Clam Farming Research Articles

Outcomes of participatory ergonomics and self-management in commercial clam farmers with chronic low back pain: a feasibility study

ABSTRACT Purpose : Participatory ergonomics engages workers in the development of strategies to reduce to workplace-related pain, offering a flexible and practical option to create individualized context-specific strategies. This paper describes the outcomes of a feasibility study using a participatory approach for self-management of low back pain in clam farmers. Methods : A within-subject time-control design with repeated baseline and post-intervention assessment was used. After refining individual and team-based strategies, stakeholder interviews, and rapid prototyping, workers selected three strategies to use for 8 weeks. Frequency and ease of use for strategies are described. Pre-post paired t-tests were used for analysis of pain-related disability, difficulty and pain with work tasks, pain-related-fear, self-efficacy, and coping. Analysis of improvements exceeding published and individual variability was calculated. Results : Participants chose both team and individual strategies, most using strategies 5 days a week >50% of the time. Significant improvements for pain-related disability, pain during specific tasks, pain-related anxiety, and coping were seen after 8 weeks of implementing strategies. No changes in task difficulty, fear, self-efficacy and average resting pain were reported. Pain improvements > MDC95 were reported by 74% with 56-64% > personalized MDC95 for lifting tasks. Conclusions : Pain-related disability, work activity pain ratings and related pain anxiety and coping improved beyond individual variability in this feasibility study. Multiple strategies allowed workers to choose relevant self-management options. Introduction of work-related changes in the workplace, visual demonstration, review of team videos and reminders were helpful. Further studies of this approach are needed.

Functional characterization of a putative tumor necrosis factor superfamily member 10 in blood clam (Tegillarca granosa)

Tumor necrosis factor superfamily member 10 (TNFSF10), also known as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or Apo-2L, is one of the important members of the TNF superfamily. It is well demonstrated that TNFSF10 preferentially induces a variety of tumor cell apoptosis, and therefore exerts an important role in tumor immune surveillance. However, the function of TNFSF10 in pathogen defense is poorly understood, especially in invertebrates. The blood clam (Tegillarca granosa), an important commercial marine bivalve, plays an important ecological role in the marine ecosystem. The identification of immune genes will provide new perspective for disease control in the blood clam (T. granosa) farming. To better understand the biological function of TNFSF10 protein, the full-length cDNA of TNFSF10 homologous gene of T. granosa (TgTNFSF10) was cloned and identified for the first time, which was found to contain 1239 base pairs and encode 254 amino acids with a molecular weight of 29.5 kDa and a conserved TNF domain in the C-terminal. Quantitative RT-PCR analysis showed that TgTNFSF10 gene was constitutively expressed in all tested tissues, with the highest expression in hemocytes. LPS, Vibrio alginolyticus and Vibrio parahaemolyticus stimulations dramatically increased the expression of TgTNFSF10 in T. granosa (11.47-fold, 3.71-fold and 8.29-fold compared with the control respectively). In vitro experiments showed that recombinant TgTNFSF10 protein strongly inhibited the proliferation of HepG2 cells. Further confocal microscopy and flow cytometry analysis showed that obvious apoptosis occurred in TgTNFSF10-treated hemocytes and HepG2 cells. To sum up, our study demonstrated that TgTNFSF10 had strong apoptosis-inducing activity, which may participate in the innate immune response of T. granosa to pathogen invasion.

