Oyster Survival Research Articles

Intertidal Grow-Out Technique, Not Eelgrass (Zostera marina), Influences Performance of Pacific Oysters (Magallana gigas)

Colocation of farmed shellfish in seagrass, although not permitted in some regions of the USA, has been proposed as a means to reach cobenefits of habitat and food production. Seagrass could benefit bivalves through protection from predation or abiotic stressors but conversely can reduce water flow and food delivery. At 10 farm sites in Washington state (USA), we tested the performance of Pacific oysters (Magallana (Crassostrea) gigas) grown in ground culture or off-bottom culture across a range of seagrass densities. Oysters averaged 32 m−2 and 30% shell cover on ground culture beds. Oysters in off-bottom culture showed a negative relationship between size and density across beds, consistent with growth and mortality through the crop cycle, and the largest oysters were at densities similar to ground culture. Within each farm site, ground and off-bottom beds were selected with each of three categories of seagrass (none, sparse, dense). Dense seagrass on aquaculture beds was half the density of nearby unfarmed seagrass beds. For outplanted oysters over 3–9 months, many aspects of oyster performance improved when oysters were elevated above the sediment. Relative to ground culture, off-bottom oysters had better survival (85% vs. 69%), 7% larger size, and 48% higher condition after 3 months in summer, and the survival advantages persisted over winter. Oyster survival on-bottom was especially impaired in finer sediment. No oyster performance differences were associated with seagrass, except for 9-month results, available for five of 10 farms. After 9 months at these five farms, oyster survival showed a small negative effect of dense seagrass, and shell size showed a small positive effect of sparse seagrass. Consequently, seagrass may not provide a boost to colocated intertidal shellfish, but we found little evidence of trade-offs in which maintaining seagrass would reduce yield of farmed oysters. Moving oysters out of the boundary layer and away from soft sediment improves both survival and tissue growth aspects of yield.

Defence mechanisms of Pinctada fucata martensii to Vibrio parahaemolyticus infection: Insights from proteomics and metabolomics

Survival of pearl oysters is not only challenged by coastal pollution, but also pathogen infection that may eventually incur substantial economic losses in the pearl farming industry. Yet, whether pearl oysters can defend themselves against pathogen infection through molecular mechanisms remains largely unexplored. By using iTRAQ proteomic and metabolomic analyses, we analysed the proteins and metabolites in the serum of pearl oysters (Pinctada fucata martensii) when stimulated by pathogenic bacteria (Vibrio parahaemolyticus). Proteomic results found that a total of 2,242 proteins were identified in the experimental (i.e., Vibrio-stimulated) and control groups, where 166 of them were differentially expressed (120 upregulated and 46 downregulated in the experimental group). Regarding the immune response enrichment results, the pathway of signal transduction was significantly enriched, such as cytoskeleton and calcium signalling pathways. Proteins, including cathepsin L, heat shock protein 20, myosin and astacin-like protein, also contributed to the immune response of oysters. Pathogen stimulation also altered the metabolite profile of oysters, where 49 metabolites associated with metabolism of energy, fatty acids and amino acids were found. Integrated analysis suggests that the oysters could respond to pathogen infection by coordinating multiple cellular processes. Thus, the proteins and metabolites identified herein not only represent valuable genetic resources for developing molecular biomarkers and genetic breeding research, but also open new avenues for studies on the molecular defence mechanisms of pearl oysters to pathogen infection.

Impact of exposure temperature rise on mass mortality of tidal flat pacific oysters

