Seawater Transfer Research Articles

Analysis and experimental results of frequency splitting of underwater wireless power transfer

Underwater wireless power transfer (UWPT) is an important technique to power underwater devices while its frequency splitting phenomena are not fully elucidated. In this study, frequency splitting phenomena of a symmetrical planar two-coil wireless power transfer (WPT) system resonated at 90 kHz are investigated in seawater and freshwater. A concise frequency splitting analysis of this WPT system in air based on circuit model is given first and then experimental data are reported to show there is little difference between power transfer in air, freshwater and seawater in the range of 40–140 kHz of this WPT system. Consequently, the frequency splitting analysis and observations in air are also applicable in freshwater and seawater. It is found a V-type frequency splitting pattern exists in this WPT system under seawater and freshwater. Frequency shift is observed in this UWPT system in overcoupled region, and no frequency shift is observed in undercoupled region. In undercoupled region, in the low frequency zone of 40–90 kHz the load voltage characteristics in three media are identical; in the high-frequency zone of 90–140 kHz, the load voltage in air is slightly larger than those in freshwater and seawater.

Genetic background and embryonic temperature affect DNA methylation and expression of myogenin and muscle development in Atlantic salmon (Salmo salar).

The development of ectothermic embryos is strongly affected by incubation temperature, and thermal imprinting of body growth and muscle phenotype has been reported in various teleost fishes. The complex epigenetic regulation of muscle development in vertebrates involves DNA methylation of the myogenin promoter. Body growth is a heritable and highly variable trait among fish populations that allows for local adaptations, but also for selective breeding. Here we studied the epigenetic effects of embryonic temperature and genetic background on body growth, muscle cellularity and myogenin expression in farmed Atlantic salmon (Salmo salar). Eggs from salmon families with either high or low estimated breeding values for body growth, referred to as Fast and Slow genotypes, were incubated at 8°C or 4°C until the embryonic ‘eyed-stage’ followed by rearing at the production temperature of 8°C. Rearing temperature strongly affected the growth rates, and the 8°C fish were about twice as heavy as the 4°C fish in the order Fast8>Slow8>Fast4>Slow4 prior to seawater transfer. Fast8 was the largest fish also at harvest despite strong growth compensation in the low temperature groups. Larval myogenin expression was approximately 4–6 fold higher in the Fast8 group than in the other groups and was associated with relative low DNA methylation levels, but was positively correlated with the expression levels of the DNA methyltransferase genes dnmt1, dnmt3a and dnmt3b. Juvenile Fast8 fish displayed thicker white muscle fibres than Fast4 fish, while Slow 8 and Slow 4 showed no difference in muscle cellularity. The impact of genetic background on the thermal imprinting of body growth and muscle development in Atlantic salmon suggests that epigenetic variation might play a significant role in the local adaptation to fluctuating temperatures over short evolutionary time.

Ig-seq: Deep sequencing of the variable region of Atlantic salmon IgM heavy chain transcripts

Immunoglobulin M plays a key role in systemic protection of Atlantic salmon against pathogens. Until recent, studies have focused on antigen-specific antibodies and little is known about the IgM repertoire: its size, developmental changes and responses to antigens. We report the development of deep sequencing protocol to characterize the repertoire of IgM heavy chain variable region. Its structure and changes were examined at the early stages of life and after infection with virus of cardiac myopathy. Clonotypes are identified by the V and J gene segments and amino acid sequences of CDR3, which determine the contribution of the heavy chain to the antigen binding properties. A major fraction of transcripts are functional while the rest are either sterile (transcribed from noncoding parts of Ig loci) or include stop codons. Despite marked difference in frequencies of combinations of V and J genes, the size of repertoire is large. The IgM diversity steadily increases after hatch followed with temporal reduction during smoltification and recovery after seawater transfer. Most clonotypes are present only in one fish. However multiple transcripts in uninfected fish are produced exclusively from a small fraction of shared clonotypes. While only 4.7% of clonotypes are detected in three and more fish, they comprise 35% of transcripts. Increased frequencies of most abundant clonotypes were detected in the head kidney and blood at ten weeks after viral infection and all were shared. Occurrence of the same clonotypes in multiple individuals can be explained with either their simple structure or exposure to common antigens. Complexity of CDR3 assessed by contents of non complementary nucleotides is slightly lower in shared clonotypes but difference is small. High nucleotide diversity of CDR3 with identical amino acid sequences suggests selection.