Antibiogram of Escherichia coli isolated from semi-closed system farmed Asian clam (Corbicula fluminea)

In the present study, antibiogram of Escherichia coli isolated from farmed Asian clam, Corbiculafluminea was characterised. Asian clam or locally known as ‘etak’ is processed to became smokedclam and consumed as snack by Kelantanese. However, there are many diarrhoea cases afterconsuming smoked clam. Furthermore, there are also insufficient information about the E.coli levelin Asian clam farm and effective antibiotic in controlling the bacteria in the litereature. Hence, thisstudy was carried out to provide information of antibiogram of E.coli to be reference in the future.Eosin Methylene Blue agar (EMB) was used to isolate E. coli. A total of 100 isolated bacteria weresubjected to antibiotic sensitivity test using disk diffusion method. A total of 18 types of antibioticsnamely novobiocin (30µg/disk), fosfomycin (50 µg/disk), tetracycline (30µg/disk), lincomycin(15µg/disk), flumequine (30µg/disk), sulphamethoxazole (25 µg/disk), amoxycillin (25 µg/disk),chloramphenicol (30 µg/disk), oleandomycin (15 µg/disk), spiramycin (100 µg/disk), ampicillin(10 µg/disk), oxytetracycline (30 µg/disk), doxycycline (30 µg/disk), nalidixic acid (30 µg/disk),florfenicol (30 µg/disk), erythromycin (15 µg/disk), kanamycin (30 µg/disk) and oxolinic acid (2µg/disk). The findings of the present study showed total plate count of E. coli was 6.45 x 103 colonyforming unit (CFU/100g) of sampled Asian clam. Hence, the clam is needed to be under cleansingtreatment before can consider safe for human consumption. Antibiotic results showed 51 % wasrecorded as antibiotic resistance case, 44 % antibiotic sensitive case and 5 % as antibioticintermediary sensitive case. None of the tested antibiotics was successfully inhibited the growth ofthe present bacterial isolates indicating more antibiotics are needed to be screen in the future studyto find out the most effective antibiotic in controlling isolated E. coli.

Chronic lower back pain in aquaculture clam farmers: adoption and feasibility of self-management strategies introduced using a rapid prototype participatory ergonomic approach

Objectives. Lower back pain (LBP) is extremely prevalent in seafood harvesters who often have limited or no access to ergonomic consultation, occupational health support and rehabilitation services. This pilot study aimed to describe a participatory ergonomic approach and determine the feasibility and extent of adoption of self-management strategies in clam farmers with LBP. Methods. A rapid prototype participatory ergonomic approach was used to develop context-specific self-management strategies. Options to adjust lifting and repetitive stress were introduced using video clips, demonstrations and discussions in the workplace. Workers chose and implemented three strategies for 8 weeks with weekly reminders. Survey and qualitative data from focus groups were analyzed. Results. Team strategies were the most popular, but individual options were used more often. Strategies were considered feasible, acceptable and relatively easy to use. Strategies were implemented relatively consistently, and most improved productivity with decreased pain. Challenges for uptake included changing habit, culture and team dynamics. Conclusions. Participatory rapid prototyping provided a feasible and efficient option to introduce strategies for clam farmers with small teams, variable work processes and workloads, and time restrictions. Strategies were considered acceptable and easy to use, and most increased productivity. These methods show potential for future research.

Building Structure Mapping on Level Terrains and Sea Surfaces in Vietnam

Mapping building structures is crucial for environmental change and impact assessment, and is especially important to accurately estimate fossil fuel CO2 emissions from human settlements. In this regard, the objective of this study is to develop novel and robust methods using time-series data acquired from Sentinel-1 synthetic aperture radar (SAR) to identify and map persistent building structures from coastal plains to high plateaus, as well as on the sea surface. From annual composites of SAR data in the two-dimensional VV-VH polarization space, we determined the VV-VH domain for detecting building structures, whose persistence was defined based on the number of times that a pixel was identified as a building in time-series data. Moreover, the algorithm accounted for misclassified buildings due to water-tree interactions in radar signatures and due to topography effects in complex mountainous landforms. The methods were tested in five cities (Bạc Liêu, Cà Mau, Sóc Trăng, Tân An, and Phan Thiết) in Vietnam located in different socio-environmental regions with a range of urban configurations. Using in-situ data and field observations, we validated the methods and found that the results were accurate, with an average false negative rate of 10.9% and average false positive rate of 6.4% for building detection. The algorithm could also detect small houses in rural settlements and in small islands such as in Hòn Sơn and Hòn Tre. Over sea surfaces, the algorithm effectively identified lines of power poles connecting islands to the mainland, guard shacks in marine blood clam farms in Kiên Giang, individual wind towers in the off-shore wind farm in Bạc Liêu, and oilrigs in the Vũng Tàu oil fields. The new approach was developed to be robust against variations in SAR incidence and azimuth angles. The results demonstrated the potential use of satellite dual-polarization SAR to identify persistent building structures annually across rural–urban landscapes and on sea surfaces with different environmental conditions.

