Years In Seawater Research Articles

60 Years’ marine corrosion of aluminium alloy 24S (2024) from an historic aircraft wreck site: implications for conservation

ABSTRACT Aluminium alloys forming the remnants of Lockheed P38 of Antoine de Saint-Exupéry was identified as the 24S aluminium alloy developed in 1930s. After 60 years in sea water, thick corrosion layers composed of aluminium hydroxide, copper salts and nanometre pure copper particles. In addition, the ancient aluminium alloy has undergone a very important intergranular corrosion. After the synthesis of Al2Cu, Al7Cu2Fe and Al2CuMg intermetallic phases, the study of their electrochemical behaviour in NaCl medium explains the significant presence of pure copper, because all the phases undergo a dealloying process. Electrochemical impedance spectroscopy measurements show that the kinetic of dealloying is constant versus immersion time, and is not limited by diffusion which explains the complete formation of copper sponge in NaCl medium in the conditions of long-term corrosion on aluminium artefacts.

Estimation of the Environmental Load of High- and Low-Density Polyethylene From South Korea Using a Mass Balance Approach.

The accumulation of marine plastic debris is one of the main emerging environmental issues of the twenty first century. Numerous studies in recent decades have reported the level of plastic particles on the beaches and in oceans worldwide. However, it is still unclear how much plastic debris remains in the marine environment because the sampling methods for identifying and quantifying plastics from the environment have not been standardized; moreover, the methods are not guaranteed to find all of the plastics that do remain. The level of identified marine plastic debris may explain only the small portion of remaining plastics. To perform a quantitative estimation of remaining plastics, a mass balance analysis was performed for high- and low-density PE within the borders of South Korea during 1995-2012. Disposal methods such as incineration, land disposal, and recycling accounted for only approximately 40 % of PE use, whereas 60 % remained unaccounted for. The total unaccounted mass of high- and low-density PE to the marine environment during the evaluation period was 28 million tons. The corresponding contribution to marine plastic debris would be approximately 25,000 tons and 70 g km(-2) of the world oceans assuming that the fraction entering the marine environment is 0.001 and that the degradation half-life is 50 years in seawater. Because the observed concentrations of plastics worldwide were much lower than the range expected by extrapolation from this mass balance study, it is considered that there probably is still a huge mass of unidentified plastic debris. Further research is therefore needed to fill this gap between the mass balance approximation and the identified marine plastics including a better estimation of the mass flux to the marine environment.

Fabrication of Copper Nanowire Films and their Incorporation into Polymer Matrices for Antibacterial and Marine Antifouling Applications

With the ban of tributyltin, copper‐based biocides are now widely used in antifouling coatings as the major active ingredients. Given the past experience of heavy‐metal accumulation in harbors with limited water exchange, there is a significant interest in developing copper materials that greatly reduce the amount of copper ions released into marine surroundings. In this paper, copper nanowires (NWs) encapsulated in polymer matrices are investigated as the means to control the release of copper ions and to achieve a long‐lasting antifouling effect. Very long CuNWs with high aspect ratio in organic solution are drop‐coated onto substrates to fabricate uniform thin films. They are then incorporated into an elastomeric polydimethylsiloxane (PDMS) matrix. A small amount of CuNWs in PDMS can inhibit barnacle cyprid settlement, while it exhibits low mortality to cyprids and nauplii present in the surrounding seawater environment. The low levels of copper released after 50 days suggest that the intersecting and interconnected CuNWs embedded in PDMS could potentially release copper ions continuously over a few years in seawater. This approach provides a novel platform to use hybrid materials as effective marine antifouling coatings, and may be applied to fouling release materials to enhance their antifouling properties.

