Determining how functionally diverse intertidal sediment species preserve mudflat ecosystem properties after abrupt biodiversity loss

As a result of anthropogenic climate change, extreme climatic events have increased in frequency, severity, and longevity. The consequences for community structure after a catastrophic event have been well studied. However, changes in ecosystem functioning that occur after such an event, including ecosystemrecovery, are still uncertain. A catastrophic event was simulated in an intertidalsedimentary habitat. Postevent sediment replicates were assigned to one of four recovery scenarios: (1) no recovery, (2) migration recovery, and recovery by differential opportunistic colonisation by (3) the polychaete worm Hediste diversicolor and (4) the mud snail Peringia ulvae, two locally dominant infauna species. These are compared with a control scenario not subjected to the event. The simulated extreme event caused a shift in habitat state due to a reduction in mobile macrofauna abundance and an increase in microphytobenthos biomass. Migratory recovery of species and the simulated opportunistic expansion of a single species ameliorated this shift and, for some metrics, functional compensation for the loss of other species and the preservation of certain ecosystem functions was observed. The dominant species identity during postevent habitat recovery can have considerable effects on important ecosystem processes and functions with consequences that may result in functional regime shifts in a habitat and alter coastal stability

Detection and characterisation of microplastics and microfibres in fishmeal and soybean meal

Aquaculture is an increasingly important source of nutrition for global food security, which is reliant on animal- and plant-based feeds. Anthropogenic particles, including microplastics and semi-synthetic cellulosic fibres, are prolific marine pollutants that are readily consumed by marine organisms, including small pelagic fish commonly used in fishmeal. Conversely, there is no indication plants can accumulate anthropogenic microparticles. We explore whether aquaculture feed presents a route of contamination for farmed fish. Commercially-sourced aquaculture feedstocks, including fishmeals and soybean meal, were processed (KOH digestion and ZnCl2 density separation) and anthropogenic particles characterised using microscopy and spectroscopic methods. Both fishmeal and soybean meals contained anthropogenic particles, with concentrations ranging 1070–2000 particles kg−1. The prevalence of anthropogenic particles in plant-based feeds indicates that the majority of contamination occurs post-harvest. Based on our findings, farmed Atlantic salmon may be exposed to a minimum of 1788–3013 anthropogenic particles from aquaculture feed across their commercial lifespan

Microplastic shape influences fate in vegetated wetlands

Coastal areas are prone to plastic accumulation due to their proximity to land based sources. Coastal vegetated habitats (e.g., seagrasses, saltmarshes, mangroves) provide a myriad of ecosystem functions, such as erosion protection, habitat refuge, and carbon storage. The biological and physical factors that underlie these functions may provide an additional benefit: trapping of marine microplastics. While microplastics occurrence in coastal vegetated sediments is well documented, there is conflicting evidence on whether the presence of vegetation enhances microplastics trapping relative to bare sites and the factors that influence microplastic trapping remain understudied. We investigated how vegetation structure and microplastic type influences trapping in a simulated coastal wetland. Through a flume experiment, we measured the efficiency of microplastic trapping in the presence of branched and grassy vegetation and tested an array of microplastics that differ in shape, size, and polymer. We observed that the presence of vegetation did not affect the number of microplastics trapped but did affect location of deposition. Microplastic shape, rather than polymer, was the dominant factor in determining whether microplastics were retained in the sediment or adhered to the vegetation canopy. Across the canopy, microfibre concentrations decreased from the leading edge to the interior which suggests that even on a small-scale, vegetation has a filtering effect. The outcome of this study enriches our understanding of coastal vegetation as a microplastics sink and that differences among microplastics informs where they are most likely to accumulate within a biogenic canopy

Impact of polyester and cotton microfibers on growth and sublethal biomarkers in juvenile mussels

Anthropogenic microfibres are a prevalent, persistent and globally distributed form of marine debris. Evidence of microfibre ingestion has been demonstrated in a range of organisms, including Mytilus spp. (mussels), but the extent of any impacts on these organisms are poorly understood. This study investigates, for the first time, the effect of exposing juvenile mussels to polyester and cotton microfibres at environmentally relevant concentrations (both current and predicted future scenarios) over a chronic timescale (94 days). Sublethal biomarkers included growth rate, respiration rate and clearance rate. Mussels were exposed to polyester (median length 149 µm) and cotton (median length 132 µm) microfibres in three treatments: polyester (~ 8 fibres L−1), polyester (~ 80 fibres L−1) and cotton (~ 80 fibres L−1). Mussels exposed to 80 polyester or cotton microfibres L−1 exhibited a decrease in growth rate of 35.6% (polyester) and 18.7% (cotton), with mussels exposed to ~ 80 polyester microfibres L−1 having a significantly lower growth rate than the control population (P < 0.05). This study demonstrates that polyester microfibres have the potential to adversely impact upon mussel growth rates in realistic future scenarios, which may have compounding effects throughout the marine ecosystem and implications for commercial viability

Genomic epidemiology of SARS-CoV-2 in a UK university identifies dynamics of transmission

AbstractUnderstanding SARS-CoV-2 transmission in higher education settings is important to limit spread between students, and into at-risk populations. In this study, we sequenced 482 SARS-CoV-2 isolates from the University of Cambridge from 5 October to 6 December 2020. We perform a detailed phylogenetic comparison with 972 isolates from the surrounding community, complemented with epidemiological and contact tracing data, to determine transmission dynamics. We observe limited viral introductions into the university; the majority of student cases were linked to a single genetic cluster, likely following social gatherings at a venue outside the university. We identify considerable onward transmission associated with student accommodation and courses; this was effectively contained using local infection control measures and following a national lockdown. Transmission clusters were largely segregated within the university or the community. Our study highlights key determinants of SARS-CoV-2 transmission and effective interventions in a higher education setting that will inform public health policy during pandemics.</jats:p