Downscaling With an Unstructured Coastal-Ocean Model to the Goro Lagoon and the Po River Delta Branches

The Goro Lagoon Finite Element Model (GOLFEM) presented in this paper concentrates on the high-resolution downscaled model of the Goro Lagoon, along with five Po river branches and the coastal area of the Po delta in the northern Adriatic Sea (Italy) where crucial socio-economic activities take place. GOLFEM was validated by means of validation scores (bias – BIAS, root mean square error – RMSE, and mean absolute error – MAE) for the water level, current velocity, salinity and temperature measured at several fixed stations in the lagoon. The range of scores at the stations are: for temperature between −0.8 to +1.2°C, for salinity from −0.2 to 5 PSU, for sea level 0.1 m. The lagoon is dominated by an estuarine vertical circulation due to a double opening at the lagoon mouth and sustained by multiple sources of freshwater inputs. The non-linear interactions among the tidal forcing, the wind and the freshwater inputs affect the lagoon circulation at both seasonal and daily time scales. The sensitivity of the circulation to the forcings was analyzed with several sensitivity experiments done with the exclusion of the tidal forcing and different configurations of the river connections. GOLFEM was designed to resolve the lagoon dynamics at high resolution in order to evaluate the potential effects on the clam farming of two proposed scenarios of human intervention on the morphology of the connection with the sea. We calculated the changes of the lagoon current speed and salinity, and using opportune fitness indexes related to the clams physiology, we quantified analytically the effects of the interventions in terms of extension and persistence of areas of the clams optimal growth. The results demonstrate that the correct management of this kind of fragile environment relies on both long-term (intervention scenarios) and short-term (coastal flooding forecasts and potential anoxic conditions) modeling, based on a flexible tool that is able to consider all the recorded human interventions on the river connections. This study also demonstrates the importance of designing a seamless chain of models that are capable of integrating local effects into the coarser operational oceanographic models.

Traceability and Authentication of Manila Clams from North-Western Adriatic Lagoons Using C and N Stable Isotope Analysis.

In the Adriatic lagoons of northern Italy, manila clam (Ruditapes philippinarum) farming provides important socio-economic returns and local clams should be registered with the Protected Designations of Origin scheme. Therefore, there is a need for the development of rapid, cost-effective tests to guarantee the origin of the product and to prevent potential fraud. In this work, an elemental analysis (EA) coupled with isotope ratio mass spectrometry (IRMS) was employed to identify the isotopic fingerprints of clams directly collected onsite in three Adriatic lagoons and bought at a local supermarket, where they exhibited certification. In particular, a multivariate analysis of C/N, δ13C and δ15N in manila clam tissues as well as δ13C in shells and 13C (calculated as δ13Cshell–δ13Ctissues) seems a promising approach for tracking the geographical origin of manila clams at the regional scale.

