Suspended microplastics in a highly polluted bay: Abundance, size, and availability for mesozooplankton
Introduction
Plastics are widely used worldwide, and its production, which started in the 1940s and continues to increase, has already reached 311 million tons a year (PlasticsEurope, 2015). High production is associated with prolonged durability and degradation, and the inadequate management of plastic waste as a whole has resulted in the large accumulation of residuals in aquatic ecosystems. Jambeck et al. (2015) found that in 2010, 192 coastal countries produced 275 million metric tons of plastic waste, of which 4.8 to 12 million metric tons ended up in the ocean.
The effects of plastics on the ingestion and entanglement of marine organisms such as turtles, birds, mammals, and fishes are well known (e.g., Laist, 1997; Eriksson and Burton, 2003; Nelms et al., 2016; Vendel et al., 2017); however, information on the impact of microplastics on marine organisms is only scarce (Wright et al., 2013). Studies that focused on microplastics appeared during the 1970s (e.g., Carpenter and Smith, 1972; Carpenter et al., 1972). However, with the growing concern on microplastic relevance to marine ecology and public health, there has been an increase in interest in the last decade (Ivar do Sul and Costa, 2014; Auta et al., 2017; Avio et al., 2017). However, so far, there is no consensus on essential concepts, such as classification of size and sampling methodology. Some recent reviews have emphasized the importance of establishing standard concepts and methods to obtain a better picture of microplastic origin, distribution, trajectory, fate, and its effects on marine ecosystems as a whole (Cole et al., 2011; Hidalgo-Ruz et al., 2012; Ivar do Sul and Costa, 2014; Lusher et al., 2014; Avio et al., 2017). One important pathway by which microplastics enter the ecosystems is through interactions with marine biota, particularly by ingestion (Eriksen et al., 2014; Clark et al., 2016; Auta et al., 2017).
Because microplastics are on the same size scale as that of planktonic organisms, they are potentially available to several plankton predators (Hidalgo-Ruz et al., 2012; Wright et al., 2013), which possibly mistake them for food (Desforges et al., 2015). Microplastic ingestion may affect predator-prey relationships and the carbon cycle (Galloway et al., 2017) and cause physical and chemical hazards to the organism (Wright et al., 2013). As plankton is the basis of marine food webs, any threat to them may have serious and far-reaching effects such as contaminant transfer and biomagnification, thereby affecting many marine organisms (Andrady, 2011). Therefore, it is relevant to address the size of microplastics accessible to organisms, as prey size is one of the main constraints that determines zooplankton feeding (Hansen et al., 1997; Barton et al., 2013).
Plastic sizes vary over a wide range, and the definition of microplastics is, as yet, dissonant (see Rodríguez-Seijo and Pereira, 2017). Studies have defined microplastics as plastic particles of size <5 mm (Arthur et al., 2009). It has been proposed that plastic particles of these sizes can be divided into two fractions: large (1 to 5 mm) and small (< 1 mm) particles (MSFD Technical Subgroup on Marine Litter, 2013; Van Cauwenberghe et al., 2015; Lusher et al., 2017; Rodríguez-Seijo and Pereira, 2017). The lowest limit is assumed to be the mesh size of the plankton net used, often ≥300 μm (MSFD Technical Subgroup on Marine Litter, 2013). Studies assessing microplastic size and abundance tend to provide either total abundance or microplastic abundance at wide size intervals (e.g., ~300–1000 μm; e.g., Zhao et al., 2015; Gajšt et al., 2016). Although this is useful for comparing marine systems, it provides no information on accessibility to zooplankton organisms. Therefore, studies describing microplastic abundance at narrow size intervals are more useful when focusing on interactions between plastics and planktonic organisms.
