Polybridge Technical Report

This study examined the physical and chemical properties of a novel, fully-recirculated prawn and polychaete production system that incorporated polychaete-assisted sand filters (PASF). The aims were to assess and demonstrate the potential of this system for industrialisation, and to provide optimisations for wastewater treatment by PASF. Two successive seasons were studied at commercially-relevant scales in a prototype system constructed at the Bribie Island Research Centre in Southeast Queensland. The project produced over 5.4 tonnes of high quality black tiger prawns at rates up to 9.9 tonnes per hectare, with feed conversion of up to 1.1. Additionally, the project produced about 930 kg of high value polychaete biomass at rates up to 1.5 kg per square metre of PASF, with the worms feeding predominantly on waste nutrients. Importantly, this closed production system demonstrated rapid growth of healthy prawns at commercially relevant production levels, using methods that appear feasible for application at large scale. Deeper (23 cm) PASF beds provided similar but more reliable wastewater treatment efficacies compared with shallower (13 cm) beds, but did not demonstrate significantly greater polychaete productivity than (easier to harvest) shallow beds. The nutrient dynamics associated with seasonal and tidal operations of the system were studied in detail, providing technical and practical insights into how PASF could be optimised for the mitigation of nutrient discharge. The study also highlighted some of the other important advantages of this integrated system, including low sludge production, no water discharge during the culture phase, high ecosystem health, good prospects for biosecurity controls, and the sustainable production of a fishery-limited resource (polychaetes) that may be essential for the expansion of prawn farming industries throughout the world. Regarding nutrient discharge from this prototype mariculture system, when PASF was operating correctly it proved feasible to have no water (or nutrient) discharge during the entire prawn growing season. However, the final drain harvest and emptying of ponds that is necessary at the end of the prawn farming season released 58.4 kg ha-1 of nitrogen and 6 kg ha-1 of phosphorus (in Season 2). Whilst this is well below (i.e., one-third to one-half of) the current load-based licencing conditions for many prawn farms in Australia, the levels of nitrogen and chlorophyll a in the ponds remained higher than the more-stringent maximum limits at the Bribie Island study site. Zero-net-nutrient discharge was not achieved, but waste nutrients were low where 5.91 kg of nitrogen and 0.61 kg of phosphorus was discharged per tonne of prawns produced. This was from a system that deployed PASF at 14.4% of total ponded farm area which treated an average of 5.8% of pond water daily and did not use settlement ponds or other natural or artificial water remediation systems. Four supplemental appendices complement this research by studying several additional aspects that are central to the industrialisation of PASF. The first details an economic model and decision tool which allows potential users to interactively assess construction and operational variables of PASF at different scales. The second provides the qualitative results of a prawn maturation trial conducted collaboratively with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) to assess dietary inclusions of PASF-produced worms. The third provides the reproductive results from industry-based assessments of prawn broodstock produced using PASF. And the fourth appendix provides detailed elemental and nutritional analyses of bacterial biofilm produced by PASF and assesses its potential to improve the growth of prawns in recirculated culture systems

Polybridge Season 3: Ecosystem effects of polychaete-assisted sand filters

This study is an extension of research undertaken in the first two seasons of the Polybridge Project (2013-2016: for results see Palmer et al., 2016), which sought to investigate operational aspects of polychaete-assisted sand filters (PASF) when deployed for scaled prawn farm recirculation at the Bribie Island Research Centre (BIRC). The aims of the present work were to assess its functionality with increased organic loading rates provided by higher prawn stocking densities than previously trialled, and to assess the ecological effects on this integrated farming system when using PASF to initially fill ponds for a range of biosecurity purposes. Using prawn postlarval stocking densities in excess of 44 m-2, prawn production of up to 12 tonnes ha-1 was achieved without discharge of any wastewater during the production season (2015-16). However, the average production for the two ponds was 9.4 tonnes ha-1, which was lower than in the previous season (9.9 tonnes ha-1 in 2014/15) which used a lower prawn stocking density (37.5 postlarvae m-2). The prawns and worms produced were again healthy and of high commercial quality and value, but slower prawn growth (particularly after 140 d) and lower worm survival limited overall production in the fully-recirculated system. There were also several concerning aspects to this closed-system approach that need to be highlighted. Firstly, nutrient levels in the pond waters rose to particularly high levels, and some of the more toxic parameters, such as ammonia, reached critical levels that could be considered dangerous for routine prawn culture operations. Worm production in the PASF beds also suffered from the very rich wastewaters in the integrated system, and the capacity of PASF to filter water via percolation was limited by excessive sand clogging and a build-up of organic matter on the upper surface of the sand beds. The resultant excessive anoxic conditions created in the sand beds appeared to reduce worm productivity which, in turn, reduced their sand cleansing actions, for an overall lower functionality in terms of nutrient (and particularly nitrogen) removal rates. Alternatively, within the confines of the overall study, there were no significant deleterious effects on worm production or nutrient removal efficacies from using the PASF beds to initially fill the prawn production pond. The apparent effect of this on pond plankton communities was: 1) to slow the development of copepod populations; and 2) change the assemblage of algal species in the first few weeks after filling. This slower development of natural feed organisms in the PASF-filled pond may have provided lower survival of the particularly-young (PL 13) prawn seedstock used to stock the pond. Importantly however, there may be several potential remedies to this issue. These include management for a longer period for bloom development after fill and before stocking, and assuming a greater reliance on artificial feeds more suited to small prawns. As expected, this pond-fill strategy appeared to beneficially help exclude some problematic algal species, and greatly reduced barnacle fouling, though tube worm fouling did not appear overly affected. The project successfully demonstrated a third successive season of zero-water discharge from an integrated prawn/ worm production system, though ultimately, the water in ponds with some residual nutrients were discharged. The expansion of prawn farming in Australia is limited by nutrient discharge issues, and biosecurity measures are also of increasing interest to this industry. In this legacy project, polychaete-assisted sand filters are further demonstrated to hold potential for biosecurity controls whilst minimising nutrient discharge