Oysters are a major commercial and ecological fishery resource. Recently, the oyster industry has experienced mass mortality in summer due to environmental factors. Generally, the survival of oysters in aquatic environments is mainly impacted by environmental stressors such as elevated sea temperatures and reduced salinity; however, the stressors impacting tidal flat oysters that are repeatedly exposed to air remain poorly understood. Hence, we studied the relationship between environmental factors and the survival of tidal flat pacific oysters in Incheon, South Korea, where mass mortality is common. Principal component analysis and Bayesian networks revealed that air temperature (in spring and summer) and sea temperature (in summer) are related to oyster production. In habitats of the tidal flat oysters during the summer, high temperatures of 34.7–35.4°C (maximum 47.6°C) were observed for average durations of 0.8–1.9 hours (maximum 3.6 hours). Furthermore, heat waves occurred for up to 12 consecutive days. Results from the multiple stress test showed that when exposed to 45°C (air temperature) for 4 hours per day, the survival rate of oysters was 42.5% after only 2 days and 0% after 6 days. The findings stemming from the field observations and stress tests suggest that high temperatures during emersion may contribute to mass mortality of oysters in summer, indicating a potential threat to oysters due to climate change. To understand the effects of future thermal stress on oysters more accurately, simultaneous long-term trend analyses and field-based observations are required.

The comparative growth and survival of juvnile tropical oyster (Magallana bilineata, Roding, 1798) using different intensive nursery systems

The comparative growth and survival of juvnile tropical oyster (Magallana bilineata, Roding, 1798) using different intensive nursery systems

Effects of different aquaculture patterns on growth, survival and yield of diploid and triploid Portuguese oysters (Crassostrea angulata)

Bivalve molluscs are increasingly being promoted as an alternative to land-based meat production due to their high levels of high-quality protein and lipids. The Crassostrea angulata, also known as the Portuguese oyster, has been a globally productive and renowned oyster species. In this study, we evaluated the aquaculture performance of C. angulata over two consecutive culture periods (pre-harvest phase, post-harvest phase) at different stocking densities and water depths, and compared the survival, growth and yield of diploid and triploid oysters. The experiment spanned 13 months, beginning in June 2022 and ending in June 2023. The results indicated that both stocking density and water depth significantly affected the aquaculture performance of C. angulata and exhibited distinct patterns in the two culture phases. Overall, compared to diploid C. angulata, triploid oysters showed significant culture advantages in the pre-harvest period, the growth rates and total yield of which were much higher than those of diploids. In the pre-harvest phase, the depth of 1 m and low-density culture (5 substrates/rope) favored the survival and growth of triploid oysters, while diploid C. angulata presented higher growth rates at high-density cultivation (15 substrates/rope), and the total oyster yield under 5 m culture reached a minimum for both diploids and triploids. In the post-harvest phase, the survival rate was stabilized, water depths of 1–3 m were optimal, and diploid oysters grew better at low (50 ind/cage) and medium (100 ind/cage) densities, whereas triploids had a higher growth rate of shell height at medium and high (150 ind/cage) densities. The findings of this research provide theoretical guidelines for exploring efficient C. angulata cultivation methods in the future, which will be beneficial to its commercial production.

Nursery upweller type has minimal impact on subsequent grow-out of Eastern oysters (Crassostrea virginica)

Demand for oysters in the premium half-shell market drives the need for research to optimize and improve oyster aquaculture production methods. After setting, oysters are typically maintained in nursery upwellers that provide nutrients and oxygen while removing waste. They remain in the nursery until they are large enough to be deployed in aquaculture gear. Land-based upweller systems include silo and bottle upwellers, with bottles requiring less space and maintenance. However, it is unknown if upweller type influences oyster growth, shape, or survival after field deployment. This study reared Eastern oysters, Crassostrea virginica, to 2 mm in silo or bottle upwellers and deployed them to floating bags for a six-week grow-out period. Oysters were sampled initially, then size graded, counted, and redeployed every two weeks. Changes in growth parameters, quality ratios, survival, and hinge backbend deformity prevalence were determined after six weeks. Initially, silo-reared oysters were larger than those reared in bottles, likely due to the need for flow rate optimization and/or the tumbling action that breaks the fragile growing edge of the shell. Despite these initial differences, there were minimal size differences between upweller types after six weeks of growth in the field. There were no significant differences in survival, hinge backbend abnormality prevalence, or size class distribution between upweller types. These results indicate that upweller choice has minimal impact on the grow-out phase of oyster production and both systems are acceptable for Eastern oyster production in the northern Gulf of Mexico.

Submarine groundwater discharge interacts with creek geomorphology to affect eastern oyster Crassostrea virginica growth rates in a coastal Georgia creek.

