Distribution coefficients of trace metals between modern coral-lattices and seawater in the northern South China Sea: Species and SST dependencies

https://doi.org/10.1016/j.jseaes.2019.104082Get rights and content

Highlights

  • Distribution coefficients were species dependent, indicating some biologic controls.

  • No significant correlation between D values of metals except Cd and SST was found.

  • Metal in coral skeleton is a reliable proxy for dissolved metal in surface seawater.

Abstract

Scleractinian corals provide an excellent archive of geochemical proxies that allow the reconstruction of the oceanographic and climatic changes in the oceans. However, limited knowledge regarding the distribution coefficients (D) of trace metals between coral lattices and seawater has complicated efforts to obtain accurate quantitative data for seawater chemistry. Here we estimated the D values of five trace metals (Cu, Zn, Pb, Cd and Cr) for three coral species (Favia palauensis, Porites lutea, and Pavona decussata) and in situ seawater around Weizhou Island in the northern South China Sea. Despite several variations that could not be explained solely by species, our results were within the approved ranges of the previous reported estimates, and provide the most accurate D values for the these species to date. We also focused on the possible effects of surface seawater temperature (SST) on D vaules, finding no significant relationship. Nevertheless, the effects of SST, which could impact the distribution behavior of trace metals (especially Cd) should be paid more attention in the context of global climate change. The more precise D values for corals provided here represent important basic data for future research on coral reefs and expanded our knowledge of chemical signatures in biogenic lattices with regard to ocean composition.

Introduction

Corals growing in tropical reef ecosystems have been proven to contain important paleoclimate archives; a wide variety of geochemical tracers within coral skeletons have been extensively utilized as proxies for climatic and oceanographic conditions over multi-century time scales (Gagan et al., 2000, Yu, 2012). Trace metal-to-calcium (Metal/Ca) ratios in the skeletons of scleractinian corals have received significant attention for this purpose (DeCarlo et al., 2015) due to their sensitivity to environmental changes, ease of testing, high measurement precision, and quantization ability (Saha et al., 2016). Although disagreements exist regarding the extent to which skeletal metal concentrations quantitatively reflect the bioavailable metals in surface seawater (Saha et al., 2016), Metal/Ca ratios in coral skeletons have been invaluable tools for investigating past changes. For example, heavy metals in Porites lutea coral skeletons have been widely applied to reestablish historical records for human activities and climate change in locations throughout the world, including the South China Sea (SCS) (Chen et al., 2010, Chen et al., 2015, Chen et al., 2016, Jiang et al., 2017a, Jiang et al., 2017b, Nguyen et al., 2013, Song et al., 2014, Sun et al., 2016), the Great Barrier Reef (Mcculloch et al., 2003, Saha et al., 2018a, Saha et al., 2018b), the South Pacific Ocean (Fallon et al., 2002), and the Western Indian Ocean (Fleitmann et al., 2007).

To obtain accurate quantitative data for seawater chemistry from secular trends in measurements, knowledge of the distribution coefficients (D) between coral lattices and seawater is necessary (Morse and Bender, 1990, Sholkovitz and Shen, 1995). Trace element incorporation into coral skeletons can be described in terms of the Henderson-Kracek D value (Akagi et al., 2004, Sholkovitz and Shen, 1995, Wyndham et al., 2004):D =(Metal/Ca)coral/(Metal/Ca)seawater

where the Ca concentration in seawater is assumed to be constant at ~10.3 mmol⋅kg−1 (Kelly et al., 2009, Quinby-Hunt and Turehian, 1983), while the other parameters can be defined through sampling. At present, the D values of trace metals for various coral species have been estimated according to the coral and local seawater samples in some coral reefs. For example, the D value of Cu was reported as ~0.3 for the Pavona clavus from the equatorial eastern Pacific Ocean (Linn et al. 1990), and 0.3–7.2 for various corals, mainly from the Atlantic Ocean (Livingston and Thompson, 1971). The D value of Zn was estimated as ~1 for Diploria strigosa from the northern Atlantic Ocean by Shen (1986) and 0.3–15.9 for various corals, mainly from the Atlantic Ocean (Livingston and Thompson, 1971). The D value of Pb for Diploria strigosa corals from the western North Atlantic Ocean was estimated as ~2.1 and ~2.3 by Shen and Boyle (1987). The D value of Cd for Pavona clavus was reported as 0.7–1.3 in the southern Pacific Ocean (Shen and Sanford, 1990), ~1 in the northern Atlantic Ocean (Shen et al., 1987, Shen and Boyle, 1988), and ~0.76 in the Gulf of Panama (Grottoli et al., 2013). Although the D value of Cr has not been reported based on local coral and seawater samples, Saha et al. (2016) roughly estimated tthis as ~0.3, using the data from Montastrea faveolata (now known as Orbicella faveolata) in the Caribbean Sea as reported by Prouty et al. (2008) and the Cr concentrations of global average seawater.

Theoretically, the D value for the same coral species should be consistent in different locations, assuming that cations are incorporated into coral lattices via inorganic substitutions for calcium (Morse and Bender, 1990). However, other non-species-dependent factors can affect the incorporation of trace metals into coral lattices, including surface seawater temperature (SST) and pH (Akagi et al., 2004, Kelly et al., 2009, Wyndham et al., 2004). Therefore, in reality the D value varies slightly for any given coral species, as shown by the research cited above.

