Trace MetalsAnalysis Along the Fildes Peninsula Coastline Using Two Red Algae, Rhodymenia antarctica and Iridaea cordata, as Monitors

LIU Yang, DU Guoying, and MAO Yunxiang



Trace MetalsAnalysis Along the Fildes Peninsula Coastline Using Two Red Algae,and, as Monitors

LIU Yang1), 3), DU Guoying1), 3), and MAO Yunxiang1), 2), 3), *

1),,266003,2),,266237,3),,266003,

Two red algae,and(Rhodophyta), were employed to investigate the pollution situation along Fildes Peninsula coastline, King George Island. Ten sites from east and west coastlines were investigated, and the concentrations of Cu,Pb, Zn,Cd,Cr, As and Hg were determined. The metal pollution index (MPI) was used to evaluate the overall pollution level represented by the investigated sites and for interregional comparisons. The two algae exhibited different preference to special trace metal.could accumulate more Cd (0.63mgkg−1) and Hg (0.026mgkg−1) than(Cd 0.34mgkg−1, Hg 0.019mgkg−1).could accumulate more As (15.53mgkg−1) than(10.11mgkg−1). There was no significant difference in accumulating Cu, Pb, Zn and Cr between the two algaecould be used to monitor Cd and Hg.would be more appropriate for monitoring As. MPI monitored by the two algae were from 1.02 to 2.26 (), and 1.03 to 1.25 (), respectively. Pollution situation of Fildes Peninsula was becoming serious, especially of the east coastline. The objective of this research was to gather the baseline information for trace metals investigation in Antarctic.

Fildes Peninsula;;; trace metal; MPI

1 Introduction

In the study of trace metal pollution, many living aquatic organisms have been extensively used as natural monitors for their ability of absorbing the trace metals. Macroalgae, responding basically to metals present in water, are often used as biomonitors, which are considered as the uptake of trace metals by an organism directly from the abiotic environment with several orders of magnitude above the environmental levels (Majer., 2014; Chakraborty., 2014). Algae are considered as the optimum ones because of their wide distribution, the integration of the global variations of environment, as well as faster response to the environment and easier detected than organisms at higher trophic levels (Chakraborty., 2014).,,,among others have been proved to be used as potential biomonitors for trace metal pollution detection (Chakraborty., 2014). Pollution index MPI (Metal Pollution Index), evaluating the global pollution level, was highly effective for the comparison between different species and between different sites (El- Din., 2014).

Antarctica used to be perceived as a symbol of the last great wilderness untouched by human disturbance, but cannot escape the local and global anthropogenic pollution (Moreno., 1997; Jerez., 2013; Majer., 2014). The Fildes Peninsula locates on the southwest part of the King George Island, South Shetland Islands, and experiences a sub-Antarctic cold, moist, maritime climate with a mean annual air temperature of −2.2℃ and a mean summer air temperature above 0℃ for up to four months (Liu., 1992). The region is the largest ice-free and accessible area on the island and attracts more and more scientists and tourists. Five permanent research stations and one airportexist in this region (Hughes., 2013).The east of Fildes Peninsula faces the Maxwell Bay, an important shipping channel for research stations and tourists. And a continuous contamination does exist due to human intensive and extensive activities, such as shipping, boating, travelling, scientific researching among others (Moreno., 1997).The trace metals (.., Cu,Pb, Zn, Cd, Cr,As and Hg) may be continuouslyreleased to the marine coastline environment. Thus it is imperativeto monitor the situation of trace metal pollution in Fildes Peninsula.Some works have been conducted to analyze the pollution of trace metals in Antarctic continent using macroalgae as monitors.Farías. (2002) analyzed the trace metals of 11 macroalgae in Potter Cove, King Geor- ge Island and foundcould be used as an adequate monitor for further study.Runcieand Riddle (2004)employed 8 algae to evaluate the contamination of Brown Bay and compared with that far from the source of contamination. Moreno. (1997) finished a comprehensive survey to evaluate the levels of essential and non-essential trace metals in Antarctic organisms, and7species of algae (,sp.,sp.,sp.,sp.,and.) from King George Island were employed as monitors.However, no research has been conducted to analyze the pollution ofcoastline alongFildes Peninsula using macroalgae as monitors, especially using..