Eastern oysters, Crassostrea virginica, are commercially important coastal species that provide many ecosystem services for coastal communities. Unfortunately, 85% of oyster reefs have been lost globally, prompting investments in restoration efforts to rebuild populations. Managers often consider several well-studied environmental and water quality parameters when making restoration site decisions. However, recent research suggests that submarine groundwater discharge (SGD) may play a role in driving the distribution of oysters in some estuaries. Specifically, SGD may result in localized areas of low dissolved oxygen and low pH that could inhibit oyster recruitment and survival. However, SGD may interact with other potential oyster stressors, including creek geomorphology. On point bars, sediment accumulation could alter growth rates of oysters and physiology, and it is possible that the two factors, SGD and creek geomorphology, could interact to impact oyster growth. We conducted a field experiment to examine the effects of SGD and creek geomorphology on oyster growth rates in a marsh-lined tidal creek in Georgia, USA. High and low SGD sites were paired within point bars and cut banks. Oysters were deployed in cages for 72 days and growth rates were determined. We found a significant interaction between SGD and creek geomorphology on oyster growth rates. Oysters grew at significantly faster rates at locations on accretionary point bars regardless of SGD flux, whereas, on erosional cut banks, high SGD flux significantly reduced oyster growth rate relative to low SGD flux. It appears that SGD may negatively influence oyster growth at specific creek locations, likely due to the presence of other stressors. Therefore, it is important to consider potential interacting and confounding stressors when managing oyster populations. As SGD is still a relatively understudied potential stressor for oysters, it is critical to continue to examine how groundwater might influence oysters in other locations and in combination with other stressors. Regardless, this study provides further evidence that SGD should be considered in future management efforts.

Genome architecture and selective signals compensatorily shape plastic response to a new environment

Transcriptional plasticity interacts with natural selection in complex ways and is crucial for the survival of species under rapid climate change. How 3D genome architecture affects transcriptional plasticity and its interaction with genetic adaptation are unclear. We transplanted estuarine oysters to a new environment and found that genes located in active chromatin regions exhibited greater transcriptional plasticity, and changes in these regions were negatively correlated with selective signals. This indicates a trade-off between 3D active regions and selective signals in shaping plastic responses to a new environment. Specifically, a mutation, lincRNA, and changes in the accessibility of a distal enhancer potentially affect its interaction with the ManⅡa gene, which regulates the muscle function and survival of oysters. Our findings reveal that 3D genome architecture compensates for the role of genetic adaptation in environmental response to new environments and provide insights into synergetic genetic and epigenetic interactions critical for fitness-related trait and survival in a model marine species.

Phenotypic evaluation of two genetically improved strains selected from the reciprocal hybrids of Crassostrea gigas and C. angulata

The Pacific oyster (Crassostrea gigas) is one of the most economically important aquaculture shellfish in China, but further development of its industry is constrained by germplasm degradation and summer mass mortality episodes. To this end, a three-generation mass selection on the reciprocal hybrids, GA-C. gigas ♀ × C. angulata ♂ and AG-C. angulata ♀ × C. gigas ♂, was conducted to develop two strains (GA and AG selected strain) with fast-growing and warm-adapted characteristics. The aim of the present study was to determine whether the genetic improvement in growth, survival and thermal tolerance could be achieved by mass selection. For shell height, a genetic gain of 7.77–14.60%, a selection response of 0.67–0.91, and a realized heritability of 0.39–0.57 were observed in the selected strains after three generations of selection; for total weight, a genetic gain of 11.33–14.85%, a selection response of 0.73–1.06, and a realized heritability of 0.41–0.67 were observed in the selected strains after three generations of selection. The significant selection response of growth traits suggests the potential for genetic improvement of growth traits in both strains. With selection, the LT50 increased from 41.81 °C to 42.10 °C in the GA selected strain and from 41.61 °C to 42.06 °C in the AG selected strain. By the F3 generation, the summer survival rates of the GA and AG selected strain were 10.53% and 8.98% higher than that of the control strain, respectively, and 20.80% and 18.14% higher than that of the C. gigas strain, respectively. The consistent results of LT50 and summer survival suggest that thermotolerance selection may provide a viable strategy for improving summer survival in oysters. After three generations of selection, the total yield of the two strains increased by 29.63% and 19.78%, respectively, compared to C. gigas strain. This study provides a source of superior strains for the sound development of the oyster industry and can be used as a reference for shellfish breeding strategies.

