Genetic comparison of two populations of the deep-sea vent shrimp Rimicaris exoculata (Decapoda: Bresiliidae) from the Mid-Atlantic Ridge

Allozyme data are presented for populations of the bresiliid shrimp Rimicaris exoculata from two hydrothermal vent fields, Trans-Atlantic Geotraverse (TAG) and Broken Spur, located along the Mid-Atlantic Ridge. These indicate that all morphotypes of R. exoculata examined, including those previously interpreted as representing separate species, are conspecific. Conversely, genetic identity between a single specimen of Chorocaris sp. and R. exoculata was high for intergeneric comparisons. Genetic variation in the populations of R. exoculata (H _o =0.034 to 0.056) was in the lower range of that estimated for other vent organisms, but similar to values obtained for other species of caridean shrimps in previous genetic studies. F-statistics were used to examine the population structure of R. exoculata. Estimates of variance of allele frequencies among populations (F _ST ) between TAG and Broken Spur were very low (mean F _ST =0.001), indicating no significant genetic differentiation between these populations although they were separated by 370 km. The number of migrants per generation was estimated from F _ST and by a private-alleles method, and indicates that migration between the two fields exceeds 100 individuals per generation. This may be because of efficient larval or adult migration or a combination of both. Estimates of the correlation between homologous alleles between individuals within local populations (F _IS ) of R. exoculata were high at two enzyme loci and indicate a heterozygote deficiency which caused a significant deviation from genotype frequencies expected under Hardy-Weinberg conditions. This deficiency was caused by the occurrence of rare homozygous genotypes in small individuals. In large individuals, rare alleles decreased in frequency or disappeared completely. This is discussed in relation to previous genetic investigations on other vent and nonvent organisms.     

Hardness corrections for copper are inappropriate for protecting sensitive freshwater biota

Toxicity testing using a freshwater alga (Chlorella sp.), a bacterium (Erwinnia sp.) and a cladoceran (Ceriodaphnia cf. dubia) exposed to copper in synthetic and natural freshwaters of varying hardness (44-375 mg CaCO3/l), with constant alkalinity, pH and dissolved organic carbon concentration, demonstrated negligible hardness effects in the pH range 6.1-7.8. Therefore, the use of a generic hardness-correction algorithm, developed as part of national water quality guidelines for protecting freshwater biota, is not recommended for assessing the toxicity of copper to these, and other, sensitive freshwater species. Use of the algorithm for these sensitive species will be underprotective because the calculated concentrations of copper in water that cause a toxic effect will be higher.     

Impact of transverse and longitudinal dispersion on first-order degradation rate constant estimation

A two-dimensional analytical model is employed for estimating the first-order degradation rate constant of hydrophobic organic compounds (HOCs) in contaminated groundwater under steady-state conditions. The model may utilize all aqueous concentration data collected downgradient of a source area, but does not require that any data be collected along the plume centerline. Using a least squares fit of the model to aqueous concentrations measured in monitoring wells, degradation rate constants were estimated at a former manufactured gas plant (FMGP) site in the Midwest U.S. The estimated degradation rate constants are 0.0014, 0.0034, 0.0031, 0.0019, and 0.0053 day(-1) for acenaphthene, naphthalene, benzene, ethylbenzene, and toluene, respectively. These estimated rate constants were as low as one-half those estimated with the one-dimensional (centerline) approach of Buscheck and Alcantar [Buscheck, T.E., Alcantar, C.M., 1995. Regression techniques and analytical solutions to demonstrate intrinsic bioremediation. In: Hinchee, R.E., Wilson, J.T., Downey, D.C. (Eds.), Intrinsic Bioremediation, Battelle Press, Columbus, OH, pp. 109-116] which does not account for transverse dispersivity. Varying the transverse and longitudinal dispersivity values over one order of magnitude for toluene data obtained from the FMGP site resulted in nearly a threefold variation in the estimated degradation rate constant-highlighting the importance of reliable estimates of the dispersion coefficients for obtaining reasonable estimates of the degradation rate constants. These results have significant implications for decision making and site management where overestimation of a degradation rate may result in remediation times and bioconversion factors that exceed expectations. For a complex source area or non-steady-state plume, a superposition of analytical models that incorporate longitudinal and transverse dispersion and time may be used at sites where the centerline method would not be applicable.     

Assessment of intrinsic bioremediation of a coal-tar-affected aquifer using Two-dimensional reactive transport and Biogeochemical mass balance approaches.

Expedited site characterization and groundwater monitoring using direct-push technology and conventional monitoring wells were conducted at a former manufactured gas plant site. Biogeochemical data and heterotrophic plate counts support the presence of microbially mediated remediation. By superimposing solutions of a two-dimensional reactive transport analytical model, first-order degradation rate coefficients ((day-1) ) of various compounds for the dissolved-phase plume were estimated (i.e., benzene [0.0084], naphthalene [0.0058], and acenaphthene [0.0011]). The total mass transformed by aerobic respiration, nitrate reduction, and sulfate reduction around the free-phase coal-tar dense-nonaqueous-phase-liquid region and in the plume was estimated to be approximately 4.5 kg/y using a biogeochemical mass-balance approach. The total mass transformed using the degradation rate coefficients was estimated to be approximately 3.6 kg/y. Results showed that a simple two-dimensional analytical model and a biochemical mass balance with geochemical data from expedited site characterization can be useful for rapid estimation of mass-transformation rates.     

