Growth rates of Fe-Mn nodules and age and sedimentation rates of host sediments from the Southeast Pacific

Growth rates of nine ferromanganese nodules collected from the Southeast Pacific were estimated using the alpha radiogpaphic technigue. Growth rates range from 1 to 16 mm per million years. In three nodules measurements were made on two opposite sides; two of them showed no growth in one of measured directions during the last 300 ky, whereas in the third nodule growth rates on the opposite sides differ by factor 2. Average sedimentation rate of deposits underlying the nodules estimated by the radiocarbon and excess 230Th methods, were 4 mm/1000 years with rather minor variations. Difference between sedimentation rates and nodule growth rates is caused by activity of benthic fauna, as suggested by inversion of radiocarbon dates with depth.

Rising longevity, education, savings, and growth

This paper examines the impact of declines in adult mortality on growth in an overlapping generations model. With public education and imperfect annuity markets, a decline in mortality affects growth through three channels. First, it raises the saving rate and thereby increases the rate of physical capital accumulation. Second, it reduces accidental bequests, lowers investment, and thereby lowers the rate of physical capital accumulation. Third, it may lead the median voter to increase the tax rate for public education initially but lower the tax rate in a later stage. Starting from a high mortality rate as found in many Third World populations, the net effect of a decline in mortality is to raise the growth rate. However, starting from a low mortality rate such as is found in most industrial populations, the net effect of a further decline in mortality is to reduce the growth rate. The findings appear consistent with recent empirical evidence. (C) 2002 Elsevier Science B.V All rights reserved.

The effects of density on the growth and survival of different families of juvenile Penaeus japonicus Bate

Variations in the growth and survival of six families of juvenile (initial mean weight = 4.16 g) Penaeus japonicus were examined at two densities (48 and 144 individuals m(-2)) in a controlled laboratory experiment. Survival was very high throughout the experiment (95.4%), but differed significantly between densities and rearing tanks. Family, sex and family x density interaction did not significantly affect survival. Mean specific growth rate (SGR) of the shrimp was 18% faster at the low density (1.93 +/- 0.05% day(-1)) than at high density (1.64 +/- 0.03% day(-1)). However, there was a small but significant interaction between family and density indicating that growth of the families was not consistent at both densities. The inconsistent growth of the families across the two densities resulted in a change in the relative performance (ranking) of families at each density. Sex, rearing tank and rearing cage also affected growth of the shrimp. Mean SGR of the females (1.79 +/- 0.03% day(-1)) was 5% faster than males (1.70 +/- 0.03% day(-1)) when averaged across both densities. Shrimp grew significantly faster in rearing tank 3 than rearing tank 1 or 2 at both densities. Results of the present study suggest that family x density interaction could affect the efficiency of selection for growth if shrimp stocks produced from shrimp breeding programs are to be grown across a wide range of densities. Crown Copyright (C) 2004 Published by Elsevier B.V. All rights reserved.

Prediction of the growth of wear-type rail corrugation

The growth behaviour of the vibrational wear phenomenon known as rail corrugation is investigated analytically and numerically using mathematical models. A simplified feedback model for wear-type rail corrugation that includes a wheel pass time delay is developed with an aim to analytically distil the most critical interaction occurring between the wheel/rail structural dynamics, rolling contact mechanics and rail wear. To this end, a stability analysis on the complete system is performed to determine the growth of wear-type rail corrugations over multiple wheelset passages. This analysis indicates that although the dynamical behaviour of the system is stable for each wheel passage, over multiple wheelset passages, the growth of wear-type corrugations is shown to be the result of instability due to feedback interaction between the three primary components of the model. The corrugations are shown analytically to grow for all realistic railway parameters. From this analysis an analytical expression for the exponential growth rate of corrugations in terms of known parameters is developed. This convenient expression is used to perform a sensitivity analysis to identify critical parameters that most affect corrugation growth. The analytical predictions are shown to compare well with results from a benchmarked time-domain finite element model. (C) 2004 Elsevier B.V. All rights reserved.