Triploid atlantic salmon (Salmo salar L.) post-smolts accumulate prevalence more slowly than diploid salmon following bath challenge with salmonid alphavirus subtype 3.

Triploid Atlantic salmon (Salmo salar L.) may play an important role in the sustainable expansion of the Norwegian aquaculture industry. Therefore, the susceptibility of triploid salmon to common infections such as salmonid alphavirus (SAV), the causative agent of pancreas disease (PD), requires investigation. In this study, shortly after seawater transfer, diploid and triploid post-smolts were exposed to SAV type 3 (SAV3) using a bath challenge model where the infectious dose was 48 TCID50 ml-1 of tank water. Copy number analysis of SAV3 RNA in heart tissue showed that there was no difference in viral loads between the diploids and triploids. Prevalence reached 100% by the end of the 35-day experimental period in both infected groups. However, prevalence accumulated more slowly in the triploid group reaching 19% and 56% at 14 and 21 days post exposure (dpe) respectively. Whereas prevalence in the diploid group was 82% and 100% at the same time points indicating some differences between diploid and triploid fish. Both heart and pancreas from infected groups at 14 dpe showed typical histopathological changes associated with pancreas disease. Observation of this slower accumulation of prevalence following a natural infection route was possible due to the early sampling points and the exposure to a relatively low dose of virus. The triploid salmon in this study were not more susceptible to SAV3 than diploid salmon indicating that they could be used commercially to reduce the environmental impact of escaped farmed fish interbreeding with wild salmon. This is important information regarding the future use of triploid fish in large scale aquaculture where SAV3 is a financial threat to increased production.

Water temperature and dietary histidine affect cataract formation in Atlantic salmon (Salmo salar L.) diploid and triploid yearling smolt

The aim of the present study was to investigate cataract development in diploid (2N) and triploid (3N) Atlantic salmon smolts and post-smolts at two water temperatures (10 and 16°C) given diets with different histidine supplementation (LH, 10.4 and HH, 13.1gkg-1 ) before and after seawater transfer. In freshwater, a severe cataract outbreak was recorded in both ploidies reared at 16°C. The cataract score was significantly higher in triploids compared to diploids, and the severity was lower in both ploidies fed the HH diet. The cataract development at 10°C was minor. Low gill Na+ , K+ -ATPase activity in fish reared at 16°C before seawater transfer was followed by osmoregulatory stress with elevated plasma electrolyte concentrations and high mortality in sea water. Both diploids and triploids reared at 10°C developed cataracts during the seawater period, with higher severities in triploids than diploids and a reduced severity in the fish fed the HH diet. The findings of this study demonstrate the importance of environmental conditions in the husbandry of Atlantic salmon, and particularly triploids, with regard to smoltification and adjusted diets to mitigate cataract development in fresh and sea water.

Phytoplankton of the Kuyalnik estuary in 2015 – 2017

The sharp change in the salinity of the Kuyalnitsky estuary in the second half of the twentieth century. Caused a significant reorganization of its ecosystem, which led to loss of fishing, deterioration of the quality of water. At the beginning of the XXI century the study of the Kuyalnitsky estuary biota, which exists in hypergalian conditions, was unsystematic, so information on the quantitative characteristics of phytoplankton and its distribution in the estuary is extremely limited. Purpose. To obtaining detailed information about current composition and quantitative characteristics of phytoplankton species in the estuary during the period from March 2015 to March 2017, i.e. when influenced by the transfer of sea water from the Odessa Bay. Methods. Concentration of the collected samples was done by sedimentation method. The samples collected during microalgal blooms have not been concentrated. Results. The phytoplankton was monodominant all over the estuary in 2015 – 2017 due to development of Dunaliella salina (Dunal) Teodor., which was presented by two different life forms. Some water samples contained benthoplankton species of diatomic algae, as well as Chlorophyta and Cyanobacteria. During the period of study algae blooms of D. salina was registered in 36 water samples; some cases of Bacillariophyta and Chlorophyta blooming were observed as well. During the period 2015-2017 the total number of phytoplankton species in the northern and central part of the estuary reached 23; in the southern part 69 species were registered. Conclusions. It has been established that phytoplankton of Kuyalnik Estuary can quickly adapt to salinity reduction caused by the filling of the estuary with sea water, which is one of the reasons of frequent algal blooms in 2015-2017.

