Human Consumption of Microplastics Cox, Kieran D; Covernton, Garth A; Davies, Hailey L ...
Environmental science & technology,
06/2019, Volume:
53, Issue:
12
Journal Article
Peer reviewed
Microplastics are ubiquitous across ecosystems, yet the exposure risk to humans is unresolved. Focusing on the American diet, we evaluated the number of microplastic particles in commonly consumed ...foods in relation to their recommended daily intake. The potential for microplastic inhalation and how the source of drinking water may affect microplastic consumption were also explored. Our analysis used 402 data points from 26 studies, which represents over 3600 processed samples. Evaluating approximately 15% of Americans’ caloric intake, we estimate that annual microplastics consumption ranges from 39000 to 52000 particles depending on age and sex. These estimates increase to 74000 and 121000 when inhalation is considered. Additionally, individuals who meet their recommended water intake through only bottled sources may be ingesting an additional 90000 microplastics annually, compared to 4000 microplastics for those who consume only tap water. These estimates are subject to large amounts of variation; however, given methodological and data limitations, these values are likely underestimates.
Microplastic particles (MPs) are widely distributed in seawater. Fibrous MPs (microfibres) are often reported as the most commonly encountered shape of particle. To estimate MP concentrations in ...seawater, samples are often collected using towed nets (generally 300–350-μm mesh) and may underestimate the amount of microfibres present, which may pass through the mesh due to their narrow width. We compared the potential microplastic particle (PMP) concentration estimates provided by two different seawater sampling methods conducted at three commercial shellfish farms and three unfarmed sites in Baynes Sound, British Columbia, Canada. The methods were: 10-L bucket samples sieved through 63-μm mesh in situ and subsequently filtered through an 8-μm polycarbonate membrane; and 1-L bulk samples collected in jars and subsequently filtered to 8 μm. The jar samples yielded PMP concentrations averaging approximately 8.5 times higher than the bucket samples per L of water (at the site level), largely driven by differences in the number of microfibres. There was no significant difference in PNP concentration between shellfish farms and unfarmed sites. An analysis of MP concentrations and mesh sizes reported in the literature suggests that using a 300–350-μm mesh may underestimate total MP concentrations by one to four orders of magnitude compared with samples that are filtered through much smaller mesh sizes (e.g. <100 μm), despite the effect of sample volume. Particles <300 μm in diameter make up a large component of MPs commonly found in fish and invertebrates. As such, common sampling practices fail to adequately measure a biologically relevant class of MPs, thereby undermining the ability to quantify ecological risk. We suggest that seawater sampling methods be designed to filter to <10 μm (the approximate width of many microfibres), either using pressurized pumps for large-volume samples, or by using sufficient replication of small-volume discrete samples.
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•Seawater sampling may be underestimating microplastic and microfibre concentrations.•Field-based sampling with 8- and 65-μm filtration were compared.•Methods and particle concentrations reported in the literature were also explored.•Reported microplastic concentrations decrease exponentially with greater mesh size.•Quantification of particles that animals commonly ingest requires small mesh size.
Abstract
Diel vertical migration (DVM) is a behaviour observed across zooplankton taxa in marine and limnetic systems worldwide. DVM influences biogeochemical cycling and carbon drawdown in oceanic ...systems and alters prey availability for zooplanktivorous species. DVM has been well studied among zooplankton, and many exogenous and endogenous triggers as well as adaptive significances have been hypothesized. However, second-order variability in DVM timing, the deviation of DVM times to respective dawn and dusk times throughout the year, is a less-studied phenomenon that can help identify the factors influencing migration timing as well as demonstrate the changes of DVM behaviours within and across systems. Here, we quantified seasonal trends in second-order variability of DVM timing of euphausiids at Brooks Peninsula, Clayoquot Canyon, and Saanich Inlet near Vancouver Island, British Columbia, Canada, over multiple years using upward-facing moored echosounders. We used generalized additive mixed models to characterize this seasonality. DVM timing relative to civil twilight times showed strong seasonality at all locations, with euphausiids remaining near the surface longer than expected in spring and summer, and shorter than expected in winter. Euphausiids spent less time near the surface at Brooks Peninsula and Clayoquot Canyon than at Saanich Inlet throughout the year. Increased primary productivity in Saanich Inlet, which reduced light penetration and hid euphausiids from visual predators, likely drove this difference. Our findings confirm that proper understanding of DVM behaviours must account for seasonal variability due to context-specific oceanographic and ecological parameters. This is particularly pertinent when attempting to model the biogeochemical or predator–prey interactions influenced by DVM behaviours.
