Effects of Major Water Quality Variables on Shrimp Production in Inland,Low‐Salinity Ponds in Alabama

Common water quality variables in nine, inland low‐salinity shrimp ponds in Alabama exhibited wide variation in concentrations among ponds and over time. Shrimp performance also varied considerably among ponds in 2008 as follows: survival, 16–128%; production, 928–5950 kg/ha; feed conversion ratio (FCR), 1.18–2.89. Measured water quality variables were not at concentrations high enough to be lethal to shrimp; but water temperature, dissolved oxygen, carbon dioxide, total ammonia nitrogen, calcium, and magnesium were occasionally outside optimum ranges for shrimp production and may have stressed shrimp. Survival and production both were positively correlated (P < 0.05) with increasing concentrations of methyl orange alkalinity, total alkalinity, and calcium hardness. Negative correlations (P < 0.05) between production and higher pH and water temperature may have resulted from lower water temperature and pH during final days of the crop in ponds harvested in October rather than from an actual effect of temperature and pH on growth. Nevertheless, those variables that were outside optimal ranges or correlated with shrimp survival or growth should be further investigated to ascertain whether or not excursions outside optimum ranges are harmful and to determine if observed correlations are causal.     

Trace elements in waters of inland,low‐salinity shrimp ponds in Alabama

Trace element concentrations in waters of 10, inland, low‐salinity shrimp ponds in Alabama tended to be greater than those found in normal seawater – molybdenum, boron and silicon were exceptions. Concentrations of most trace elements varied greatly among ponds on individual sampling dates, and average concentrations based on all sampling dates in individual ponds also varied considerably. The analytical method used, digestion of water samples in nitric acid followed by inductively coupled plasma atomic emission spectrophotometry, measured total concentrations of trace elements – free ions, hydrolysis products, ion pairs, coordination compounds (chelated forms) and particulate forms. Free ions are the toxic forms of most trace elements and the ionic concentration is much less than the total concentration of a trace element. Based on total concentrations of trace elements, it is doubtful that free‐ionic concentrations of trace elements were great enough to harm shrimp. The fact that no negative correlations were noted between trace element concentrations and shrimp survival and production supports this conclusion. However, positive correlations (P < 0.05) between shrimp survival and production and increasing concentrations of zinc, cobalt and iron should be investigated further to ascertain if additions of these elements to ponds might improve shrimp performance.     

Water Temperature in Inland,Low-Salinity Shrimp Ponds in Alabama

Water temperature in eight ponds and air temperatures were monitored at 2-h intervals during the 2010 growing season at an inland, low-salinity shrimp farm in Alabama. There was a high correlation (P < 0.01) between mean daily air and water temperatures; pond water usually averaged 3° to 4°C warmer than air. Monthly mean water temperatures among eight ponds differed by 3.40°C in May and by 2.83°C in September, but there was less than 1°C difference among ponds in June, July, and August. Differences in temperature among ponds were not related to pond water surface:volume ratio, but in July and September there was a negative correlation (P < 0.05) with increasing aeration rate. Negative correlations (P < 0.05) between average water temperature over the entire culture period and survival and production of Pacific white shrimp, Litopeneaus vannamei, possibly resulted from variation in crop duration and were not causal. Nevertheless, differences in water temperature among ponds in May and September were great enough to have possibly caused differential shrimp survival and production among ponds.     

Equilibrium and kinetic modeling of the adsorption of indigo carmine onto silk

Quantitative adsorption kinetic and equilibrium parameters for indigo carmine dyeing of silk were studied using UV-visible absorption spectroscopy. The effect of initial dye concentration, contact time, pH, material to liquor ratio (MLR), and temperature were determined to find the optimal conditions for adsorption. The mechanism of adsorption of indigo carmine dyeing onto silk was investigated using the pseudo first-order and pseudo second-order kinetic models. The adsorption kinetics was found to follow a pseudo-second-order kinetic model with an activation energy (E _a) of 51.06 kJ/mol. The equilibrium adsorption data of indigo carmine dye on silk were analyzed by the Langmuir and Freundlich models. The results indicate that the Langmuir model provides the best correlation. Adsorption isotherms were also used to obtain thermodynamic parameters such as free energy (ΔG ^o), enthalpy (ΔH ^o), and entropy (ΔS ^o) of adsorption. The negative values of ΔG ^o and Δ^{H o} indicate the overall adsorption process is a spontaneous and exothermic one.