 2009). In coastal waters, diatoms support in worldwide range the most productive fisheries. In the open ocean, a relatively large proportion of diatom organic matter sinks rapidly from the surface, becoming food for deep-water organisms (Armbrust, 2009; Sarthou et al., 2005). Thalassiosira weissflogii, a coastal centric diatom, could be used as a model of marine phytoplankton (Liu et al., 2013) and the main diet for edible marine organisms, such as oysters (Reinfelder and Fisher, 1994), hard clams (Reinfelder and Fisher, 1994), sea urchins (Kalam Azad et al., 2010), larval echinoid (Kalam Azad et al., 2010), scallop (Liu and Wang, 2011), and Pacific white shrimp (Kent et al., 2011). Earth's climate is warming as a result of anthropogenic emissions of greenhouse gases, particularly CO 2 . Climate change results in ocean is getting warmer, sea ice coverage reducing (or sea ice melt increasing), global sea-level rising, surface evaporation increasing, and patterns of deep-water ventilation changing, potentially altering future surface ocean carbonate conditions and acidification (Liu et al., 2016; McNeil and Matear, 2008). Along with air and ocean temperatures warming, increased sea ice melt can lead to salinity declining (Massom and Stammerjohn, 2010). Where mixing with fresh water runoff from river mouths or near melting glaciers, seawater salinity can be substantially decline. The possible biological consequences of these changes are increasingly impact marine organisms and ecosystems, such as calcification rates, acid-base regulation, blood circulation and respiration, nervous system, biodiversity changes, and trophic interactions (Fabricius et al., 2011; Fabry et al., 2008; Frommel et al., 2011; Hall-Spencer et al., 2008; Hoegh-Guldberg et al., 2007). Zinc (Zn) is essential for human health. Adequate dietary Zn is needed for successful pregnancy outcomes and child development, immune function, and neurological development, yet an estimated 17.3% of the global population may have insufficient dietary Zn intake (Wessells and Brown, 2012). Zn, which is used as a cofactor in many enzymes, is an essential element for phytoplankton (Xu et al., 2012). Copper (Cu) is an essential metal for all living organisms but can be toxic when high intake occurs (Pan and Wang, 2009). Marine diatom excretion and its complexation with Cu in seawater could be affected by fixed carbon (Fisher and Fabris, 1982). Cadmium (Cd) is an important environmental pollutant for human health due to its long half-life in the human body (15–30 years) and its damaging effects on kidney function and bone density (Emanuelli et al., 2014). Cadmium has also been associated with increased risk of lung, brain, bladder, breast, and endometrial cancer (Ken et al., 2005). Cd is known to replace Zn for some biological functions in some phytoplankton, including the model species T. weissflogii, fostering better growth under Zn-limited conditions (Xu et al., 2012). In T. weissflogii, Cd can replace Zn as a cofactor in the carbonic anhydrase (Lane and Morel, 2000; Xu et al., 2012). There is made particularly interesting because Cu, Cd, and Zn are involved in inorganic carbon acquisition in marine phytoplankton (Morel et al., 2002). They play crucial biological roles in ecosystem and their supply controls the structure and possibly productivity of marine ecosystems (Morel and Price, 2003; Morel et al., 2003). The requirements of them in organisms may be affected by the increase in ambient PCO2, while metal uptake may be affected by a change in metal speciation caused by acidification (Xu et al., 2012). However, little is known about dietary diatom-associated changes, especially for diatom heavy metal consumption sensitivity to these processes, which is important for seafood safety and nutrition assessment. At the same time, desalination can be related to the influence of dilute water, and the coexistence of acidification and desalination can also be linked to acidic deposition to estuarine. In the present work we investigated the influence of ocean acidification and desalination on trace metal bioavailability by T. weissflogii thoroughly.

