Showing papers by "University of Maine published in 2004"

Physiology of Batrachochytrium dendrobatidis, a chytrid pathogen of amphibians

Abstract: Batrachochytrium dendrobatidis is a patho- gen of amphibians that has been implicated in severe population declines on several continents. We inves- tigated the zoospore activity, physiology and protease production of B. dendrobatidis to help understand the epidemiology of this pathogen. More than 95% of zoospores stopped moving within 24 h and swam less than 2 cm before encysting. Isolates of B. den- drobatidis grew and reproduced at temperatures of 4- 25 C and at pH 4-8. Growth was maximal at 17-25 C and at pH 6-7. Exposure of cultures to 30 C for 8 d killed 50% of the replicates. B. dendrobatidis cul- tures grew on autoclaved snakeskin and 1% keratin agar, but they grew best in tryptone or peptonized milk and did not require additional sugars when grown in tryptone. B. dendrobatidis produced extra- cellular proteases that degraded casein and gelatin but had no measurable activity against keratin azure. The proteases were active against azocasein at tem- peratures of 6-37 C and in a pH range of 6-8, with the highest activity at temperatures of 23-30 C and at pH 8. The implications of these observations on disease transmission and development are discussed.

Fine-scale phylogenetic architecture of a complex bacterial community

Abstract: Although molecular data have revealed the vast scope of microbial diversity, two fundamental questions remain unanswered even for well-defined natural microbial communities: how many bacterial types co-exist, and are such types naturally organized into phylogenetically discrete units of potential ecological significance? It has been argued that without such information, the environmental function, population biology and biogeography of microorganisms cannot be rigorously explored. Here we address these questions by comprehensive sampling of two large 16S ribosomal RNA clone libraries from a coastal bacterioplankton community. We show that compensation for artefacts generated by common library construction techniques reveals fine-scale patterns of community composition. At least 516 ribotypes (unique rRNA sequences) were detected in the sample and, by statistical extrapolation, at least 1,633 co-existing ribotypes in the sampled population. More than 50% of the ribotypes fall into discrete clusters containing less than 1% sequence divergence. This pattern cannot be accounted for by interoperon variation, indicating a large predominance of closely related taxa in this community. We propose that such microdiverse clusters arise by selective sweeps and persist because competitive mechanisms are too weak to purge diversity from within them.

Genome sequence of Silicibacter pomeroyi reveals adaptations to the marine environment

Abstract: Since the recognition of prokaryotes as essential components of the oceanic food web1, bacterioplankton have been acknowledged as catalysts of most major biogeochemical processes in the sea. Studying heterotrophic bacterioplankton has been challenging, however, as most major clades have never been cultured2 or have only been grown to low densities in sea water3,4. Here we describe the genome sequence of Silicibacter pomeroyi, a member of the marine Roseobacter clade (Fig. 1), the relatives of which comprise ∼10–20% of coastal and oceanic mixed-layer bacterioplankton2,5,6,7. This first genome sequence from any major heterotrophic clade consists of a chromosome (4,109,442 base pairs) and megaplasmid (491,611 base pairs). Genome analysis indicates that this organism relies upon a lithoheterotrophic strategy that uses inorganic compounds (carbon monoxide and sulphide) to supplement heterotrophy. Silicibacter pomeroyi also has genes advantageous for associations with plankton and suspended particles, including genes for uptake of algal-derived compounds, use of metabolites from reducing microzones, rapid growth and cell-density-dependent regulation. This bacterium has a physiology distinct from that of marine oligotrophs, adding a new strategy to the recognized repertoire for coping with a nutrient-poor ocean.

A Deep Wide-Field, Optical, and Near-Infrared Catalog of a Large Area around the Hubble Deep Field North*

Abstract: We have conducted a deep multicolor imaging survey of 0.2 deg2 centered on the Hubble Deep Field North (HDF-N). We shall refer to this region as the Hawaii HDF-N. Deep data were collected in U, B, V, R, I, and z' bands over the central 0.2 deg2 and in HK' over a smaller region covering the Chandra Deep Field North. The data were reduced to have accurate relative photometry and astrometry across the entire field to facilitate photometric redshifts and spectroscopic follow-up. We have compiled a catalog of 48,858 objects in the central 0.2 deg2 detected at 5 σ significance in a 3'' aperture in either R or z' band. Number counts and color-magnitude diagrams are presented and shown to be consistent with previous observations. Using color selection we have measured the density of objects at 3 5.5 using the Lyman break technique suffer from more contamination by low-redshift objects than suggested by previous studies.

