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Applied economics within pearl farming value chains supporting community livelihoods in Fiji and Tonga
Get PDFNatural marine pearls were a rare and valuable by-product of a fishery targeting pearl oyster shells for their mother-of-pearl (MOP). This fishery developed around the world throughout the 18th century and increased significantly through the 19th century in Australia and the Pacific islands. Overfishing of the MOP resource led to the development of pearl oyster spat collection techniques to assist stock replenishment. While the MOP industry eventually ceased in the 20th century, spat collection provided a basis for pearl culture industries in the Pacific, that utilised pearl nucleated techniques developed in Japan.
Today, French Polynesia is the largest producer of cultured round pearls in the south Pacific using the endemic black-lip pearl oyster, Pinctada margaritifera. The successful French Polynesian pearl industry was a catalyst for development of pearl culture in other Pacific island countries such as the Cook Islands and Fiji. As well as significant export income, pearl culture offers livelihood opportunities (upstream and downstream) to coastal communities at a number of levels including collection of pearl oyster spat (juveniles) for on-selling to pearl farms as juveniles, and jewellery and MOP shell craft production. Despite being compatible with local lifestyles, round pearl culture has significant barriers to entry including high initial investment, high operational costs, and a requirement for a high level of technical skills.
Alternatively, significant opportunities for coastal communities exist from production of mabé pearls (half pearls) because, although not as valuable as high-grade round pearls, they are cheaper to produce, with a shorter culture period, their production requires fewer technical skills and pearls can be produced by local people with minimal training. Diversification of round pearl farms into mabé pearl production, or the establishment of stand-alone mabé pearl farms, is increasingly prevalent in Pacific pearl producing nations, motivated by risk minimisation, a broader market base and a much simpler and less costly entry pathway to the sector. The overall objective of this study was to generate economic knowledge for targeted components of the pearl culture value chains in Fiji and Tonga, improve understanding of the viability of the pearl sector, documentation of operational costs and inputs to successful pearl culture, assessment of farm viability thresholds, and the impact of adopting new technologies as decision-making tools for pearl farmers. This research was conducted within six research chapters
Core Soil Microorganisms and Abiotic Properties as Key Mechanisms of Complementary Nanoscale Zerovalent Iron and Nitrification Inhibitors in Decreasing Paclobutrazol Residues and Nitrous Oxide Emissions
No full textAgrochemical residues and nitrous oxide (N2O) emissions have caused considerable threats to agricultural soil ecology. Nanoscale zerovalent iron (nZVI) and nitrification inhibitors might be complementary to each other to diminish soil agrochemical residues and N2O emissions and enhance soil bacterial community diversities. Compared to the control, the nZVI application declined soil paclobutrazol residues by 5.9% but also decreased the bacterial community co-occurrence network node. Combined nZVI and Dicyandiamide applications significantly decreased soil N2O emission rates and paclobutrazol residues but promoted Shannon diversity of the bacterial community. The increased soil pH, ammonium nitrogen, and Actinobacteriota could promote soil paclobutrazol dissipation. The nZVI generated double-edged sword effects of positively decreasing paclobutrazol residues and N2O emissions but negatively influencing soil multifunctionalities. The nZVI and Dicyandiamide could be complementary to each other in diminishing soil agrochemical residues and N2O emission rates but promoting soil bacterial community diversities simultaneously
Isolation, small population size, and management influence inbreeding and reduced genetic variation in K’gari dingoes
Get PDFSmall island populations are vulnerable to genetic decline via demographic and environmental stochasticity. In the absence of immigration, founder effects, inbreeding and genetic drift are likely to contribute to local extinction risk. Management actions may also have a greater impact on small, closed populations. The demographic and social characteristics of a species can, however, delay the impact of threats. K’gari, a ~ 1 660 km2 island off the Australian east coast and UNESCO World Heritage Site (Fraser Island 1842–2023), supports an isolated population of approximately 70–200 dingoes that represent an ideal opportunity to explore the small island paradigm. To examine temporal and spatial patterns of genetic diversity in this population we analysed single nucleotide polymorphism (SNP) genotype data (72 454 SNPS) for 112 K’gari dingoes collected over a 25-year period (1996 to 2020). Genetic diversity was lower in K’gari dingoes than mainland dingoes at the earliest time point in our study and declined significantly following a management cull in 2001. We did not find any spatial genetic patterns on the island, suggesting high levels of genetic connectivity between socially discrete packs. This connectivity, combined with the social structure and behaviour of dingoes, may act in concert to buffer the population from the impacts of genetic drift in the short term. Nevertheless, a general decline in genetic variation via inbreeding and drift has occurred over the past 20 years which we suggest should be considered in any future management planning for the population. Monitoring patterns of genetic variation, together with a clearer understanding of the social ecology of K’gari dingoes, will aid in the development of measurable genetic targets set over ecologically meaningful timelines, and help ensure continued survival of this culturally important population