Although research on coral geochemical proxies has been relatively common in the SCS, the D values for many metals in coral have yet to be estimated. In addition, most reported D values for corals in this area were not estimated based on in situ coral and seawater samples (Saha et al., 2016), severely hindering the determination of accurate D values. Thus, we collected and analyzed three coral species (Favia palauensis, Porites lutea, and Pavona decussata) and corresponding in situ surface seawater samples at six locations around Weizhou Island in order to define the D values of five trace metals (Cu, Zn, Pb, Cd and Cr) for these species in the SCS; those for Zn and Cr were estimated based on in situ sampling for the first time. We also assessed the dependencies of trace metal partitioning in this context. Our results provide useful data for coral geochemistry research in the SCS and globally, expanding our understanding of the relationship between chemical signatures in biogenic lattices and ocean composition, extending ultimately to climatic and oceanographic processes.

Section snippets

Material and methods

The SCS is the largest marginal sea bordering China and stretches from the tropics to the subtropics. Weizhou Island (21°03′N, 109°07′E) is located ~48 km from the mainland in the northern SCS (Fig. 1) and is the largest and youngest volcanic island along the Chinese coast with an area of 26 km2 and a maximum elevation of 79 m. Data from the Weizhoudao meteorological station show that Weizhou Island has a tropical oceanic monsoon climate with suitable average annual precipitation (~1380.2 mm),

Trace metal characteristics in coral and seawater

The average concentrations of trace metals (Cu, Zn, Pb, Cd and Cr) in three species coral (Favia palauensis, Porites lutea, and Pavona decussata) samples from Weizhou Island, along with the Porites lutea coral data on certain trace metals in the northern SCS obtained from the related reports, were presented in Table 1. Though previous research has produced a variety of data on coral trace metals, coverage of coral species remains limited. Most reports have focused on the Porites lutea due to

Conclusion

We determined the D values of five trace metals (Cu, Zn, Pb, Cd, and Cr) with regard to three coral species (Favia palauensis, Porites lutea, and Pavona decussata) and in situ surface seawater in the northern SCS. The estimated values were clearly species dependent, indicating some biologic controls. Although several variations in D value could not be explained solely by species, our results were still consistent and dependable after eliminating extremely abnormal values. Our results fell

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 41603091, 41976059 and 91428203) and the Guangxi Scientific Projects (Grant Nos. AD17129063, AA17204074). Yu thanks the BaGui Scholars Program Foundation (Grant No. 2014BGXZGX03). Special thanks are due to the responsible editor and two anonymous reviewers for their critical reviews and constructive comments, which helped us improve significantly our manuscript.

References (49)

  • P. Matthiessen et al.

    Sources and Potential Effects of Copper and Zinc Concentrations in the Estuarine Waters of Essex and Suffolk, United Kingdom

    Mar. Pollut. Bull.

    (1999)
  • J.W. Morse et al.

    Partition coefficients in calcite: Examination of factors influencing the validity of experimental results and their application to natural systems

    Chem. Geol.

    (1990)
  • L.D. Nothdurft et al.

    Rare earth element geochemistry of Late Devonian reefal carbonates, Canning Basin, Western Australia: confirmation of a seawater REE proxy in ancient limestones

    Geochim. Cosmochim. Acta

    (2004)
  • M.K. Reuer et al.

    A mid-twentieth century reduction in tropical upwelling inferred from coralline trace element proxies

    Earth Planet. Sci. Lett.

    (2003)
  • N. Saha et al.

    Seasonal to decadal scale influence of environmental drivers on Ba/Ca and Y/Ca in coral aragonite from the southern Great Barrier Reef

    Sci. Total Environ.

    (2018)
  • N. Saha et al.

    Influence of marine biochemical cycles on seasonal variation of Ba/Ca in the near-shore coral Cyphastrea, Rat Island, southern Great Barrier Reef

    Chem. Geol.

    (2018)
  • N. Saha et al.

    Coral skeletal geochemistry as a monitor of inshore water quality

    Sci. Total Environ.

    (2016)
  • G. Shen et al.

    Trace element indicators of climate variability in reef-building corals

    Elsevier oceanography series

    (1990)
  • G.T. Shen et al.

    Lead in corals: reconstruction of historical industrial fluxes to the surface ocean

    Earth Planet. Sci. Lett.

    (1987)
  • G.T. Shen et al.

    Determination of lead, cadmium and other trace metals in annually-banded corals

    Chem. Geol.

    (1988)
  • G.T. Shen et al.

    Environmental controls on uranium in reef corals

    Geochim. Cosmochim. Acta

    (1995)
  • E. Sholkovitz et al.

    The incorporation of rare earth elements in modern coral

    Geochim. Cosmochim. Acta

    (1995)
  • D.J. Sinclair

    RBME coral temperature reconstruction: An evaluation, modifications, and recommendations

    Geochim. Cosmochim. Acta

    (2015)
  • Y. Song et al.

    Past 140-year environmental record in the northern South China Sea: evidence from coral skeletal trace metal variations

    Environ. Pollut.

    (2014)
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