Diapycnal mixing across the photic zone of the NE Atlantic

Variable physical conditions such as vertical turbulent exchange, internal wave, and mesoscale eddy action affect the availability of light and nutrients for phytoplankton (unicellular algae) growth. It is hypothesized that changes in ocean temperature may affect ocean vertical density stratification, which may hamper vertical exchange. In order to quantify variations in physical conditions in the northeast Atlantic Ocean, we sampled a latitudinal transect along 17 ± 5∘ W between 30 and 63∘ N in summer. A shipborne conductivity–temperature–depth (CTD) instrumented package was used with a custom-made modification of the pump inlet to minimize detrimental effects of ship motions on its data. Thorpe-scale analysis was used to establish turbulence values for the upper 500 m from three to six profiles obtained in a short CTD yo-yo, 3 to 5 h after local sunrise. From south to north, average temperature decreased together with stratification while turbulence values weakly increased or remained constant. Vertical turbulent nutrient fluxes did not vary significantly with stratification and latitude. This apparent lack of correspondence between turbulent mixing and temperature is likely due to internal waves breaking (increased stratification can support more internal waves), acting as a potential feedback mechanism. As this feedback mechanism mediates potential physical environment changes in temperature, global surface ocean warming may not affect the vertical nutrient fluxes to a large degree. We urge modellers to test this deduction as it could imply that the future summer phytoplankton productivity in stratified oligotrophic waters would experience little alterations in nutrient input from deeper waters

Deconvolution imaging conditions and cross-talk suppression

Deconvolution imaging conditions offer improved resolution over standard, crosscorrelation-based imaging conditions. Additionally, these imaging conditions produce a result more directly related to a reflection coefficient than do crosscorrelation-based imaging conditions. In simple analytical cases, deconvolution imaging conditions also offer the possibility of eliminating crosstalk (i.e., energy in the image due to reflected energy arriving at a location at the same time as incident energy that did not cause the reflected energy) when the full up- and down-going wavefields are used. This means that in such cases, surface-related multiples can be eliminated from the image, or that multiple shots could potentially be fired simultaneously without degrading the image. However, this cross-talk-suppression property is not observed in most situations. We show that this is due to a number of issues: the correct order of deconvolution must be used, stabilization causes imperfect deconvolution, finite apertures lead to some of the signal being lost, and an assumption of horizontal stratification is often not being met. Further, imperfect knowledge of the incident and reflected field due to such factors as anisotropy, poorly estimated velocity fields, and measurement noise can also lead to imperfect deconvolution. Thus, deconvolution imaging conditions should not be counted on to completely eliminate crosstalk from images. </jats:p

Evidence for density-dependent effects on body composition of a large omnivore in changing Greater Yellowstone Ecosystem

Understanding the density-dependent processes that drive population demography in a changing world is critical in ecology, yet measuring performance–density relationships in long-lived mammalian species demands long-term data, limiting scientists' ability to observe such mechanisms. We tested performance–density relationships for an opportunistic omnivore, grizzly bears (Ursus arctos, Linnaeus, 1758) in the Greater Yellowstone Ecosystem, with estimates of body composition (lean body mass and percent body fat) serving as indicators of individual performance over two decades (2000–2020) during which time pronounced environmental changes have occurred. Several high-calorie foods for grizzly bears have mostly declined in recent decades (e.g., whitebark pine [Pinus albicaulis, Engelm, 1863]), while increasing human impacts from recreation, development, and long-term shifts in temperatures and precipitation are altering the ecosystem. We hypothesized that individual lean body mass declines as population density increases (H1), and that this effect would be more pronounced among growing individuals (H2). We also hypothesized that omnivory helps grizzly bears buffer energy intake from changing foods, with body fat levels being independent from population density and environmental changes (H3). Our analyses showed that individual lean body mass was negatively related to population density, particularly among growing-age females, supporting H1 and partially H2. In contrast, population density or sex had little effect on body fat levels and rate of accumulation, indicating that sufficient food resources were available on the landscape to accommodate successful use of shifting food sources, supporting H3. Our results offer important insights into ecological feedback mechanisms driving individual performances within a population undergoing demographic and ecosystem-level changes. However, synergistic effects of continued climate change and increased human impacts could lead to more extreme changes in food availability and affect observed population resilience mechanisms. Our findings underscore the importance of long-term studies in protected areas when investigating complex ecological relationships in an increasingly anthropogenic worl

Density Dependence, Whitebark Pine Decline and Vital Rates of Grizzly Bears in The Greater Yellowstone Ecosystem

