Required sampling intensity for community analyses of intertidal infauna to detect a mechanical disturbance

In coastal ecosystems, infaunal (animals living within the sediment) invertebrates are used to study and monitor disturbances. However, it is an open question as to the minimal required sampling intensity to detect that a disturbance has influenced such communities. As such, we implemented a manipulative experiment using an infaunal community with a known response (community composition and population abundances) to a mechanical disturbance (sediment scour), to determine the minimum sampling intensity required to detect differences in the infaunal community. Statistically significant differences (α = 0.05) between the infaunal community of the disturbed and reference replicates were observed in case studies consisting of 99 (4 samples per m²) to 5 (0.2 samples per m²) samples per treatment. Below 5 samples, the known statistical and biological difference was undetectable. However, at least 10 samples per treatment (0.4 samples per m²) were required for the observed infaunal community to be within 93% similarity of our most accurate assessments of the infaunal community. These findings suggest that studies attempting to identify disturbances may require a minimal sampling intensity equivalent to 0.2 samples per m², while studies attempting to determine how the infaunal community varies with disturbances may require 0.4 samples per m². These potential minimal required sampling intensities will be of use in the theoretical exploration of disturbances, as well as in applied conservation, restoration, and monitoring projects.

Large size (>100-μm) microplastics are not biomagnifying in coastal marine food webs of British Columbia, Canada

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.

Depuration of anthropogenic particles by Pacific oysters (Crassostrea gigas): Feasibility and efficacy

Anthropogenic particles (APs) generated from both natural and synthetic materials are widespread in the aquatic environment and contaminate seafood products, including shellfish. Depuration, involving the placement of filter-feeding shellfish in clean water for a period of time, often several days, is used to reduce contaminant concentrations, but the practicality of its use by the shellfish industry for APs has not yet been examined. In the present study, cultured adult Pacific oysters (Crassostrea gigas) were depurated for 10 days in a facility with limited airflow and filtered seawater. On average, there was a 73 % reduction in oyster AP concentration after 5 days, but no further reduction at 10 days, potentially due to the difficulty in depurating some particles or to re-contamination from the experimental environment. Long-term feasibility for industry will depend on future guidelines for safe AP consumption levels and the practicality and financial feasibility of creating and running clean facilities.

Global COVID-19 lockdown highlights humans as both threats and custodians of the environment

The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus, initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness.

A Bayesian analysis of the factors determining microplastics ingestion in fishes

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.

Human Consumption of Microplastics

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.

Human Consumption of Microplastics

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.

Human Consumption of Microplastics

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.

Size and shape matter: A preliminary analysis of microplastic sampling technique in seawater studies with implications for ecological risk assessment

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.

Microplastics in juvenile Chinook salmon and their nearshore environments on the east coast of Vancouver Island

Microplastics are a significant issue in the world's oceans. These small plastic particles (<5 mm in size) are becoming globally ubiquitous in the marine environment and are ingested by various fish species. Here we investigate the incidence of microplastics in juvenile Chinook salmon and their nearshore marine environments on the east coast of Vancouver Island, British Columbia. We completed a series of beach seines, plankton tows and sediment cores in nearshore areas of importance to juvenile salmon. Microplastics were extracted from fish, water and sediment samples and concentrations were quantified. Microplastics analysis, consisting predominantly of fibrous plastics, showed juvenile Chinook salmon contained 1.2 ± 1.4 (SD) microplastics per individual while water and sediment samples had 659.9 ± 520.9 microplastics m^-3 and 60.2 ± 63.4 microplastics kg^-1 dry weight, respectively. We found no differences in microplastic concentrations in juvenile Chinook and water samples among sites but observed significantly higher concentrations in sediment at the Deep Bay site compared to Nanaimo and Cowichan Bay sites. Chinook microplastic concentrations were relatively low compared to literature values and, given the size and type of microplastics we observed, are unlikely to represent an immediate threat to fish in this area. However, microplastics less than 100 μm in size were not included in the study and may represent a greater threat due to their ability to translocate through tissues.

Sound the alarm: A meta-analysis on the effect of aquatic noise on fish behavior and physiology

The aquatic environment is increasingly bombarded by a wide variety of noise pollutants whose range and intensity are increasing with each passing decade. Yet, little is known about how aquatic noise affects marine communities. To determine the implications that changes to the soundscape may have on fishes, a meta-analysis was conducted focusing on the ramifications of noise on fish behavior and physiology. Our meta-analysis identified 42 studies that produced 2,354 data points, which in turn indicated that anthropogenic noise negatively affects fish behavior and physiology. The most predominate responses occurred within foraging ability, predation risk, and reproductive success. Additionally, anthropogenic noise was shown to increase the hearing thresholds and cortisol levels of numerous species while tones, biological, and environmental noise were most likely to affect complex movements and swimming abilities. These findings suggest that the majority of fish species are sensitive to changes in the aquatic soundscape, and depending on the noise source, species responses may have extreme and negative fitness consequences. As such, this global synthesis should serve as a warning of the potentially dire consequences facing marine ecosystems if alterations to aquatic soundscapes continue on their current trajectory.