The Effect of Cover Thickness to Corrosion Characteristics of Reinforced Steel Bar Emedded in Mortar Specimen (W/C:0.6) Aged 5 Years in Seawater

Reinforced concrete structures have been increasingly widely used through numerous industrial fields. These structures are often exposed to severely corrosive environments such as sea water, contaminated water, acid rain, and the seashore. Thus, corrosion problems of the steel bars embedded in concrete are very important from a safety and economic point of view. In this study, the effects of cover thickness on the corrosion properties of reinforced steel bar embedded in mortar specimen (W/C:0.6) were investigated using electrochemical methods such as corrosion potentials, polarization curves, cyclic voltammograms, galvanostat and potentiostat. Corrosion potentials shifted to the noble direction, and the value of AC impedance also exhibited a higher value with increasing cover thickness, furthermore, polarization resistance also increased with increasing cover thickness. This is probably that the thinner cover thickness, seawater solution is easy to arrive at embedded steel compared to other thicker cover thickness, so, its steel bar may be easily corroded due to chloride ion, which is resulted in shifting corrosion potential to negative direction, decreasing polarization resistance. Consequently, it is considered that the relation between corrosion resistance of reinforced steel and cover thickness is nearly matched with each other. However, its corrosion resistance estimated by measurement of corrosion potential was not well in agreement with value obtained by polarization curves.

Corrosion Characteristics of Reinforced Steel Bar Emedded in Mortar Specimen(W/C:0.4) Aged 5 Years in Seawater

Reinforced concrete structures have been increasingly widely used in numerous industrial fields. These structures are often exposed to severely corrosive environments such as sea water, contaminated water, acid rain, and the seashore. Thus, corrosion problems of the steel bars embedded in concrete are very important from a safety and economic point of view. In this study, the effects of cover thickness on the corrosion properties of reinforced steel bar embedded in mortar specimen were investigated using electrochemical methods such as corrosion potentials, polarization curves, cyclic voltammograms, galvanostat and potentiostat. Corrosion potentials shifted in the noble direction, and the value of AC impedance also exhibited a higher value with decreasing cover thickness, furthermore, polarization resistance also increased with decreasing cover thickness. This is probably that the thinner cover thickness, it is easy for the dissolved oxygen and chloride ion to intrude and diffuse to the steel bar, thereby making it easier to corrode on the steel surface compared to thicker cover thickness, which is resulted in forming the corrosive products on the steel surface. Therefore, it is considered that the corrosive products plays a role to provide nobler value of corrosion potential and higher value of impedance. Consequently, it seems that the corrosion resistance of inner steel bar may depend on mainly not cover thickness but the resistance polarization due to corrosive products in the case of immerged for 5 years in this experiment.

Corrosion Characteristics of Reinforced Steel Bar Emedded in Multiple Mortar Specimen(W/C:0.5) Aged 5 Years in Seawater

Reinforced concrete structures have been increasingly widely used in numerous industrial fields. These structures are often exposed to severely corrosive environments such as seawater, contaminated water, acid rain, and the seashore. Thus, the corrosion problems that occur with the steel bars embedded in concrete are very important from the safety and economic points of view. In this study, the effects of the cover thickness on the corrosion properties of reinforced steel bars embedded in multiple mortar test specimens immersed in seawater for 5 years were investigated using electrochemical methods such as the corrosion potentials, polarization curves, cyclic voltammograms, galvanostat, and potentiostat. The corrosion potentials shifted in the noble direction, and the value of the AC impedance also exhibited a higher value with increasing cover thickness. Furthermore, the polarization resistance increased with increasing cover thickness, which means that the oxide film that is deposited on the surface of a steel bar surrounded by alkali environment exhibits better corrosion resistance because the water, chloride ions and dissolved oxygen have difficulty penerating to the surface of the steel bar with increasing cover thickness. Consequently, it is considered that the corrosion resistance of reinforced steel can be improved by increasing the cover thickness. However, the corrosion resistance values of a steel bar estimated by measuring the corrosion potential, impedance and polarization resistance were not in good agreement with its corrosion resistance obtained by polarization curves.

Water temperature manipulation can induce oocyte maturation and ovulation in the common Japanese conger, Conger myriaster