2. Methods 2.1. Seawater sample and phytoplankton culture Seawater was collected from the Taiwan strait (22.65°N, 118.82°E) shown in Fig. S1, stored at 4 °C for about 6 months, and filtered through 0.22 μm acid-washed capsule filters (Pall Supor membrane, Acropak 200) before use. T. weissflogi used as model species were gotten from the State Key Laboratory for Marine Environmental Science, Xiamen University. The cultured growth cycle curve was shown in Fig. S2 (Liu et al., 2016). Exponentially growing cells of T. weissflogii cells were cultured in seawater at different concentrations of salinity (Sal) (29, 30, 31, or 32, respectively) and/or pH/pCO2 (7.8/770 ppm, predicted CO2 levels in 2100; 7.9/600 ppm, predicted CO2 levels in 2060; 8.0/470 ppm, predicted CO2 levels in 2030; and 8.1/380, current CO2 levels, respectively) (Ellycia Harrould-Kolieb, 2009). After determination of Sal and pH in the medium, their values were maintained through compensating addition daily of Na2CO3 (0.1 mol/L) and CO2 for 4 days, respectively, i.e., semi-continuous culture was adopted, as described in detail previously (Liu et al., 2016). 2.2. Test methods Cell density was counted microscopically, the results were shown in Fig. S3–S4, as described in detail previously (Liu et al., 2016). After culture 4 days, cells in 500 mL of the medium were collected onto a 3.0 μm membrane filter. Our preliminary experiments indicated that trace metals adsorbed on the cell surface could be removed using a trace metal clean reagent (Tovar-Sanchez et al., 2003; Tovar-Sanchez et al., 2004). The washed cell was added into a closed vessel with mixture solution of HNO3 and H2O2 (v:v = 2:1), microwave-digested for 7 min at 1.01 × 106 Pa, and then analyzed for the concentrations of trace metals absorbed by algal cells (Li et al., 2013). The intracellular concentration was calculated by subtracted the concentration of experimental and background concentration in cells of T. weissflogii. The concentration was greater than, equal to, or less than zero indicated that metal could be uptake, no uptake or excreted by metal binding ligands. Sterile trace metals clean techniques were applied for culturing and experimental manipulations (Andersen, 2005; Shi et al., 2010), as described in detail previously (Li et al., 2013). Accuracy and detection limits of trace metal determination were evaluated by analyzing certified reference materials, including NIES-03 (green algae, Chlorella Kessleri) and NASS-5 (standard seawater). Results of these analyses were good agreed with certified concentration in both CRMs (Table S1). So, the described method was applicable for the determination of low levels (μg g−1 or μg/L) of trace elements (Cu, Zn, and Cd) in coastal seawater and marine organisms. 2.3. Statistical analysis Analysis of variance was calculated by SASPROC MIXED (Littell et al., 1996) and p-value was calculated by two-way ANOVA. The methods of statistical analysis as described in detail previously (Liu et al., 2013). 2.4. Conditional stability constants and speciation analysis Conditional stability constants and speciation analysis for the formation of metal complexes were calculated by the software of Chemical Equilibrium Diagrams (Eq-Calcs 32). 3. Results and discussion Seawater Sal and pH were 32.5 and 8.10, respectively, which were measured three times using Salinometer Meter and Delta 320-S pH meter (Mettler-Toledo, Greifensee, Switzerland). The


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Fig. 1. Influence of salinity (Sal) and/or acidity (pH) on the single-cell intracellular Cu concentration. Concentration N 0 is considered uptake; concentration = 0 is considered no uptake; concentration b 0 is considered release. (pH 7.8, 7.9, 8.0, and 8.1 (seawater), salinity 29, 30, 31, 32, and 32.5 (seawater), respectively).