Coping with a changing environment: the effects of early life stress.

Ongoing rapid domestication of Atlantic salmon implies that individuals are subjected to evolutionarily novel stressors encountered under conditions of artificial rearing, requiring new levels and directions of flexibility in physiological and behavioural coping mechanisms. Phenotypic plasticity to environmental changes is particularly evident at early life stages. We investigated the performance of salmon, previously subjected to an unpredictable chronic stress (UCS) treatment at an early age (10 month old parr), over several months and life stages. The UCS fish showed overall higher specific growth rates compared with unstressed controls after smoltification, a particularly challenging life stage, and after seawater transfer. Furthermore, subjecting fish to acute stress at the end of the experiment, we found that UCS groups had an overall lower hypothalamic catecholaminergic and brain stem serotonergic response to stress compared with control groups. In addition, serotonergic activity was negatively correlated with final growth rates, which implies that serotonin responsive individuals have growth disadvantages. Altogether, our results may imply that a subdued monoaminergic response in stressful farming environments may be beneficial, because in such situations individuals may be able to reallocate energy from stress responses into other life processes, such as growth.

Smoltification and seawater transfer of Atlantic salmon (Salmo salar L.) is associated with systemic repression of the immune transcriptome

Smoltification and seawater adaptation of Atlantic salmon are associated with profound alterations in the endocrine status, osmoregulation and behaviour. Little is known about immunological changes during smoltification, although increased incidences of infectious diseases after seawater transfer (SWT) may indicate weakened protection. We report microarray gene expression analyses in farmed Atlantic salmon during smoltification stimulated with constant light and early seawater adaptation (one and three weeks after SWT). Gene expression changes were large, their magnitude in the head kidney and proximal intestine was greater than in the gill. Among 360 differentially expressed immune genes, 300 genes were down-regulated, and multiple functional groups were affected such as innate antiviral immunity, chemokines, cytokines and receptors, signal transducers, effectors of humoral and cellular innate immunity, antigen presentation and lymphocytes, especially T cells. No recovery was observed after three weeks in seawater. A notable exception was a transient up-regulation of immunoglobulin transcripts in the gill after SWT. Genes involved in stress responses and xenobiotic metabolism were up-regulated in respectively intestine and gill. The duration of this observed immune suppression and the possible consequences for susceptibility to infections and diseases need further exploration.

Effects of seawater transfer and fasting on the endocrine and biochemical growth indices in juvenile chum salmon (Oncorhynchus keta)

Insulin-like growth factor (IGF)-I, IGF-binding protein (IGFBP)-1 and RNA/DNA ratio are endocrine and biochemical parameters used as growth indices in fish, however, they are subjected to environmental modulation. Chum salmon (Oncorhynchus keta) migrate from freshwater (FW) to seawater (SW) at fry/juvenile stage weighing around 1g and suffer growth-dependent mortality during the early phase of their marine life. In order to reveal environmental modulation of the IGF/IGFBP system and establish a reliable growth index for juvenile chum salmon, we examined effects of SW transfer and fasting on IGF-I, IGFBP-1 and RNA/DNA ratio, and correlated them to individual growth rate. Among serum IGF-I, liver and muscle igf-1, igfbp-1a, igfbp-1b and RNA/DNA ratio examined, muscle RNA/DNA ratio and muscle igfbp-1a responded to SW transfer. Serum IGF-I, liver igf-1 and liver RNA/DNA ratio were sensitive to nutritional change by being reduced in 1week in both FW and SW while muscle igf-1 was reduced 2weeks after fasting. In contrast, igfbp-1a in both tissues was increased by 2weeks of fasting and igfbp-1b in the liver of SW fish was increased in 1week. These results suggest that the sensitivity of igf-1 and igfbp-1s to fasting differs between tissues and subtypes, respectively. When chum salmon juveniles in SW were marked and subjected to feeding or fasting, serum IGF-I showed the highest correlation with individual growth rate. Liver igfbp-1a and -1b, and muscle igf-1 exhibited moderate correlation coefficients with growth rate. These results show that serum IGF-I is superior to the other parameters as a growth index in juvenile chum salmon in term of its stability to salinity change, high sensitivity to fasting and strong relationship with growth rate. On the one hand, when collecting blood from chum salmon fry/juveniles is not practical, measuring liver igfbp-1a and -1b, or/and muscle igf-1 is an alternative.