The aim of present work was to use two common red algae,and, living in intertidal zone of coastline along Fildes Peninsula,as potential biomonitorsto assess the pollution situation. MPI was used to compare the pollution level in this area with other areas in Antarctic, as well as to evaluatethe extent of trace metals contamination in the selectedstudying sites which would serve as a baseline for futurestudies.

2 Materials and Methods

2.1 Studying Area and Sample Collection

Fivesites from east coastline of Fildes Peninsulaincluding Norma Cove,ArdleyIsland, Great Wall Cove,Wanglong Rock andJiuquan River were selected and named as E1, E2, E3, E4 and E5 and five sites from west coastline including Xingfu Cove, Fengbao Cove, Biologist Cove, Horatio Cove and Geography Cove were named as W1, W2, W3, W4 and W5were chosen to collect the algae.

Two red algae,and,were em- ployed as biomonitors of trace metal pollution of Fildes Peninsula. Samples were collected in intertidal zonesdur- ing the 2013 austral summer season. The detail of sample collection was shown in Fig.1.

Fig.1 Sampling sites along Fildes Peninsula, King George Island, South Shetland Islands. E1, Norma Cove (62˚11.328´S, 58˚55.005´W); E2, Ardley Island (62˚12.550´S, 58˚56.586´W); E3, Great Wall Cove (62˚13.037´S, 58˚57.513´W); E4, Wanglong Rock (62˚13.217´S, 58˚57.129´W); E5, Jiuquan River (62˚13.476´S, 58˚57.146´W); W1, Xingfu Cove (62˚10.430´S, 58˚58.217´W); W2, Fengbao Cove (62˚11.166´S, 58˚59.634´W); W3, Biologist Cove (62˚12.117´S, 58˚59.908´W); W4, Horatio Cove (62˚12.481´S, 59˚00.432´W); W5, Geography Cove (62˚13.216´S, 59˚00.691´W).

The whole body of algae was picked up and transported to the laboratory in seawater. Epiphyta and sediments were then removed from the algae using nylon brushes under tap water. Then the algal materials were rinsed several times using ultrapure water very quickly (to minimize possible metal loss), inserted into polyethylene bags, and stored at −20℃ until use.

2.2 Sample Digestion and Analysis

To analyze the concentration of trace metals, samples were freezing-dried, ground to fine power in agate mortar.Microwave digestion machine was employed to digest the samples. There replicate solutions of each sample were prepared by MW-assist acid digestion.A 0.5g portion of each sample was weighed directly into a digestion teflon tube, then 5mL nitric acid (ultrapure grade) and 2mL liquor hydrogen peroxide (ultrapure grade) were added. Mixture was left overnight until it was subjected to a microwave digestion. Digestion blanks were also carried out to the same procedure. The details of the MW procedure were in Table 1.

The digestion was carried out till the solution became completely clear and homogeneous. Then the whole solution was transferred to a teflon crucible and slowly eva- porated to near dryness. The residue was allowed to cool down and diluted to a final volume of 50mL with ultra- pure water.The trace metal concentrations of algae were determined by Atomic Absorption Spectrometry (AAS) and Atomic Fluorescence Spectrometer (AFS). Flame AAS was used for Zn, graphite furnace AAS was used for Cu,Pb, Cd and Cr. The concentrations of As and Hg were confirmed byAFS.

Table 1 Procedure of digesting algal samples with MW (Faríaset al., 2002)

To assess the accuracy and precision of previous me- thod, the certified reference material (CRM)GBW10023(National Center for StandardMaterials, China) was performed in parallel with the corresponding analyzing pro- cess.All the wares used in this experiment had to be soaked in 10% nitric acid (ultrapure grade) for more than 24h.

To compare the total content of metals at different sitesalongFildes Peninsula, the Metal Pollution Index (MPI) (Usero., 1997) was employed and the equation was:

whereCfwas the concentration of trace metal andwas the metal number. Comparison of the concentrations of trace metals orbetween the algae or the sampling sites was performed by one-way analysis of variance (ANOVA).