To develop seed production techniques for aquaculture of the common Japanese conger, Conger myriaster, we attempted to induce ovarian maturation and ovulation without exogenous hormone treatment and examined the changes in steroid hormones to understand the endocrine condition of the fish during their maturation process. Juveniles caught in November 2001 (20 to 30cm in total length) were reared for 1.5years in seawater at temperatures ranging from 10 to 20°C before the experiments. Then, 141 randomly selected female eels (58 to 82cm in total length) were maintained at a water temperature of 6°C from April 2003 to March 2004. The initial GSI values (5.0 to 12.0) and oocyte diameters (300 to 400μm) recorded in April 2003 had increased to maximum values of 30.0 and 650μm, respectively, at the end of experiment, in March 2004. In late December 2003, 12 fish with oocytes measuring over 600μm in diameter were selected and divided into an elevated temperature group from 6 to 10°C and a control group of 6°C for 43days. The mean oocyte diameter in the elevated temperature group increased significantly, and one fish (estimated GSI, 47.0) ovulated eggs with an average diameter of 995±46μm on the 41st day at a water temperature of 10°C, in contrast, the control group showed no significant changes in oocyte diameter, and no fish ovulated. Plasma T levels, examined via ELISA, increased with oocyte maturation, with the highest level detected at the migratory nucleus stage, and declined after ovulation. In contrast, plasma E2 was maintained at high levels during the vitellogenic stage, exhibiting the highest value after ovulation. The present study demonstrates that ovarian maturation and ovulation in the common Japanese conger could be achieved through water temperature manipulation.

Using Trace Elements in Pectoral Fin Rays to Assess Life History Movements in Sturgeon: Estimating Age at Initial Seawater Entry in Klamath River Green Sturgeon

AbstractTo investigate the timing of the initial entry of green sturgeonAcipenser medirostrisinto seawater, we examined the ratios of strontium and barium to calcium in pectoral fin rays via laser ablation‐inductively coupled plasma‐mass spectrometry. In a reference group of six hatchery fish that was reared 1‐2 years in freshwater and 1‐3 years in seawater, we found a significant increase in the Sr:Ca ratio, a decrease in the Ba:Ca ratio, and an increase in the Sr:Ba ratio in calcified growth zones during the transition from freshwater to seawater. In 10 wild adults captured in the Klamath River, California, combined evaluation of the Sr:Ca and Ba:Ca ratios provided a clearer understanding of fish movements than the Sr:Ba ratio, probably because wild fish have a more complex life history. The Ba:Ca ratio dropped significantly between growth zones 1 and 2 (ages 0.5‐1.5), indicating a transition into saline waters, such as the Klamath River estuary. The Sr:Ca ratio increased slightly in the same location but attained the values found in reference fish held in seawater between growth zones 3 and 4 (ages 2.5‐3.5). The Sr:Ca, Ba:Ca, and Sr:Ba ratios in growth zones 4‐6 (ages 4.5‐6.5) of wild fish were similar to those found in reference fish held in seawater and corroborated the results of previous physiological studies as well as the limited field data. These results demonstrate the usefulness of trace element analyses of green sturgeon pectoral fin rays and confirm an early age of entry into seawater for this species.

Use of Archaeological Glass to Predict the Long-Term Behavior of HLW

AbstractThe predictability of models describing long-term nuclear glass behavior in a geological repository can be tested by means of natural or archaeological analogs. This study covers fractured archaeological glass blocks from a shipwreck discovered near the Mediterranean island of Embiez (France). The blocks were examined mainly because of their morphological analogy with nuclear glasses. Fractured after production (as in the case of nuclear glass), these blocks had been leached for 1800 years in seawater. The laboratory investigation led to the development and subsequent validation on archaeological objects of a geochemical model capable of accurately simulating the coupling between chemistry and transport to account for the alteration state of the cracks according to their geometric characteristics. Laboratory experiments allowed us to determine the kinetic and thermodynamic parameters for modeling glass alteration. The model was then tested against short-term experiments before simulating the crack alteration over 1800 years. We show that cracks in the outer regions of the block are the most severely altered because of rapid solution renewal, whereas internal cracks are very slightly altered because of a rate-limiting effect of water transport due to the formation of secondary phases. This study also establishes a direct link between data obtained at lab scale and the long-term evolution of a complex system in a natural environment, indicating that the key phenomena have been identified experimentally. The analogous behavior of archaeological and nuclear glass during leaching experiments and the similarities in their crack networks allow us to consider applying the model to nuclear glasses under geological repository conditions. This study clearly shows that the internal crack network does not play a major role in the overall long-term alteration of archeological glass blocks. The issue of the transposition studies will be to determine whether this conclusion can be generalized to nuclear glasses.

