bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Enhancement of Resistance to Alternaria Leaf Blight in Sunflower through Cyclic Gametophytic and Sporophytic Selections
Authors: Rani T. Shobha , Ravikumar R. L.
Published: July 2010

Only partial resistance has been reported so far in Helianthus species for leaf blight caused by Alternaria helianthi (Hansf.). Therefore, in the present study one to two cycles of recurrent selection based on sporophytic and gametophytic selection was effected to increase resistance to leaf blight in the base population. The base population was synthesized by random mating five diverse early generation breeding lines. The gamete selection was practiced by applying pathogen culture filtrate to stigma and style 1 h before pollination. The selection response was measured by recording observations on percent disease index (PDI) at flowering, 15 d after flowering and at physiological maturity. In both gametophytic and sporophytic selection cycles significant reduction in PDI was observed. The populations improved through gametophytic selection were more promising as the pollen selection could allow high selection intensity and absence of dominance effects. In sporophytic selection the rare favorable allelic combination is hardly detected. The progress in resistance in two cycles of selection was not very high for their use in crop improvement. There is a need to increase the number of cycle of selection to maximize the desirable alleles to achieve high level of resistance. The gametophytic selection combined with the conventional sporophytic selection can be considered as an effective tool in improving populations for partial resistance.
Evidence for a Selective Sweep on Chromosome 1 of Cultivated Sorghum
Authors: Casa Alexandra M. , Mitchell Sharon E. , Jensen Jeffrey D. , Hamblin Martha T. , Paterson Andrew H. , Aquadro Charles F. , Kresovich Stephen
Published: July 2010

Recently, a simple sequence repeat (SSR)‐based genome‐wide diversity scan of Sorghum bicolor (L.) Moench identified several candidate loci with patterns of variation consistent with directional selection in cultivated lines. Data were insufficient, however, to determine if selection had actually occurred at or near candidate SSR loci or if the unusual diversity patterns observed were due to the effects of demographic factors such as population bottlenecks or mating system. In the present study, we collected DNA sequences from 10 segments within a 99 kb region flanking one of the previously identified candidates, SSR locus Xcup15, located near the distal end of chromosome 1. We performed statistical tests both to address alternative hypotheses to selection and to aid in localizing the selection target. Analyses of genomic DNA sequences from a panel of 17 cultivated and 13 wild accessions indicated that cultivated lines had reduced diversity in this region (about one‐third of the diversity present in wild sorghums) and a moderate degree of differentiation was observed between cultivated and wild groups (Fst = 0.15). Several features of the data support the hypothesis that recent directional selection shaped diversity patterns around Xcup15, including overall low levels of variation and extensive haplotype structure (a predominant haplotype occurred over the 99 kb region) in cultivated sorghum, and a derived fixed difference at the 5′ untranslated region (UTR) of a protein phosphatase 2C (PP2C) gene between cultivated and wild sorghums. Moreover, two of the four tests employed to detect deviations from the neutral, equilibrium model, the Hudson Kreitman Aguadé (HKA), and the composite likelihood ratio (CLR) tests indicated that patterns of diversity in the Xcup15 region were consistent with a selective sweep. Although we were unable to rule out demography as a possible explanation for the diversity patterns observed along this region, this study supported previous findings based on SSR diversity and identified candidates for the target of selection; the confirmation of which will require functional and association studies.
Response to Recurrent Selection for Resistance to Striga hermonthica (Del.) Benth in a Tropical Maize Population
Authors: Menkir A. , Kling J. G.
Published: July 2010

Striga hermonthica (Del.) Benth is an obligate root parasite infecting maize (Zea mays L.) and causing considerable yield losses in Africa. Few studies have been conducted to determine the effectiveness of recurrent selection for improving resistance to S. hermonthica in maize. The objective of this study was to evaluate genetic gain achieved in a composite subjected to six cycles of selection under S. hermonthica infestation. The selection cycles and checks were evaluated with and without S. hermonthica infestation at two locations in Nigeria for 2 yr. Selection for improved performance under S. hermonthica infestation significantly increased grain yield by 24% cycle‐1 and ears per plant by 9% cycle‐1. At the same time, the gain per cycle was −7% for relative yield loss, −5% for host damage rating, −9% for emerged S. hermonthica plants, −4% for anthesis–silking interval, and −5% for ear aspect. Selection under S. hermonthica infestation was accompanied by a concomitant increase in grain yield and improvement in plant aspect and ear aspect without S. hermonthica infestation. The observed progress in performance under S. hermonthica infestation demonstrates the effectiveness of recurrent selection for increasing polygenetic resistance against the parasite in tropical populations.
Peroxidase Gene Polymorphism in Buffalograss and Other Grasses
Authors: Gulsen O. , Shearman R. C. , Heng‐Moss T. M. , Mutlu N. , Lee D. J. , Sarath G.
Published: July 2010