concentrations of Cu, Cd, and Zn in the seawater were 1.63, 0.205, and 0.0003 μg/L, respectively, which measured in triplicate by ICPMS. The relative standard deviations were less than 1.10% for all investigated metals. Trace heavy metals sorption by marine phytoplankton, including absorption and adsorption by algal cells, is an important factor for depletion of trace metals in seawater. The influence of Sal and/or pH on single-cell and total intracellular trace metal concentration was shown in Figs. 1–3 and Table 1, respectively. With pH decrease from 8.10 to 7.80 or Sal decrease from 32 to 29, the single-cell / total intracellular concentration of Zn was higher than 0, i.e., it could be uptake by phytoplankton. Whenever desalination or its

coexistence with acidification, the single-cell/total intracellular concentrations of Cu and Cd were lower than 0, indicated that metals in marine phytoplankton could be released by phytoplankton. Interesting was the fact that the variation trend of Cu, Zn, and Cd single-cell/ total intracellular concentration was similar when Sal decreased from 32 to 29, and that of Cu and Cd single-cell/total intracellular concentrations affected by pH decrease from 8.10 to 7.80 was also similar. Heavy metal consumption activity in decreasing order was acidification b acidification + desalination b desalination for Zn, acidification b desalination b acidification + desalination for Cu and Cd, i.e., metal uptake (or release) were controlled by environmental stress.

Fig. 2. Influence of salinity (Sal) and/or acidity (pH) on the single-cell intracellular Zn concentration. Concentration N 0 is considered uptake; concentration = 0 is considered no uptake; concentration b 0 is considered release. (pH 7.8, 7.9, 8.0, and 8.1 (seawater), salinity 29, 30, 31, 32, and 32.5 (seawater), respectively).

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Fig. 3. Influence of salinity (Sal) and/or acidity (pH) on the single-cell intracellular Cd concentration. Concentration N 0 is considered uptake; concentration = 0 is considered no uptake; concentration b 0 is considered release. (pH 7.8, 7.9, 8.0, and 8.1 (seawater), salinity 29, 30, 31, 32, and 32.5 (seawater), respectively).

There were significant inter-metals relationships in single-cell/total intracellular concentration of Cu, Zn, and Cd. (Fig. 4, Table 2). Under desalination stress, the relationships between Cu, Zn, and Cd were all positively correlated, especially between Cu and Zn (r = 0.989, total intracellular concentration) and between Zn and Cd (r = 0.962, single-cell intracellular concentration). According to p-value analysis as shown in Table 3, the single-cell/ total intracellular concentration of Cu and Cd could be significantly affected by desalination (P b 0.05), but that three metals affected by acidification were not significant (P N 0.05).

We found that the consumption of Zn and Cd could be affected by pH, with similar influence trends for previous reported (Bidwell and Gorrie, 2006; Xu et al., 2012). With pH decreases, carbonic anhydrase activity of diatoms T. weissflogii could be inhibited and it should result in a lower Zn and Cd requirement at high PCO2 (Xu et al., 2012). The decrease in pH will result in reducing the concentrations of hydroxide (OH–) in most natural surface waters. Ocean desalination also will reduce the concentration of anion, such as Cl− and OH– (Liu et al., 2016). According to the stability constants (Table S2), KcZnOH+ b KcCuOH + b KcCdOH+, KcZnCl+ b KcCuCl + b KcCdCl + , i.e., the

Table 1 Influence of salinity (Sal) and/or acidity (pH) on total intracellular trace metals (Cu, Zn, and Cd) concentration. (pH 7.8, 7.9, 8.0, and 8.1 (seawater), Salinity 29, 30, 31, 32, and 32.5 (seawater), respectively). pH Sal

