Predicting the dispersal of SARS-CoV-2 RNA from the wastewater treatment plant to the coast

Viral pathogens including SARS-CoV-2 RNA have been detected in wastewater treatment effluent, and untreated sewage overflows, that pose an exposure hazard to humans. We assessed whether SARS-CoV-2 RNA was likely to have been present in detectable quantities in UK rivers and estuaries during the first wave of the Covid-19 pandemic. We simulated realistic viral concentrations parameterised on the Camel and Conwy catchments (UK) and their populations, showing detectable SARS-CoV-2 RNA concentrations for untreated but not for treated loading, but also being contingent on viral decay, hydrology, catchment type/shape, and location. Under mean or low river flow conditions, viral RNA concentrated within the estuaries allowing for viral build-up and caused a lag by up to several weeks between the peak in community infections and the viral peak in the environment. There was an increased hazard posed by SARS-CoV-2 RNA with a T90 decay rate >24 h, as the estuarine build-up effect increased. High discharge events transported the viral RNA downstream and offshore, increasing the exposure risk to coastal bathing waters and shellfisheries – although dilution in this case reduced viral concentrations well below detectable levels. Our results highlight the sensitivity of exposure to viral pathogens downstream of wastewater treatment, across a range of viral loadings and catchment characteristics – with implications to environmental surveillance

Predicting microbial water quality with models: Over-arching questions for managing risk in agricultural catchments

The application of models to predict concentrations of faecal indicator organisms (FIOs) in environmental systems plays an important role for guiding decision-making associated with the management of microbial water quality. In recent years there has been an increasing demand by policy-makers for models to help inform FIO dynamics in order to prioritise efforts for environmental and human-health protection. However, given the limited evidence-base on which FIO models are built relative to other agricultural pollutants (e.g. nutrients) it is imperative that the end-user expectations of FIO models are appropriately managed. In response, this commentary highlights four over-arching questions associated with: (i) model purpose; (ii) modelling approach; (iii) data availability; and (iv) model application, that must be considered as part of good practice prior to the deployment of any modelling approach to predict FIO behaviour in catchment systems. A series of short and longer-term research priorities are proposed in response to these questions in order to promote better model deployment in the field of catchment microbial dynamics

Biological nitrogen fixation by soybean (Glycine max [L.] Merr.), a novel, high protein crop in Scotland, requires inoculation with non-native bradyrhizobia

It is currently not recommended to grow soybean (Glycine max [L.] Merr.) further than 54° North, but climate change and the development of new high latitude-adapted varieties raises the possibility that it could be introduced into Scotland as a novel high protein crop deriving most of its nitrogen (N) requirements through biological N fixation (BNF). This was evaluated via field trials in 2017 and 2018 near Dundee (56.48°N). As there are no native soybean-nodulating bacteria (SNB) in UK soils, soybean requires inoculation to exploit its BNF potential. In 2017, three commercial inoculants containing elite Bradyrhizobium strains significantly increased plant biomass in plot trials with a soybean 000 maturity group variety (ES Comandor). Rhizobia were isolated from the nodules and identified as the original inoculant species, B. diazoefficiens and B. japonicum. One inoculant (Rizoliq Top) was used for larger-scale trials in 2018 with two varieties (ES Comandor, ES Navigator); inoculation doubled the grain yield to 1 t ha-1 compared to the uninoculated crop. The inoculated soybean obtained most of its N through BNF in both years regardless of plant genotype i.e. >73%Ndfa, with BNF contributions to aerial biomass exceeding 250 kg N ha-1 yr-1 in 2017 and that to grain 50 kg N ha-1 yr-1 in 2018. These data suggest that N-fixing soybean could be grown in Scotland without mineral N-fertiliser, either for forage as animal feed, or as green pods for human consumption (“edamame”), and potentially, even as dry grain. The potential for survival of the Bradyrhizobium inoculant strains in soils was also demonstrated through the detection of the inoculant strain B. diazoefficiens SEMIA 5080 at relatively high populations (104 g-1 dry soil) using a qRT-PCR method with SNB-specific nodZ primers. Microbiome data obtained from soil using 16S rRNA primers demonstrated that the diversity of bacteria belonging to the genus Bradyrhizobium increased in soybean-cropped soils compared to bulk soil regardless of inoculation status. The economic and practical implications of residual inoculum, as well as those arising from introducing a non-native plant and alien bacteria into Scottish soils in terms of their impact on the native soil microbiota are discussed

Can macrophyte harvesting from eutrophic water close the loop on nutrient loss from agricultural land?

This work was supported by the UK Natural Environment Research Council, as part of the Recycling Biomass to Agricultural LANd: Capitalising on Eutrophication (ReBALAN:CE) project (NE/K015710/1)Eutrophication is a major water pollution issue and can lead to excessive growth of aquatic plant biomass (APB). However, the assimilation of nutrients into APB provides a significant target for their recovery and reuse, and harvesting problematic APB in impacted freshwater bodies offers a complementary approach to aquatic restoration, which could potentially deliver multiple wider ecosystem benefits. This critical review provides an assessment of opportunities and risks linked to nutrient recovery from agriculturally impacted water-bodies through the harvesting of APB for recycling and reuse as fertilisers and soil amendments. By evaluating the economic, social, environmental and health-related dimensions of this resource recovery from 'waste' process we propose a research agenda for closing the loop on nutrient transfer from land to water. We identify that environmental benefits are rarely, if ever, prioritised as essential criteria for the exploitation of resources from waste and yet this is key for addressing the current imbalance that sees environmental managers routinely undervaluing the wider environmental benefits that may accrue beyond resource recovery. The approach we advocate for the recycling of 'waste' APB nutrients is to couple the remediation of eutrophic waters with the sustainable production of feed and fertiliser, whilst providing multiple downstream benefits and minimising environmental trade-offs. This integrated 'ecosystem services approach' has the potential to holistically close the loop on agricultural nutrient loss, and thus sustainably recover finite resources such as phosphorus from waste.Publisher PDFPeer reviewe

