Comparison of Three Culture Methods for the Intensive Culture of Northern Quahog Seed, Mercenaria mercenaria

A number of approaches have been utilized for growing bivalve hatchery seed (1 mm) to a size suitable for field planting (< 8 mm) but few have been directly compared. This study evaluated the growth and survival of northern quahog seed in three different culture systems and two different stocking densities. The three systems were: 1) a stacked-tray unit with downward water flow; 2) traditional upweller culture units with water flowing upward without seed bed expansion; and 3) upweller culture units with water flowing upward at fluidization velocities to provide seed bed expansion. The two stocking densities were 1.0 and 3.0 g whole wet weight clam/cm² respectively. During each trial period the seed clams were fed a 1% daily ration (% dry weight algae per wet weight clam per day) of the cultured diatom Chaetoceros muelleri . After 14 d of culture at the 1.0 g whole wet weight/cm² stocking density, seed clams (4.4 ± 0.6 mm initial shell length) under fluidized-flow condition exhibited better growth (0.54/d), and a greater final shell length (5.9 ± 1.0 mm). At the high density stocking conditions, after 28 d of culture, seed clams (4.2 ± 0.6 mm initial shell length) in the fluidized-flow culture conditions again exhibited better growth rate (0.031/d) and a greater final shell length (6.0 ± 1.0 mm). The preliminary evaluation of fluidized-flow for seed clam culture in land-based nurseries indicates its potential as a suitable alternative to raceway, downwelling, or traditional forced-flow culture methods.     

Environmental genome shotgun sequencing of the Sargasso Sea

We have applied "whole-genome shotgun sequencing" to microbial populations collected en masse on tangential flow and impact filters from seawater samples collected from the Sargasso Sea near Bermuda. A total of 1.045 billion base pairs of nonredundant sequence was generated, annotated, and analyzed to elucidate the gene content, diversity, and relative abundance of the organisms within these environmental samples. These data are estimated to derive from at least 1800 genomic species based on sequence relatedness, including 148 previously unknown bacterial phylotypes. We have identified over 1.2 million previously unknown genes represented in these samples, including more than 782 new rhodopsin-like photoreceptors. Variation in species present and stoichiometry suggests substantial oceanic microbial diversity.     

Trees enhance soil carbon sequestration and nutrient cycling in a silvopastoral system in south-western Nicaragua

Tree occurrence in silvopastoral systems of Central America has been under pressure for various reasons including attempts to improve grassland productivity and the need for wood. However, scattered isolated trees are also recognized to provide ecosystem services like shade, fodder and fruits that are important to cattle in the dry season. In addition, trees may enhance the climate change mitigation potential of silvopastoral systems through increased carbon (C) uptake and subsequent soil carbon sequestration. Through differences in plant traits like nutrient uptake, canopy structure and litter quality, tree species may have an effect on C and nutrient cycling. Due to a prevailing north-easterly wind in the study area, three distinct areas associated with the impact of tree litter deposition were identified: (1) open pasture—no tree litter deposition; (2) tree canopy—above and belowground tree litter; and (3) leaf litter cone—aboveground tree litter deposition. Furthermore, the effect of tree species, Guazuma ulmifolia and Crescentia alata, were considered. The presence of trees, as compared to pasture, caused larger topsoil C, N and P contents. In the subsoil, C content was also larger due to tree presence. Soil fractionation showed that tree-induced larger litter input subsequently increased free and occluded OM fractions and ultimately increased stabilized SOM fractions. Therefore, trees were found to enhance soil C sequestration in these silvopastoral systems. This is also supported by the soil respiration data. Although the respiration rates in the pasture subplots were lower than in the leaf litter subplots, the difference was not significant, which suggests that part of the extra C input to the leaf litter subplots stayed in the soil. Nutrient cycling was also enhanced by tree presence, but with a clear differentiation between species. C. alata (Jícaro) enhanced available and stabilized forms of organic N, while G. ulmifolia (Guácimo) enhanced available soil P and stabilized organic P.     

Housing of dogs and cats in animal shelters]

The results of an examination of 10 animal shelters was, that anyone was unical. The everyday and fundamental problems in administration, housing animals and animal care were the same: Most of them employ laity, which do their job with a lot of commitment but without knowledge. Therefore they come into conflict with the demands of animal protection. Veterinary surgeons, responsible authorities and communities are strongly asked to take steps against the situation. The reason for the fact, that such steps are missed, is, that there is no guideline or recommendation available for these persons, which handles animal shelters relative to "animal justice" and the right housing of animals. The results of the survey helps to make a guideline for animal home owners and builders, veterinary surgeons, veterinary authorities and communities, which gives suggestions to build, equip and run animal shelters for cats and dogs responsible regarding the individual circumstances and in the best way for animals.     