A fractured roman glass block altered for 1800 years in seawater: Analogy with nuclear waste glass in a deep geological repository

Fractured archaeological glass blocks altered 1800 years in seawater are investigated because of their morphological analogy with vitrified nuclear waste. They provide an opportunity for understanding glass alteration in variable confined media (cracks), by studying an actual ancient system in a known stable natural environment. Characterization of the crack network from two-dimensional trace maps (length, alteration thickness, orientation) allows us to determine the three-dimensional geometric parameters (crack density, fracture ratio) and the percentage of alteration, using stereological relations. This methodology could be applied to nuclear glass. From a representative archaeological glass block, we showed that the surface developed by the cracks is 86 ± 27 times greater than the geometric surface but the volumetric alteration is 12.2 ± 4.1%, which is only 12 times greater than the volumetric alteration of the block periphery (about 1 vol%). This unexpected low value is explained by the large variation of the alteration thicknesses in the different types of cracks in relation with their location in the block. The alteration thickness is usually smaller in the internal zone than in the border zone. The alteration layers resulted from three main mechanisms (interdiffusion, glass dissolution, and secondary phase precipitation) leading to two different alteration products (a sodium-depleted layer and mainly a Mg-smectite). Geometric parameters such as the glass surface area/solution volume ratio and transport parameters (renewal of the alteration solution) strongly affected the glass dissolution kinetics. The confined conditions and the diffusive transport of reactive species favor low alteration kinetics. The precipitation of secondary phases also results in sealing of the cracks. Consequently, although it is not known if subcritical crack growth occurred, internal cracks account for only a minor contribution to the overall alteration. These results improve our understanding of alteration in cracks for assessing the predominant physical and chemical parameters that must be considered in long-term nuclear glass modeling.

Morphology, stomach contents and growth of the endangered salmonid, Sakhalin taimen Hucho perryi, captured in the Sea of Okhotsk, northern Japan: evidence of an anadromous form

We describe a total of 25 anadromous Sakhalin taimen Hucho perryi collected on the coast of Sarufutsu, northern Hokkaido, Japan in June 1997 and 1999. We examined morphology, stomach contents and growth of three anadromous taimen (one male and two females) in detail, which were preserved in good condition. The three taimen were aged and one female still had some eggs retained in her abdomen. The stomach contents of the three taimen consisted of sand lance Ammodytes personatus Girard and sculpin Triglops sp. On the basis of scale analyses, the growth rate of the three taimen was estimated by using the back-calculation method, and the highest rates were observed at young ages. Guanine pigmentation was present at the base of the caudal fin of each taimen and is considered as a potential morphological trait to differentiate anadromous from fluvial specimens. Another anadromous taimen, of which some individuals had reared for more than 3 years in seawater are also reported. For the conservation of this rare and endangered species, their migration route between rivers and sea should be protected

Reproductive cycle in reared male common Japanese conger, Conger myriaster

Annual changes in gonadal histology, gonadosomatic index (GSI), and plasma 11-ketotestosterone (11KT) levels were investigated in reared male common Japanese congers, Conger myriaster. Young fish, 20–30 cm in total length and around 20 g in body weight, caught in November 1996 (group 1) and in September 1999 (group 2) were reared for 3 years in seawater at temperatures ranging from 10 to 20 °C. In most fish, only spermatogonia occupied the testes for 1 year and a few months after capture. Spermatocytes appeared in February, and both spermatids and spermatozoa appeared in March, in 1998 for group 1 and in 2001 for group 2. Spermiation was observed from May to September and reduction in testis was observed after October in both groups. GSI and plasma 11KT levels changed with progression of spermatogenesis. Although GSI was less than 1.0 and the plasma 11KT level less than 1.0 ng/ml, in the first year in most fish, both increased in the second year of rearing. GSI peaked in June 1998 (5.3±3.0; mean±standard deviation) in group 1 and May 2001 (2.3±1.3) in group 2, and bottomed in October (0.3±0.1) in both groups. Plasma 11KT levels peaked in March 1998 (5.8±1.9 ng/ml) in group 1 and May 2001 (4.4±2.4 ng/ml) in group 2, and bottomed in August in group 1 and September in group 2 (around 0.1 ng/ml in both groups). Spermatogenesis and changes in GSI and plasma 11KT levels were repeated the following year in both groups. These observations indicate that males have an annual reproductive cycle under rearing conditions. It is possible that wild male common Japanese congers also have multiple spawning seasons in their lives.