3 Results

3.1 Trace metals in R. antarcticaand I. cordata

Mean concentrations of 7 trace metals and MPI ofare listed in Table 2.To the alga, collected from 10 sites, samples from E5 showed the maxi- mum values forPb (3.75mgkg−1), Zn (36.98mgkg−1), Cd (0.90mgkg−1) and Hg (0.058mgkg−1). The highest concentrations ofCu,As and Cr were found at W1 (2.43mgkg−1), W2 (12.65mgkg−1) and E4 (4.81mgkg−1), respectively.While the minimum values for Pb(0.16mgkg−1) and Zn (15.42mgkg−1) were found at W2. The minimum values for Cu (1.05mgkg−1),Cd (0.41mgkg−1),As (6.42mgkg−1),Cr (1.34mgkg−1)and Hg (0.022mgkg−1) were found at E4, W5, E1, W3 and W2, respectively. The descending order of MPI monitored usingwas E5>E2>E1>E3>E4>W4>W1>W3>W5>W2.

Due to the influence of tide,was collected at 5sites including E3, E4, W1, W3 and W4. The samples from W3 showed the maximum values for Cu(2.64mgkg−1),Zn(25.86mgkg−1) and Cr(3.04mgkg−1) (Table 3). The minimum values for thesethree trace metalswere found at E3 (Cu 1.02mgkg−1, Zn 20.17mgkg−1) and W4 (Cr 1.64mgkg−1). The maximum values for Cd(0.55mgkg−1) and Hg(0.023mgkg−1) were found at W1, while the minimum values were found at E3 (Cd 0.16mgkg−1, Hg 0.014mgkg−1). E4 and E3 showed the minimum and maximum values for Pb (0.12 and 3.25mgkg−1, respectively).To the trace metal As, the highest concentration(19.50mgkg−1) was found at W4 and the lowest(12.14mgkg−1) one was found at W1. The descending order of MPI monitored usingwas E3>W1>E4>W4>W3.

Table2 Mean concentrations(mgkg−1 dry weight) of trace metals in R.antarctica and MPI monitored using R. antarcticaalong the FildesPeninsula coastline, King George Island

Note: Data are given as mean±standard deviation (three size groups analyzed).

Table 3 Mean concentrations (mgkg−1 dry weight)of trace metals in I.cordata and MPI monitored using I.cordataalong the FildesPeninsula coastline,King George Island

Note: Data are given as mean±standard deviation (three size groups analyzed).

3.2 Comparison of Trace Metals Uptake Ability Between Two Algae

A comparison of the concentrations of trace metals between two algal species collected at E3, E4, W1, W3 and W4 revealed that the two algae exhibited different preference to special trace metal(Fig.2).accumulated more Cd (0.63. 0.34mgkg−1,=0.026) and Hg (0.026. 0.019mgkg−1,=0.001) than. However,showed preference to As (15.53. 10.11mgkg−1,=0.006) than.To the trace metals Cu,Pb, Zn and Cr, there was no significant difference between two algae, thusaccumulated more Cd and Hg and less As than.

Fig.2 Comparison of trace metalsconcentrations in two algae collected at sites including E3, E4, W1, W3 and W4.

4 Discussion

Macroalgae could accumulate dissolved trace metals, reflecting the trace metal levels in seawater and sediment,thus they were considered as optimal tools to monitor the levels of trace metal contamination and environmental quality ofinvestigated areas (Sawidis., 2001).As stated earlier, no much work had been done to investigate the pollution of trace metals in Antarctic using algae as monitors. The data set was compared with the values of other sites around Antarctica, especially those using red algae as monitors. Comparingandcollected from Artigas Base, King George Island (Moreno., 1997), the same site named as E1 (Norma Cove) in this research, the concentrations of Cu, Zn and Cd were higher in this study (Table 4). Comparing with the algacollected from Potter Cove(Farías., 2002) that was at the east of the E3 (Great Wall Cove) and was 15 kilometers away, the concentrations of Cu and Zn were higher,Pb, Cd, Cr and Aswere lower in this research.Research had been carried out to investigate the concentrations of Hg and Zn in Admiralty Bay, King George Island,using(Rhodophyta) as monitor. It was found the concentrations of Hg and Zn were 0.020mgkg−1and 37.8mgkg−1, respectively (Santos., 2005), and the concentration of Zn was higher than the result in this research.Riva. (2003)hadinvestigated the contamination of Ross Sea, Antarctica, and found the concentrations of Hg inand(Rhodophyta) were 0.03mgkg−1and <0.009mgkg−1, respectively; Cd were 5.95mgkg−1and 4.01mgkg−1, respectively, and the concentrations of Cd in both algae were higher than the results detected in this research.