The Farming Models Adapting to Climate Change in the Eastern Coastal Area of the Mekong River Delta, Vietnam

The Eastern coastal area of the Mekong River Delta has distinctly ecological zones and a potentiality for development of agriculture, forestry and fishery according to their ecological characteristics. The farmer life is mainly depending on exploiting agriculture, aquaculture and there are many supporting the development of social-economics in delta. However, the recent years, farming rice, vegetables, crops, fruit trees and raising shrimp, hard clam as well have heavily affected by drought and salt intrusion due to climate change. This has leaded to decrease the agricultural, fishery yield and the farmer’s income, therefore, the farmer’s life in the Eastern coastal area faces to the difficulties. The previous farming models are necessary to alter and this is a significant solution to minimize the risk and to cope the climate change such as farming system changes, to sustain agricultural production or transformation to alternative systems and combination between the rotational rice-shrimp-crops farming models following the season. Thus, the study proposes the farming models that can be suitable for the Eastern coastal locals of Mekong river delta. On the basis of document synthesis of natural characteristics, morpho-sedimentology, soil, vegatation cover, innundation, salinity, tidal water level indicating ecology and traditional farming, the study has given a general ecological model for the Eastern coastal area (Mekong Delta) to adapt to the climate change context. The general farming model including five models are clam farming, mangrove forest- shrimp farming, vegetables and fruit trees farming, rotational farming of rice, and rice- vegetables, and Rotation farming rice- shrimp, fruit- shrimp and fishes.

A Case of Hepatitis A Virus Detection in River Water Flowing into Tidal Flats

In 2019, an outbreak of hepatitis A was reported in South Korea due to the ingestion of salted shellfish contaminated with hepatitis A virus. In a survey of the contamination of salted shellfish, hepatitis A virus (HAV) type IA was detected, and it was confirmed that it originated from clams produced in one of the clam farms located in the western parts of the country. The aim of this study was to determine the cycle of human infection by HAV contaminating the water flowing into the environment. We selected a clam farm that is one of the largest producers of clams in South Korea and tested for the presence of HAV in the river water flowing directly into the vicinity of that farm. An HAV detection test was performed on river water collected from 15 points in three areas of the selected clam farm. HAV was detected in one sample of the collected river water, and its genotype was confirmed as IA, which is the most common genotype causing infection in humans and the same genotype that is prevalent in South Korea. We confirmed that the HAV released via infection in humans contaminated the tidal flats through the river. This result might be a good example of the cycle of infection of HAV in the environment.

Bioaccumulation of trace elements in the hard clam, Meretrix lyrata, reared downstream of a developing megacity, the Saigon-Dongnai River Estuary, Vietnam.

A large number of white hard clam farms are in the estuary shoreline of Saigon-Dongnai Rivers, which flow through Ho Chi Minh City, a megacity, and numerous industrial zones in the basin catchment area. In this study, eleven trace elements (Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Hg, and Pb) in the hard clam Meretrix lyrata and its habitats including surface water, suspended particulate matter, and sediment were evaluated to understand the bioaccumulation of trace metals from the environment into the whole tissues of the hard clam as well as its different organs. The samples were collected monthly in dry, transition, and wet seasons of the southern part of Vietnam from March to September 2016. The results showed that seasonal and spatial variations of the studied metal concentrations in the hard clam M. lyrata might be influenced by the sea current as well as the surface runoff in the rainy season. The relationship between condition index and the element concentrations in M. lyrata might be affected by the living environment conditions and farming methods. In addition, the hazard index values of all trace elements in the hard clam M. lyrata harvested in the sampling time show that the hard clams farmed in the study area were safe for local consumers.

Life Cycle Assessment (LCA) Proves that Manila Clam Farming (Ruditapes Philippinarum) is a Fully Sustainable Aquaculture Practice and a Carbon Sink

Manila clam (Ruditapes philippinarum, Adams and Reeve, 1850) farming is a quantitatively important and valuable form of aquaculture production worldwide but, to our best knowledge, no life cycle assessments (LCA) have been undertaken on it. However, being a filter feeder and producing a thick shell during the growing cycle, the capacity of Manila clam to remove nutrients, carbon, nitrogen and phosphorous from the marine environment potentially has some positive effects on the environment. This study was performed in the Sacca di Goro lagoon, located in the southernmost part of the Po River Delta, in the northwestern Adriatic Sea. The LCA of clam farming from a cradle-to-gate perspective have been carried out, including the production stages as seed procuring, sowing, harvesting, depuration and packaging to obtain 1 ton of fresh ready-to-sell clams. The results show that area preparation, fuel combustion and plastic bags were the main contributors to the environmental impacts. The potential capability as a carbon sink of 1 ton of clams has been calculated and the effects on eutrophication reduction by fixing nitrogen and phosphorous in shells, with a net sequestration of 444.55 kg of CO2, 1.54 kg of N and 0.31 kg of P per year.