Plant peroxidases are a family of related proteins possessing highly conserved domains. Degenerate oligonucleotide primers based on these conserved domains can be used to amplify DNA sequences coding for peroxidases from plants with unsequenced genomes. Polymorphisms in peroxidase genes among buffalograss [Buchloe dactyloides (Nutt.) Engelm.] genotypes and eight other grasses were evaluated, and potential evolutionary relationships were deduced using this approach. Fourteen peroxidase specific primers with alternative forward and reverse primers using 34 rice peroxidase cDNAs were designed based on conserved motifs of this gene family. Targeted polymerase chain reaction (PCR) amplification of genomic DNA from 28 buffalograss, 4 C4, and 4 C3 grass genotypes yielded polymorphisms, differentiating diploids from polyploids within buffalograss and C3 and C4 grass species from each other. A total of 11 peroxidase gene fragments, 7 belonging to buffalograss and 4 to the other grass species, were sequenced. Five of these sequences were clustered with rice (Oryza sativa L.) ascorbate peroxidase known to have chloroplast origin. These results demonstrate that primers targeting the peroxidase gene family can be used to study genotypic diversity and evolutionary relationships on an intraspecific and interspecific basis. The PCR‐based peroxidase markers may also have potential for linkage mapping and differential gene expression studies in grasses.
Evaluating Traffic Stress by the Brinkman Traffic Simulator and Cady Traffic Simulator on a Kentucky Bluegrass Stand
Authors: Vanini J. T. , Henderson J. J. , Sorochan J. C. , Rogers J. N.
Published: July 2010

The Brinkman Traffic Simulator (BTS) has been a useful tool to simulate sports field traffic. However, rate of traffic stress produced by the BTS, a pull‐behind unit with two differentially connected studded rollers, has been questioned. The Cady Traffic Simulator (CTS), a modified walk‐behind core cultivation unit, was developed and tested to potentially produce more aggressive traffic stress. A comparison study was initiated between the BTS and CTS to evaluate these simulators on a Kentucky bluegrass (Poa pratensisL.) stand. Playing surface data collected were surface hardness, traction, soil moisture, bulk density, porosity, and plant counts. Higher surface hardness, lower traction, and lower plant count values resulted when the CTS applied 10 passes per week (PPW) compared with other treatments. Surface hardness, traction, and bulk density values were statistically similar when the CTS applied 2 PPW, and BTS applied 10 PPW.
Reaction of Wild Emmer Wheat Accessions to Fusarium Head Blight
Authors: Oliver R. E. , Stack R. W. , Miller J. D. , Cai X.
Published: July 2010

Fusarium head blight (FHB), caused mainly by Fusarium graminearum Schwabe, is a serious disease of wheat (Triticum spp.) worldwide. Host resistance has proven the most effective method of controlling FHB in common wheat (T. aestivum L., 2n = 6x = 42, genomes AABBDD). Progress in breeding for FHB resistance in durum wheat (T. turgidum L. ssp. durum, 2n = 4x = 28, genomes AABB), however, has been limited by a lack of resistance sources. Fortunately, durum wheat has a large number of tetraploid relatives, which represent a gene pool for improvement of FHB resistance in durum. The objective of this study was to search for sources of FHB resistance in wild emmer wheat [T. turgidum L. ssp. dicoccoides (Körn. ex Asch. & Graebner) Thell., 2n = 4x = 28, genomes AABB] (TDIC). We evaluated 416 accessions of wild emmer wheat for reaction to FHB using the point inoculation method in a greenhouse environment. Accessions exhibiting a low FHB disease rating in preliminary evaluations were retested in fully replicated experiments. Among the 416 accessions tested, there was wide variation in response to FHB, ranging from highly resistant to highly susceptible. Several accessions showed minimal disease development across two or more seasons and represent potential new sources to enhance resistance of durum wheat to FHB.
Hunting impact on the population dynamics of Pyrenean grey partridgePerdix perdix hispaniensis
Authors: Besnard Aurélien , Novoa Claude , Gimenez Olivier
Published: July 2010

