Biological production of nitrite in seawater

The relative importance of 3 different sources for biological production of nitrite in seawater was studied. Decomposition of fecal pellets of the copepod Calanus helgolandicus (at a concentration of approximately 12 g-at N/l), in seawater medium, released small amounts of ammonia over a 6 week period. It nitrifying bacteria were added to the fecal pellets nitrite was barely detectable over the same period. Decomposition of phytoplankton (present at a concentration of about 8 g-at particulate plant N/l) with added heterotrophic bacteria, released moderate amounts of ammonia over a 12 week period. If the ammonia-oxidizing bacterium Nitrosocystis oceanus was added to the decomposing algae, nitrite was produced at a rate of 0.2 g-at N/l/week. Heterotrophic nitrification was not observed when 7 open-ocean bacteria were tested for their ability to oxidize ammonia. The diatom Skeletonema costatum, either non-starved or starved of nitrogen, produced nitrite when growing with 150 or 50 g-at NO ₂ ^- -N/l at a light intensity of about 0.01 ly/min. When nitrate in the medium was exhausted, S. costatum assimilated nitrite. If starved of vitamin B₁₂, both non-N-starved and N-starved cells of S. costatum produced nitrite in the medium with 150 g-at NO ₃ ^- -N/l. Nitrate was not exhausted and cell densities reached 2x10⁵/ml due to vitamin B₁₂ deficiency. If light intensity was reduced to 0.003 ly/min under otherwise similar conditions, cells did not grow due to insufficient light, and nitrite was not produced. In the sea, it appears that, in certain micro-environments, decomposition of particulate matter releases ammonia with its subsequent oxidation to nitrite. The amounts of these nutrients and the rate at which they are produced are dependent upon the nature of the materials undergoing decomposition and the associated bacteria. In certain other areas of the sea, where phytoplankton standing stock is high and nitrate is non-limiting, excretion by these organisms is a major source of nitrite.     

Hydrolytic enzymes in the two North Sea ctenophores Pleurobrachia pileus and Beroe gracilis

Hydrolytic enzyme activities were determined in tissue extracts of the two North Sea ctenophores Pleurobrachia pileus and Beroe gracilis. The following activities were measured in field samples and characterized according to their mean specific activities and their pH optima: protease, aminopeptidase, amylase, N-acetylglucosaminidase, -glucosidase, chitinase, carboxylesterase, phosphatase. Many of the enzyme activities are correlated, indicating their control by the same factors (i.e. nutritional conditions). Differences found between the phosphatase activities and the apparent lack of the chitinolytic system in B. gracilis reflect the differences in body composition and food specialization in both ctenophores, respectively. The low amylase and -glucosidase activities in both ctenophores agree with the low carbohydrate content of their prey. In spite of high carboxylesterase activities, no lipolytic activity was detected in either of the ctenophores. In a laboratory feeding experiment with P. pileus, the enzyme activities increased but did not reach the activities found in the field samples. In B. gracilis, seasonal variations of some enzyme activities are discussed in relation to the seasonal abundance of its prey, P. pileus.     

Effects of β-cyclodextrin on adsorption and desorption of carbofuran in soils of divergent texture

Laboratory studies were conducted to determine the adsorption/desorption equilibrium of carbofuran between four divergently textured soils and distilled water and an aqueous solution of 0.01?mol?L^?1 β-cyclodextrin using a batch equilibrium technique. The determined adsorption isotherms for silt loam soils were of L-shaped, for sandy loam soil S-shaped, in agreement with a Freundlich isotherm. In the presence of β-cyclodextrin, the adsorption of carbofuran to the four soils was lower than with distilled water. Positive hysteresis was observed in all soils with distilled water, negative hysteresis when using a solution of β-cyclodextrin as desorbent. The results indicate the potential use of β-cyclodextrin for remediation of pesticide-contaminated soils.     

Anatomy of structures associated with air-breathing in Orchestia gammarellus (Crustacea: Amphipoda: Talitridae): coxal plates and gills

The structure of the coxal gills and coxal plates of the semi-terrestrial beachflea Orchestia gammarellus (Pallas) (Crustacea: Amphipoda: Talitridae) is described in relation to their possible use for aerial gas exchange and ion exchange. Anatomical evidence is presented to support the hypothesis that the medial surface of the coxal plates functions as an extrabranchial aerial gas-exchange site in O. gammarellus. Thus, the effective diffusion distance across the medial (or inside-facing) surface of O. gammarellus coxal plates (mean±SD=5.4±0.3 m; n=9, cuticle thickness 4.4±0.5 m, n=21) is only a third of the equivalent distance across both the coxal gills (18.4±6.0 m, n=10; cuticle thickness 1.7±0.6 m, n=7) and the lateral (or external) surface of the coxal plates (19.4±0.7 m, n=5; cuticle thickness 8.7±0.8 m, n=7). Chloride-ion-permeable areas were located using a silver-staining technique. All ten coxal gills appeared to be equally permeable to chloride ions after examination with a light microscope. However, the coxal plates and the rest of the integument do not appear to be chloride-permeable.     