Spatial and temporal variability in forest–atmosphere CO2 exchange

Abstract: Seven years of carbon dioxide flux measurements indicate that a ~ 90-year-old spruce dominated forest in Maine, USA, has been sequestering 174±46 gCm-2 yr-1 (mean±1 standard deviation, nocturnal friction velocity (u*) threshold >0.25ms-1). An analysis of monthly flux anomalies showed that above-average spring and fall temperatures were significantly correlated with greater monthly C uptake while above-average summer temperatures were correlated with decreased net C uptake. Summer months with significantly drier or wetter soils than normal were also characterized by lower rates of C uptake. Years with above-average C storage were thus typically characterized by warmer than average spring and fall temperatures and adequate summer soil moisture.

Defining competencies in psychology supervision: a consensus statement.

Abstract: Supervision is a domain of professional practice conducted by many psychologists but for which formal training and standards have been largely neglected. In this article, supervision is proposed as a core competency area in psychology for which a number of elements reflecting specific knowledge, skills, and values must be addressed to ensure adequate training and professional development of the trainee. Supra-ordinate factors of supervision viewed as permeating all aspects of professional development are proposed. These include the perspective that professional development is a lifelong, cumulative process requiring attention to diversity in all its forms, as well as legal and ethical issues, personal and professional factors, and self- and peer-assessment. A competencies framework is presented with particular elements representing knowledge (e.g., about psychotherapy, research, etc.), skills (including supervising modalities, relationship skills, etc.), values (e.g., responsibility for the clients and supervisee rests with supervisor, etc.), and meta-knowledge. Social contextual factors and issues of education and training, assessment, and future directions also are addressed, with specific elements listed. Suggestions for future work in this area are addressed, including the need to refine further and operationalize competences, develop clear expectations for accreditation and licensure regarding supervision competencies, and expand the description of developmental levels of supervisors from minimal to optimal competence. This is one of a series of articles published together in this issue of the Journal of Clinical Psychology. Several other articles that resulted from the Competencies Conference: Future Directions in Education and Credentialing in Professional Psychology will appear in Professional Psychology: Research and Practice and The Counseling Psychologist.

Physical-Biological Oceanographic Coupling Influencing Phytoplankton and Primary Production in the South China Sea

Abstract: [1] Two cruises were carried out in the summer and winter of 1998 to study coupled physical-chemical-biological processes in the South China Sea and their effects on phytoplankton stock and production. The results clearly show that the seasonal distributions of phytoplankton were closely related to the coupled processes driven by the East Asian Monsoon. Summer southwesterly monsoon induced upwelling along the China and Vietnam coasts. Several mesoscale cyclonic cold eddies and anticyclonic warm pools were identified in both seasons. In the summer, the upwelling and cold eddies, both associated with rich nutrients, low dissolved oxygen (DO), high chlorophyll a (Chl a) and primary production (PP), were found in the areas off the coast of central Vietnam, southeast of Hainan Island and north of the Sunda shelf, whereas in the winter they form a cold trough over the deep basin aligning from southwest to northeast. The warm pools with poor nutrients, high DO, low Chl a, and PP were found in the areas southeast of Vietnam, east of Hainan, and west of Luzon during the summer, and a northwestward warm jet from the Sulu Sea with properties similar to the warm pools was encountered during the winter. The phytoplankton stock and primary production were lower in summer due to nutrient depletion near the surface, particularly PO4. This phosphorus depletion resulted in phytoplankton species succession from diatoms to dinoflagellates and cyanophytes. A strong subsurface Chl a maximum, dominated by photosynthetic picoplankton, was found to contribute significantly to phytoplankton stocks and production.