Induced defenses as a management tool: Shaping individuals to their environment

Many prey species can adjust morphology to reduce predation risk in response to predator cues. Enhancing prey defenses using predator cues may improve survival of cultivated species and enhance species restoration efforts, but assessment of such benefits at industrially relevant scales is needed. We examined how raising a model foundation species, oysters (Crassostrea virginica), under commercial hatchery conditions with cues from two common predator species can improve survival across a variety of predator regimes and environmental conditions. Oysters responded to predators by growing stronger shells than controls, but had subtle variations in shell characteristics depending on the predator species. Predator-induced changes significantly increased oyster survival up to 600% and survivorship was maximized when cue source was matched with local predator regime. Overall, our findings demonstrate the utility of using predator cues to enhance the survival of target species across landscapes and highlight the opportunity to employ nontoxic methods to control pest-based mortality.

Growth performance and survival of oyster, Saccostrea cucullata (Born, 1778) and green mussel, Perna viridis (Linnaeus, 1758) cultivated in Bangladesh Coast

Oyster and mussel farming along the coasts and the desire to increase fishing revenue have created a boom in these types of farms. An experiment on culture of edible oyster (Saccostrea cucullata) and green mussel (Perna viridis) was performed at Gangamoti estuary in Kuakata, Bay of Bengal coast of Bangladesh from December 2021 to March 2022 to find out the appropriate culture method of the oyster, S. cucullata and green mussel, P. viridis. Initially, the average shell heights of S. cucullata and P. viridis were 8.8±1.62 and 6.9±1.89 cm, respectively; where average weights were153.4±13.23 and 84.78±11.78 g, respectively. After the culture period, oysters shell height and weight grew up to 9.1±1.98 cm and 163.2±12.54 g, respectively in rectangular basket and 8.9±1.45 cm and 157.2±11.31 g, respectively in velon screen bag. In case of oysters, the rectangular basket and velon screen bag displayed the minor progress in specific growth rate, 0.09±0.01 and 0.07±0.03, respectively. But green mussels did not show any growth rate. Oysters cultured in rectangular basket showed total mortality at day-90 and velon screen bag at day-75. Green mussels showed 100% mortality within 21 days of culture. Our experiment was the first attempt to culture these two mollusks in the Kuakata coast of Bangladesh. However, further intensive researches would be required to evaluate the culture feasibility of these two mollusks’ species in the Kuakata coast of Bangladesh.

Grow-out Culture of Oyster Magallana bilineata (Röding, 1798) Using Pouches: A Comparison of Growth and Survival in the River and Earthen Pond

Oysters are among the most in-demand aquaculture commodities in the Philippines and worldwide. With the decreasing culture area and the deteriorating water quality of oyster beds, there is a need to explore new culture sites and techniques to address the problems of dwindling stocks and the increasing demand for better quality oysters. This study compared the growth and survival of the oysters Magallana bilineata, the new accepted name of Crassostrea iredalei, cultured in an earthen pond and the river using pouches suspended from rafts. Mean growth rates of oysters in length and weight were significantly higher in those reared in the river (0.56 ± 0.02 cm mo-1; 10.27 ± 0.42 g mo-1) than those in the pond (0.41 ± 0.03 cm mo-1; 5.99 ± 0.22 g mo-1), but the meat yield of oysters reared in the river (25.96 ± 0.92%) was almost the same as in the pond (24.05 ± 1.41%). Likewise, the proximate composition was the same for oysters coming from the river and the pond, respectively, 58.04 ± 0.14% and 53.86 ± 0.38% crude protein, 7.00 ± 0.08% and 7.93 ± 0.38% crude fat, 24.68 ± 0.07% and 28.54 ± 0.74% nitrogen-free extract, and 10.27 ± 0.01% and 9.68 ± 0.01% ash. Oyster survival at harvest was significantly higher in the river (70.21 ± 2.84%) than in the pond (13.10 ± 1.57%). However, with some interventions, ponds may still be utilized for oyster culture despite the low survival results in this study. Extending oyster culture in these aquaculture facilities may serve as a basis for interventions to make the pond more habitable for oysters and may help boost production in the country.