Short-term Effects of Hypertonic Shock on Na+, K+-ATPase Responses in Gills and Kidneys of the Spotted Green Pufferfish, Tetraodon nigroviridis.

Chia-Hao Lin and Tsung-Han Lee (2016) Freshwater (FW) spotted green pufferfish (Tetraodon nigroviridis) could be directly transferred to seawater (SW). This indicated that the spotted green pufferfish possesses an efficient osmoregulatory mechanism to overcome salinity challenges. Although previous studies explored osmoregulation in the spotted green pufferfish in FW and SW acclimation, to our knowledge, no study has addressed short-term time-course changes to elucidate the responsible mechanism. In the present study, spotted green pufferfish were transferred directly from FW to SW. We explored time-course changes in plasma osmolality, and Na+ and Cl- concentrations, as well as Na+, K+-ATPase (NKA) responses (activity and protein expression) in gills and kidneys in a short-term (96 h) time-course experiment using the spotted green pufferfish. Plasma osmolality and Cl- levels were upregulated within 3 h post-transfer, and were constant thereafter. Plasma Na+ concentration responded with a rapid increase 6 h post-transfer, and returned to the original level at 48 h post-transfer. Gills and kidneys are vital osmoregulatory organs, and NKA expressed in these organs provides the driving force for osmoregulation in euryhaline teleosts. Herein, both branchial and renal NKA responses were modulated soon after SW transfer. Branchial NKA responses including activity and protein abundance of α-subunit were significantly stimulated at 3 h post-transfer; thenceforth were maintained in at a steady state. In contrast, the activity and protein expression of renal NKA were downregulated at 3 and 12 h post-transfer, respectively. The physiological profiles found in this study illustrated how spotted green pufferfish cope with direct transferred from FW to SW.

Past seawater experience enhances seawater adaptability in medaka, Oryzias latipes.

BackgroundDuring the course of evolution, fishes have acquired adaptability to various salinity environments, and acquirement of seawater (SW) adaptability has played important roles in fish evolution and diversity. However, little is known about how saline environments influence the acquirement of SW adaptability. The Japanese medaka Oryzias latipes is a euryhaline species that usually inhabits freshwater (FW), but is also adaptable to full-strength SW when transferred through diluted SW. In the present study, we examined how past SW experience affects hyposmoregulatory ability in Japanese medaka.ResultsFor the preparation of SW-experienced fish, FW medaka were acclimated to SW after pre-acclimation to 1/2 SW, and the SW-acclimated fish were transferred back to FW. The SW-experienced fish and control FW fish (SW-inexperienced fish) were transferred directly to SW. Whereas control FW fish did not survive direct transfer to SW, 1/4 of SW-experienced fish adapted successfully to SW. Although there were no significant differences in blood osmolality and plasma Na+ and Cl− concentrations between SW-experienced and control FW medaka in FW, increments in these parameters following SW transfer were lower in SW-experienced fish than in control FW fish. The gene expression of SW-type Na+, K+-ATPase (NKA) in the gills of SW-experienced medaka increased more quickly after direct SW transfer compared with the expression in control FW fish. Prior to SW transfer, the density of NKA-immunoreactive ionocytes in the gills was higher in SW-experienced fish than in control FW fish. Ionocytes expressing CFTR Cl− channel at the apical membrane and those forming multicellular complexes, both of which were characteristic of SW-type ionocytes, were also increased in SW-experienced fish.ConclusionThese results indicate that past SW experience enhances the capacity of Na+ and Cl− secretion in ionocytes and thus hypoosmoregulatory ability of Japanese medaka, suggesting the presence of epigenetic mechanisms involved in seawater adaptation.Electronic supplementary materialThe online version of this article (doi:10.1186/s40851-016-0047-2) contains supplementary material, which is available to authorized users.