Contaminant washout in a hydraulically integrated serial turbidostat algal reactor (HISTAR)

A hydraulically integrated serial turbidostat algal reactor (HISTAR) was mathematically modeled and designed for large-scale production of microalgae. HISTAR, which combines turbidostats with a series of continuous-flow stirred-tank reactors (CFSTRs), was designed with contaminant mitigation as a primary design parameter. The concept of contaminant mitigation in the series of CFSTRs is discussed and three mathematical models presented to predict contaminant washout within the CFSTRs. Model simulations indicated that the hydraulic regime within each CFSTR is crucial to the contaminant mitigation process in the series of CFSTRs. Experiments on the HISTAR system with a liquid volume of about 8500 l, culturing Chaetoceros muelleri (CHAET 10), demonstrated that 0.8 million live rotifers, intentionally added to the first CFSTR, were washed out of the six CFSTRs at a local dilution rate of 4 day⁻¹. In another experiment, Thalassiosira sp. cultured at a dilution rate of 0.667 day⁻¹ fell victim to a few rotifers that inadvertently entered the CFSTRs. The validity of the washout concepts was demonstrated further when the ≈300 million live rotifers in the CFSTRs were completely washed out by simply increasing the dilution rate to 4 day⁻¹.     

Development of a Model for Describing Accumulation of Color and Subsequent Destruction by Ozone in a Freshwater Recirculating Aquaculture System

The purpose of this study was to develop a mathematical model to assist in the determination of design numbers for color destruction by ozone as a function of feed rate. A mass balance model was developed that takes into account methods of introduction and removal of color, including removal by ozone. Because direct measurement of color mass or concentration is difficult, a representative unit was developed during this study called the color mass equivalent (CME). The CME represents a direct measurement of absorbance at 436 nm, which is a unitless measurement, multiplied by the system volume. The CME is directly proportional to the true concentration of color causing compounds at that wavelength. Once the model was developed, two studies were run to test the model. A 1,500-L recirculating fish system was set up with a 57-L bead filter and six 1-L fluidized sand beds. Approximately 45 kg of channel catfish Ictalurus puncfatus were placed in the system and fed 0.25 kg of 32% protein feed per day (0.55% body wt.). Once the system reached stable conditions, the system was flushed with clean water and samples were taken to estimate the accumulation rate of color in the system. After 5 wk, an ozone unit was activated and samples were taken to determine the destruction rate for color. Once an accumulation rate had been determined, a second study was performed to corroborate this value. The same ozone unit was installed on a 5,000-L recirculating fish system being fed 0.49 kg per day with a 171-L bead filter. Samples were taken to determine the destruction rate for color. The accumulation rate for color was 12.6 CME/kg feed and the destruction rates were 1.7 CME/g O₃ in the first study and 0.82 CMWg O₃ in the second study. This calculates to a range of 7 to 15 g O₃/kg feed to remove the color produced by the feed.     

Microalgal production using a hydraulically integrated serial turbidostat algal reactor (HISTAR): a conceptual model

A hydraulically integrated, serial turbidostat algal reactor (HISTAR) was mathematically modeled and developed for the mass production of microalgae. HISTAR, which hydraulically links precisely controlled turbidostats with continuous-flow stirred-tank reactors (CFSTRs) into a single production technology, was conceptualized emphasizing contaminant mitigation at the design stage to maintain system stability. This paper discusses the conceptual basis for the development of HISTAR and presents a theoretical overview of the CFSTRs. Mathematical modeling, using first-order algal growth kinetics combined with CFSTR reactor kinetics, was used to investigate the effects of system dilution rate, D_s; net algal specific growth rate, U_a; number of reactors, N; input algal biomass, X_i; and contaminant concentration, C_n, on algal productivity, as well as local dilution rate, D_n, on suspended contaminant washout. The simulation results allowed the determination of preliminary design ranges for prototype development.     

Multi-scale effects of landscape complexity and crop management on pollen beetle parasitism rate

Improving our understanding about how natural enemies respond to semi-natural habitats and crop management scattered in the landscape may contribute to the development of ecologically based pest management strategies maximising biological control services. We investigated how soil tillage and semi-natural habitats influenced the parasitism rates of pollen beetle (Meligethes aeneus F.) larvae at 8 different spatial scales (from 250 to 2000 m radius circular sectors) in 42 oilseed rape (OSR) fields. We used multimodel inference approaches to identify and rank the influence of soil tillage and semi-natural habitats on parasitism rates, and to quantify the importance of each scale. Parasitism rates were due to three univoltine parasitoid species (Tersilochus heterocerus, Phradis morionellus and P. interstitialis) and varied from 0 to 98%. We found that both fine and large scales contributed to explain significantly parasitism rates, indicating that biological control of pollen beetle is a multi-scale process. At the 250 m scale, parasitism rates of T. heterocerus were positively related to the proportion of semi-natural habitats and the proximity to previous year OSR fields. At large scales (1500 to 2000 m), parasitism rates of T. heterocerus were positively related to semi-natural habitats and negatively related to the proportion of previous year OSR fields with conventional soil tillage. Parasitism rates of Phradis spp. were only positively related to the proportion of semi-natural habitats at the 1250 and 1500 m scales. These multi-scale effects are discussed in relation to the influence of semi-natural habitats and soil tillage on parasitoid populations and their movement behaviours within the landscape.     

办公室计算机的日常维护

办公室计算机日常使用时简单的软硬件维护和操作,从而使计算机发挥出它的最大性能,更好的满足工作需要.