The previous comparison results indicated that the concentrations of each trace metal varied a great deal from specie to specie and from one site to another, being not able tosuggest a clear pattern of pollution. Thus MPI was employed to evaluate the pollution level of the Fildes Peninsula.Usingas monitor, MPI was calculatedwith the data (calculated with mean concentrations of Cu, Zn and Cd) from Artigas Base(Moreno., 1997)was0.67, lower than MPI (range from 1.46 to 3.03) calculated with the same three trace metals in this research. MPI (calculated with mean concentrations of Cu,Pb, Zn, Cd, Cr and As) monitored byranged from 1.93 to 4.17 in Fildes Peninsula, which was higher than the MPI (<1.13, using the same five trace metals) from Potter Cove.Thus the pollution of Fildes Peninsula was becoming more serious than that of the Potter Cove (data from 2002).MPI was also used to evaluate the pol- lution distinction between east and west coastlines along Fildes Peninsula. MPI ofin east coastline was significantly higher (<0.05) than that of the west coastline, and the highest one was found at E5 (Jiuquan River). However, MPI monitored byshowed no significant difference (>0.05) between the two coastlines, while MPI of E3 (Great Wall Cove) was the highest. The progress of sampling algae found that the pollution of the east coastline should be more serious than the west. Amaro. (2015) found that the east coastline of Fildes Peninsula was subjected to a large environmental pressure. There were several reasons attributing to this fact. First, more than five research stations were located on the east coast of Fildes Peninsula, including Great Wall Station, Artigas Station, Bellingshausen Station, Marsh Station and Feri Station. Much household refuse were discharged into the sea, and building materials were piled up on the east coast. Thus the anthropogenic impact to the east coast was heavier than to the west. Additionally, the east coast was one part of Maxwell Bay. As the bay was an important waterway to the research stations, much shipping garbage were discharged into the bay. This result could also attribute to the geographic factor. The west coast faced the Drake Passage and trace metal can be easily transported by ocean current.

Table 4 A comparison of the mean concentrations (mgkg−1 dry weight) of trace metals determined in this research with the findings of other studies

Not all the algae could be used as monitors. Various in- trinsic factors (assimilation efficiency, efflux rate or growth rate) and extrinsic factors (turbidity, nutrient availability, light intensity, salt content or temperature) could influ- ence metal uptake ability (Majer., 2014). The ability of accumulating trace metals varied a great deal from species to species. Comparing the trace metals uptake ability ofand, there was significant difference (<0.05) except Cu, Pb, Zn and Cr. The two potential monitors exhibited different accumulation ability to the trace metals. Thus only special algae could be used to monitor target trace metal.could be used to monitor Cd and Hg, whilewould be more preferable to monitor As.

In this study, the pollution status of the coastline along Fildes Peninsula was assessed using two red algae,andThe global pollution situation of investigated locations was determined for the first time. The results showed that the pollution situation of Fildes Peninsula was becoming serious. However, due tothe small number of species studied, the results must be viewedwith caution, and more algal species must be analyzed to confirm the pollution situation of this area. Furthermore, more studies are necessary to investigate the trace metal concentration in the seawater or sediment where the algae live, and find the relationship between algae and the surrounding environment.Nevertheless, it must be strongly highlighted that the Antarctic pollution situation is becoming serious and strict environmental protocols should be implemented to prevent it.

Acknowledgements

This work is financially supported by the Chinese Polar Environment Comprehensive Investigation and Assess- ment Program (Nos. CHINRE2015-02-01, CHINARE-04- 01). The authors also thank the team members of 30th CHINAREsfor helpingcollect the samples.

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E-mail: yxmao@ouc.edu.cn

(Edited by Qiu Yantao)