Domestication compromises athleticism and respiratory plasticity in response to aerobic exercise training in Atlantic salmon (Salmo salar)

Commercially selective breeding of Atlantic salmon (Salmo salar) primarily for rapid growth may compromise cardiorespiratory robustness and its related phenotypes. Therefore, a suite of respiratory indices was used to evaluate aerobic capacity and hypoxia tolerance to test the hypothesis that exercise training can improve the athletic robustness in both domesticated and wild strains of Atlantic salmon, but with the domesticated strain having a less cardiorespiratory plasticity and a lower athletic robustness than the wild strain. We also tested a second hypothesis that a constant acceleration screening protocol should segregate fish according to athletic robustness based on their swimming ability. These hypotheses were tested with parr from Bolaks (domesticated) and Lærdal (wild) strains of Atlantic salmon that were reared under identical hatchery conditions. After screening into either inferior (bottom 20%) or superior (top 20%) swimmers, the four groups of fish (two strains and two swimming performance levels) either were given an 18-day exercise-training regime (an incremental water current of 2.0–2.8forklengthss−1), or were maintained at the control water current (0.5forklengthss−1) for 18days. Subsequently, fish were sampled for metabolic enzyme analysis in red and white swimming muscles (citrate synthase, CS, and lactate dehydrogenase, LDH; n=15 from each group) and their individual respiratory capacities were comprehensively assessed by measuring the standard metabolic rate (SMR), maximum rate of oxygen uptake (ṀO2max), absolute aerobic scope (AAS), factorial aerobic scope (FAS), excess post-exercise oxygen consumption (EPOC), critical oxygen level (O2crit) and incipient lethal oxygen saturation (ILOS). Contrary to our expectations, the inferior and superior swimmers were indistinguishable in either strain and these data were pooled. While exercise training produced several tangible benefits for the wild fish, it produced very few for the domesticated fish. For example, the wild strain, but not the domesticated strain, had a significantly higher ṀO2max, AAS and EPOC as a result of training. Also, CS activity in red muscle increased after training to a larger extent in the wild strain than in the domesticated strain. When compared with the wild strain, the domesticated strain had a significantly lower ṀO2max, AAS, FAS and CS activity in white muscle. Thus, the domesticated strain appeared to be athletically less robust than the wild strain. These results imply that approximately ten generations of selective breeding for rapid growth in commercial aquaculture have reduced the overall athletic robustness of domesticated salmon as compared to their wild conspecifics, and given the success in improving athletic robustness of the wild strain, it still remains to be seen whether an exercise training protocol can be developed that will provide benefits to the salmon aquaculture industry. Statement of relevanceThis manuscript fits perfectly with the scope of aquaculture. We address the possibility that the Norwegian Atlantic salmon (Salmo salar) breeding program that extensively focuses on commercial benefits traits may be compromising the cardiorespiratory system, which may contribute to the mortality of smolts after seawater transfer. We hypothesized that a combination of exercise-screening and exercise-training protocols could select for superior cardiorespiratory performance. This hypothesis was tested by comparing domesticated and wild Norwegian Atlantic salmon strains, and using comprehensive measurements of athletic and hypoxia performance in individual fish.We believe this paper will be of specific interest to aquaculture professionals who are seeking the enhanced husbandry approaches for achieving higher survival rate over seawater transfer as well as general physiologists. To our knowledge our study is the first to comprehensively illustrate athleticism of domesticated Atlantic salmon from biochemical and cardiorespiratory system levels. Furthermore, we believe this is the first study to show the promising results of enhancing cardiorespiratory system of domesticated Atlantic salmon strain in a hatchery setting.We used a suite of respiratory indices to evaluate athletic robustness and hypoxia performance in individual fish. We discovered that a domesticated strain of Atlantic salmon demonstrated a reduced athleticism and less plasticity in response to a short exercise-training regime compared with a wild strain of Atlantic salmon. We conclude that commercial aquaculture practices may trade off the robustness of the cardiorespiratory system, but not to an extent of completely losing the potential of benefiting from exercise training.