Effects of phosphorus on the growth and nitrogen fixation rates of Lyngbya majuscula: implications for management in Moreton Bay, Queensland

Significant acetylene reduction and therefore N-2 fixation was observed for Lyngbya majuscula only during dark periods, which suggests that oxygenic photosynthesis and N-2 fixation are incompatible processes for this species. Results from a series of batch and continuous-flow-culture reactor studies showed that the specific growth rate and N-2 fixation rate of L, majuscula increased with phosphate (P-PO4) concentration up to a maximum value and thereafter remained constant. The P-PO4 concentrations corresponding to the maximum N-2 fixation and maximum growth rates were -0.27 and -0.18 muM respectively and these values are denoted as the saturation values for N-2 fixation and growth respectively. Regular monitoring studies in Moreton Bay, Queensland, show that concentrations Of P-PO4 generally exceed these saturation values over a large portion of the Bay and therefore, the growth of the bloom-forming L, majuscula is potentially maximised throughout much of the Bay by the elevated P-PO4 concentrations. Results from other studies suggest that the elevated P-PO4 concentrations in the Bay can be largely attributed to discharges from waste-water treatment plants (WWTPs), and thus it is proposed that the control of the growth of L. majuscula in Moreton Bay will require a significant reduction in the P load from the WWTP discharges. If the current strategy of N load reduction for these discharges is maintained in the absence of substantial P load reduction, it is hypothesised that the growth of L, majuscula and other diazotrophs in Moreton Bay will increase in the future.

Green turtle somatic growth dynamics in a spatially disjunct Great Barrier Reef metapopulation

The growth dynamics of green sea turtles resident in four separate foraging grounds of the southern Great Barrier Reef genetic stock were assessed using a nonparametric regression modeling approach. Juveniles recruit to these grounds at the same size, but grow at foraging-ground-dependent rates that result in significant differences in expected size- or age-at-maturity. Mean age-at-maturity was estimated to vary from 25-50 years depending on the ground. This stock comprises mainly the same mtDNA haplotype, so geographic variability might be due to local environmental conditions rather than genetic factors, although the variability was not a function of latitudinal variation in environmental conditions or whether the food stock was seagrass or algae. Temporal variability in growth rates was evident in response to local environmental stochasticity, so geographic variability might be due to local food stock dynamics. Despite such variability, the expected size-specific growth rate function at all grounds displayed a similar nonmonotonic growth pattern with a juvenile growth spurt at 60-70 cm curved carapace length, (CCL) or 15-20 years of age. Sex-specific growth differences were also evident with females tending to grow faster than similar-sized males after the Juvenile growth spurt. It is clear that slow sex-specific growth displaying both spatial and temporal variability and a juvenile growth spurt are distinct growth behaviors of green turtles from this stock.

Spatial and temporal variability in somatic growth of green sea turtles (Chelonia mydas) resident in the Hawaiian Archipelago

The somatic growth dynamics of green turtles ( Chelonia mydas) resident in five separate foraging grounds within the Hawaiian Archipelago were assessed using a robust non-parametric regression modelling approach. The foraging grounds range from coral reef habitats at the north-western end of the archipelago, to coastal habitats around the main islands at the southeastern end of the archipelago. Pelagic juveniles recruit to these neritic foraging grounds from ca. 35 cm SCL or 5 kg ( similar to 6 years of age), but grow at foraging-ground-specific rates, which results in quite different size- and age-specific growth rate functions. Growth rates were estimated for the five populations as change in straight carapace length ( cm SCL year) 1) and, for two of the populations, also as change in body mass ( kg year) 1). Expected growth rates varied from ca. 0 - 2.5 cm SCL year) 1, depending on the foraging-ground population, which is indicative of slow growth and decades to sexual maturity, since expected size of first-time nesters is greater than or equal to 80 cm SCL. The expected size- specific growth rate functions for four populations sampled in the southeastern archipelago displayed a non-monotonic function, with an immature growth spurt at ca. 50 - 53 cm SCL ( similar to 18 - 23 kg) or ca. 13 - 19 years of age. The growth spurt for the Midway atoll population in the northwestern archipelago occurs at a much larger size ( ca. 65 cm SCL or 36 kg), because of slower immature growth rates that might be due to a limited food stock and cooler sea surface temperature. Expected age-at-maturity was estimated to be ca. 35 - 40 years for the four populations sampled at the south-eastern end of the archipelago, but it might well be > 50 years for the Midway population. The Hawaiian stock comprises mainly the same mtDNA haplotype, with no differences in mtDNA stock composition between foraging-ground populations, so that the geographic variability in somatic growth rates within the archipelago is more likely due to local environmental factors rather than genetic factors. Significant temporal variability was also evident, with expected growth rates declining over the last 10 - 20 years, while green turtle abundance within the archipelago has increased significantly since the mid-1970s. This inverse relationship between somatic growth rates and population abundance suggests a density-dependent effect on somatic growth dynamics that has also been reported recently for a Caribbean green turtle stock. The Hawaiian green turtle stock is characterised by slow growth rates displaying significant spatial and temporal variation and an immature growth spurt. This is consistent with similar findings for a Great Barrier Reef green turtle stock that also comprises many foraging-ground populations spanning a wide geographic range.