Spatial and temporal heterogeneity of bacteria across an intertidal shellfish bed: Implications for regulatory monitoring of faecal indicator organisms

Routine bacterial monitoring of shellfish beds using indicator species is a common global practice designed to prevent human consumption of contaminated shellfish products. However, current bacteriological monitoring procedures which focus on the quantification of faecal indicator organisms (FIOs) as a proxy for microbial pollution may not be representative of total bacterial contamination levels present in shellfish harvesting areas. The objective of this study was to critically assess the accuracy of current monitoring strategies by quantifying the spatial (lateral and longitudinal distance) and temporal (seasonality and tidal state) concentrations of FIOs (Escherichia coli and total coliforms) within a single intertidal commercially harvested shellfish bed. Spatial and temporal FIO dynamics, including the effects of tidal state and seasonality, were quantified in mussel flesh and sediment samples from a single intertidal mussel (Mytilus edulis) bed. Our results confirmed that FIO concentrations across a shellfish bed were heterogeneous over larger spatial and temporal scales, but showed no relation to the concentrations of autochthonous bacteria, such as Vibrio spp., or the physico-chemical parameters of the sediment. These results have important implications for both public health and the economic prosperity of the shellfish industry, and demonstrate the importance of accommodating both spatial and temporal fluctuations in routine bacteriological monitoring protocols. We conclude that current FIO monitoring procedures may not accurately represent levels of microbial contamination within shellfish harvesting areas and that more robust microbiological testing procedures need developing

Grazing intensity is a poor indicator of waterborne Escherichia coli O157 activity

Contamination of watercourses with fecal matter represents a significant risk to public health due to the associated risk from human pathogens (e.g. Escherichia coli O157, norovirus). In addition, water contamination may also perpetuate the re-infection cycle of human pathogens within domesticated and wild animal populations. While diffuse pollution from agricultural fields has been identified as a major source of these pathogens, the relationship between livestock grazing intensity and subsequent pathogen persistence in water is not well established. Our aim was to critically evaluate the importance of land use management on the activity of E. coli O157 in freshwaters collected from a livestock dominated catchment in the UK. We inoculated replicate batches of both filter-sterilised and non-sterile freshwaters with a chromosomally lux-marked E. coli O157 and monitored pathogen survival and activity over a 5 d period. Our results indicate that the greatest risk for pathogens entering freshwater is probably associated with high intensity livestock areas, although their subsequent survival is greatest in waters from low intensity livestock areas. We ascribe this enhanced persistence in the latter to reduced competition and predation within these aquatic environments. These results have serious implications for the reliability of pathogen Q2 risk exposure maps which are based on grazing intensity alone

Liquid chromatography post-column oxidation (PCOX) method for the determination of paralytic shellfish toxins in mussels, clams, oysters, and scallops: Collaborative study

Sixteen laboratories participated in a collaborative study to evaluate method performance parameters of a liquid chromatographic method of analysis for paralytic shellfish toxins (PST) in blue mussels (Mytilus edulis), soft shell clams (Mya arenaria), sea scallops (Placopectin magellanicus), and American oysters (Crassostrea virginicus). The specific analogs tested included saxitoxin, neosaxitoxin, gonyautoxins-1 to -5, decarbamoyl-gonyautoxins-2 and -3, decarbamoyl-saxitoxin, and N-sulfocarbamoylgonyautoxin- 2 and -3. This instrumental technique has been developed as a replacement for the current AOAC biological method (AOAC Official MethodSM 959.08) and an alternative to the pre-column oxidation LC method (AOAC Official MethodSM 2005.06). The method is based on reversed-phase liquid chromatography with post-column oxidation and fluorescence detection (excitation 330 nm and emission 390 nm). The shellfish samples used in the study were prepared from the edible tissues of clams, mussels, oysters, and scallops to contain concentrations of PST representative of low, medium, and high toxicities and with varying profiles of individual toxins. These concentrations are approximately equivalent to = maximum level (ML), ML, or 2 7ML established by regulatory authorities (0.40, 0.80, and 1.60 mg ST\u1e8adiHCl eq/kg, respectively). Recovery for the individual toxins ranged from 104 to 127%, and recovery of total toxin averaged 116%. Horwitz Ratio (HorRat) values for individual toxins in the materials included in the study were generally within the desired range of 0.3 to 2.0. For the estimation of total toxicity in the test materials, the reproducibility relative standard deviation ranged from 4.6 to 20%. A bridging study comparing the results from the study participants using the post-column oxidation (PCOX) method with the results obtained in the study director's laboratory on the same test materials using the accepted reference method, the mouse bioassay (MBA; AOAC Official MethodSM 959.08), showed that the average ratio of results obtained from the two methods was 1.0. A good match of values was also achieved with a new certified reference material. The results from this study demonstrated that the PCOX method is a suitable method of analysis for PST in shellfish tissue and provides both an estimate of total toxicity, equivalent to that determined using the MBA AOAC Official MethodSM 959.08, and a detailed profile of the individual toxin present in the sample. \ua9 2012 Publishing Technology.Peer reviewed: YesNRC publication: Ye