Carbon budgets of two typical polyculture pond systems in coastal China and their potential roles in the global carbon cycle

The role of aquaculture systems in the global carbon cycle is poorly understood to date. We investigated the carbon budgets in 2 polyculture systems (PM: swimming crab Portunus trituberculatus with kuruma shrimp Marsupenaeus japonicus; and PMR: crab, shrimp and short-necked clam Ruditapes philippinarum) during the farming season (125 d in total). The main carbon input occurred via water (PM: 55.06%; PMR: 62.50%), followed by that via feed. PM absorbed 21.55 g C m-2 across the air-water interface, accounting for 13.27% of the total input. The carbon output via water was the main output in both PM (89.17%) and PMR (46.43%). PMR emitted 53.00 g C m-2 into the atmosphere during the farming season, accounting for 32.53% of the total output. The carbon output by harvested animals in PMR accounted for 19.48% of the total output, which was much higher than that in PM (5.71%). Carbon accumulation in the sediment was significantly higher in PM than in PMR (p < 0.05), but the value of both represented a small portion of the total output. Clam farming in the polyculture system profoundly altered the carbon budgets by changing the CO2 flux direction, reducing carbon accumulation in water and sediments and increasing the carbon output by harvested animals. In terms of the global warming potential, which was calculated from the results of CO2 and CH4 fluxes across the air-water interface, PM had the potential for mitigating the greenhouse effect on the 20 yr horizon, whereas PMR exacerbated global warming. Our results suggest that PM acted as a net carbon sink in the global carbon cycle, while PMR acted as a carbon source.

Effect of filter-feeding mollusks on growth of green macroalgae and nutrient cycling in a heavily exploited coastal lagoon

An increasing number of coastal lagoons are being exploited for intensive farming of bivalve filter-feeders. One of the most important farming sites in Europe for the Manila clam (Ruditapes philippinarum) is the Sacca di Goro lagoon (Po River Delta, Italy). Here, while on the one hand river runoff enhances high clam productivity, on the other hand it stimulates extensive blooms of green seaweeds of the genus Ulva. The latter can affect clams when macroalgal biomass collapses and decomposes. We hypothesized that the filtration of suspended particulate matter by farmed clams could enhance inorganic nitrogen and phosphorus recycling and simultaneously reduce phytoplankton biomass, thus facilitating macroalgal growth. An experiment simulating the effects of clams on early Ulva development was conducted over 7 days in outdoor flow-through mesocosms containing lagoon sediments with and without clams. On day 1, 3 and 7, macroalgal biomass and thallus elemental composition, water-dissolved nutrients and chlorophyll-a concentrations were recorded. On day 7, sediment-water nutrient fluxes were also measured on sediment cores sampled from each mesocosm. The presence of clams clearly stimulated Ulva growth and enhanced nutrient recycling rates. Furthermore, Ulva grown with clams had higher chlorophyll-a, nitrogen and phosphorus content. While sediments showed a net release of both soluble reactive phosphorus and ammonium when clams were present, in mesocosms without clams sediments constituted a sink for both dissolved inorganic phosphorus and nitrogen. Based on this evidence we can conclude that intensive clam farming over wide lagoon areas could significantly affect nutrient cycling, thus facilitating macroalgal blooms, with serious consequences for farming sustainability and for the functioning of the whole lagoon ecosystem.