Kuroshio intrusion and the circulation in the South China Sea

Abstract: [1] The Princeton Ocean Model is used to study the circulation in the South China Sea (SCS) and its seasonal transition. Kuroshio enters (leaves) the SCS through the southern (northern) portion of the Luzon Strait. The annually averaged net volume flux through the Luzon Strait is ∼2 Sv into the SCS with seasonal reversals. The inflow season is from May to January with the maximum intrusion of Kuroshio water reaching the western SCS during fall in compensation of summertime surface offshore transport associated with coastal upwelling. From February to April the net transport reverses from the SCS to the Pacific. The intruded Kuroshio often forms an anticyclonic current loop west of the Luzon Strait. The current loop separates near the Dongsha Islands with the northward branch continuously feeding the South China Sea Warm Current (SCSWC) near the shelf break and the westward branch becoming the South China Sea Branch of Kuroshio on the slope, which is most apparent in the fall. The SCSWC appears from December to February on the seaward side of the shelf break, flowing eastward against the prevailing wind. Diagnosis shows that the onshore Ekman transport due to northeasterly monsoon generates upwelling when moving upslope, and the particular distributions of the density and sea level associated with the cross shelf motion supports the SCSWC.

Salvage Harvesting Policies After Natural Disturbance

Abstract: The authors of this Policy Forum examine a range of issues associated with salvage harvesting policies after major natural disturbances such as fire, windstorms, and volcanic eruptions. Although natural disturbances can have important benefits for ecosystems, salvage harvesting can have major negative impacts on ecosystem recovery, the persistence of elements of biota, and the maintenance of key ecological processes. Better informed policies are needed to guide where, when, how, and if salvage harvesting takes place.

Sexual Harassment as a Gendered Expression of Power

Abstract: Drawing on recent insights from the study of legal consciousness and gender relations, the authors test the generality of Catharine MacKinnon's theory of the sexual harassment of adult women. Survey and interview data from the Youth Development Study and the General Social Survey are analyzed to identify a behavioral syndrome of sexual harassment for males and females during adolescence and young adulthood and to compare the syndrome against subjective reports of sexual harassment. A clear harassment syndrome is found for all age and sex groups and MacKinnon's predictions about the influence of workplace power and gender relations are generally supported. Financially vulnerable men as well as women are most likely to experience harassing behaviors, and men pursuing more egalitarian gender relationships are most likely to identify such behaviors as sexual harassment. Nevertheless, adult women remain the most frequent targets of classic sexual harassment markers, such as unwanted touching and invasion of pe...

Particulate backscattering ratio at LEO 15 and its use to study particle composition and distribution

Abstract: [1] Particulate scattering and backscattering are two quantities that have traditionally been used to quantify in situ particulate concentration. The ratio of the backscattering by particles to total scattering by particles (the particulate backscattering ratio) is weakly dependent on concentration and therefore provides us with information on the characteristics of the particulate material, such as the index of refraction. The index of refraction is an indicator of the bulk particulate composition, as inorganic minerals have high indices of refraction relative to oceanic organic particles such as phytoplankton and detrital material that typically have a high water content. We use measurements collected near the Rutgers University Long-term Ecosystem Observatory in 15 m of water in the Mid-Atlantic Bight to examine application of the backscattering ratio. Using four different instruments, the HOBILabs Hydroscat-6, the WETLabs ac-9 and EcoVSF, and a prototype VSF meter, three estimates of the ratio of the particulate backscattering ratio were obtained and found to compare well. This is remarkable because these are new instruments with large differences in design and calibration. The backscattering ratio is used to map different types of particles in the nearshore region, suggesting that it may act as a tracer of water movement. We find a significant relationship between the backscattering ratio and the ratio of chlorophyll to beam attenuation. This implies that these more traditional measurements may be used to identify when phytoplankton or inorganic particles dominate. In addition, it provides an independent confirmation of the link between the backscattering ratio and the bulk composition of particles.

The effect of water on the adsorption of CO2 and C3H8 on type X zeolites

Abstract: The effect of small amounts of water, in regard to inhibiting the adsorption of carbon dioxide (CO2), on several different cationic forms of zeolite X has been investigated using the zero length column (ZLC) technique, coupled with temperature-programmed desorption (TPD) measurements. This is shown to be a very effective way to study the effect of a strongly adsorbed species (water) on the adsorption of a less-strongly adsorbed species (CO2 or propane (C3H8)). It was observed that, for all systems studied, the Henry constant declines exponentially with the loading of water. As expected, this effect is stronger for CO2 than for C3H8.