High levels of plasma cortisol and impaired hypoosmoregulation in a mutant medaka deficient in P450c17I

scl is a spontaneous medaka mutant deficient in P450c17I, which is required for production of sex steroids, but not of cortisol, the major role of which is osmoregulation in teleost fish. The scl mutant provides a new model to study the functions of these hormones. We first found that fish homozygous for this mutation have plasma cortisol constitutively at a high physiological level (1000 nM). Since we previously showed that this level reversed the seawater-type differentiation of the medaka gastrointestinal tract, hypoosmoregulation of the scl mutant was analyzed. Muscle water contents in freshwater were normal in scl homozygotes, but the contents were lower than those of the wild type (WT) after seawater transfer. There were no differences in gill mRNA levels of corticosteroid receptors or ion transporters between scl homozygotes and WT. In the intestine, expression of glucocorticoid receptors and Na+/K+/2Cl− cotransporter were induced in WT during seawater acclimation, but not in scl homozygotes. The high plasma cortisol may prevent hypoosmoregulation by inhibition of increased intestinal water absorption, essentially by the Na+/K+/2Cl− cotransporter, in seawater.

Smoltification and breeding for rapid growth may suppress immunity of atlantic salmon: Evidence from transcriptome analyses

The first months after seawater transfer (SWT) of fish are a period of heavy losses in commercial farming of Atlantic salmon. A large part of the mortality is due to infectious diseases, but unsuccessful smoltification and various undetected pathogens may contribute to cases that remain unexplained. SWT is preceded with smoltification, which is associated with dramatic endocrine and metabolic changes. Farmed Atlantic salmon has spent many generations under intense selective breeding for rapid growth and other commercially important traits. Given the high energy costs of smoltification and growth one may anticipate a trade off between these processes and immunity. We report studies that used gene expression profiling with oligonucleotide microarrays and RNA-seq. (1) Smoltification was induced with photoperiod manipulation, and microarray analyses were performed in samples from the head kidney, gill and intestine. Massive down-regulation of immune genes was revealed, starting from the middle of stimulation and remained constant to the end of experiment – three weeks after SWT. The innate antiviral immunity showed greatest suppression. The only deviation from the common trend was a transient increase of Ig transcripts in the gill shortly after SWT. (2) RNA-seq analyses in hearts of farmed parr and smolts produced similar results: all functional groups of immunity were down-regulated while expression of Ig increased. All immune genes in hearts of wild salmon showed higher expression in comparison with farmed fish. (3) Parr and smolts from the same batch reared respectively in fresh and seawater were challenged with PRV, the causative agent of HSMI. Microarray analyses found a minor difference between the uninfected fish. Further, parr developed more rapid responses to the pathogen, as observed by earlier induction of innate antiviral and B cells responses in the head kidney and to a lesser extent in the spleen. Clearance of PRV from spleen was more effective in parr. (4) Microarray analyses found slight but significant up-regulation in several groups of immune genes in the gill of wild anadromous salmon during smoltification, which was in contrast to farmed salmon. In conclusion, results obtained in several independent experiments, including different research stations, wild and commercial fish of different origin, provided indications for compromised immune competence. It remains unknown however, whether down-regulation of immune genes affects resistance of Atlantic salmon to pathogens and if recovery takes place in seawater. It is also important to figure out if immune suppression is linked to and a consequence of breeding for rapid growth.