Changes in oxidative stress biomarkers in Sinonovacula constricta in response to toxic metal accumulation during growth in an aquaculture farm

Clam farming comprises an important part of China’s economy. However, increasing pollution in the ocean caused by toxic metals has led to the bioaccumulation of toxic metals in marine animals, especially the bivalves such as clams, and the consequence of heavy metal-associated toxicity in these animals. Such toxicity can enhance the production of reactive oxygen species (ROS) within the tissues of the animals. In aquatic species, oxidative stress mechanisms have been studied by measuring the antioxidant and oxidative damage index in the tissues. The objectives of this study were to investigate the levels of different toxic metals and the extent of oxidative stress responses in the clam Sinonovacula constricta at different growth periods (from May to October) in an aquaculture farm in Wengyang, an important economic shellfish culture zone in Zhejiang Province, China. Water and sediment samples taken from the farm were subjected to Pb, Hg, Cd, Cr assays. Overall, the levels of these metals in the water and sediment could be considered as light pollution, though the levels of Hg in the water (0.266) and Cd in the sediment (0.813) could be considered as reaching moderate pollution. In addition, the levels of these metals, H2O2, MDA and GSH content, antioxidant enzyme (CAT, SOD, GPx) activities as well as the level of metallothioneins (MT) mRNA in the tissues of S. constricta were also analyzed. The levels of Pb, Hg, Cd, Cr increased with increasing culturing time, and a higher level of these metals was accumulated in the visceral mass than in the foot. The levels of MDA and GSH, as well as the level of SOD activity in the viscera and foot of S. constricta increased with increasing metal accumulation. However, CAT and GPX activities, H2O2 level and the expression of MT initially increased and then decreased. This suggested that S. constricta might have the ability to control oxidative damage by triggering antioxidant defense in coordination with the metal sequestering response. The results also implied that toxic metal pollution should be taken into account when selecting the site to be used as an aquaculture farm. In addition, the visceral mass should be considered to be a good tissue for measuring the level of metal pollutants.

Metagenome Sequences from the Environment of Diseased Otter Clams, Lutraria rhynchaena, from a Farm in Vietnam.

Otter clam farming in Vietnam has recently encountered difficulties due to swollen-siphon disease. Here, we report the metagenome sequences of microorganisms extracted from the siphon tissue of infected otter clams. The data comprised bacterial and viral sequences which likely include those derived from the disease-causing agent.

Improving Model of Hard Clam (Meretrix lyrata) Seed Nursing in the Coastal Area - Case Study in Tra Vinh Province, Mekong River Delta, Vietnam

The model of clam seed nursery in the coastal area of Tra Vinh province was carried out from June 2019 to February 2020 in the coastal dune and tidal flat in Thanh Dat Cooperative. The clam seed source is the natural seed harvested in the coast of Tra Vinh province with the goal of exploiting and using local resources to provide clam seeds for the cooperative clam farming. The model consists of two phases: the first phase of nursing is in ponds on the coastal dune and the second phase of nursing is on the tidal flat in natural condition. It indicates that during the first phase, the input of model used 50 kg clam grade I (150,000 ind./ kg) was released into the nursing ponds, the nursing pond with oxygen supplementation is a good facility resulting high survival rate of 62.8% in comparison to 43.5% in case of pond without oxygen supplementation. In October 2019, total 285 kg of grade II clams (15,000 ind./ kg) was obtained and released on 6,000 m2 clam ground in Thanh Dat Cooperative. In February 2020, total 2.33 million clam individuals were harvested, it is about 3,880 kg clam seed with the size of 600 ind./ kg. The model of clam seed nursing in the tidal flat was completed with clam seed survival rate of 54.5%. All of clam seed is continued culturing to the commercial clam production on the same ground of Thanh Dat Cooperative.