Characterisation of Nematoda and Digenea in selected Australian freshwater snails
Get PDFFreshwater snails are integral to local ecosystems as a primary food source for various vertebrate species, thereby contributing significantly to ecological food webs. However, their role as intermediate hosts also makes them pivotal in the transmission of parasites. In Australia, research on freshwater snails has predominantly focused on their role as intermediate hosts for livestock parasites, while there has been limited exploration of the impact of these parasites on snail health and population dynamics. The aim of this study was to determine parasitic infection in freshwater snails. This study was conducted in the south-eastern region of Australia, in 2022. A total of 163 freshwater snails from four different species were collected and examined in the Murrumbidgee catchment area in the southeastern part of Australia during the Southern Hemisphere summer and autumn months (February to May). The species included Isidorella hainesii, Glyptophysa novaehollandica, Bullastra lessoni (endemic species), and Physella acuta (an introduced species). Through the analysis of sequence data from the various regions of the nuclear ribosomal DNA, we determined that the Digenea species in this study belonged to three distinct species, including Choanocotyle hobbsi, Petasiger sp. and an unidentified species belonging to Plagiorchioidea. Additionally, analysis of the sequences from Nematoda found in this study, revealed they could be categorized into two separate taxa, including Krefftascaris sp. and an unidentified nematode closely associated with plant and soil nematodes. This research holds significant implications for the future understanding and conservation of Australian freshwater ecosystems. Most parasites found in the present study complete their life cycle in snails and turtles. As many of freshwater snail and turtle species in Australia are endemic and face population threats, exploring the potential adverse impacts of parasitic infections on snail and turtle health, is crucial for advancing our understanding of these ecosystems and also paving the way for future research and conservation efforts. While none of the native snail species in the present study have been listed as endangered or threatened, this may simply be attributed to the absence of regular population surveys
Stakeholder perspectives on landslide triggers and impacts in five countries
Get PDFExpert perspectives drive landslide mitigation and post-disaster policy planning. This study examines landslide risk perceptions among the stakeholders (government officials, academics, policy experts, local community representatives, and representatives of NGOs/civil society) across Brazil, Colombia, Nepal, Iran, and Pakistan, identifying both shared concerns and local heterogeneity. Key informants revealed a discrepancy in their degree of concern about landslides, with government officials exhibiting greater apprehension compared to local community representatives. Local community representatives incorrectly perceived landslides to be the result of natural phenomena. In contrast, governmental and academic stakeholders felt that human-induced triggers, specifically those related to land use and land cover change, were significant contributors to landslide occurrences, necessitating stringent law enforcement. The comprehensive impacts of landslides included economic losses, infrastructure disruption, agricultural losses, and food security concerns, underscoring the multifaceted nature of this hazard. Our results suggest the need for proactive citizen engagement in landslide monitoring, recognizing the importance of local contexts. We end by proposing a dual-pronged policy approach that emphasizes the socio-economic context of each region
Climate change increases net CO2 assimilation in the leaves of strawberry, but not yield
Get PDFFruit growth in strawberry is dependent on photosynthesis in the leaves. The main scenarios for climate change include an increase in the concentration of CO2 in the atmosphere and an increase in temperature. This review examined photosynthesis in strawberry. The mean photosynthetic photon flux (PPF) for the saturation of CO2 assimilation was 1,031?±?447?µmol per m2 per s, the median was 1,000?µmol per m2 per s, and the range was from 467 to 2,200?µmol per m2 per s (N?=?59). The mean concentration of CO2 for the saturation of assimilation was 869?±?306 ppm, the median was 900 ppm, and the range was from 410 to 1,750 ppm (N?=?32). The optimum temperature range for CO2 assimilation was 20° to 30°C, with lower photosynthesis at lower or higher temperatures. The optimum temperatures for photosynthesis are higher than those for flowering and fruit growth. The impact of climate change on production varies across growing areas. In warm locations, higher temperatures increase photosynthesis, but not yield. In cool locations, higher temperatures increase plant growth and the length of the production season, but this comes at the expense of flower initiation
Microbial decomposition of organic matter and wetting–drying promotes aggregation in artificial soil but porosity increases only in wet-dry condition
Get PDFAggregation is one of the key properties influencing the function of soils, including the soil’s potential to stabilise organic carbon and create habitats for micro-organisms. The mechanisms by which organic matter influences aggregation and alters the pore geometry remain largely unknown. We hypothesised that rapid microbial processing of organic matter and wetting and drying of soil promotes aggregation and changes in pore geometry. Using microcosms of silicate clays and sand with either rapidly decomposable glucose or slowly decomposable cellulose, the degree of aggregation (P < 0.001), was greater in glucose treatments than controls that did not receive added carbon or microbial inoculum. We link this to microbial activity through measurements in soil respiration, phospholipids and microbially derived carbon. Our results demonstrate that rapid microbial decomposition of organic matter and microbially derived carbon promote aggregation and the aggregation process was particularly strong in the wet-dry condition (alternating between 30 % and 15 % water content) with significant modification of porosity (P < 0.05) of the aggregates