High temperature aggravates mortalities of the Pacific oyster (Crassostrea gigas) infected with Vibrio: A perspective from homeostasis of digestive microbiota and immune response

Long-lasting high temperature and bacterial exposure are two critical environmental factors contributing to the mass mortality of oysters in summer. In this study, we investigated the effects of high-temperature exposure and Vibrio alginolyticus infection on the mortality of the Pacific oysters, Crassostrea gigas. The results of survival experiment demonstrated that the overall survival of Vibrio-infected oysters was significantly reduced at high-temperature stress. The 16S rRNA amplicon sequencing showed that high temperature significantly disrupted the structure of the infected oyster's digestive gland microbiota and increased the abundance of potentially pathogenic bacteria. Transcriptome profiling showed that expression of critical genes associated with inflammation was suppressed in the early phase of infection but was induced in the later phase. In contrast, genes related to apoptosis and oxidative stress were continuously upregulated, indicating that homeostasis of inflammatory response was maintained in the early phase but was eventually destroyed upon continuous high temperature exposure. This work is of practical significance for deciphering the cause of oyster mortality in summer and monitoring disease outbreaks in the oyster culture.

RGO-PDMS Flexible Sensors Enabled Survival Decision System for Live Oysters.

The shell-closing strength (SCS) of oysters is the main parameter for physiological activities. The aim of this study was to evaluate the applicability of SCS as an indicator of live oyster health. This study developed a flexible pressure sensor system with polydimethylsiloxane (PDMS) as the substrate and reduced graphene oxide (rGO) as the sensitive layer to monitor SCS in live oysters (rGO-PDMS). In the experiment, oysters of superior, medium and inferior grades were selected as research objects, and the change characteristics of SCS were monitored at 4 °C and 25 °C. At the same time, the time series model was used to predict the survival rate of live oyster on the basis of changes in their SCS characteristics. The survival times of superior, medium and inferior oysters at 4 °C and 25 °C were 31/25/18 days and 12/10/7 days, respectively, and the best prediction accuracies for survival rate were 89.32%/82.17%/79.19%. The results indicate that SCS is a key physiological indicator of oyster survival. The dynamic monitoring of oyster vitality by means of flexible pressure sensors is an important means of improving oyster survival rate. Superior oysters have a higher survival rate in low-temperature environments, and our method can provide effective and reliable survival prediction and management for the oyster industry.

Evaluation of Moringa oleifera and corn starch as feed for seed production of the pearl oyster Pteria sterna (Gould,1851)

In the search for complementary diets to improve performance in bivalve farming, the use of terrestrial plants with nutritional and nutraceutical properties has been proposed as an alternative. The effectiveness of moringa leaf meal Moringa oleifera (Mo) was evaluated under controlled laboratory conditions (30 days), as a dietary supplement during the pre-growth stage of Pteria sterna seeds (7.2 ± 0.59 mm), as well as its combinations with microalgae and corn starch (Co), on growth and survival in the laboratory and its subsequent initial suspended culture in the sea. Diets were formulated with a mixture of the microalgae Tetraselmis suecica and Chaetoceros gracilis (M), diet M; M and 5% Mo (M + Mo); diet M and 5% corn starch (M + Co); 100% moringa leaf meal (Mo); 100% corn starch (Co), and diet M with 2.5% Mo and 2,5% Co (M + Mo + Co). The Mo diet did not provide pre-seed sustainability, resulting in 100% mortality at 30 days. From the rest of the diets, M obtained the lowest oyster survival, while M + Mo and M + Mo + Co showed the highest growth rates. At the end of the laboratory bioassay, the seeds were sown in a culture system in the open sea (50 days), where the highest growth occurred in the juveniles previously fed with M + Mo + Co. The results suggest that, in the nursery, P. sterna pre-seeds can be maintained with a diet of 100% corn starch, but not with 100% moringa flour, probably due to its poor digestibility. However, moringa used as an additive to the microalgae diet provided a higher yield in the oyster, which is reflected in a higher yield in the initial culture outdoors.