Thermal performance analysis of SuperORV heat transfer tube at supercritical pressure

Super open rack vaporizer (SuperORV) is a new-type of liquefied natural gas (LNG) vaporizer whose lower half of heat transfer tubes has double tube structure. A distributed parameter model based on energy balance is developed in the present paper with the aim to simulate the thermal performance of SuperORV heat transfer tube at supercritical pressure. Corresponding empirical correlations are used to evaluate the convection heat transfer of LNG and seawater, and the heat transfer enhancement effects of inner fin and twisted tape insert are considered in computation. Good agreement between calculated and experimental data implies the calculation model is reliable. On this basis, the temperature and ice thickness profiles along the heat transfer tube are obtained by numerical solution with or without ice layer presence, the thermal performance of heat transfer tube is analyzed, and the effects of operating parameters and heat transfer enhancement techniques on the thermal performance are discussed. The results indicate that both the operating parameters and the heat transfer enhancement techniques have great influence on the thermal performance, including required minimum tube length, ice thickness and length of formed ice layer. The heat transfer enhancement techniques can improve the heat transfer performance markedly, and the required tube length is reduced by 47.7% while both inner fin and twisted tape insert are applied.

Characterization of a microbial consortium that converts mariculture fish waste to biomethane

Environmentally responsible disposal of solid organic wastes from land-based brackish and marine recirculating aquaculture systems is critical for promoting widespread acceptance and implementation, but conversion efficiency of saline sludge to biomethane is generally low. We describe the development of a microbial consortium that can convert marine organic fish waste solids to biomethane at over 90% efficiency. The halotolerant microbial consortium, which was developed by sequential transfer in seawater with fish waste, is optimized for low COD:N ratios typical of organic fish waste and does not require addition of amendments such as organic carbon or nutrients. Temperatures for maximum rates of conversion range from 26 to 35°C. Five predominant phylotypes identified in the microbial consortium by denaturing HPLC were isolated. Two isolates included anaerobic fermentative bacteria identified as a strain of Dethiosulfovibrio and a strain closely related to Fusobacterium spp., which both hydrolyze and ferment proteins, peptides and amino acids. The other three isolates included an acetate-utilizing methanogenic archaeon identified as a strain of Methanosarcina and two hydrogen-utilizing methanogenic archaea identified as strains of Methanogenium and Methanoplanus. Bioconversion rates of sterile fish waste with the reconstituted microbial consortium containing all five isolates were equivalent to rates observed with the original enriched consortium after one sequential transfer. The results demonstrate unequivocally that halotolerant consortia of bacteria and archaea can be developed for bioconversion of saline organic solid waste with high efficiencies equivalent to those attained with non-saline waste systems. Understanding the microbial community composition is critical for management of solid organic waste from land-based marine aquaculture systems and to maintain or restore microbiota during start up and throughout the production process. Statement of relevanceAppropriate disposal of solid organic wastes from land-based brackish and marine recirculating aquaculture systems is critical for promoting widespread acceptance and implementation. We demonstrate that halotolerant consortia of bacteria and archaea can be developed for bioconversion of saline fish waste with high efficiencies equivalent to those attained with non-saline waste systems.

Atlantic multi-decadal oscillation covaries with Agulhas leakage.

The interoceanic transfer of seawater between the Indian Ocean and the Atlantic, ‘Agulhas leakage', forms a choke point for the overturning circulation in the global ocean. Here, by combining output from a series of high-resolution ocean and climate models with in situ and satellite observations, we construct a time series of Agulhas leakage for the period 1870–2014. The time series demonstrates the impact of Southern Hemisphere westerlies on decadal timescales. Agulhas leakage shows a correlation with the Atlantic Multi-decadal Oscillation on multi-decadal timescales; the former leading by 15 years. This is relevant for climate in the North Atlantic.

First Description of a New Disease in Rainbow Trout (Oncorhynchus mykiss (Walbaum)) Similar to Heart and Skeletal Muscle Inflammation (HSMI) and Detection of a Gene Sequence Related to Piscine Orthoreovirus (PRV).