Modelling the effect of fibropapilloma disease on the somatic growth dynamics of Hawaiian green sea turtles

The effect of the tumour-forming disease, fibropapillomatosis, on the somatic growth dynamics of green turtles resident in the Pala'au foraging grounds (Moloka'i, Hawai'i) was evaluated using a Bayesian generalised additive mixed modelling approach. This regression model enabled us to account for fixed effects (fibropapilloma tumour severity), nonlinear covariate functional form (carapace size, sampling year) as well as random effects due to individual heterogeneity and correlation between repeated growth measurements on some turtles. Somatic growth rates were found to be nonlinear functions of carapace size and sampling year but were not a function of low-to-moderate tumour severity. On the other hand, growth rates were significantly lower for turtles with advanced fibropapillomatosis, which suggests a limited or threshold-specific disease effect. However, tumour severity was an increasing function of carapace size-larger turtles tended to have higher tumour severity scores, presumably due to longer exposure of larger (older) turtles to the factors that cause the disease. Hence turtles with advanced fibropapillomatosis tended to be the larger turtles, which confounds size and tumour severity in this study. But somatic growth rates for the Pala'au population have also declined since the mid-1980s (sampling year effect) while disease prevalence and severity increased from the mid-1980s before levelling off by the mid-1990s. It is unlikely that this decline was related to the increasing tumour severity because growth rates have also declined over the last 10-20 years for other green turtle populations resident in Hawaiian waters that have low or no disease prevalence. The declining somatic growth rate trends evident in the Hawaiian stock are more likely a density-dependent effect caused by a dramatic increase in abundance by this once-seriously-depleted stock since the mid-1980s. So despite increasing fibropapillomatosis risk over the last 20 years, only a limited effect on somatic growth dynamics was apparent and the Hawaiian green turtle stock continues to increase in abundance.

The effect of life expectancy on fertility, saving, schooling and economic growth: theory and evidence

We construct a simple growth model where agents with uncertain survival choose schooling time, life-cycle consumption and the number of children. We show that rising longevity reduces fertility but raises saving, schooling time and the growth rate at a diminishing rate. Cross-section analyses using data from 76 countries support these propositions: life expectancy has a significant positive effect on the saving rate, secondary school enrollment and growth but a significant negative effect on fertility. Through sensitivity analyses, the effect on the saving rate is inconclusive, while the effects on the other variables are robust and consistent. These estimated effects are decreasing in life expectancy. Copyright The editors of the Scandinavian Journal of Economics 2005.

The secondary nucleation threshold and crystal growth of alpha-glucose monohydrate in aqueous solution

Investigation of the secondary nucleation threshold (SNT) of alpha-glucose monohydrate was conducted in aqueous solutions in agitated batch systems for the temperature range 10 to 40 degrees C. The width of the SNT decreased as the induction time increased and was found to be temperature independent when supersaturation was based on the absolute concentration driving force. Nonnucleating seeded batch bulk crystallizations of this sugar were performed isothermally in the same temperature range as the SNT experiments, and within the SNT region to avoid nucleation. The growth kinetics were found to be linearly dependent on the supersaturation of total glucose in the system when the mutarotation reaction is not rate limiting. The growth rate constant increases with increasing temperature and follows an Arrhenius relationship with an activation energy of 50 +/- 2 kJ/mol. alpha-Glucose monohydrate shows significant crystal growth rate dispersion (GRD). For the seeds used, the 95% range of growth rates was within a factor of 6 for seeds with a narrow particle size distribution, and 8 for seeds with a wider distribution that was used at 25 degrees C. The results will be used to model the significance of the mutarotation reaction on the overall crystallization rate of D-glucose in industrial crystallization.