Growth performance and sexual maturation in diploid and triploid Atlantic salmon ( Salmo salar L.) in seawater tanks exposed to continuous light or simulated natural photoperiod

Triploid Atlantic salmon are considered to be functionally sterile and the use of these in intensive fish farming would potentially reduce interactions between escapees and wild stocks. However, variable performance under commercial production conditions in seawater has been reported. The experiment described here is part of a larger comprehensive study on triploid Atlantic salmon, and investigates seasonal growth performance in diploid and triploid salmon under simulated natural light, and an accelerated production regime using continuous light during winter and spring. Four full-sib families of diploid and triploid Atlantic salmon postsmolts were held in six 20-m 3 circular indoor tanks in the January–October period after their transfer to seawater in July. Two tanks were given continuous light (LL) from January to June and subsequently put on simulated natural photoperiod (SNP), while four tanks were kept on SNP throughout. Variation in feed intake was monitored by waste feed collection, and fish were sampled monthly for weight and length. A depression in feed consumption was noted in the LL groups during the first 6–8 weeks after onset of light. As expected, the LL groups outperformed their SNP counterparts, but displayed an unexpected equal incidence of sexual maturation. Triploids displayed distinctly enhanced feed intake during their second sea autumn, which resulted in their being heavier and significantly longer than diploid fish in October. This increased feed intake in triploids was advanced in the LL treated fish. Only males showed signs of becoming ‘sexually mature’ (increased GSI) as grilse (after 1.5 years in seawater), and equal proportions of the diploid and triploid fish were characterised as sexually mature. Thus, lack of ‘sexual maturation’ could not explain the improved triploid growth. There were no distinct differences in mortality or occurrence of deformities between ploidy types. Both triploids and diploids responded to the accelerated light regime with an advanced seasonal development of growth and condition factor, long-term enhanced growth and an indicated improved feed conversion. In general, all sibling groups responded to the ploidy and light treatments. Growth differences between sibling groups within treatments were mainly ascribed to different proportions of sexual maturation. This study indicated that triploid Atlantic salmon performed equally, or better, compared to diploid conspecifics reared in indoor seawater tanks.

Nonadditive genetic effects and inbreeding depression for body weight in Atlantic salmon ( Salmo salar L.)

For four sub-populations of Atlantic salmon ( Salmo salar) in Norway, additive, dominance and additive by additive genetic variances and inbreeding depression were estimated for body weight at slaughter after two years in sea-water. The data used were from a hierarchical mating design, in which each sire was mated with two to seven dams. In each generation, 104 to 206 full-sib groups and 18 to 110 paternal half-sib groups were produced. Data from each sub-population covered three successive generations with pedigrees traced one generation further back to the base population. In the four sub-populations, the number of fish recorded ranged from 51 969 to 62 162 offsprings of 96 to 187 sires and 386 to 525 dams. A sire–dam model was applied separately to each of the sub-populations. In addition to the random additive, dominance and additive by additive genetic effects, the model also included the random environmental effect common to members of a full-sib group, a covariate of body weight on inbreeding coefficient, and a fixed subclass effect of year by farm by cage by sex. Variance components were estimated using an algorithm based on the tilde-hat approximation to REML with solutions for random effects obtained by iteration on data. In each of the four sub-populations, dominance and additive by additive genetic variances were at least equal to the additive genetic variance in magnitude. In every case, the inclusion of nonadditive genetic effects in the model lead to a 50 to 79% decline in the estimates of additive genetic variances, while reductions in the error variances were negligible. Estimates of common environmental effects ranged from 4 to 6% of the total phenotypic variance. Estimated inbreeding depression in the analysed data sets ranged from 0.6 to 2.6% per 10% increase in inbreeding coefficient.

Light intensity affects growth and sexual maturation of Atlantic salmon (Salmo salar) postsmolts in sea cages

The aim of the present study is to test the extent to which different intensities of continuous additional light affect somatic growth and sexual maturation in Atlantic salmon postsmolts in sea cages. Postsmolts (9 200 individuals) were randomly distributed among four commercial sized sea cages and exposed to either natural light or natural light + continuous additional light of low, medium or high intensity from January to June. In May the high light intensity group had a signiticantly higher mean live body weight than the other groups, and at the end of the experiment in June, all groups differed in mean gutted weight. There was a positive logarithmic regression between level of light intensity exposure during night and mean gutted weight. A small proportion of fish matured sexually (after 1.5 years in seawater) in the natural light group, whereas no maturation was detected in the light groups. These results suggests that to affect growth and proportion or maturation in Atlantic salmon by additional light, there might be different threshold values of light intensity.