The grey partridge Perdix perdix used to be a common and widespread species throughout the temperate zone of western Eurasia, but its populations have markedly declined in most parts of its native range since the 1950s. The Pyrenean subspeciesP. p. hispaniensisis threatened by alteration of its habitat, and despite ecological and hunting interest in this subspecies, the impact of harvest on population sustainability remains largely unknown. We assessed mortality of Pyrenean grey partridge and its influence on the population growth rate during 1992‐2001 in the French Pyrenees. Cause‐specific mortality rates were estimated using multistate capture‐recapture models based on fates of 67 radio‐equipped birds. Annual recruitment was estimated as the ratio of juvenile birds to adult birds in harvested samples. Mammalian predators and raptors were each responsible for a 5% monthly mortality rate. At the peak of hunting activity (i.e. October), hunting was responsible for a 30% mortality rate in some years. Modeled population growth rates appeared stable without hunting but negative with hunting. The estimated difference in population growth rates under the two regimes was 0.46. Our estimates of population growth suggest that the population was decreasing during our study, whereas it appeared stable based on ground counts. We discuss this discrepancy and proposed management actions.
Spatial patterns of accumulated browsing and its relevance for management of red deer Cervus elaphus
Authors: Mysterud Atle , Askilsrud Harald , Loe Leif Egil , Veiberg Vebj⊘rn
Published: July 2010

The substantial increase of deer populations in Europe and North America in recent decades has led to concerns regarding the long‐term sustainability of current management from an ecosystem perspective. Key questions to be answered are how herbivore density relates to available resource levels, e.g. food availability and browsing pressure, and how this relation should be monitored and included in management. In Norway, the harvest of red deer Cervus elaphus has increased from 1,479 to 35,700 during 1960‐2008. Current monitoring programmes focus on deer body mass and number of seen deer rather than on the state of the vegetation communities. In our study, we quantify browsing frequency on common shrubs and trees in two municipalities, Gloppen and Flora, in the county of Sogn and Fjordane, Norway, to document current browsing pressure levels and to evaluate the potential of using browsing frequency of indicator species as a tool in the monitoring of red deer populations. We found that several species were heavily browsed (median browsing frequency > 60%). Due to their wide availability, we analysed the spatial patterns of accumulated browsing of the highly selected rowan Sorbus aucuparia compared to the less selected bilberry Vaccinium myrtillus and birch Betula sp. We predicted less spatial variation in browsing frequency of the highly selected rowan. However, we found that the best model predicting browsing on rowan (forest type, habitat productivity, canopy cover, aspect, slope and distance to arable land) based on habitat variables was more complicated than for birch (habitat productivity and altitude) and bilberry (forest type, habitat productivity, altitude and distance from the coast). This suggests large spatial variation in browsing frequency of rowan even though the average browsing frequency of rowan was higher than for bilberry and birch. Browsing frequency for all species was positively correlated with faeces counts, but only bilberry showed additional correlation with red deer (harvest) density at the local management unit scale. Due to its wide distribution and promising link to local red deer density, bilberry stands out as the most promising species to monitor among winter browse species. However, browsing frequency on different species was not always correlated. It remains to be determined to which extent browsing on bilberry can be used as an indicator for the browsing pressure on the whole vegetation community. The documentation of high browsing frequencies clearly suggests that further focus on these issues is warranted.
N-Cyclohexyl-11-(octylthio)undecanamide
Authors: Schön Eva-Maria , Díaz David D.
Published: July 2010

A practical synthesis of N-cyclohexyl-11-(octylthio)undecanamide by thiol-ene click coupling reaction under UV light irradiation is reported. The title compound was characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR and MS spectroscopic methods. This molecule was found to be an efficient gelator for fluid oils, and the main physical parameters of the formed gels were also examined.
Synthesis and Odor Evaluation of Five New Sulfur-Containing Ester Flavor Compounds from 4-Ethyloctanoic Acid
Authors: Liu Yuping , Chen Haitao , Yin Decai , Sun Baoguo
Published: July 2010

Five sulfur-containing flavor compounds were synthesized for the first time by the reaction of 4-ethyloctanoyl chloride with sulfur-containing alcohols or mercaptans. The synthesized compounds are 3-(methylthio)propyl 4-ethyloctanoate, 2-methyl-3-tetrahydro-furanthiol 4-ethyloctanoate, 4-methyl-5-thiazoleethanol 4-ethyloctanoate, 2-furan-methanethiol 4-ethyloctanoate and 2-methyl-3-furanthiol 4-ethyloctanoate. These five synthetic sulfur-containing ester flavor compounds all have meaty odor and might be used in foods if approved for this purpose in the future.
Automated Signal Processing Applied to Volatile-Based Inspection of Greenhouse Crops
Authors: Jansen Roel , Hofstee Jan Willem , Bouwmeester Harro , Henten Eldert van
Published: July 2010

