Continental margins are dynamic, heterogeneous settings that can include canyons, seamounts, and banks. Two of the largest canyons in the world, Zhemchug and Pribilof, cut into the edge of the ...continental shelf in the southeastern Bering Sea. Here currents and upwelling interact to produce a highly productive area, termed the Green Belt, that supports an abundance of fishes and squids as well as birds and marine mammals. We show that in some areas the floor of these canyons harbors high densities of gorgonian and pennatulacean corals and sponges, likely due to enhanced surface productivity, benthic currents and seafloor topography. Rockfishes, including the commercially important Pacific ocean perch, Sebastes alutus, were associated with corals and sponges as well as with isolated boulders. Sculpins, poachers and pleuronectid flounders were also associated with corals in Pribilof Canyon, where corals were most abundant. Fishes likely use corals and sponges as sources of vertical relief, which may harbor prey as well as provide shelter from predators. Boulders may be equivalent habitat in this regard, but are sparse in the canyons, strongly suggesting that biogenic structure is important fish habitat. Evidence of disturbance to the benthos from fishing activities was observed in these remote canyons. Bottom trawling and other benthic fishing gear has been shown to damage corals and sponges that may be very slow to recover from such disturbance. Regulation of these destructive practices is key to conservation of benthic habitats in these canyons and the ecosystem services they provide.
The red tree coral Primnoa pacifica is an important habitat forming octocoral in North Pacific waters. Given the prominence of this species in shelf and upper slope areas of the Gulf of Alaska where ...fishing disturbance can be high, it may be able to sustain healthy populations through adaptive reproductive processes. This study was designed to test this hypothesis, examining reproductive mode, seasonality and fecundity in both undamaged and simulated damaged colonies over the course of 16 months using a deepwater-emerged population in Tracy Arm Fjord. Females within the population developed asynchronously, though males showed trends of synchronicity, with production of immature spermatocysts heightened in December/January and maturation of gametes in the fall months. Periodicity of individuals varied from a single year reproductive event to some individuals taking more than the 16 months sampled to produce viable gametes. Multiple stages of gametes occurred in polyps of the same colony during most sampling periods. Mean oocyte size ranged from 50 to 200 µm in any season, and maximum oocyte size (802 µm) suggests a lecithotrophic larva. No brooding larvae were found during this study, though unfertilized oocytes were found adhered to the outside of polyps, where they are presumably fertilized. This species demonstrated size-dependent reproduction, with gametes first forming in colonies over 42-cm length, and steady oocyte sizes being achieved after reaching 80-cm in length. The average fecundity was 86 (± 12) total oocytes per polyp, and 17 (± 12) potential per polyp fecundity. Sub-lethal injury by removing 21-40% of colony tissue had no significant reproductive response in males or females over the course of this study, except for a corresponding loss in overall colony fecundity. The reproductive patterns and long gamete generation times observed in this study indicate that recruitment events are likely to be highly sporadic in this species increasing its vulnerability to anthropogenic disturbances.
Abstract
This work provides evidence that a large fraction of C iv narrow absorption lines (NALs) seen along the line of sight to distant quasars are due to accretion disc winds, while also seeking ...to understand the relationship between NALs and certain quasar-intrinsic properties. We extend the results from past work in the literature using ${\sim}105\, 000$ NALs from a sample of ${\sim}58\, 000$ SDSS quasars. The primary results of this work are summarized as follows: (1) the velocity distribution (dN/dβ) of NALs is not a function of radio loudness (or even detection) once marginalized by optical/UV luminosity; (2) there are significant differences in the number and distribution of NALs as a function of both radio spectral index and optical/UV luminosity, and these two findings are not entirely interdependent; (3) improvements in quasar systemic redshift measurements and differences in the NAL distribution as a combined function of optical luminosity and radio spectral index together provide evidence that a significant portion of NALs are due to outflows; (4) the results are consistent with standard models of accretion disc winds governed by the LUV–αox relationship and line-of-sight orientation indicated by radio spectral index, and (5) possibly support a magnetically arrested disc model as an explanation for the semistochastic nature of strong radio emission in a fraction of quasars.