Phenotypic and genetic parameters of body size traits in Atlantic salmonSalmo SalarL.

Data on two year classes of Atlantic salmon, Salmo salar L., reared for 2 years in sea water, were analysed. Records were obtained on 1271 offspring of 58 sires and 171 dams mated hierarchically. Medium-high sire heritabilities (0.30-0.38) were found for ungutted and gutted body weights, body length, body circumference and condition factor (whole-body traits). Corresponding estimates for height and width of cutlet and average thickness of the abdominal wall ranged from 0.23 to 0.27. The latter measurements were made on a transversal section anterior to the dorsal fin. Heritability estimates derived from the dam component of variance corresponded in general to the sire estimates, indicating the absence of non-additive genetic and environmental effects common to full sibs. Estimated phenotypic and genetic correlations among the traits were all positive. With regard to the likely breeding goal of a commercial selection programme, the genetic correlations of ungutted and gutted body weights with condition factor (rG=0.36-0.37) were judged unfavourable. The results revealed substantial impact of sex and sexual maturation status on growth. The need is stressed for proper adjustment for these effects when assessing growth or growth-related data.

Merremia discoidesperma: Its taxonomy and capacity of its seeds for ocean drifting

Merremia discoidesperma (Donn. Sm.) O’Donell (Mary’s-bean) is a rarely collected and inadequately described high climbing woody liana of Chiapas, Mexico; Guatemala; Costa Rica; Hispaniola; and Cuba. There is only one record of this species being cultivated and this from Guanajuato, Mexico in 1894, though seeds are used in folk remedies. These seeds are topographically unlike other known convolvulaceous seeds, thus permitting their positive identification. Because seeds remain buoyant for more than three years in seawater, those produced in the Caribbean and Atlantic drainage region may be transported by the Gulf Stream System as far north as the Norwegian coast, a distance of about 9,500 km. Seeds produced in the Pacific drainage region from Chiapas, Mexico south to Costa Rica may be transported by the North Pacific Equatorial Current as far west as Wotho Atoll in the Marshall Islands, a distance of about 11,000 km. Records of drifting and subsequent stranding of these and other tropical New World disseminules are supported by drift bottle studies and drift debris records in the Atlantic Ocean. In the Pacific Ocean region distribution of stranded Mary’s-bean seeds is supported by a similar distribution of New World pumice. There is an indication in the literature that Mary’s-bean seeds may drift to the Philippines. The record from Wotho Atoll to Norway constitutes the widest drift range of any seed or fruit which has been documented. Other tropical disseminules may drift as far or farther, but their origins cannot be ascertained with certainty. The plant is described, its synonyms listed, and its distribution as well as the distribution of its stranded seeds recorded.

Zinc as a Self-Regulating Galvanic Anode For Ship Hulls

Abstract This report presents results of service trials of up to three years duration for high purity and alloyed zinc hull anodes. The trials demonstrated that zinc anodes of suitable composition are capable of providing complete cathodic protection for ship hulls for extended periods in sea water. The current output of alloyed anodes (0.3% aluminum or 0.1% aluminum + 0.05% cadmium) is reliable and predictable because these materials do not polarize with time. Zinc hull anodes of suitable design can have useful current outputs for periods of eight to ten years in sea water. Bolting is a satisfactory method of fastening zinc anodes to a ship's hull. Zinc anodes cause little or no accelerated break-down of the adjacent hull paint. The two outstanding advantages of the zinc anode systems namely, self-regulation and improved current distribution, are available at a competitive price. Compared to the cheapest of the controlled type systems, whether of the galvanic or impressed voltage type, the zinc anode system at 13 cents per sq. ft. per year costs: (a) slightly more for large wetted hull areas of around 50,000 sq. ft., (b) slightly less for hull areas of around 15,000 sq. ft. and (c) markedly less for smaller hull areas. Recommendations are made for: (1) The more widespread use of zinc anodes for cathodic protection systems both on and in ships. (2) The use of high purity (ASTM Special High Grade) zinc alloyed with either aluminum, or aluminum plus cadmium, as the standard zinc anode material for all sea water applications. 5.2.2