Factors Affecting Population Assessments of Desert Tortoises

Abstract: Desert tortoises have been a subject of controversy since their listing as threatened in 1990. With a wide geographic range and more living individuals than any other listed land animal, biologists have needed to detect population trends against a "noisy" background of strong annual changes. We obtained annual population estimates of desert tortoises over 6 consecutive years at a 2.59-km² plot in Joshua Tree National Park, California. Our estimates, based on weekly spring surveys, varied substantially, particularly between wet and dry years. Concurrently, we followed 10 radiotagged animals for 3 years to corroborate the surveys. Population density was determined separately for each year and for all years combined. Our best population estimate was an average of 67 adult tortoises, three times more than the density reported in a 1978 survey of the same site. Annual mortality was low ( <10%), and the animals showed extreme site fidelity. Apparent changes in population size were most strongly related to the animals' varying susceptibility to capture. In dry years, home ranges decreased, captures decreased, and effort required to find each tortoise nearly doubled. Our data confirm that tortoises are likely to be undercounted during dry years and call into question earlier studies conducted during droughts.     

SOME GEOMORPHIC RELATIONSHIPS AND HYDROGRAPH ANALYSIS1

ABSTRACT: First order drainage channels originate when the tractive force exerted by flowing water is sufficient to move surface sediment. The amount of runoff available to move sediment is a function of geologic and climatic characteristics. An experimental analysis showed that soils derived from fine grained rocks had lower infiltration rates and higher runoff volume than soils derived from coarser grained rocks in a semi-arid climate. Root density and penetration increased in a more humid climate and increased infiltration rates. The number of first order channels was inversely proportional to the infiltration capacity of the soil. Each first order channel acts as a source area for surface runoff. The distribution of first order channel distances from the gage determines the timing of the delivery of water to the gage. A comparison of the frequency histogram of first order channel distances for drainage basins in Pennsylvania and their hydxographs of runoff from general storms showed marked similarity. This close correspondence indicated the shape of the surface runoff hydrograph and was largely controlled by the distribution of first order channel distances.     

Pre-incubation in soil improves the nitrogen fertiliser value of hair waste

Global generation of human hair waste and its disposal at landfills could contribute to the leaching of nitrates into ground water. High concentrations of nitrogen (N) and other elements suggest that the waste could be a source of plant nutrients and differences in ethnic hair types could affect nutrient release and fertiliser value. The objective of this study was to determine the effects of hair type, as an N source, and pre-incubation time on dry-matter yield, nutrient uptake by spinach (Spinacia oleracea L.) and residual soil nutrients. Salons in Pietermaritzburg provided bulk African and Caucasian hair waste, without distinguishing age, sex, health status or livelihood of the individuals. The hair waste was analysed for elemental composition. A pot experiment was set up under glasshouse conditions. The hair waste was incorporated (400 kg N ha^?1) into a loamy oxisol and pre-incubated for 0, 28, 56 and 84 days before planting spinach. Potassium (K) and phosphorus (P) were corrected to the same level for all treatments. Spinach seedlings were then cultivated for 6 weeks. Shoot dry-matter and the uptake of all nutrients, except P, were increased by the pre-incubation of hair. African hair pre-incubated for 28 days resulted in greater dry-matter, N, K, Mn and S uptake than Caucasian hair. Increasing pre-incubation resulted in a decline in the residual soil pH and exchangeable K. The findings suggested that pre-incubation improves the N fertiliser value of hair and that African hair has greater value than Caucasian hair when pre-incubated for a short period.     

Measurements of PCB Fluxes into the Atmosphere from a Site Receiving Stabilized Dredged Material

A 50 ha known contaminated site in Bayonne, New Jersey, U.S.A. is permitted to receive up to 3 × 10⁶ m³ of sediment dredged from navigation channels in the New York/New Jersey Harbor. Much of the sediment is expected to contain low to moderate concentrations of industrial and agricultural chemicals, including Polychlorinated Biphenyls (PCBs). The dredged material brought to the site is stabilized with cement and then placed as a capping and grading layer. The flux of PCBs from drying stabilized dredged material has been estimated from measurements of PCB air concentrations at two heights above the ground along with micrometeorological observations. A statistically significant gradient in PCB concentrations has been consistently measured in the first 3 m above the ground. Observed PCB fluxes were highest over freshly placed stabilized dredged sediment and decreased as it cured. The highest flux observed in this study was 7214 ng/m²/h, but during subsequent sampling intervals at the same site, the flux estimates decreased by an order of magnitude over a 5-day interval.     

Shellfish-Borne Viral Outbreaks: A Systematic Review

Investigations of disease outbreaks linked to shellfish consumption have been reported in the scientific literature; however, only few countries systematically collate and report such data through a disease surveillance system. We conducted a systematic review to investigate shellfish-borne viral outbreaks and to explore their distribution in different countries, and to determine if different types of shellfish and viruses are implicated. Six databases (Medline, Embase, Scopus, PubMed, Eurosurveillance Journal and Spingerlink electronic Journal) and a global electronic reporting system (ProMED) were searched from 1980 to July 2012. About 359 shellfish-borne viral outbreaks, alongside with nine ProMED reports, involving shellfish consumption, were identified. The majority of the reported outbreaks were located in East Asia, followed by Europe, America, Oceania, Australia and Africa. More than half of the outbreaks (63.6 %) were reported from Japan. The most common viral pathogens involved were norovirus (83.7 %) and hepatitis A virus (12.8 %). The most frequent type of consumed shellfish which was involved in outbreaks was oysters (58.4 %). Outbreaks following shellfish consumption were often attributed to water contamination by sewage and/or undercooking. Differences in reporting of outbreaks were seen between the scientific literature and ProMED. Consumption of contaminated shellfish represents a risk to public health in both developed and developing countries, but impact will be disproportionate and likely to compound existing health disparities.