The Association between Broiler Litter Microbiota and the Supplementation of Bacillus Probiotics in a Leaky Gut Model
Get PDFProbiotics provided from hatch have a major influence on microbiota development, and together with environmental and bedding microbiota, shape the microbial community of the litter. We investigated the influence of probiotic supplementation and a leaky gut challenge induced using dexamethasone (DEX) on the litter microbial community and litter parameters. The probiotic product was a mix of three Bacillus amyloliquefaciens strains. The litter microbiota were compared to the microbial communities from other gut sections. The litter samples had higher microbial diversity compared to the caecum, gizzard, jejunum, and jejunal mucosa. The high similarity between the litter phylum-level microbiota and gizzard microbiota detected in our study could be a consequence of ingested feed and litter passing through the gizzard. Moreover, the litter microbial community is fundamentally distinct from the intestinal microbiota, as evidenced by the number of genera present in the litter but absent from all the intestinal sections and vice versa. Furthermore, LEfSe analysis identified distinct microbial taxa across different groups, with specific genera associated with different treatments. In terms of litter quality, the birds in the DEX groups had a significantly higher moisture content, indicating successful leaky gut challenge, while probiotic supplementation did not significantly affect the moisture levels. These findings provide comprehensive insights into the distinct microbiota characteristics of litter
Carbon to nitrogen stoichiometry of organic amendments influences the improvement of aggregate stability of a cropping vertisol
Get PDFSoil aggregation is one of the key processes controlling air, water and gas transport in soil. Long-term cropping without returning organic matter in the soil can reduce the water stability of the aggregates. Microbial decomposition of organic matter plays a significant role in aggregate formation and hence can reverse the decline in the water stability of the aggregates. The inoculation of soil with beneficial microbes can improve the aggregate stability of cropping soil, potentially restoring its condition to healthy soil. However, the restoration of the aggregate stability may also be dependent on the C:N ratio of added organic matter. We hypothesize that a higher C:N ratio of added organic matter and microbial inoculation can trigger a more persistent improvement in aggregates. We treated pasture (aggregates were water-stable) and cropping (aggregates were unstable in water) vertisols with sugarcane (C:N = 104) and lucerne (C:N = 23) residues with and without microbial inoculant that had both bacteria and fungi. After 4 months of incubation, we found that the slaking index dropped by 46% in sugarcane-treated cropping soils, whereas the reduction was 27% in lucerne treatment. A similar reduction in the slaking index was also observed in the pasture soil but the magnitude of the reduction was lower than in the cropping soils. However, microbial inoculation did not show a statistically significant influence on reducing the slaking of cropping or pasture soils in this study. The reduction of slaking in both soils was supported by an increase in mean weight diameter (MWD), macro-aggregates and the aggregate-associated soil organic carbon. Our results demonstrated that organic carbon input with a high C:N ratio facilitates the restoration of water stability of the structurally unstable cropping soils
Biological control of cat's claw creeper (Dolichandra unguis-cati; Bignoniaceae): Current status and future prospects
Get PDFCat's claw creeper (Dolichandra unguis-cati), native to tropical South America, is a major invasive species and a target for biological control in Australia, South Africa and some South Pacific Island countries. Native range surveys in Argentina, Brazil, Paraguay and Venezuela have identified eight insects and four fungal pathogens as potential agents. Five leaf-feeding insects a tortoise beetle Charidotis auroguttata, two tingids Carvalhotingis visenda and C. hollandi, a leaf-tying moth Hypocosmia pyrochroma and a leaf-mining beetle Hedwigiella jureceki, have been tested and all were released in South Africa. Four of these have become established but are not widespread and cause only limited damage. In Australia, only three of these, C. visenda, H. pyrochroma and H. jureceki were released, while C. auroguttata was not approved due to perceived non-target risks. All agents have become widely established, except for H. pyrochroma which is restricted to riparian corridors in southeast Queensland. In South Africa, an accidentally introduced leaf-spot pathogen, Neoramulariopsis unguis-cati, causes necrotic lesions and premature abscission of leaves in cat's claw creeper infestations, resulting in widespread defoliation. Based on its impact and field-host specificity in its native range and in South Africa, the pathogen has been prioritised for evaluation as a potential additional agent in Australia. The current priority is to seek approval for the introduction of this leaf-spot pathogen into Australia. Future research should focus on the gall-inducing rust Uropyxis rickiana and the seed-feeding weevil Apteromechus notatus as prospective agents