BGC

Seawater

(a) Cu (μg/L) Seawater 29 30 31 32

21.0 ± 0.21 61.3 ± 0.56 61.3 ± 0.56 33.8 ± 0.31 33.8 ± 0.31

−16.1 ± 0.16 −30.4 ± 0.30 −35.0 ± 0.35 −25.6 ± 0.26 −35.2 ± 0.35

−20.0 ± 0.20 −67.6 ± 0.68 −88.8 ± 0.89 −52.4 ± 0.52 −49.2 ± 0.49

−19.1 ± 0.19 −66.8 ± 0.67 −69.2 ± 0.69 −47.2 ± 0.47 −46.6 ± 0.47

2.60 ± 0.03 −79.4 ± 0.79 −81.2 ± 0.81 −44.2 ± 0.44 −12.5 ± 0.12

−7.54 ± 0.08 −17.7 ± 0.18 −106 ± 1.06 −45.6 ± 0.46 5.82 ± 0.06

(b) Zn (μg/L) Seawater 29 30 31 32

243 ± 2.31 335 ± 3.40 335 ± 3.40 364 ± 3.57 364 ± 3.57

257 ± 2.57 263 ± 2.63 −10.2 ± 0.01 739 ± 7.39 9.60 ± 0.01

548 ± 5.48 −69.2 ± 0.69 169 ± 1.69 −215 ± 2.15 −156 ± 1.56

201 ± 2.01 40 ± 0.40 −221 ± 2.21 238 ± 2.38 −442 ± 4.42

223 ± 2.23 −87.4 ± 087. 859 ± 8.59 −120 ± 1.20 416 ± 4.16

129 ± 1.29 350 ± 3.50 −141 ± 1.41 −94.4 ± 0.94 813 ± 8.13

(c) Cd (μg/L) Seawater 29 30 31 32

7.70 ± 0.07 1.76 ± 0.02 1.76 ± 0.02 1.17 ± 0.01 1.17 ± 0.01

1.06 ± 0.01 −0.751 ± 0.01 −0.877 ± 0.01 −0.575 ± 0.01 −1.16 ± 0.01

0.252 ± 0.01 −8.12 ± 0.08 −6.24 ± 0.06 −0.924 ± 0.01 −0.736 ± 0.01

1.10 ± 0.01 −13.8 ± 0.14 −11.0 ± 0.11 −1.85 ± 0.02 −0.442 ± 0.01

1.82 ± 0.02 −12.8 ± 0.13 −13.2 ± 0.13 −1.19 ± 0.01 −0.382 ± 0.01

−0.955 ± 0.01 −10.2 ± 0.10 −13.9 ± 0.14 −2.06 ± 0.02 −1.07 ± 0.01

“BGV”: Background concentrations in cells of T. weissflogii; “-” reflects excreted by metal binding ligands; “μg/L”: microgram per litre cell volume.

7.80

7.90

8.00

8.10


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Fig. 4. Correlations between single-cell/total intracellular trace metals (Cu, Zn, and Cd) concentration under different salinity (Sal). (pH 7.8, 7.9, 8.0, and 8.1 (seawater), salinity 29, 30, 31, 32, and 32.5 (seawater), respectively).

ability of metal combined with chloride and hydroxide was Cd N Cu N Zn. When the concentrations of Cl− and OH– were decreased, the ions were released in the order of Zn2+ N Cu2+ N Cd2+. The binding of Cu, Zn, and Cd by strong ligands in surface seawater results in very low concentrations of the free metal ions, Cu2+, Zn2+, and Cd2 +, and of the total free metals, Cu′, Zn′, and Cd′, which we define as the sum of the concentrations of the metal complexes with the major Table 2 Correlations between single-cell/total intracellular trace metals (Cu, Zn, and Cd) concentration under different salinity (Sal) and acidity (pH). Single-cell Sal

Zn Cd

− 2− inorganic ligands of seawater, principally, CO2– 3 , Cl , and SO4 , in addi– tion to OH and H2O (Xu et al., 2012). According to calculation by EqCalcs 32, when pH in the range from 7.8 to 8.1 and Sal from 29 to 32, the speciation of Zn included ZnCO3, Zn(CO3)22 −, Zn(OH)+, ZnCl+, 2− Zn2+, ZnClOH, ZnCl2, and ZnHCO+ 3 , Cu was CuCO3 and Cu(CO3)2 , and

Table 3 Statistically significant analysis of variance by single-cell/total intracellular trace metals (Cu, Zn, and Cd) concentration of T. weissflogii under different salinity (Sal) or acidity (pH). p-Value Single-cell

Total pH

Sal

Sal

pH

Cu

Zn

Cu

Zn

Cu

Zn

Cu

Zn

0.875 0.889

0.962⁎

−0.675 0.417

0.0692

0.989⁎ 0.888

0.846

−0.513 0.268

0.0464

⁎ Significant difference at 0.01 b p b 0.05.