Selection of aquaculture sites by using an ensemble model method: a case study of Ruditapes philippinarums in Moon Lake

Manila clam Ruditapes philippinarum is one of the most important bivalve species, with high commercial value, cultured in coastal areas around the world. However, few studies have attempted to model the suitable habitats of this species. For farming, knowledge of suitable habitat is critical information. Here, we use an ensemble-modelling approach implemented in the biomod2 platform to examine potential suitable habitats in Moon Lake. Initially, nine single-algorithm species distribution models (SDMs) were constructed by combining 96 Manila clam actual presence-and-absence data with oceanographic and sediment data. A weighted ensemble model was then derived from the different individual models. Results showed that the contribution of the six predictor variables differed among modelling techniques, in general, the substrate-related variables contributed the best at predicting habitat suitability. The performance of single-algorithm models ranged from poor to excellent, and the weighted ensemble model performed better than any individual modelling technique according to performance metrics. The use of an ensemble of predictions allowed us to identify potentially suitable areas for clam farming. The predicted suitable, secondary suitable and general suitable habitat for R. philippinarum accounted for 7.69%, 9.03% and 11.80% of the total area of Moon Lake, respectively. And both the average shell length and biomass of Manila clam displayed positive relationships with HSI value. This ensemble-modelling approach could be a useful tool to identify suitable aquaculture sites for Manila clam farming.

Effects of hypoxia on survival, behavior, metabolism and cellular damage of Manila clam (Ruditapes philippinarum).

The Manila clam Ruditapes philippinarum has become a common and dominant macrobenthic species in coastal areas of the northwestern Pacific and temperate waters of Europe; it is also a major cultured shellfish, with annual worldwide production exceeding 3.3 million tonnes. This species faces greater risk of exposure to hypoxia as eutrophication worsens throughout its coastal habitats; however, its tolerance to hypoxia remains unclear, and the toxicological indicators including LC50 and LT50 have not yet been assessed. Previous studies on the effects of hypoxia on marine benthos have focused largely on functional responses, such as metabolism and gene expression, leaving potential structural damage to the mitochondria or the cells unknown. In this study we assessed the effects of hypoxia on Manila clam in terms of survival, behavior, metabolism and cellular damage, using a newly designed automated hypoxia simulation device that features exceptional accuracy and good stability. The clams exhibited strong tolerance to hypoxia as the 20-day LC50 for dissolved oxygen (DO) was estimated to be 0.57 mg L-1, and the LT50 at 0.5 mg L-1 DO was 422 hours. Adaptations included fewer buried clams and a depressed metabolism, while the unexpected rise in the activities of key enzymes involved in glycolysis may indicate a diverse strategy of shellfish under hypoxia. Cellular damage was observed as collapse of the mitochondrial cristae and both cellular and mitochondrial vacuolization. This multi-level study complements and updates our knowledge of the effects of hypoxia on marine benthos, by improving our understanding of the potential for marine ecological transformation under hypoxic conditions and providing useful information for Manila clam farming.

A Needs Analysis of Historical Learning Model to Reinforce Student’s Local Character using Local Wisdom Values of Turonggo Yakso Art

This research is part of the initial development activities to find out the problems that occur in schools so that model development needs to be done. The problem that happened in SMA Negeri 1 Panggul, Trenggalek, East Java is the lack of ecological intelligence of students this is evidenced by the school yard still scattered with garbage, students still use non-biodegradable waste and concern for the impact of goods consumed is still low. Student environment as part of student life is an important point to be developed as an effort to fix the problem. One effort that can be done as a school channel of education distributors is to integrate the local values in the community into the curriculum and learning unit. One of the local values that have the meaning of ecological wisdom is the values of the local wisdom of Turonggo Yakso art that is still thick with Javanese culture. The values ​​of the local wisdom of Turonggo Yakso art have the highest values ​​that can be a reference for someone to act and have been known by most people of Trenggalek district. The values ​​contained in the art of Turonggo Yakso are not widely known and applied by the students, therefore they need to be revitalized through the education system. This study used a descriptive qualitative method with interviews of teachers and students and lesson plan document analysis (RPP), curriculum and syllabus used in learning. The results of the interview and questionnaires analysis suggest that teachers need to develop a learning model based on local wisdom values ​​of Turonggo Yakso art as an effort to improve the learning problems at school. Ecological intelligence needs to be owned by students as the agent of change to be able to participate in doing sustainable development in facing the challenge of globalization and have good character to the natural environment.
 Keywords
 Need analysis, historical learning, model, reinforce, student, local character, local wisdom, values, Turonggo Yakso Art.
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Heavy metal fractionation studies in tidal sediment cores in the clam farms from Tan Thanh commune, Go Cong dong district, Tien Giang province, Vietnam