Generalised growth models for aquatic species with an application to blacklip abalone (Haliotis rubra)

This paper presents a maximum likelihood method for estimating growth parameters for an aquatic species that incorporates growth covariates, and takes into consideration multiple tag-recapture data. Individual variability in asymptotic length, age-at-tagging, and measurement error are also considered in the model structure. Using distribution theory, the log-likelihood function is derived under a generalised framework for the von Bertalanffy and Gompertz growth models. Due to the generality of the derivation, covariate effects can be included for both models with seasonality and tagging effects investigated. Method robustness is established via comparison with the Fabens, improved Fabens, James and a non-linear mixed-effects growth models, with the maximum likelihood method performing the best. The method is illustrated further with an application to blacklip abalone ( Haliotis rubra) for which a strong growth-retarding tagging effect that persisted for several months was detected

Cops, Teachers, and the Art of the Impossible: Explaining the lack of diffusion of impossible job innovations

In their now classic Impossible Jobs in Public Management, Hargrove and Glidewell (1990) argue that public agencies with limited legitimacy, high conflict, low professional authority, and weak agency myths have essentially impossible jobs. Leaders of such agencies can do little more than cope, which is also a theme of James Q. Wilson (1989), among others. Yet in the years since publication of Impossible Jobs, one such position, that of police commissioner has proven possible. Over a sustained 17-year period, the New York City Police Department has achieved dramatic reductions in crime with relatively few political repercussions, as described by Kelling and Sousa (2001). A second impossible job discussed by Wilson and also by Frederick Hess (1999), city school superintendent, has also proven possible, with Houston and Edmonton having considerable academic success educating disadvantaged children. In addition, Atlanta and Pittsburgh enjoyed significant success in elementary schooling, though the gains were short-lived for reasons we will describe. More recently, under Michelle Rhee, Washington D.C. schools have made the most dramatic gains among city school systems. These successes in urban crime control and public schooling have not been widely copied. Accordingly, we argue that the real conundrum of impossible jobs is why agency leaders fail to copy successful innovations. Building on the work of Teodoro (2009), we will discuss how the relative illegitimacy of clients and inflexibility of personnel systems combine with the professional norms, job mobility and progressive ambition of agency leaders to limit the diffusion of innovations in law enforcement and schooling. We will conclude with ideas about how to overcome these barriers

Integrated Economic and Climate Modeling

This survey examines the history and current practice in integrated assessment models (IAMs) of the economics of climate change. It begins with a review of the emerging problem of climate change. The next section provides a brief sketch of the rise of IAMs in the 1970s and beyond. The subsequent section is an extended exposition of one IAM, the DICE/RICE family of models. The purpose of this description is to provide readers an example of how such a model is developed and what the major components are. The final section discusses major important open questions that continue to occupy IAM modelers. These involve issues such as the discount rate, uncertainty, the social cost of carbon, the potential for catastrophic climate change, algorithms, and fat-tailed distributions. These issues are ones that pose both deep intellectual challenges as well as important policy implications for climate change and climate-change policy

A Research Agenda for Helminth Diseases of Humans: Basic Research and Enabling Technologies to Support Control and Elimination of Helminthiases