Cu Zn Cd

Total pH

–3⁎⁎

3.23 × 10 0.994 3.87 × 10–3⁎⁎

0.362 0.500 0.168

⁎ Significant difference at 0.01 b p b 0.05. ⁎⁎ Significant difference at p b 0.01.

Sal

pH –2⁎

2.46 × 10 0.999 8.52 × 10–4⁎⁎

0.254 0.539 6.65 × 10−2

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Cd was CdCl2, CdCl+, and CdCl− 3 . Significant fraction of Cu′ and Cd′ was its carbonate and chloride complexes, respectively, only Zn2+ could be existed, which was similar as the reports by Byrne and MillerO et al. (Byrne et al., 1988; MillerO, 2009). The observation was good agreed with the results that Zn could be uptaken by phytoplankton exposed to acidification and/or desalination, but Cu and Cd could be released by phytoplankton. The influence of desalination on metal speciation wasn't significant, but this effect could be enhanced by acidification, similar influence trend was reported (Calow and Forbes, 1998; El-Alfy and Schlenk, 1998; El-Alfy et al., 2001). Both pH and Sal salinity might control metal bioavailability through its influence on metal speciation. Trace metal bioavailability could be affected seriously by the acidification and desalination. 4. Conclusions Our findings disclosed that trace metal consumption was already responded and would probably continue to respond to ongoing excessive carbon dioxide-associated ocean acidification and desalination. Heavy metal consumption activity in decreasing order was acidification b acidification + desalination b desalination for Zn, acidification b desalination b acidification + desalination for Cu and Cd, i.e., heavy metal uptake (or release) were controlled by environmental stress. It was important for risk assessment of climate change on coastal diatom heavy metal consumption and seafood web safety of future oceans. Acknowledgments This work was supported by the Natural Science Foundation of China (41206096, 21475055, 40506020, and 21175115), the Program for New Century Excellent Talents in University (NCET-110904). Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.scitotenv.2016.05.196. References Andersen, R.A., 2005. Algal Culturing Techniques: Academic Press. Armbrust, E.V., 2009. The life of diatoms in the world's oceans. Nature 459, 185–192. Bidwell, J.R., Gorrie, J.R., 2006. The influence of salinity on metal uptake and effects in the midge Chironomus maddeni. Environ. Pollut. 139, 206–213. Byrne, R.H., Kump, L.R., Cantrell, K.J., 1988. The influence of temperature and pH on trace metal speciation in seawater. Mar. Chem. 25, 163–181. Calow, P., Forbes, V.E., 1998. How do physiological responses to stress translate into ecological and evolutionary processes? Comp. Biochem. Physiol. A Mol. Integr. Physiol. 120, 11–16. Chao, M., Shen, X., Lun, F., Shen, A., Yuan, Q., 2012. Toxicity of fuel oil water accommodated fractions on two marine microalgae, Skeletonema costatum and Chlorela spp. Bull. Environ. Contam. Toxicol. 88, 712–716. El-Alfy, A., Schlenk, D., 1998. Potential mechanisms of the enhancement of aldicarb toxicity to Japanese medaka, Oryzias latipes, at high salinity. Toxicol. Appl. Pharmacol. 152, 175–183. El-Alfy, A.T., Grisle, S., Schlenk, D., 2001. Characterization of salinity-enhanced toxicity of aldicarb to Japanese medaka: sexual and developmental differences. Environ. Toxicol. Chem. 20, 2093–2098. Ellycia Harrould-Kolieb, J.S., 2009. Acid test: can we save our oceans from CO2? Oceana 2, 1–32. Emanuelli, T., Milbradt, B.G., da Graça Kolinski, M., 2014. Wheat bran and cadmium in human health. Wheat and Rice in Disease Prevention and Health: Benefits, Risks and Mechanisms of Whole Grains in Health Promotion, p. 241.

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