Heritability estimates for growth in the tropical abalone Haliotis asinina using microsatellites to assign parentage

The tropical abalone Haliotis asinina is a wild-caught and cultured species throughout the Indo-Pacific as well as being an emerging model species for the study of haliotids. H. asinina has the fastest recorded natural growth rate of any abalone and reaches sexual maturity within one year. As such, it is a suitable abalone species for selective breeding for commercially important traits such as rapid growth. Estimating the amount of variation in size that is attributable to heritable genetic differences can assist the development of such a selective breeding program. Here we estimated heritability for growth-related traits at 12 months of age by creating a single cohort of 84 families in a full-factorial mating design consisting of 14 sires and 6 dams. Of 500 progeny sampled, 465 were successfully assigned to their parents based on shared alleles at 5 polymorphic microsatellite loci. Using an animal model, heritability estimates were 0.48 +/- 0.15 for shell length, 0.38 +/- 0.13 for shell width and 0.36 +/- 0.13 for weight. Genetic correlations were > 0.98 between shell parameters and weight, indicating that breeding for weight gains could be successfully achieved by selecting for shell length. (c) 2006 Elsevier B.V. All rights reserved.

Age and growth in olive ridley seaturtles (Lepidochelys olivacea) from the north-central Pacific: a skeletochronological analysis

The olive ridley is the most abundant seaturtle species in the world but little is known of the demography of this species. We used skeletochronological data on humerus diameter growth changes to estimate the age of North Pacific olive ridley seaturtles caught incidentally by pelagic longline fisheries operating near Hawaii and from dead turtles washed ashore on the main Hawaiian Islands. Two age estimation methods [ranking, correction factor (CF)] were used and yielded age estimates ranging from 5 to 38 and 7 to 24 years, respectively. Rank age-estimates are highly correlated (r = 0.93) with straight carapace length (SCL), CF age estimates are not (r = 0.62). We consider the CF age-estimates as biologically more plausible because of the disassociation of age and size. Using the CF age-estimates, we then estimate the median age at sexual maturity to be around 13 years old (mean carapace size c. 60 cm SCL) and found that somatic growth was negligible by 15 years of age. The expected age-specific growth rate function derived using numerical differentiation suggests at least one juvenile growth spurt at about 10–12 years of age when maximum age-specific growth rates, c. 5 cm SCL year−1, are apparent.

Application of DNA parentage analyses for determining relative growth rates of Penaeus japonicus families reared in commercial ponds

The ability to track large numbers of individuals and families is a key determinant of the power and precision of breeding programs, including the capacity to quantify interactions between genotypes and their environment. Until recently, most family based selective breeding programs for shrimp, and other highly fecund aquaculture species, have been restricted by the number of animals that can be physically tagged and individually selected. Advances in the development of molecular markers, such as microsatellite loci, are now providing the means to track large numbers of individuals and families in commercial production systems. In this study microsatellites, coupled with DNA parentage analyses, were used to determine the relative performance of 22 families of R japonicus reared in commercial production ponds. In the experimental design 6000 post-larvae from each of 22 families, whose maternal parents had been genotyped at 8 microsatellite loci, were stocked into each of four I ha ponds. After 6 months the ponds were harvested and a total of 6000 individuals were randomly weighed from each pond. Mean wet weight of the shrimp from one pond was significantly lower than that of the other three ponds demonstrating a possible pond effect on growth rate. The representation of families in the top 10% of each pond's weight distribution was then determined by randomly genotyping up to 300 individuals from this upper weight class. Parentage analyses based on individual genotypic data demonstrated that some families were over-represented in the top 10% in all ponds, while others were under-represented due to slower growth rates. The results also revealed some weak, but significant, male genotype x environment (G x E) interactions in the expression of shrimp growth for some families. This indicates that G x E effects may need to be factored into future R japonicus selective breeding programs. This study demonstrated the utility of DNA parentage analyses for tracking individual family performance in communally stocked shrimp pond populations and, its application to examining G x E effects on trait expression under commercial culture conditions. Crown Copyright (c) 2005 Published by Elsevier B.V. All rights reserved.