According to Kiørboe and Hirst (2014), the ingestion and clearance rates of pelagic marine organisms depend on the size and concentration of prey. Thus, high microplastic abundance would increase the probability of encounters with potential predators and consequential ingestion (Wright et al., 2013). A precise description of microplastic abundance is crucial for comparing ecosystems and defining interactions with marine organisms. Nevertheless, the application of various criteria for microplastic collection (e.g., sampling depth, net mesh, and opening diameter) has precluded comparison between ecosystems. Most microplastic samples are collected from the surface of water column and using nets of ≥200 μm mesh size (Collignon et al., 2014; Eriksen et al., 2014; Frias et al., 2014; Ivar do Sul et al., 2014; Kang et al., 2015). However, evidence suggests that this may not be the best or even the only method that can be applied. First, neustonic haul is based on the low density of plastic materials, because of which plastic materials tend to float and accumulate at the surface of water column (Collignon et al., 2014). In contrast, Andrady (2011) pointed out the relevance of collecting samples from midwater to avoid the underestimation of microplastics. Indeed, microplastic particles may sink in water column because: some plastics have higher density than seawater, biofouling make particles to be heavier and more likely to sink, and higher water temperatures and lower salinity conditions decrease marine water density, thereby altering the ratio of the density of plastics to that of water (Gorokhova, 2015; Galloway et al., 2017; Karlsson et al., 2017). Thus, considering that microplastics are differentially distributed in water columns (Cole et al., 2011), sampling should be performed both at the surface and column midwater, especially because the presence of organisms that may potentially ingest microplastics are not restricted only to the surface. Furthermore, large mesh sizes, although widely employed for collecting microplastics, seem inappropriate for microplastics of smaller sizes (Gorokhova, 2015). Thus, comparison among simultaneous collections at different depths using fine and coarse meshes help to elucidate the best methodology for sampling.
Studies focusing on the effects of microplastics on marine organisms are crucial. According to Jambeck et al. (2015), Brazil produces 0.07–0.19 million metric tons of marine plastic refuse per year, thus occupying the 16th place among the top 20 countries in terms of plastic waste mismanagement. Therefore, plastic pollution has become an urgent national issue. Guanabara Bay located at Rio de Janeiro, Brazil, is highly polluted with a large amount of floating plastics, part of which are microplastics that could have a detrimental impact on local zooplankton through ingestion. The aims of this study were to (i) compare sampling methodologies, before choosing the most appropriate one for determining microplastic abundance, (ii) determine microplastic type, color, polymer composition, and abundance per size, (iii) determine the size of zooplankton groups to assess their preferential prey sizes, and (iv) determine microplastic abundance within the same size range of the zooplankton preferential prey. These data help to fill the small microplastic (<1000 μm) data gaps regarding abundance per size and availability to mesozooplankton, which is a means of indicating their potential microplastic ingestion, and suggest that, besides net samplers, supplementary sampling methods should be incorporated in microplastic monitoring.
Section snippets
Study area
Guanabara Bay, southeastern Brazil, comprises an area of ~384 km2, with an average depth of 5.7 m, and a 6-km-wide connection with the coastal region, where water exchange occurs through a semi-diurnal tide cycle, amplitude ~1.4–0 m (Amador, 1997). Half of the water in the Bay is renewed in ~11 days (Kjerfve et al., 1997). The drainage of 35 rivers and channels, some extremely polluted, which comprise the Guanabara Bay basin, contributes to freshwater inflow (Coelho, 2007). In typical years, on
Environmental conditions
The water column was stratified on March 21, except in Governador Island (temperature ~26 °C and salinity ~29), and mixed on September 2 (temperature ~23 °C and salinity ~31). In March, stratification occurred during both tides in the channel (temperature ~27 and 20 °C and salinity ~28 and 35 at surface and bottom, respectively) and at Fundão Island (temperature ~28 and 22 °C and salinity ~27 and 33 at surface and bottom, respectively). Monthly rainfalls in March (283 mm) and September (78 mm)
Effects of rainfall and tide on microplastic particle abundance
Seasonal variation in particle abundance was compared; however, in both months of sample collection (March and September), rainfall influenced microplastic abundance. Even though September is usually a dry month, in 2016, it rained twice as much as that expected, especially on the day before sampling (more than half of the monthly total). In March, it rained for the whole month. Water quality in Guanabara Bay is strongly influenced by the discharge of organic matter and solid litter by rivers (
Conclusion
The results show that a high microplastic abundance is obtained when fine 64-μm nets are used and indicate the relevance of surface and water column sampling for providing more accurate estimates. Microplastic abundance in Guanabara Bay was higher than that in most other marine ecosystems, especially in the 100–1000 μm fraction. Despite this, microplastic abundance is too diluted compared to the high density of copepods, the preferential prey for these predators, for particles to be found and
Acknowledgments
We thank F. Matos for the assistance during the sampling and Dr. P. Paiva for providing valuable suggestions to this manuscript. We kindly thank M. Almeida from the Institute of Macromolecules Professor Eloisa Mano, Federal University of Rio de Janeiro (UFRJ), for the FT-IR analysis. This study was part of the Long Term Ecological Project (PELD) funded by CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico (403809/2012-6)) and FAPERJ (Fundação de Amparo à Pesquisa do Estado do
References (71)
Microplastics in the marine environment
Mar. Pollut. Bull.