Do Midas cichlids win through prowess or daring? It depends

Summary Individual Midas cichlids (Cichlasoma citrinellum) show persistent differences in aggressive behavior toward dummy fish. The starting question was whether the level of such behavior can be used to predict the winner of a fight. In the first (long-term) experiment two fish were matched for size, color, and sex. After 24 h the opaque barrier separating the 2 fish was removed; they immediately behaved aggressively. Scores for aggression toward dummies did not predict the winners, nor did taking the initiative in escalation. But weight did foretell the winners, who averaged only 2% heavier than their opponents. The conventional display phase of such fights was brief (20% of total duration), and escalation was rapid. Both winners and losers sustained damage, but losers accumulated damage faster than winners. In the subsequent (short-term) experiment the fish were separated only 1–2 h. Now aggression scores predicted winners, and winners were the fish who escalated. Weight of fish had no effect. The conventional phase was relatively much longer, about half the length of the fight. Losers accumulated damage at the same rate as the losers in the long-term experiment, but the fights were shorter; winners suffered little damage. The fish had difficulty assessing one another. Fighting prowess was remarkably uniform when weight was factored out. Daring to escalate, in contrast, varied among individuals and correlated with aggression scores. Prowess (=weight) determined the outcome in the long-term experiment, which may find its parallel in nature in intraterritorial disputes. Daring to escalate determined the winner in the short-term experiment; this may be comparable to establishing a territory in nature.Prowess probably results from strong directional selection because it has low costs and high benefits. In contrast, daring is subject to bi-directional selection because both costs and benefits are high. Resource holding potential is conventionally viewed as deriving from prowess of self and opponent and value of resource; to that one must add the individual's inherent aggressiveness.     

Design and Testing of a New Size Classifying Isokinetic Sequential Aerosol Sampler

Two versions of a size-classifying isokinetic sequential aerosol sampler (SCISAS) have been designed, built, tested, and deployed in a field program in the southwestern United States. The SCISAS units can operate at unattended sites, exposing four or more filter types simultaneously, in two size ranges, for six sampling time Intervals. Design considerations included theoretical estimates of aerosol particle losses in the 0-15 μm size range.

SCISAS prototypes have been tested to evaluate their sampling efficiency as a function of flow rate, the sensitivity of the sampling efficiency to isokinetic matching within the SCISAS sampling stack, the equivalency of their sampling ports, and their passive deposition characteristics. The prototypes were also compared to several other types of aerosol filtration samplers already in common use. These tests show that particle loss mechanisms within the SCISAS usually cause no more than 5 percent losses, and that the SCISAS units agree, within one to two measurement uncertainty intervals, with other types of aerosol samplers.     

A multi-criteria approach to screening alternatives for converting sewage sludge to biodiesel

The search for cheaper feedstock for use in the production of biofuels such as biodiesel has turned attention to various forms of waste products including animal fats, waste oils and now lipids in sludge. With the potential of obtaining sludge at a reduced cost, free, or possibly with incentives, sewage sludge is being investigated as a potential feedstock for biofuel production. For the extraction of oils from the sewage sludge and the subsequent processing, there are various alternatives that should be designed, analyzed, and screened. In developing and screening these alternatives, it is necessary to have a consistent basis for comparing alternatives based on key criteria. While most of the design studies focus on techno-economic criteria, it is also important to include safety metrics in the multi-criteria analysis. In this work, a detailed economic analysis and a safety evaluation are performed on a process involving extraction of triglycerides and fatty acids, pre-treatment of fatty acids (direct conversion to biodiesel), and transesterification of triglycerides to biodiesel. Four solvents, toluene, hexane, methanol and ethanol, are individually used in the extraction process. The resulting triglycerides and fatty acids from each extraction are modeled in the pre-treatment process. ASPEN Plus software is used to simulate the detailed process. Economic analysis is performed using ASPEN ICARUS, and scale-up of a previously analyzed process is used to estimate the cost of the biodiesel portion of the process. A new safety metric (referred to as the Safety Index “SI”) is introduced to enable comparison of the various solvent extraction processes. The SI is based on solvent criteria as well as process conditions. A case study is presented to demonstrate the insights and usefulness of the developed approach. The results of the techno-economic analysis reveal that of the four solvents used for the initial extraction, hexane and toluene were least costly (2.89 and 2.79 $/gal, respectively). Conversely, the safety analysis utilizing the SI reveals that methanol and ethanol are the safer solvent options. The issue of cost/safety tradeoffs is also discussed.     

Specificity and sensitivity of microsatellite markers for the identification of larvae

The identification of larval marine invertebrates to species or even higher taxonomic levels by morphological examination is notoriously difficult. Many diagnostic features are absent or poorly formed at early stages in development. This is particularly true for the larvae of bivalve molluscs, for which a routine and accurate method of identification would prove valuable to both ecologists and fishery managers. A simple molecular genetic method to identify specifically larvae of the European oyster, Ostrea edulis L., 1758, is presented. The test is based on PCR amplification of highly species-specific microsatellite loci and is sensitive enough to register the presence of a single larval individual (~200 µm width) in a mixed sample of 20 mg wet weight plankton (approximately 250 larval animals). This work demonstrates that microsatellite loci can be used as highly sensitive and specific taxonomic indicators, for studies of planktonic larvae. Details of three novel microsatellite loci are also given for O. edulis, increasing the suite of molecular tools available for use in population genetic studies of this commercially important species.