In fall 2013, anorexia, lethargy and mortalities up to 10-12,000 dead fish per week were observed in rainbow trout Oncorhynchus mykiss in three fresh water hatcheries (salinity 0-1 ‰) on the west coast of Norway. The fish (25-100 g) showed signs of circulatory failure with haemorrhages, ascites and anaemia. The histopathological findings comprised inflammation of the heart and red muscle and liver necrosis. The affected fish had a common origin. Disease and mortalities were also observed up to four months after sea water transfer. Microbiological examination did not reveal presence of any known pathogens. Based on histopathological similarities to heart and skeletal inflammation (HSMI) in Atlantic salmon, associated with piscine orthoreovirus (PRV), extended investigations to detect a virus within the family Reoviridae were conducted. By the use of primer sets targeting the PRV genome, a sequence with 85% identity to a part of segment S1 of PRV was obtained. Further analysis showed that the virus sequence could only be aligned with PRV and no other reoviruses both on amino acid and nucleotide level. Two PCR assays were developed for specific detection of the virus. High amounts of the virus were detected in diseased fish at all affected farms and low amounts were detected in low prevalence at the broodfish farms. Further investigations are needed to determine if the virus is associated with the new disease in rainbow trout and to further characterize the virus with respect to classification, relationship with PRV, virulence, pathology and epidemiology.

Functional dynamics of claudin expression in Japanese medaka (Oryzias latipes): Response to environmental salinity

Salinity regulation of 13 claudin paralogs was investigated in osmoregulatory organs of euryhaline Japanese medaka. They were identified by blast-search in the medaka genome database based on representation in osmoregulatory organs of other teleosts. Our hypothesis was that, because of their sequence similarities to mammalian orthologs previously characterized as barrier- and ion-selective channel-forming proteins, these paralogs would respond to salinity according to expected modulation of osmoregulatory function. Cldn10c, -10d, -10e, -10f, -27a, -28a, -28b and -30c had 4- to 100-fold higher expression in gill than other examined organs. Two splice variants of cldn10b were predominantly expressed in kidney, while cldn15a, -15b and -25 were found mainly in intestine. In gills, cldn27a, -28a, -28b and -30c did not change between fresh water (FW) and seawater (SW)-acclimated fish, while cldn10c, -10d, -10e, and -10f were most abundant in SW. Short-term SW transfer induced up-regulation of cldn10 gill paralogs after 1day, decrease in cldn28b and no difference for cldn27a, -28a and -30c. The reverse pattern was observed after FW transfer of SW medaka. Intestinal cldn15a and -25 did not differ between FW and SW fish. However, cldn15b was 10-fold higher in FW than SW, suggesting a role in functional modulation of the intestine related to water and salt transport. In kidney, cldn10bs were elevated in SW fish, suggesting a role in paracellular ion transport in the marine nephron. Based on in silico analysis, most gill Cldn10s were predicted to form cation pores, whereas Cldn27a, 28a, 28b and 30c may increase epithelial resistance.

A report on overripe female and spent male Atlantic salmon (Salmo salar) in August

Abstract This report is based on a finding of spent males and overripe females of Atlantic salmon on 30 August 2013. The studied fish population had been reared in tanks from seawater transfer in May 2011 to April 2013, and then in a sea-cage under natural light. From May 2011 until August 2012, and then again from February until April 2013, the fish were under natural light and temperature. In between these periods, the fish were reared under continuous light and a temperature ranging between 3 and 18 °C in order to study temperature effects on food consumption and oxygen consumption rate. In February 2013, a dissection of 33 fish showed that 29% of the females and 79% of the males were maturing. In August 2013, all remaining fish ( n = 80) were inspected by dissection and measured for gonad weight; males were either spent ex-spawners (50%), maturing (25%) or immature (25%), while females were either overripe (11%), maturing (29%) or immature (61%). The fish that were classified as maturing in August had gonads that resembled the gonads of the fish that were classified as maturing 5 months earlier. The females that were overripe and the spent males in August were estimated to have been ready for spawning sometime between April and June. This is the first indication of summer ovulation of female Atlantic salmon and shows that a relatively short period of temperature manipulation combined with continuous light may be used as a tool to prolong the spawning period in salmon to all year round. This would have a major impact on salmon farming.