Modeling the Dispersion of Eastern Oyster Larvae (\u3ci\u3eCrassostrea virginica\u3c/i\u3e) and its Effects on the Movement of Disease Resistant Genes in the Delaware Bay Estuary

This study combines several models to address two primary research questions. How does the interaction of larval biology and environmental variability determine the spatial distribution of oyster larvae in Delaware Bay? What is the role of larval dispersion in the transference of disease-resistant genes? The particle-tracking module in the Regional Ocean Modeling System (ROMS) was converted into an Individual-Based model representing Eastern oyster larvae that has growth and vertical migration. Exchange of larvae between natural oyster reefs was estimated and used in an Individual-Based genetic model that simulates the genetic structure of eastern oysters. Particles were released from a number of reefs at several times and tracked until they reached a competent settlement size (330 µm). The simulated dispersal patterns showed that oyster larvae tend to drift down-estuary during the spawning season. The net result is that mixing of oyster larvae throughout Delaware Bay is extensive. Larval success is strongly affected by variability of temperature and salinity. Low temperature and salinity increases development times, which decreases the larval success. A stronger influence in the larval success is driven by salinity. The permanent salinity gradient in the estuary maintains an along estuary gradient in larval success. Larvae released in the upper bay populations encounter lower salinity than larvae release in the middle-lower bay populations. River discharge and spring-neap tides are the main forcing of the residual circulation. salinity and stratification in the Delaware estuary, playing an important role in the larval success and dispersion. Years with low success are related to large events of river discharge within the spawning season. Large river discharge also enhances the down-estuary dispersal pattern. Larvae released during spring tides are transported down-estuary to high salinity areas increasing the larval success of upper and middle bay reefs. The dominant. inflows in the subsurface layer and over the shoals during neap tides reduced the larval success by transporting larvae to low salinity areas. Thus, neap tides could be important in sustaining upper bay populations by increasing the export of larvae from middle to upper estuary populations. Nevertheless. the low exchange rates suggest that. this mechanism by itself can not completely explain the survival of upper estuary populations. The well-mixed conditions over most of the estuary maintain larvae distributed throughout the water column and overcome the effects of larval swimming behavior. The genetics simulations show larval dispersal might be important in the movement of disease-resistant genes from high (middle-lower bay) to low (upper bay) disease-resistant populations. The transference of the resistant trait will occur in periods of 5 to 100 years. The results of this research confirm that biophysical processes influence the dispersion pattern of oyster larvae, and thereby, the pattern of recruitment and genetic dispersal throughout Delaware Bay

Modeling the Dispersal of Eastern Oyster (Crassostrea virginica) larvae in Delaware Bay

The interactions of circulation and growth processes in determining the horizontal distribution of eastern oyster (Crassostrea virginica) larvae in the Delaware Bay estuary were investigated with a coupled circulation-individual-based larvae model that used environmental conditions from the spawning seasons (mid-June to mid-September) of 1984, 1985, 1986, 2000, and 2001. Particles, representing oyster larvae, were released at five-day intervals from areas in Delaware Bay that correspond to natural oyster reefs. The simulated larval development time was used to estimate potential larval success, determined by the percent of larvae that successfully reached settlement size (330 µm) within the planktonic larval duration of 30 days. Success rates for simulated larvae released in the upper estuary were less than half of those released in the lower estuary because of the reduction in growth rate from exposure to low salinity. Simulated larval success rates were further reduced during periods of increased river discharge, which produced low salinity conditions. The simulated transport patterns showed a down-estuary drift of oyster larvae during the spawning season, which is consistent with the observed reduction in settlement and recruitment rates in the upper estuary. The simulated transport pathways patterns showed that larvae originating in the middle and lower regions of the estuary had low rates of dispersion and high rates of self-settlement. Larvae released in the upper reaches of the estuary had limited contributions to the Delaware Bay oyster population, in part because of the lower overall simulated larval success in the low salinity regions. The simulated transport patterns suggested that the upper bay exports rather than receives larvae, which has implications for the establishment of genetic traits

Low-cost syngas shifting for remote gasifiers: Combination of CO2 adsorption and catalyst addition in a novel and simplified packed structure