Bonamia-free flat oyster (Ostrea edulis L.) seed for restoration projects: non-destructive screening of broodstock, hatchery production and test for Bonamia-tolerance

Native (flat) oyster (Ostrea edulis) beds, once a major component of the North Sea, largely disappeared from the region in the late 19th century. Flat oyster restoration is taking place at a number of locations in the North Sea. When flat oyster beds are restored in areas where O. edulis is functionally extinct it is advised to treat these as disease-free areas. Adult oysters were collected in the Dutch Delta area which is infected with the pathogenic parasite Bonamia ostreae. The aim of this research was to obtain Bonamia-free seed from parents collected in a Bonamia-infected area. In addition, the oysters were analysed to identify candidate genomic regions related to bonamiosis tolerance and exposed to Bonamia in the field to assess survival compared to a naïve control group. With the aid of a non-destructive screening method, Bonamia-free broodstock were selected. These oysters produced Bonamia-free larvae and seed. For comparison, broodstock oysters were collected in the Dutch Wadden Sea, an area free of Bonamia. These oysters also produced Bonamia-free larvae and seed. To study if the Delta area oysters had developed a degree of resistance to the disease, while the naïve Wadden Sea oysters had not, seed of both groups was challenged in Lake Grevelingen where Bonamia occurs. Survival of the pre-selected Bonamia-free oysters was significantly higher than the naïve group. Samples of seed were analysed for association of candidate genetic markers related to bonamiosis tolerance. A higher percentage of individuals with tolerance-associated marker genotypes was found in the screened group compared to the naïve one. However, mortality of the naïve group could not be related to Bonamia presence. Further challenge tests are needed before firm conclusions regarding the genetic markers can be made. The results show that hatchery production of Bonamia-free and potentially Bonamia-tolerant flat oysters is possible.

Genetic parameters and response to selection for thermal tolerance, summer survival and growth in hybrid oyster (Crassostrea gigas ♀ × C. angulata ♂)

The Pacific oyster Crassostrea gigas is the most commonly farmed mollusks worldwide, while its production has been hindered by massive mortalities linked to high temperatures. Selective breeding focusing on thermal tolerance is an attractive option for reducing the impact of massive mortalities, but the genetic basis underlying this trait is currently unknown. Hybridization between C. gigas and C. angulata was conducted and followed by one generation of family selection for thermal tolerance. The genetic parameters for thermal resistance, summer survival and growth and selection response were investigated by using 50 full-sibling families. The mean survival of all families ranged from 30.2 to 69.5%, reflecting the large variation of thermal tolerance in the hybrid population. The estimates of heritability for thermal tolerance were low to moderate, ranging from 0.19 ± 0.03 to 0.27 ± 0.05, confirmed that there is genetic basis for thermal tolerance. The phenotypic (r = 0.537, P < 0.01) and genetic correlations (r = 0.546, P < 0.01) between thermal tolerance and summer survival were positive and significant, while the phenotypic and genetic correlations between growth and survival (including thermal tolerance and summer survival) were positive but low (P > 0.05). High response to selection (ΔG = 36.33%) was observed after one generation of selection for thermal tolerance, and there was also corresponding response (ΔG = 14.46%) for summer survival. These results demonstrated that genetic selection to improve summer survival of oyster may be facilitated by selecting highly heat-tolerant lines.