In the Arctic, earlier snowmelt and longer growing seasons due to warming have been hypothesized to increase vegetation productivity. Using the Normalized Difference Vegetation Index (NDVI) from both ...field and satellite measurements as an indicator of vegetation phenology and productivity, we monitored spatial and temporal patterns of vegetation growth for a coastal wet sedge tundra site near Barrow, Alaska over three growing seasons (2000–2002). Contrary to expectation, earlier snowmelt did not lead to increased productivity. Instead, productivity was associated primarily with precipitation and soil moisture, and secondarily with growing degree days, which, during this period, led to reduced growth in years with earlier snowmelt. Additional moisture effects on productivity and species distribution, operating over a longer time scale, were evident in spatial NDVI patterns associated with microtopography. Lower, wetter regions dominated by graminoids were more productive than higher, drier locations having a higher percentage of lichens and mosses, despite the earlier snowmelt at the more elevated sites. These results call into question the oft-stated hypothesis that earlier arctic growing seasons will lead to greater vegetation productivity. Rather, they agree with an emerging body of evidence from recent field studies indicating that early-season, local environmental conditions, notably moisture and temperature, are primary factors determining arctic vegetation productivity. For this coastal arctic site, early growing season conditions are strongly influenced by microtopography, hydrology, and regional sea ice dynamics, and may not be easily predicted from snowmelt date or seasonal average air temperatures alone. Our comparison of field to satellite NDVI also highlights the value of in-situ monitoring of actual vegetation responses using field optical sampling to obtain detailed information on surface conditions not possible from satellite observations alone.
► Field NDVI sampling clearly resolved productivity patterns for arctic vegetation. ► Reduced vegetation productivity (NDVI) occurred in years with earlier snowmelt. ► Reduced precipitation and soil moisture best explained this reduced productivity. ► MODIS could not resolve snowmelt dates, growing season length, or peak NDVI. ► Field optical monitoring avoids cloud contamination that plagues satellite NDVI.
A trend in education is the use of electronic textbooks (e-textbook, Stone, R. W., and L. Baker-Eveleth. 2013. "Students' Expectation, Confirmation, and Continuance Intention to Use Electronic ...Textbooks." Computers in Human Behavior 29 (3): 984-990.). A variety of research has examined the motivations for e-textbook adoption as well as continuance intentions of e-textbooks after an initial adoption. This research extends the continuance intentions literature using the expectation-confirmation model (Bhattacherjee, A. 2001. "Understanding Information Systems Continuance: An Expectation-Confirmation Model." MIS Quarterly 25 (3): 351-370.) and including the constructs of e-textbook usability and its dimensions. The data were responses to an online questionnaire by students at a medium-sized (USA) university. A total of 1434 responses were received for a 12.52% response rate. These responses were partitioned to include only complete responses from students who had previously used an e-textbook. This produced a sample of 639 questionnaire responses for empirical analysis. The analysis was performed using structural equation modelling (i.e. Procedure Calis in PC SAS version 9.2). The results showed that students' continuance intentions of e-textbooks are driven by students' satisfaction with e-textbooks and perceived usefulness. Additionally, students' expectation-confirmation and e-textbook usability positively influence both students' satisfaction and perceived usefulness and hence the intentions for continued e-textbook adoptions. Finally, the usability dimensions of efficiency and effectiveness significantly influence e-textbook usability.
Background - A new species of Memecylon (Melastomataceae-Olisbeoideae) from Rwanda, Burundi and western Tanzania is described in connection with preparing the family treatment for the Flore d'Afrique ...centrale.
Methods -
Standard herbarium practices were applied.