(2011)- et al.
Distribution and importance of microplastics in the marine environment. A review of the sources, fate, effects, and potential solutions
Environ. Int.
(2017) - et al.
Plastics and microplastics in the oceans: from emerging pollutants to emerged threat
Mar. Environ. Res.
(2017) - et al.
Prevalence of microplastics in the marine waters of Qatar
Mar. Pollut. Bull.
(2016) - et al.
Evaluation of microplastics in Jurujuba Cove, Niterói, RJ, Brazil, an area of mussels farming
Mar. Pollut. Bull.
(2016) - et al.
Microplastics as contaminants in the marine environment: a review
Mar. Pollut. Bull.
(2011) - et al.
Annual variation in neustonic micro- and meso-plastic particles and zooplankton in the Bay of Calvi (Mediterranean-Corsica)
Mar. Pollut. Bull.
(2014) - et al.
Microplastic pollution of the beaches of Guanabara Bay, Southeast Brazil
Ocean Coast. Manag.
(2016) - et al.
Plastic particles in coastal pelagic ecosystems of the Northeast Pacific ocean
Mar. Environ. Res.
(2011) - et al.
Abundance, size and polymer composition of marine microplastics ≥ 10 μm in the Atlantic Ocean and their modelled vertical distribution
Mar. Pollut. Bull.
(2015)
Evidence of microplastics in samples of zooplankton from Portuguese coastal waters
Mar. Environ. Res.
Sea surface microplastics in Slovenian part of the Northern Adriatic
Mar. Pollut. Bull.
Screening for microplastic particles in plankton samples: how to integrate marine litter assessment into existing monitoring programs?
Mar. Pollut. Bull.
The applicability of reflectance micro-Fourier-transform infrared spectroscopy for the detection of synthetic microplastics in marine sediments
Sci. Total Environ.
The present and future of microplastic pollution in the marine environment
Environ. Pollut.
Screening for microplastics in sediment, water, marine invertebrates and fish: method development and microplastic accumulation
Mar. Pollut. Bull.
Oceanographic characteristics of an impacted coastal bay: Baía de Guanabara, Rio de Janeiro, Brazil
Cont. Shelf Res.
A comparison of neustonic plastic and zooplankton at different depths near the southern California shore
Mar. Pollut. Bull.
Microplastics en route: field measurements in the Dutch river delta and Amsterdam canals, wastewater treatment plants, North Sea sedimentsand biota
Environ. Int.
Distribution patterns of microplastics within the plankton of a tropical estuary
Environ. Res.
Microplastic pollution in the Northeast Atlantic Ocean: validated and opportunistic sampling
Mar. Pollut. Bull.
A Comparison of Plastic and Plankton in the North Pacific Central Gyre
A quantitative analysis of microplastic pollution along the south-eastern coastline of South Africa
Mar. Pollut. Bull.
Amberstripe scad Decapterus muroadsi (Carangidae) fish ingest blue microplastics resembling their copepod prey along the coast of Rapa Nui (Easter Island) in the South Pacific subtropical gyre
Sci. Total Environ.
Morphological and physical characterization of microplastics
On the quantity and composition of floating plastic debris entering and leaving the Tamar Estuary, Southwest England
Mar. Pollut. Bull.
Microplastic contamination in natural mussel beds from a Brazilian urbanized coastal region: rapid evaluation through bioassessment
Mar. Pollut. Bull.
Microplastics in sediments: a review of techniques, occurrence and effects
Mar. Environ. Res.
Widespread microplastic ingestion by fish assemblages in tropical estuaries subjected to anthropogenic pressures
Mar. Pollut. Bull.
The physical impacts of microplastics on marine organisms: a review
Environ. Pollut.
Suspended Microplastics in the Surface Water of the Yangtze Estuary System, China: First Observations on Occurrence, Distribution
Microplastic in three urban estuaries, China
Environ. Pollut.
Baía de Guanabara e Ecossistemas Periféricos: Homem e Natureza
Proceedings of the International Research Workshop on the Occurrence, Effects and Fate of Microplastic Marine Debris, NOAA
Accumulation and fragmentation of plastic debris in global environments
Philos. Trans. R. Soc. B
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