Interactive effects of Louisiana Sweet Crude (LSC) thin oil sheens and ultraviolet light on mortality and swimming behavior of the larval Eastern oyster, Crassostrea virginica

The Eastern oyster (Crassostrea virginica) is an important commercial bivalve species which also has numerous ecological roles including biogeochemical cycling, providing habitat for larval fish and crustaceans, and reducing the impacts of coastal storms. Oil may pose a threat to oyster larvae swimming in the water column, leading to potential negative effects on survival, growth, and development. Oil toxicity may be further enhanced by chemical changes in the presence of sunlight. This study determined the toxicity of thin oil sheens with and without ultraviolet (UV) light, then examined the latent effects of the short term exposure on longer term survival and swimming ability. Larval C. virginica were exposed to four different oil sheen thicknesses for 24 h with either no UV light or 2-h UV light. Following the exposure, larvae were transferred to clean seawater and no UV light for 96 h. The presence of a 2-h UV light exposure significantly increased oyster mortality, indicating photo-enhanced toxicity. The LC50 for a 24-h oil sheen exposure without UV was 7.26 µm (23 µg/L PAH50) while a 2 h-UV exposure lowered the sheen toxicity threshold to 2.67 µm (10 µg/L PAH50). A previous 24-h oil sheen exposure (≥0.5 µm) led to latent effects on larval oyster survival, regardless of previous UV exposure. Sublethal impacts to larval oyster swimming behavior were also observed from the previous oil sheen exposure combined with UV exposure. This study provides new data for the toxicity of thin oil sheens to a sensitive early life stage of estuarine bivalve.

Development and evaluation of a rapid, specific, and sensitive loop-mediated isothermal amplification assay to detect Tenacibaculum sp. strain pbs-1 associated with black-spot shell disease in Akoya pearl oysters

Black-spot shell disease decreases pearl quality and threatens pearl oyster survival. Establishment of a rapid, specific, and sensitive assay to detect Tenacibaculum sp. strain Pbs-1 associated with black-spot shell disease is of commercial importance. We developed a rapid, specific, and highly sensitive loop-mediated isothermal amplification (LAMP) assay to detect Tenacibaculum sp. Pbs-1 in Akoya pearl oysters Pinctada fucata. A set of five specific primers (two inner, two outer, and a loop) were designed based on the 16S-23S internal spacer region of strain Pbs-1. The optimum reaction temperature was 63°C, and concentrations of the inner and loop primers were 1.4 and 1.0µM, respectively. The LAMP product can be detected using agarose gel electrophoresis, and the color change in the reaction tube can be detected visually (by the naked eye) following the addition of malachite green. Our assay proved to be specific for strain Pbs-1, with no cross-reactivity with five other species of Tenacibaculum. The detection limit of the LAMP assay at 35min is 50pg, and at 60min it is 5fg. We evaluated the LAMP assay using diseased and healthy pearl oysters. The results demonstrate the suitability and simplicity of this test for rapid field diagnosis of strain Pbs-1.

Life‐stage‐dependent effects of multiple flood‐associated stressors on a coastal foundational species

AbstractGlobal changes in precipitation patterns have increased the frequency and duration of flooding events. Freshwater inflows into estuaries reduce salinity levels and increase nutrient inputs, which can lead to eutrophication and impaired water quality. Oysters are important ecosystem engineers in coastal environments that are vulnerable to co‐occurring environmental stressors associated with freshwater flooding events. Successful recruitment is necessary to maintain adult oyster populations, but early life stage responses to multiple stressors are not well understood. Flood‐associated stressor conditions were observed near oyster habitats at multiple locations across the northern Gulf of Mexico during peak recruitment months in the spring and summer of 2021. In the laboratory, we examined the interactive effects of acidification, hypoxia, and low salinity on larval and juvenile life stages of the eastern oyster (Crassostrea virginica) to better understand the impact of flooding events on oyster development and survival. Salinity stress in isolation reduced larval growth and settlement, and decreased survival and growth at the juvenile stage. Hypoxia was more stressful to oyster larvae than to juveniles, whereas low pH had negative effects on juvenile growth. There were no synergistic effects of multiple flood‐associated stressors on early oyster life stages and effects were either additive or predicted by the salinity stress response. The negative impacts of flooding disturbances on recruitment processes in benthic populations need to be considered in restoration planning and flood control mitigation strategies as the frequency and intensity of extreme freshwater events continue to rise worldwide.