Recent evidence suggests annual population growth of the grizzly bear (Ursus arctos) population in the Greater Yellowstone Ecosystem has slowed from 4.1–7.6 percent during 1983–2001 to 0.3–2.2 percent during 2002–2011. Substantial changes in availability of an important fall food has occurred over the past decade. Whitebark pine (Pinus albicaulis), a highly variable but important fall food source for grizzly bears, has experienced substantial mortality due to a mountain pine beetle (Dendroctonus ponderosae) outbreak that started in the early 2000s. Concurrent with changes in food resources, the grizzly bear population has reached high densities in some areas and has continued to expand, now occupying &gt;50,000 km2. We tested research hypotheses to examine if changes in vital rates detected during the past decade were more associated with grizzly bear density versus a whitebark pine decline. We focused our assessment on known-fate data to estimate survival of cubs-of-the-year, yearlings, and independent bears (? 2 yrs) and reproductive transition of females from having no offspring to having cubs.  We observed a change in survival of independent bears between the periods of 1983–2001 and 2002–2012, which was mostly a function of increased male survival; female survival did not change. Cub survival and reproductive transition declined during the last decade and were associated with an index of grizzly bear density, which indicated increasing density over time. We found no support that the decline in these vital rates was associated with the index of whitebark decline

Influence of Whitebark Pine Decline on Fall Habitat Use and Movements of Grizzly Bears in the Greater Yellowstone Ecosystem

Seeds of whitebark pine (WBP; Pinus albicaulis) are a major food item for grizzly bears (Ursus arctos) in the greater Yellowstone ecosystem. Higher rates of bear mortality and bear-human conflicts are linked with low WBP productivity. Recently, infestations of mountain pine beetle (Dendroctonus ponderosae) have killed many mature, cone-bearing WBP trees. We investigated whether this decline caused bears to reduce their use of WBP and increase use of areas near humans. We used 52,332 GPS locations of 72 individuals (89 bear-years) monitored during fall (15 Aug–30 Sep) to examine temporal changes in habitat use and movements during 2000–2011. We calculated a Manley-Chesson (MC) index for selectivity of mapped WBP habitats for each individual within its 100% local convex hull home range, and determined dates of WBP use. One third of sampled grizzly bears had fall ranges with little or no mapped WBP habitat. Most other bears (72%) had a MC index &gt; 0.5, indicating selection for WBP habitats. Over the study period, mean MC index decreased and median date of WBP use shifted about 1 week later. We detected no trends in movement indices over time. Outside of national parks, 78 percent of bears selected for secure habitat (areas ? 500 m from roads), but mean MC index decreased over the study period during years of good WBP productivity. The foraging plasticity of grizzly bears likely allowed them to adjust to declining WBP. However, the reduction in mortality risk associated with use of WBP habitat may be diminishing for bears in multiple-use areas

Phase I study of Carzelesin (U-80,244) given (4-weekly) by intravenous bolus schedule

Carzelesin is a cyclopropylpyrroloindole analogue which acts as a DNA-sequence-specific alkylating agent. In this phase I study, Carzelesin was given as a 4-weekly 10 min IV infusion to 51 patients with advanced solid tumours. Patients received a median of two courses (range 1–5) at one of nine dose levels: 24, 48, 96, 130, 150, 170, 210, 250 and 300 μg m−2. According to NCI-CTC criteria, non-haematological toxicities (grade 1/2) included fever, nausea and vomiting, mucositis and anorexia, none of which was clearly dose related. The dose-limiting toxicity was haematological and consisted mainly of neutropenia and to a lesser extent thrombocytopenia. From the dose level 150 μg m−2, the haematological toxicity (particularly thrombocytopenia) was delayed in onset, prolonged and cumulative in some patients. In several courses, double WBC nadirs occurred. The maximum tolerated dose for a single course was 300 μg m−2. From the dose level 170 μg m−2, the intended dose intensity could not be delivered to most patients receiving > 2 courses owing to cumulative haematological toxicity. The dose level with the best dose intensity for multiple courses was 150 μg m−2. The pharmacokinetics of Carzelesin and its metabolites (U-76,073; U-76,074) have been established in 31 patients during the first course of treatment using a HPLC method. Carzelesin exhibited linear pharmacokinetics. The concentration of U-76,074 (active metabolite) extended above the lower limit of quantitation (1 ng ml−1) for short periods of time and only at the higher dose levels. There was no relationship between neutropenia and the AUC of the prodrug Carzelesin, but the presence of detectable plasma levels of the active metabolite U-76,074 was usually associated with a substantial decrease in ANC values. © 1999 Cancer Research Campaig