Key results - Memecylon afroschismaticum R.D.Stone is described and illustrated. This new species is remarkable for being endemic to forests of the East African Rift region avoided by all but a few other species of African
Memecylon. A close relationship with M. flavovirens Baker (type of M. sect. Obtusifolia Engl.) is suggested by its corolla being narrowly conical-acute in bud and anther connectives with dorsal oil-gland and acute posterior extremity. However, its elliptic-ovate
and distinctly acuminate leaves resemble those of M. myrianthum Gilg (of M. sect. Polyanthema Engl.) and M. verruculosum Brenan (of M. sect. Buxifolia R.D.Stone). The known location in western Tanzania is formally protected within the Mahale Mountains
National Park, but the subpopulations in Rwanda and Burundi are unprotected and presumably threatened by high human population density and subsistence agriculture. The estimated area of occupancy is also quite small (12 km2). Memecylon afroschismaticum is thus provisionally
assessed as Endangered EN B1ab(iii)+B2ab(iii) in accordance with IUCN criteria.
In the Gulf of Alaska, commercially harvested fish species utilize habitats dominated by red tree corals (Primnoa pacifica) for shelter, feeding, and nurseries, but recent studies hint that ...environmental conditions may be interrupting the reproductive lifecycle of the corals. The North Pacific has experienced persistent and extreme thermal variability in recent years and this pattern is predicted to continue in coming decades. Recent discovery of deep-water emerged coral populations in Southeast Alaska fjords provided opportunity for detailed life-history studies and comparison to corals in managed habitats on the continental shelf. Here we show that sperm from deep colonies develops completely, but in shallow colonies, sperm development is prematurely halted, likely preventing successful production of larvae. We hypothesize that the divergence is due to differing temperature regimes presently experienced by the corals. Compared to deep populations below the thermocline, shallow populations experience much greater seasonal thermal variability and annual pulses of suspected near-lethal temperatures that appear to interrupt the production of viable gametes. The unique opportunity to comprehensively study emerged populations presently affected by thermal stress provides advance warning of the possible fate of deep corals in the Gulf of Alaska that will soon experience similar ocean conditions.
Primnoa pacifica is the most ecologically important coral species in the North Pacific Ocean and provides important habitat for commercially important fish and invertebrates. Ocean acidification (OA) ...is more rapidly increasing in high-latitude seas because anthropogenic CO2 uptake is greater in these regions. This is due to the solubility of CO2 in cold water and the reduced buffering capacity and low alkalinity of colder waters. Primnoa pacifica colonies were cultured for six to nine months in either pH 7.55 (predicted Year 2100 pH levels) or pH 7.75 (Control). Oocyte development and fecundity in females, and spermatocyst stages in males were measured to assess the effects of pH on gametogenesis. Oocyte diameters were 13.6% smaller and fecundities were 30.9% lower in the Year 2100 samples. A higher proportion of vitellogenic oocytes (65%) were also reabsorbed (oosorption) in the Year 2100 treatment. Lower pH appeared to advance the process of spermatogenesis with a higher percentage of later stage sperm compared to Control. There was a laboratory effect observed in all measurement types, however this only significantly affected the analyses of spermatogenesis. Based on the negative effect of acidification on oogenesis and increased rate of oosorption, successful spawning could be unlikely in an acidified ocean. If female gametes were spawned, they are likely to be insufficiently equipped to develop normally, based on the decreased overall size and therefore subsequent limited amount of lipids necessary for successful larval development.
The research investigates the influence of the System Understanding Aid (SUA), on students' learning of accounting cycles and controls. The SUA requires students to enter 15 transactions and perform ...related accounting activities. The theoretical model uses Bloom's Taxonomy and Scaffold method. The study's objectives are to identify if SUA completion method (i.e. manual or digital) influences students' SUA scores and if these scores influence performance on an end of the semester assessment regarding accounting cycles and controls. The data were collected from 274 students in a required accounting information systems course at an AACSB accredited accounting department across seven consecutive semesters. The data were analyzed using systems of linear equations and three-stage least squares estimation. The results provide evidence that SUA scores have a positive relationship to student learning of accounting cycles and controls. Supplemental analysis also indicates that digital completion of the SUA influences student scores.
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