ZONES OF NITRIFICATION1

ABSTRACT: This paper advances the hypothesis that nitrification exists in shallow streams as a result of surface activity and in estuaries due to growth in the water phase. Between these zones no significant levels of nitrification occur. Field measurements of ammonia, nitrite and nitrate nitrogen, enumerations of Nitrosomonas and Nitrobacter, and respirometry on two small streams and two moderately large rivers are presented. The appropriate mathematical models to describe nitrification must be based on the mechanisms involved - bacterial growth kinetics for estuaries and zero kinetics for the surface activity in shallow streams.     

Results of the European Commission Marina II study: part II--effects of discharges of naturally occurring radioactive material

Enhanced levels of naturally occurring radioactive materials (NORM) are produced through various industrial operations and may lead to discharges to the marine environment. A recent study, called MARINA II, carried out for the European Commission considered discharges of radionuclides from the NORM industries to north European marine waters and their consequences. There are two main sources that were considered in the study. The use of phosphogypsum during the production of phosphoric acid by the fertiliser industry and the pumping of oil and gas from the continental shelf in the North Sea which produces large quantities of water contaminated with enhanced levels of naturally occurring radionuclides. Discharges of alpha emitting radionuclides from these two industries have contributed significantly to the total input of alpha emitters to north European waters over the period 1981-2000 (data were not available prior to 1981). Discharges due to the use of phosphogypsum have declined since the early 1990s and are now very low. Discharges from the oil and gas industries stabilised in the second half of the 1990s and are now the major contributor to alpha discharges to the region. As most European countries do not report discharges of radioactivity with the water produced during extraction, there is considerable uncertainty in the discharges used in the study. The impact of the discharges has been estimated both in terms of the effect on non-human biota and the radiological impact for people. In the 1980s the radiation dose rates to marine biota in the region around a phosphate plant on the north-west coast of England were as high due to the discharges from the phosphate plant as those near to the Sellafield reprocessing plant due to its discharges. In recent years the additional dose to marine biota in this region due to the past NORM discharges is of the same order of magnitude as the natural background. The collective dose rate was estimated to determine the radiological impact on people. The peak collective dose rate from the NORM industries occurred in 1984 and was just over 600 manSv y(-1). The collective dose rate fell with time as discharges from the phosphate industry reduced and was estimated as under 200 manSv y(-1) in 2000.     

The effects of helpers in cooperatively breeding purple gallinules

Summary The effects of helpers in a population of cooperatively breeding purple gallinules (Porphyrula martinica) were examined. All young birds past the age of 2 months helped feed and protect subsequent broods of chicks and participated in territorial defense. Most helpers remained on their natal territories for approximately 1 year. The number of helpers varied both among and within breeding groups. Clutch production and chick survival were related positively to the number of helpers in the group. The increase in chick survival was independent of several measures of territory quality. Helpers possibly aided chick survival by provicing extra food for the chicks and decreasing predation risk. Helpers were necessary in order for a breeding pair to keep a territory long enough to produce more than one clutch of eggs. A change in the number of helpers (increase or decrease) often was followed by a similar change in territory size. These results suggest that purple gallnule helpers can increase the reproductive success of the breeding group and may be vital for the continued maintenance of a breeding territory.     

Effects of Habitat Area on the Distribution of Grassland Birds in Maine

We used multiple and logistic regression analysis to study the breeding-area requirements of 10 species of grassland and early-successional birds at 90 grassland-barren sites in Maine. The incidence of six of the species was clearly sensitive to the area of grassland. Upland Sandpipers, the species with the largest area requirements, were infrequent at sites of less than 50 ha and reached 50% incidence at those of about 200 ha. Grasshopper Sparrows reached 50% incidence at about 100 ha, Vesper Sparrows at about 20 ha, and Savannah Sparrows at about 10 ha. Incidence for three edge species, Brown Thrasher, Common Yellowthroat, and Song Sparrow, was negatively correlated with open area, and incidence for Field Sparrows was not strongly influenced by grassland size. These results indicate that grasslands need to be approximately 200 ha in area if they are to be likely to support a diverse grass land bird fauna. However, large grasslands or grassland-barrens are rare; random samples indicated that in Maine only 1% of hayfields and only 8% of grassland-barrens were more than 64 ha in area. Conservation efforts seeking to protect habitat for rare grassland birds need to consider sites of at least 100 ha—and preferably 200 ha—in size, and these are notably rare in Maine and probably throughout New England and eastern North America. Airports provide some of the last extensive patches of grassland habitat in the northeast. To maintain viable populations of area-sensitive grassland birds, management of these sites for nesting birds will become increasingly important.     