Microplastic particles (MPs) occur widely in aquatic ecosystems and are ingested by a wide range of organisms. While trophic transfer of MPs is known to occur, researchers do not yet fully understand ...the fate of MPs in food webs. We explored the factors influencing reported ingestion of MPs in marine and freshwater fishes by conducting a literature review of 123 studies published between January 2011 and June 2020. We used Bayesian generalized linear mixed models to determine whether MP ingestion by fishes varies by Food and Agricultural Organization fishing area, trophic level, body size, taxa, and study methodology. After accounting for methodology, strong regional differences were not present, although ingested MP concentrations were slightly different among some FAO areas. According to the reviewed studies, MP concentrations in fish digestive tracts did not increase with either trophic level or body size, suggesting that biomagnification of MPs did not occur, although larger fish were more likely to contain MPs. Researchers reported higher concentrations of MPs in clupeids compared with other commonly studied taxonomic families, which could be due to their planktivorous feeding strategy. Methodology played an influential role in predicting reported concentrations, highlighting the need to harmonize methods among studies.
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•Data on fish ingestion of microplastics were compiled from 123 studies.•We modeled factors influencing reported microplastic concentration in fishes.•Biomagnification of microplastics between trophic levels was not observed.•Smallest detectable particle size influenced reported concentrations.•Small planktivorous fish may ingest more microplastics.
AIM: The benthic fauna of seamounts typically includes organisms that are slow‐growing, long‐lived and sensitive to mechanical disturbance, making seamounts susceptible to anthropogenic impacts. Such ...impacts may arise from mining cobalt‐rich crusts, envisaged for seamounts in the central North Pacific; this scenario requires that environmental guidelines for mining operations on seamounts be developed. Here, we provide the biological information essential for effective conservation planning of deep‐sea features targeted for such mining. LOCATION: Central North Pacific, Hawaiian Seamount Chain. METHODS: Spatial analysis of seamount benthos using a large biological dataset (> 600 taxa) obtained from 144 submersible dives (depth range: 113–1985 m) on 27 seamounts covering a distance of over 2200 km of ocean. RESULTS: Benthic assemblages of invertebrates are structurally different between seamounts located inside and outside a region with cobalt‐rich crusts. This spatial contrast results from variations in species composition and relative abundance of species, rather than differences in species richness, challenging historical notions of an impoverished cobalt‐rich crust fauna in the region. Seamount assemblages also have high species turnover with depth and distance at the scale of individual seamounts, but geographic separation was a poor predictor of ecological separation for the region at large. MAIN CONCLUSION: Several implications for the design of spatial management and conservation tools with respect to mining emerge: (1) conservation of seamounts outside the cobalt‐rich crust region is unlikely to capture the full range of ecological features found inside the region; (2) conservation areas need to encompass a broad bathymetric gradient; (3) ideally, mining blocks on individual seamounts should not exceed 2 km in length. Overall, the life history characteristics and morphological traits of the deep‐water invertebrate fauna typical of seamounts in the region imply that any recovery from mechanical impacts is likely to be very slow.
Spatial structures of larval fish in the Strait of Georgia (British Columbia, Canada) were quantified in the springs of 2009 and 2010 to investigate linkages to environmental heterogeneity at ...multiple scales. By applying a multiscale approach, principal coordinate neighborhood matrices, spatial variability was decomposed into three predefined scale categories: broad scale (>40 km), medium scale (20∼40 km), and fine scale (<20 km). Spatial variations in larval density of the three dominant fish taxa with different early life histories (Pacific herring (Clupea pallasii), Pacific hake (Merluccius productus), and northern smoothtongue (Leuroglossus schmidti)) were mainly structured at broad and medium scales, with scale-dependent associations with environmental descriptors varying interannually and among species. Larval distributions in the central-southern Strait were mainly associated with salinity, temperature, and vertical stability of the top 50 m of the water column on the medium scale. Our results emphasize the critical role of local estuarine circulation, especially at medium spatial scale, in structuring hierarchical spatial distributions of fish larvae in the Strait of Georgia and suggest the role of fundamental differences in life-history traits in influencing the formation and maintenance of larval spatial structures.
Microplastics (MPs) contamination in marine environments is of increasing concern, as plastic particles are globally ubiquitous across ecosystems. A large variety of aquatic taxa ingest MPs, but the ...extent to which animals accumulate and transfer MPs through food webs is largely unknown. In this study, we quantified MP uptake in bivalves, crabs, echinoderms, and fish feeding at different trophic levels at three sites on southern Vancouver Island. We paired stable‐isotope food web analysis with MP concentrations in digestive tracts across all trophic levels and in fish livers. We then used Bayesian generalized linear mixed models to explore whether bioaccumulation and biomagnification were occurring. Our results showed that MPs (100–5000 μm along their longest dimension) are not biomagnifying in marine coastal food webs, with no correlation between the digestive tract or fish liver MP concentrations and trophic position of the various species. Ecological traits did, however, affect microplastic accumulation in digestive tracts, with suspension feeder and smaller‐bodied planktivorous fish ingesting more MPs by body weight. Trophic transfer occurred between prey and predator for rockfish, but higher concentrations in full stomachs compared with empty ones suggested rapid excretion of ingested MPs. Collectively, our findings suggested the movement of MP through marine food webs is facilitated by species‐specific mechanisms, with contamination susceptibility a function of species biology, not trophic position. Furthermore, the statistical methods we employ, including machine learning for classifying unknown particles and a probabilistic way to account for background contamination, are universally applicable to the study of microplastics. Our findings advance understanding of how MPs enter and move through aquatic food webs, suggesting that lower‐trophic‐level animals are more at risk of ingesting >100‐μm MPs, relative to higher‐trophic‐level animals. Our work also highlights the need to advance the study of <100‐μm MPs, which are still poorly understood and may need to be considered separately in ecological risk assessments.