Results are presented from a study of the distribution of heavy metals in chemical fractions in tidal sediment cores at 4 sample stations inside the baby clam breeding plain, inside the harvested clam breeding plain, and on the frontier between the plains in the clam farms in Tan Thanh, Go Cong Dong, Tien Giang, Vietnam. The partitioning of metals among the compartments of the sediment solid phase was investigated indirectly by selective sequential extractions of a seven-step procedure adapted from Leleyter and Probst. The chemical forms were labeled according to the targeted geochemical compartments during each extraction step include water-soluble, exchangeable, bound to carbonates, bound to Mn oxides, bound to amorphous Fe oxides, bound to crystalline Fe oxides, associated with organics and residual. The heavy metal content (Co, Zn, As, Cd, Hg, Pb, Cr) in chemical fractions in sediment cores sliced in three depths (0-20 cm, 20-40 cm and 40 – 60cm) was analyzed by ICP-MS. The highest concentration of heavy metals was found in the oxidable fraction. The data more than 60% shows an important role of organic matters in the oxidable condition at the surficial sediment layer. The heavy metal concentrations depend on the depth of sediment show that clam’s digestive activity or the decomposition of tissue and shell of clams possibly affects the content of heavy metals.
 Bài báo giới thiệu các kết quả nghiên cứu về sự phân bố kim loại nặng dưới các dạng liên kết khác nhau trong các mẫu lõi trầm tích tại các bãi nuôi nghêu giống, bãi nuôi nghêu sau khi đã thu hoạch, vàranh giới giữa các bãi nuôi nghêu tại xã Tân Thành, huyện Gò Công Đông, tỉnh Tiền Giang, Việt Nam. Các dạng pha liên kết bao gồm: 1.pha hòa tan; 2. pha trao đổi; 3.liên kết với các bô nát; 4. liên kết với Man gan ô xít; 5. liên kết với sắt ô xít vô định hình; 6. liên kết với sắt ô xít dạng tinh thể; 7. liên kết với thành phần hữu cơ và; 8. Phần bã rắn. Trong các kim loại nặng (KLN) được phân tích, hàm lượng Zn và Hg vượt quá tiêu chuẩn cho phép QCVN 43:2012/BTNMT lần lượt từ 1,12 – 3,53 và 24,58 – 171,96 lần. Hàm lượng KLN tồn tại nhiều nhất dưới dạng liên kết với các thành phần có khả năng ô xi hóa với tỉ lệ hơn 60% chỉ ra vai trò của thành phần hữu cơ trong điều kiện ô xi hóa tại lớp trầm tích tầng mặt. Sau các thành phần có khả năng ôxi hóa, các KLN hiện diện trong phần bã rắn nhiều hơn trong các pha khác. Sự có mặt của KLN trong phần bã rắn chỉ ra mức độ ô nhiễm của hệ thống sông: càng nhiều phần trăm KLN có mặt trong phần bã rắn, càng ít ô nhiễm trong môi trường bởi phần bã rắn này liên quan đến các thành phần không thể bị rửa tách. Sự phụ thuộc theo độ sâu của hàm lượng kim loại nặng đưa ra khả năng về sự ảnh hưởng của hoạt động tiêu hóa và quá trình phân hủy của nghêu lên hàm lượng kim loại nặng.