This paper presents the technical validation of a novel, low-complexity alternative based on the inclusion of a patented (IEPI-MU-2016-185) packed bed for improving the performance of remote, small-scale gasification facilities. This study was carried out in an updraft, atmospheric-pressure gasifier, outfitted with a syngas reflux line, air and oxygen feed, and an upper packed-bed coupled to the gasification unit to improve the syngas quality by catalytic treatment and CO2 adsorption. The experimental facility is located in the rural community San Pedro del Laurel, Ecuador. Gasification experiments, with and without packed material in the upper chamber, were performed to assess its effect on the syngas quality. The assessment revealed that the packed material increases the carbon monoxide (CO) content in the syngas outlet stream while carbon dioxide (CO2) was reduced. This option appears to be a suitable and low-complexity alternative for enhancing the content of energy vectors of syngas in gasification at atmospheric pressure since CO/CO2 ratios of 5.18 and 3.27 were achieved against reported values of 2.46 and 0.94 for operations which did not include the addition of packed material. It is concluded that the upper packed-bed is an active element able to modify syngas characteristics since CO2 content was reduce

Circulation and Behavior Controls on Dispersal of Eastern Oyster (Crassostrea virginica) Larvae in Delaware Bay

The degree of genetic connectivity among populations in a metapopulation has direct consequences for species evolution, development of disease resistance, and capacity of a metapopulation to adapt to climate change. This study used a metapopulation model that integrates population dynamics, dispersal, and genetics within an individual-based model framework to examine the mechanisms and dynamics of genetic connectivity within a metapopulation. The model was parameterized to simulate four populations of oysters (Crassostrea virginica) from Delaware Bay on the mid-Atlantic coast of the United States. Differences among the four populations include a strong spatial gradient in mortality, a spatial gradient in growth rates, and uneven population abundances. Simulations demonstrated a large difference in the magnitude of neutral allele transfer with changes in population abundance and mortality (on average between 14 and 25% depending on source population), whereas changes in larval dispersal were not effective in altering genetic connectivity (on average between 1 and 8%). Simulations also demonstrated large temporal changes in metapopulation genetic connectivity including shifts in genetic sources and sinks occurring between two regimes, the 1970s and 2000s. Although larval dispersal in a sessile marine population is the mechanism for gene transfer among populations, these simulations demonstrate the importance of local dynamics and characteristics of the adult component of the populations in the flow of neutral alleles within a metapopulation. In particular, differential adult mortality rates among populations exert a controlling influence on dispersal of alleles, an outcome of latent consequence for management of marine populations

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Parasite transmission through suspension feeding

Suspension-feeding bivalve molluscs are confronted with a wide range of materials in the benthic marine environment. These materials include various sized plankton and the organic material derived from it, macroalgae, detritus and a diversity of microbial parasites that have adapted life stages to survive in the water column. For bivalve parasites to infect hosts though, they must first survive and remain infectious in the water column to make initial contact with hosts, and once in contact, enter and overcome elaborate pathways for particle sorting and selection. Even past these defenses, bivalve parasites are challenged with efficient systems of mechanical and chemical digestion and highly evolved systems of innate immunity. Here we review how bivalve parasites evade these hurdles to complete their life cycles and establish within bivalve hosts. We broadly cover significant viral, bacterial, and protozoan parasites of marine bivalve molluscs, and illustrate the emergent properties of these host-parasite systems where parasite transmission occurs through suspension feeding

Syngas composition in atmospheric pressure gasifiers after a catalytic treatment

The current work describes the experimental results of the composition of syngas obtained from gasification of municipal solid waste (MSW). This particular study was carried out in an updraft, atmospheric-pressure, and pilot-scale gasifier. The gasifier is also outfitted with a gas reflux line, air and oxygen feed, and a catalytic packed-bed reactor coupled to the gasification unit in order to improve the syngas quality. Characteristics and operation variables related to the gas retention time along the gasifier and catalytic reactor are also mentioned and analyzed as part of the described study. The assessment was focused in increasing the carbon monoxide (CO) concentration in the outlet stream of syngas while the carbon dioxide (CO2) is reduced. Observed effects in other gaseous components of syngas are also mentioned . Preliminary results show the proposed alternative is able to increase the CO/ CO2 ratio in 30% in comparison with reported results of similar gasifiers. The described phenomenon appears as a suitable and low-cost alternative for enhancing the energy content and the content of energy vectors such as CO and hydrogen (H2) of syngas in gasification processes since high pressure conditions are avoided