Estuaries represent a transition zone for salmon migrating from fresh water to marine waters, yet their contribution to juvenile growth is poorly quantified. Here, we use genetic stock identification ...and otolith analyses to quantify estuarine habitat use by Chinook salmon (Oncorhynchus tshawytscha) — the Pacific salmon species considered most reliant on this habitat — in Canada’s most productive salmon river, the Fraser River. Two years of sampling revealed subyearling migrant (ocean-type) Chinook from the Harrison River to be the estuary’s dominant salmon population throughout the emigration period. These Chinook salmon were caught predominantly in the estuary’s brackish marshes but shifted to more saline habitats as they grew. Otolith analyses indicated that these Chinook salmon have wide-ranging entry timing (from February to May) and longer estuarine residency (weeks to months, mean 41.8 days) than estimated by prior studies, but similar daily growth rates (mean ± SD: 0.57 ± 0.13 mm) across entry dates and residency periods, implying sufficient foraging opportunities throughout the emigration period and habitats. Together, these results suggest that estuarine habitat is more important for early marine growth of subyearling migrant Chinook salmon than previously recognized.
The spring zooplankton community in the Strait of Georgia (British Columbia, Canada) is characterized by the presence of several calanoid copepod species which collectively make up ~90% of the ...mezozooplankton biomass. Here, we investigate interspecific, interannual, and geographic variability in the diets and trophic positions of these copepods using a combination of fatty acids and stable isotopes. To characterize geographic variability in diet, we compare our findings from the Strait of Georgia with similar data from Ocean Station P in the subarctic northeast Pacific. Both fatty acid and stable isotope signatures indicate the existence of three trophic levels, even within the limited size range of these copepods: Neocalanus plumchrus and Calanus marshallae are primarily omnivorous, while Euchaeta elongata is carnivorous and Eucalanus bungii is herbivorous. Fatty acid markers of trophic position (e.g., DHA/EPA, 18:1n-9/18:1n-7) correlate significantly with δ¹⁵N, while markers indicating the proportion of diatoms to flagellates in the diet (e.g., 16PUFA/18PUFA and DHA/EPA) correlate significantly with δ¹³C, after the effect of lipid concentration on δ¹³C is accounted for. Despite the general correlation between stable isotopes and fatty acids, the former are not sensitive enough to capture the range of interannual variability observed in the latter, and can only capture substantial shifts in the diet over geographic scales. However, regardless of variability in food quality, the relative trophic positions of these copepods do not change significantly either spatially or temporally.
Despite a relatively short history, the field of seamount ecology is rife with ecological paradigms, many of which have already become cemented in the scientific literature and in the minds of ...advocates for seamount protection. Together, these paradigms have created a widely held view of seamounts as unique environments, hotspots of biodiversity and endemicity, and fragile ecosystems of exceptional ecological worth. However, closer examination reveals significant gaps in our knowledge, thereby calling the accuracy of some of these paradigms into question. Here, we review the evolution of the major paradigms in seamount ecology, assess their status against the weight of existing evidence to date, identify emerging paradigms, and suggest future research directions. We find the assertions that seamount communities are vulnerable to fishing, and that these communities have high sensitivity and low resilience to bottom trawling disturbance are well supported by existing data. We find plausible evidence that seamounts are stepping stones for dispersal, oases of abundance and biomass, and hotspots of species richness. Nonetheless, the poor sampling coverage of these discrete but globally distributed environments prevents us from accepting these ideas as paradigms. Also plausible, but requiring further investigation, are the emerging paradigms that seamount communities are structurally distinct, that populations of invertebrates on seamounts are the source of propagules for nearby slope sinks, and that seamounts have acted and can act as biological refugia from large‐scale catastrophic environmental events. In contrast, the generalizations that seamounts are island habitats with highly endemic faunas that comprise unique communities distinct in species composition from other deep‐sea habitats, and that they have high production supported by localized bottom‐up forcing, are not supported by the weight of existing evidence.
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