Accelerating Trophic-level Dysfunction in Kelp Forest Ecosystems of the Western North Atlantic

Abstract: We use archaeological, historical, ecological, and fisheries data to identify three distinct and sequential phases in the trophic structure of kelp forests in the western North Atlantic’s Gulf of Maine. Phase 1 is characterized by vertebrate apex predators such as Atlantic cod, haddock, and wolffish and persisted for more than 4,000 years. Phase 2 is characterized by herbivorous sea urchins and lasted from the 1970s to the 1990s. Phase 3 is dominated by invertebrate predators such as large crabs and has developed since 1995. Each phase change resulted directly or indirectly from fisheries-induced “trophic-level dysfunction,” in which populations of functionally important species at higher trophic levels fell below the densities necessary to limit prey populations at lower trophic levels. By using fractional trophic-level analysis, we found that phase changes occurred rapidly (over a few years to a few decades) as well as relatively recently (over the past half-century). Interphase durations have declined as fishing effects have accelerated in recent years. The naturally low species diversity of the kelp forest ecosystem we studied may facilitate rapid changes because the redundancy within each trophic level is low. If the biodiversity within controlling trophic levels is a buffer against trophic-level dysfunction, then our observations from Maine may be predictive of the fate of other, more diverse systems. If fishing successively targets most, or all, strong interactors at higher trophic levels, then as those population densities decline, the potential for trophic-level dysfunction and associated instabilities will increase.

A DNA-based assay identifies Batrachochytrium dendrobatidis in amphibians.

Abstract: Chytridiomycosis caused by Batrachochytrium dendrobatidis (Chytridiomycota) has been implicated in declines of amphibian populations on four continents. We have developed a sensitive and specific polymerase chain reaction-based assay to detect this pathogen. We isolated B. dendrobatidis from captive and wild amphibians collected across North America and se- quenced the internal transcribed spacer regions of the rDNA cassette of multiple isolates. We identified two primers (Bd1a and Bd2a) that are specific to B. dendrobatidis under amplification conditions described in this study. DNA amplification with Bd1a/Bd2a primers produced a frag- ment of approximately 300 bp from B. dendrobatidis DNA but not from DNA of other species of chytrids or common soil fungi. The assay detected 10 zoospores or 10 pg of DNA from B. dendrobatidis and detected infections in skin samples from a tiger salamander (Ambystoma ti- grinum), boreal toads (Bufo boreas), Wyoming toads (Bufo baxteri), and smooth-sided toads (Bufo guttatus). This assay required only small samples of skin and can be used to process a large number of samples.

Brassica cover cropping for weed management: A review

Abstract: Cover crops offer many benefits for farmers seeking to reduce their reliance on external inputs. These include maintaining and improving soil quality, preventing erosion and, in some cases, allelopathic weed control. Allelopathic potential has been well documented for cover crops such as cereal rye (Secale cereale L.), hairy vetch (Vicia villosa Roth) and red clover (Trifolium pratense L.). Much less is known about other potentially allelopathic cover crops, including certain brassicaceous species that are normally grown for their oilseeds, including canola and rapeseed (both Brassica napus L.) and mustards (e.g., Sinapis alba L., white and yellow mustard). Because of their potential contribution to pest management, there is increased interest in growing brassicas, both as cover crops and as seed crops harvested for oil production. In this review, we first discuss unique attributes of brassicas that make them promising options for pest management, as well as generally beneficial cover crops. Next, we review the literature from controlled settings on the effects of brassicas, brassica extracts and isolated compounds contained therein on seed germination, seedling emergence and establishment, and seedling growth—effects that, combined or taken alone, could contribute to reducing the density and vigor of weed communities in the field. Field studies examining the detrimental effects of brassicas in rotation with other crops, as well as examining the effects of brassica cover crops on weed dynamics in subsequent crops, also are reviewed. Finally, we review some important agronomic considerations about the use of brassica cover crops.