Prenatal diagnosis of del(11)(p13p15)

Prenatal diagnosis of del(11)(p13p15) was made on cultured amniotic fluid cells and confirmed on fetal skin fibroblasts after termination of pregnancy. Both irides appeared behind schedule in development by 2–3 weeks in reference to the gestational age of the fetus. It is suggested that the aniridia of the aniridia-Wilms tumour association is due to developmental arrest. Confirmation of this complex is difficult at mid-gestation without critical pathological study of the eyes.     

Biological Roles of Trace Metals in Natural Waters

For decades there has been an intense interest in the toxic effects of trace metals on biological organisms in the environment. This period of time has seen increasing improvements in analytical techniques for the measurement and study of trace metals and their subsequent application to a broad spectrum of water systems around the globe. This work has included studies of the geographical distributions of trace metals in different water types in the ocean, the modes of transport and uptake of trace metals and the study of historical changes in trace metal accumulation. Early research highlighted strong similarities in the behaviours of many trace metals and those of well-understood chemical nutrients such as phosphate, nitrate and silicate, known to be essential for phytoplankton growth in the ocean. This suggests that phytoplankton regulate the trace metal composition of seawater for their own benefit. A major achievement in this regard has been the ability to measure, at the sub-nmol/L level, trace metal species that are complexed by naturally-occurring organic ligands of biological origin in ocean waters. It is now clear that the free ion activities of many essential and/or toxic trace metals are regulated by highly specific, strongly complexing ligands exuded by marine phytoplankton. This research encourages a new paradigm in which the growth rates and species composition of primary marine organisms are affected by trace metals at concentration levels orders of magnitude lower than is conventionally believed. As a consequence, the capacity of natural waters to assimilate trace metal-contaminants may be correspondingly much lower than is currently thought reasonable.     

Use of agricultural land evaluation and site assessment in Whitman County,Washington, USA

Whitman County, Washington, USA, one of the largest wheat producing counties in the country, developed a land evaluation and site assessment system for evaluating proposed conversions of agricultural land to heavy commercial uses. The system uses soil potential indices to determine a land evaluation score and a nine-factor site assessment system to weigh suitability for development. Details on each of these are provided along with results for four sample sites.Scientific Paper no. 7165, College of Argiculture and Home Economics Research Paper, Washington State University, Pullman, Washington, project no. 0010.     

Use of standardized methods to improve extinction-risk classification

Standardized classification methods based on quantifiable risk metrics are critical for evaluating extinction threats because they increase objectivity, consistency, and transparency of listing decisions. Yet, in the United States, neither federal nor state agencies use standardized methods for listing species for legal protection, which could put listing decisions at odds with the magnitude of the risk. We used a recently developed set of quantitative risk metrics for California herpetofauna as a case study to highlight discrepancies in listing decisions made without standardized methods. We also combined such quantitative metrics with classification tree analysis to attempt to increase the transparency of previous listing decisions by identifying the criteria that had inherently been given the most weight. Federally listed herpetofauna in California scored significantly higher on the risk-metric spectrum than those not federally listed, whereas state-listed species did not score any higher than species that were not state listed. Based on classification trees, state endemism was the most important predictor of listing status at the state level and distribution trend (decline in a species’ range size) and population trend (decline in a species’ abundance at localized sites) were the most important predictors at the federal level. Our results emphasize the need for governing bodies to adopt standardized methods for assessing conservation risk that are based on quantitative criteria. Such methods allow decision makers to identify criteria inherently given the most weight in determining listing status, thus increasing the transparency of previous listing decisions, and produce an unbiased comparison of conservation threat across all species to promote consistency, efficiency, and effectiveness of the listing process.     

Genetically informed captive breeding of hybrids of an extinct species of Galapagos tortoise

Hybridization poses a major challenge for species conservation because it threatens both genetic integrity and adaptive potential. Yet, hybridization can occasionally offer unprecedented opportunity for species recovery if the genome of an extinct taxon is present among living hybrids such that selective breeding could recapture it. We explored the design elements for establishing a captive-breeding program for Galapagos tortoises (Chelonoidis spp.) built around individuals with admixed ancestry involving an extinct species. The target individuals were hybrids between the extinct species from Floreana Island, C. niger, and an extant species, C. becki, which were recently found in the endemic range of C. becki, from Wolf Volcano on Isabela Island. We combined genotypic data from 35 tortoises with high ancestry from C. niger with forward-in-time simulations to explore captive breeding strategies that maximized overall genetic diversity and ancestry from C. niger while accommodating resource constraints, species biology, and the urgency to return tortoises to Floreana Island for facilitating ecosystem restoration. Overall genetic diversity was maximized when in the simulation tortoises were organized in relatively small breeding groups. Substantial amounts of the C. niger genome were captured despite limited resources available for selectively breeding tortoises in captivity. Genetic diversity was maximized when captive-bred offspring were released to the wild rather than being used as additional breeders. Our results provide genetic-based and practical guidance on the inclusion of hybrids with genomic representation from extinct taxa into species restoration programs and informs the ongoing debate on the value of hybrids in biodiversity conservation.