Successful and sustainable intervention against human helminthiases depends on optimal utilisation of available control measures and development of new tools and strategies, as well as an understanding of the evolutionary implications of prolonged intervention on parasite populations and those of their hosts and vectors. This will depend largely on updated knowledge of relevant and fundamental parasite biology. There is a need, therefore, to exploit and apply new knowledge and techniques in order to make significant and novel gains in combating helminthiases and supporting the sustainability of current and successful mass drug administration (MDA) programmes. Among the fields of basic research that are likely to yield improved control tools, the Disease Reference Group on Helminth Infections (DRG4) has identified four broad areas that stand out as central to the development of the next generation of helminth control measures: 1) parasite genetics, genomics, and functional genomics; 2) parasite immunology; 3) (vertebrate) host–parasite interactions and immunopathology; and 4) (invertebrate) host–parasite interactions and transmission biology. The DRG4 was established in 2009 by the Special Programme for Research and Training in Tropical Diseases (TDR). The Group was given the mandate to undertake a comprehensive review of recent advances in helminthiases research in order to identify notable gaps and highlight priority areas. This paper summarises recent advances and discusses challenges in the investigation of the fundamental biology of those helminth parasites under the DRG4 Group's remit according to the identified priorities, and presents a research and development agenda for basic parasite research and enabling technologies that will help support control and elimination efforts against human helminthiases

Genomic reconstruction of the SARS-CoV-2 epidemic in England.

The evolution of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus leads to new variants that warrant timely epidemiological characterization. Here we use the dense genomic surveillance data generated by the COVID-19 Genomics UK Consortium to reconstruct the dynamics of 71 different lineages in each of 315 English local authorities between September 2020 and June 2021. This analysis reveals a series of subepidemics that peaked in early autumn 2020, followed by a jump in transmissibility of the B.1.1.7/Alpha lineage. The Alpha variant grew when other lineages declined during the second national lockdown and regionally tiered restrictions between November and December 2020. A third more stringent national lockdown suppressed the Alpha variant and eliminated nearly all other lineages in early 2021. Yet a series of variants (most of which contained the spike E484K mutation) defied these trends and persisted at moderately increasing proportions. However, by accounting for sustained introductions, we found that the transmissibility of these variants is unlikely to have exceeded the transmissibility of the Alpha variant. Finally, B.1.617.2/Delta was repeatedly introduced in England and grew rapidly in early summer 2021, constituting approximately 98% of sampled SARS-CoV-2 genomes on 26 June 2021

Polybridge Technical Report

This study examined the physical and chemical properties of a novel, fully-recirculated prawn and polychaete production system that incorporated polychaete-assisted sand filters (PASF). The aims were to assess and demonstrate the potential of this system for industrialisation, and to provide optimisations for wastewater treatment by PASF. Two successive seasons were studied at commercially-relevant scales in a prototype system constructed at the Bribie Island Research Centre in Southeast Queensland. The project produced over 5.4 tonnes of high quality black tiger prawns at rates up to 9.9 tonnes per hectare, with feed conversion of up to 1.1. Additionally, the project produced about 930 kg of high value polychaete biomass at rates up to 1.5 kg per square metre of PASF, with the worms feeding predominantly on waste nutrients. Importantly, this closed production system demonstrated rapid growth of healthy prawns at commercially relevant production levels, using methods that appear feasible for application at large scale. Deeper (23 cm) PASF beds provided similar but more reliable wastewater treatment efficacies compared with shallower (13 cm) beds, but did not demonstrate significantly greater polychaete productivity than (easier to harvest) shallow beds. The nutrient dynamics associated with seasonal and tidal operations of the system were studied in detail, providing technical and practical insights into how PASF could be optimised for the mitigation of nutrient discharge. The study also highlighted some of the other important advantages of this integrated system, including low sludge production, no water discharge during the culture phase, high ecosystem health, good prospects for biosecurity controls, and the sustainable production of a fishery-limited resource (polychaetes) that may be essential for the expansion of prawn farming industries throughout the world. Regarding nutrient discharge from this prototype mariculture system, when PASF was operating correctly it proved feasible to have no water (or nutrient) discharge during the entire prawn growing season. However, the final drain harvest and emptying of ponds that is necessary at the end of the prawn farming season released 58.4 kg ha-1 of nitrogen and 6 kg ha-1 of phosphorus (in Season 2). Whilst this is well below (i.e., one-third to one-half of) the current load-based licencing conditions for many prawn farms in Australia, the levels of nitrogen and chlorophyll a in the ponds remained higher than the more-stringent maximum limits at the Bribie Island study site. Zero-net-nutrient discharge was not achieved, but waste nutrients were low where 5.91 kg of nitrogen and 0.61 kg of phosphorus was discharged per tonne of prawns produced. This was from a system that deployed PASF at 14.4% of total ponded farm area which treated an average of 5.8% of pond water daily and did not use settlement ponds or other natural or artificial water remediation systems. Four supplemental appendices complement this research by studying several additional aspects that are central to the industrialisation of PASF. The first details an economic model and decision tool which allows potential users to interactively assess construction and operational variables of PASF at different scales. The second provides the qualitative results of a prawn maturation trial conducted collaboratively with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) to assess dietary inclusions of PASF-produced worms. The third provides the reproductive results from industry-based assessments of prawn broodstock produced using PASF. And the fourth appendix provides detailed elemental and nutritional analyses of bacterial biofilm produced by PASF and assesses its potential to improve the growth of prawns in recirculated culture systems