Challenges of Modeling Ocean Basin Ecosystems

Abstract: With increasing pressure for a more ecological approach to marine fisheries and environmental management, there is a growing need to understand and predict changes in marine ecosystems. Biogeochemical and physical oceanographic models are well developed, but extending these further up the food web to include zooplankton and fish is a major challenge. The difficulty arises because organisms at higher trophic levels are longer lived, with important variability in abundance and distribution at basin and decadal scales. Those organisms at higher trophic levels also have complex life histories compared to microbes, further complicating their coupling to lower trophic levels and the physical system. We discuss a strategy that builds on recent advances in modeling and observations and suggest a way forward that includes approaches to coupling across trophic levels and the inclusion of uncertainty.

Blood Pressure-Related Cognitive Decline: Does Age Make a Difference?

Abstract: Systolic and diastolic blood pressures have been inversely related to cognitive performance in prospective and cross-sectional studies. However, in large, community-based samples, these findings have been limited to older adults. In this 20-year longitudinal study, we examined the relationship between baseline blood pressure and cognitive decline for 529 participants using 2 age groups (18 to 46 years and 47 to 83 years). Cognitive performance was measured over multiple examinations with the Wechsler Adult Intelligence Scale from which 4 scores were derived by factor analysis. A 2-stage growth curve method of analysis was used to model cognitive change. Results indicated that higher levels of baseline systolic blood pressure, diastolic blood pressure, mean arterial pressure, and blood pressure categories as defined by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure were significantly associated with decline in Visualization/Fluid abilities in both younger and older age groups. Young adults are as susceptible to blood pressure-related longitudinal decline in cognitive performance as are older adults.

Surface Deformations as Indicators of Deep Ebullition Fluxes in a Large Northern Peatland

Abstract: [1] Peatlands deform elastically during precipitation cycles by small (±3 cm) oscillations in surface elevation. In contrast, we used a Global Positioning System network to measure larger oscillations that exceeded 20 cm over periods of 4–12 hours during two seasonal droughts at a bog and fen site in northern Minnesota. The second summer drought also triggered 19 depressuring cycles in an overpressured stratum under the bog site. The synchronicity between the largest surface deformations and the depressuring cycles indicates that both phenomena are produced by the episodic release of large volumes of gas from deep semi-elastic compartments confined by dense wood layers. We calculate that the three largest surface deformations were associated with the release of 136 g CH4 m−2, which exceeds by an order of magnitude the annual average chamber fluxes measured at this site. Ebullition of gas from the deep peat may therefore be a large and previously unrecognized source of radiocarbon depleted methane emissions from northern peatlands.

From Objects to Events: GEM, the Geospatial Event Model

Abstract: This paper discusses the construction of a modeling approach for dynamic geospatial domains based on the concepts of object and event. The paper shows how such a model extends traditional object-based geospatial models. The focus of the research is the introduction of events into the object-based paradigm, and consequent work on the classification of object-event and event-event relationships. The specific geospatial nature of this model is captured in the concept of a geosetting. The paper also introduces an extension of UML diagrams to incorporate events and their relationship to each other, and to objects. The paper briefly considers an example to show the working of some of the modeling constructs, and concludes with a discussion of further research needed on event aggregation and event-based query languages.

Catastrophic Ice Shelf Breakup as the Source of Heinrich Event Icebergs

Abstract: [1] Heinrich layers of the glacial North Atlantic record abrupt widespread iceberg rafting of detrital carbonate and other lithic material at the extreme-cold culminations of Bond climate cycles. Both internal (glaciologic) and external (climate) forcings have been proposed. Here we suggest an explanation for the iceberg release that encompasses external climate forcing on the basis of a new glaciological process recently witnessed along the Antarctic Peninsula: rapid disintegrations of fringing ice shelves induced by climate-controlled meltwater infilling of surface crevasses. We postulate that peripheral ice shelves, formed along the eastern Canadian seaboard during extreme cold conditions, would be vulnerable to sudden climate-driven disintegration during any climate amelioration. Ice shelf disintegration then would be the source of Heinrich event icebergs.