Community assessment techniques and the implications for rarefaction and extrapolation with Hill numbers

Diversity estimates play a key role in ecological assessments. Species richness and abundance are commonly used to generate complex diversity indices that are dependent on the quality of these estimates. As such, there is a long-standing interest in the development of monitoring techniques, their ability to adequately assess species diversity, and the implications for generated indices. To determine the ability of substratum community assessment methods to capture species diversity, we evaluated four methods: photo quadrat, point intercept, random subsampling, and full quadrat assessments. Species density, abundance, richness, Shannon diversity, and Simpson diversity were then calculated for each method. We then conducted a method validation at a subset of locations to serve as an indication for how well each method captured the totality of the diversity present. Density, richness, Shannon diversity, and Simpson diversity estimates varied between methods, despite assessments occurring at the same locations, with photo quadrats detecting the lowest estimates and full quadrat assessments the highest. Abundance estimates were consistent among methods. Sample-based rarefaction and extrapolation curves indicated that differences between Hill numbers (richness, Shannon diversity, and Simpson diversity) were significant in the majority of cases, and coverage-based rarefaction and extrapolation curves confirmed that these dissimilarities were due to differences between the methods, not the sample completeness. Method validation highlighted the inability of the tested methods to capture the totality of the diversity present, while further supporting the notion of extrapolating abundances. Our results highlight the need for consistency across research methods, the advantages of utilizing multiple diversity indices, and potential concerns and considerations when comparing data from multiple sources.

Microplastic Ingestion by Wild and Cultured Manila Clams (Venerupis philippinarum) from Baynes Sound, British Columbia

Microplastics, plastic particles <5 mm, are an emerging concern in aquatic ecosystems. Because microplastics are small, they are available to many filter-feeding organisms, which can then be consumed by higher trophic level organisms, including humans. This study documents the quantity of microplastics present in wild and cultured Manila clams (Venerupis philippinarum). Three active shellfish farms and three reference beaches (i.e., non-shellfish farm sites) in Baynes Sound, British Columbia were chosen to examine the microplastic concentrations in wild and cultured Manila clams. Microplastics were isolated using a nitric acid digestion technique and enumerated from 54 clams (27 farmed and 27 non-farmed). Qualitative attributes, such as colour and microplastic type (fiber, fragment, or film) also were recorded. There was no significant difference (F = 1.29; df = 1,4; P = 0.289) between microplastic concentrations in cultured and wild clams. Microplastic concentrations ranged from 0.07 to 5.47 particles/g (from reference beach and shellfish farm clams, respectively). Fibers were the dominant microplastic (90 %); colourless and dark gray fibers were the most common colours observed (36 and 26 %, respectively). Although this indicates that microplastics are definitely present in seafood consumed by humans, shellfish aquaculture operations do not appear to be increasing microplastic concentrations in farmed clams in this region.

INVASION DYNAMICS OF THE VARNISH CLAM (NUTTALLIA OBSCURATA): A MATRIX DEMOGRAPHIC MODELING APPROACH

Marine invaders have become a significant threat to native biodiversity and ecosystem function. In this study, the invasion of the varnish clam (Nuttallia obscurata) in British Columbia, Canada, is investigated using a matrix modeling approach to identify the life history characteristics most crucial for population growth and to investigate population differences. Mark-recapture analyses and field collections from 2003 to 2004 were used to determine individual growth, survival rates, and fecundity for two sites. A multi-state matrix model was used to determine population growth rates and to conduct sensitivity and elasticity analyses. A life table response experiment was also used to determine what life history stage contributed most to observed differences in population growth rates. Population survey data were used in conjunction with the matrix model to determine plausible recruitment levels and to investigate recruitment scenarios. Both populations are currently declining but are likely sustainable because of the pulsed nature of large recruitment events. Survival of larger clams (>40 mm) is the most important for population growth based on elasticity and sensitivity analyses. Adult survival also had the largest influence on observed differences between site-specific population growth rates. The two populations studied differed in recruitment dynamics; one experiencing annual recruitment with higher post-settlement mortality and the other, episodic recruitment and lower post-settlement mortality. The most influential factor for the successful invasion of the varnish clam appears to be survival of the larger size classes. Therefore, any process that decreases adult survival (e.g., predation, commercial harvest) will have the greatest impact on population growth.