Occurrence of microplastics and heavy metals accumulation in native oysters Crassostrea Gasar in the Paranaguá estuarine system, Brazil
Introduction
Estuaries are important ecosystems that provide food and habitat for a large number of aquatic organisms, in addition to promoting biogeochemical processes for other environments through their connection between watersheds and coastal waters (Barletta et al., 2010; Costa and Barletta, 2016). However, there is an increasing anthropogenic interference in these environments, often caused by activities such as agriculture, industrial development and multiple uses of water, leading to inadequate waste disposal, sewage discharges and flow control (Barletta et al., 2019). Estuarine environments are thus considered important pools of heavy metals and other contaminants (Ip et al., 2004) and have attracted much attention from researchers (Hu et al., 2013; Venkatramanan et al., 2015; Wang et al., 2015; Wang et al., 2014; Xu et al., 2014; Yang et al., 2015; Zhang et al., 2015a; Zhang et al., 2015b).
Heavy metals are widespread contaminants in aquatic ecosystems, presenting particular features like high toxicity, multiple origins, refractory properties, and accumulative behavior that make them an environmental concern (Zhao et al., 2017). Heavy metal pollution can give rise to bioconcentration and bioaccumulation of toxic metals in aquatic species, resulting in long-term negative impacts for human and ecosystem health (Ip et al., 2007).
In the same way, microplastics (MPs) can cause significant environmental impacts, being ingested by marine organisms, especially filter feeders (Sleight et al., 2017; Egbeocha et al., 2018). MPs are plastic fragments smaller than 5 mm; they can be primary, manufactured for addition to certain products, or secondary, formed by physical, chemical and/or biological degradation from larger plastic residues in natural environmental processes (Wang et al., 2018).It is estimated that there are >250,000 tons of plastic in the global oceans (Eriksen et al., 2014). MPs can negatively impact animals through physical mechanisms (Browne et al., 2008), or by their physico-chemical properties (material, size, shape etc.) that can favor its toxicity, varying between several possible situations and interactions (Lithner et al., 2011), as well as via any externally adsorbed materials (Teuten et al., 2009).
Marine species can incorporate pollutants from bottom sediments, suspended particulate material, from the water column or food sources (Laffon et al., 2006). Thus biomonitoring can be an effective approach for evaluating the contamination. Bivalves are good sentinel organisms frequently used to evaluate marine environmental quality (Solé et al., 1994; Porte et al., 2000; Serafim and Bebianno, 2001). In addition, they stand out for their wide distribution in Brazil (native species) and in the world, vital ecological niches, susceptibility to pollutant absorption and close connection with marine predators and human health, as described by Li et al., 2019.
At the same time, exposure of aquatic organisms, such as bivalves to toxic contaminants could be a risk to human health if the contaminants are incorporated in the food chain (Lemiere et al., 2005). The aim of the study was to quantify heavy metals and microplastic particles in oysters (Crassostrea gasar) from sites distributed along the Paranaguá Estuarine System (PES) and its possible adsorption ratio.
The Paranagua Estuarine System (PES) is located on the north coast of the state of Paraná (SE Brazil) and consists of several regions and environments: to the west, the Bays of Paranaguá and Antonina, and to the north, the bays of Laranjeiras, Guaraqueçaba and Pinheiros and the inlets of Itaqui and Benito. The estuarine shore is occupied by extensive mangroves and hydrographical basins. In addition to the marine influence, the estuary receives considerable freshwater input from several rivers, primarily in the rainy season (summer). Two important harbors are installed in this area, Antonina and Paranaguá; the latter is one of the largest harbor for grain exportation in Latin America, reaching more than 8 million tons of shiploads in 2009 (Martins et al., 2010), posing risks to this bay. In addition, an artisanal fishery and aquaculture are two main economic and social activities in this region. However, the increase in urbanization and industrial activities in coastal regions have increased the level of pollutants in aquatic ecosystems (Pereira et al., 2006). This can lead to environmental contamination and cause health problems to humans and local fauna. Among some of the main pollutants in marine and estuarine environments, heavy metals play a prominent role and, more recently, microplastics have been shown to be important contaminants in aquatic environments (Barletta et al., 2019).
Section snippets
Methodology
Oysters were collected from 10 sampling stations along the PES (Fig. 1). These sites are representative of the estuary, being close to oyster producing communities, natural banks used for extraction and containing large human populations, with potential for high environmental pollution.
Ten oysters (n = 10) were collected at each location, which were called K1 to K10, totaling 100 organisms. In the laboratory, after collection, all oysters from each site were dissected and 30 mg of
Results and discussion
Some metals are considered essential elements since they participate in important physiological processes (Hogstrand and Haux, 2001). Others, however, are strong toxins causing dysfunctions in a variety of living organisms (Damek-Poprawa and Sawicka-Kapusta, 2003). Unfortunately, only Cr, Ni, Cu, Zn, As, Cd, Hg and Pb have maximum levels in tissues for human consumption established by Brazilian legislation (MS Ordinance n° 685/98 and Decree n° 55.871/1965). Metal levels determined in the
Conclusions
Oysters were confirmed as effective bioindicators of environmental quality. The results identified a potential risk to human health from oysters produced for consumption from PES, taking into consideration the high levels of heavy metals such as As and Zn. Likewise, MPs were found at all sampled locations, confirming the spread of this pollutant in the marine environment; its ability to bioaccumulate in oysters was also shown. However, it was not possible to establish a direct relationship
Funding
This research was funded by SNP (Secretaria Nacional de Portos).
Availability of data and material
Data will made available under request.
Code availability
Not applicable.
CRediT authorship contribution statement
Khauê Silva Vieira – Sampling, formal analysis, interpretation and discussion of data, preparation, creation and/or presentation of the published work, specifically up to the final version of the manuscript.
José Antônio Baptista Neto – Interpretation and discussion of data, writing the initial draft.
Miriam Araujo Carlos Crapez – Interpretation and discussion of data, writing the initial draft.
Christine Gaylarde – Interpretation and discussion of data, writing and review of the manuscript.
Bruno
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 research was funded by SNP (Secretaria Nacional de Portos). The authors are grateful to the Geology and Geophysics Department/LAGEMAR at UFF (Universidade Federal Fluminense), staff of the Central Laboratory of Electron Microscopy (LCME), Multiuser Laboratory of Biology Studies (LAMEB) and Laboratory of Biomarkers of Aquatic Contamination and Immunochemistry (LABCAI) at the Federal University of Santa Catarina (UFSC), Florianópolis, SC, Brazil for infrastructure and assistance with
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