Gas chromatograph–mass spectrometers (GC-MS) have been used and shown utility for volatile-based inspection of greenhouse crops. However, a widely recognized difficulty associated with GC-MS application is the large and complex data generated by this instrument. As a consequence, experienced analysts are often required to process this data in order to determine the concentrations of the volatile organic compounds (VOCs) of interest. Manual processing is time-consuming, labour intensive and may be subject to errors due to fatigue. The objective of this study was to assess whether or not GC-MS data can also be automatically processed in order to determine the concentrations of crop health associated VOCs in a greenhouse. An experimental dataset that consisted of twelve data files was processed both manually and automatically to address this question. Manual processing was based on simple peak integration while the automatic processing relied on the algorithms implemented in the MetAlignTM software package. The results of automatic processing of the experimental dataset resulted in concentrations similar to that after manual processing. These results demonstrate that GC-MS data can be automatically processed in order to accurately determine the concentrations of crop health associated VOCs in a greenhouse. When processing GC-MS data automatically, noise reduction, alignment, baseline correction and normalisation are required.
Detecting Solenoid Valve Deterioration in In-Use Electronic Diesel Fuel Injection Control Systems
Authors: Tsai Hsun-Heng , Tseng Chyuan-Yow
Published: July 2010

The diesel engine is the main power source for most agricultural vehicles. The control of diesel engine emissions is an important global issue. Fuel injection control systems directly affect fuel efficiency and emissions of diesel engines. Deterioration faults, such as rack deformation, solenoid valve failure, and rack-travel sensor malfunction, are possibly in the fuel injection module of electronic diesel control (EDC) systems. Among these faults, solenoid valve failure is most likely to occur for in-use diesel engines. According to the previous studies, this failure is a result of the wear of the plunger and sleeve, based on a long period of usage, lubricant degradation, or engine overheating. Due to the difficulty in identifying solenoid valve deterioration, this study focuses on developing a sensor identification algorithm that can clearly classify the usability of the solenoid valve, without disassembling the fuel pump of an EDC system for in-use agricultural vehicles. A diagnostic algorithm is proposed, including a feedback controller, a parameter identifier, a linear variable differential transformer (LVDT) sensor, and a neural network classifier. Experimental results show that the proposed algorithm can accurately identify the usability of solenoid valves.
Striving for Sustainability and Resilience in the Face of Unprecedented Change: The Case of the Mountain Pine Beetle Outbreak in British Columbia
Authors: Burton Philip J.
Published: July 2010

A massive insect outbreak in the public forests of central British Columbia (Canada) poses a serious challenge for sustainable forest management planning. Tree mortality caused by natural disturbances has always been a part of wild and managed forests, but climate change is accentuating the uncertainty around such losses. Policy responses to accelerate overall timber harvesting levels to prevent further tree mortality and to aggressively salvage value from dead wood before it deteriorates can be disruptive and even counter-productive in the long run. Current alternatives are to strategically redirect existing timber harvesting quotas to the most vulnerable areas, minimize overall uplifts in cutting activity, prolong the period over which harvested timber can be processed, avoid the harvesting of mixed species stands or those with good advance regeneration, employ more partial cutting or “selective logging” techniques, and relax standards for acceptable species and inter-tree spacing during post-disturbance stand recovery. At the same time, careful attention to species composition and evolving landscape risk profiles may facilitate adaptation to anticipated climate change and reduce vulnerability to future disturbances. Harvest levels must be set conservatively over the full planning horizon if it is important to assure continuity of the timber supply with few disruptions to regional socio-economics and less stress to ecosystems. Broader lessons in sustainability include the option to emphasize persistence, continuity and flexibility over the long term, though at the expense of maximized production and full resource utilization in the short term.
Losing the Forest for the Trees: Environmental Reductionism in the Law
Authors: Bosselmann Klaus
Published: July 2010

Environmental laws and policies have saved some “trees”, but the “forest” is being lost as critical global issues including climate change, biodiversity loss, and our ecological footprint continue to worsen. Existing laws and policies mitigate the ecological damage inflicted by industrial economies and western lifestyles. The article essentially makes the case for a sustainability approach to law that aims for transformation rather than environmental mitigation. Relevant trends in international law and domestic law reflective of a sustainability approach are discussed, and the article describes some contours of “law for sustainability” or “sustainability law”.
Caring for Older Adults with Dementia when Disaster Strikes
Authors: Adelman Deborah S. , Legg Timothy J.
Published: July 2010

Disaster emergencies are occurring with seemingly increased frequency. The likelihood that gerontological nurses will be involved in a disaster scenario, regardless of practice setting, is real. Instead of recoiling from this likelihood, the best approach is preparedness. In this article we examine what constitutes a disaster and how it differs from an emergency, as well as the potential impact of a disaster on older adults in general and those with dementia in particular. Concepts of sheltering in place, caring for older adults with dementia in a temporary shelter, and partnering with nurses in acute care settings are discussed.
Indicators of a New Depression Diagnosis in Nursing Home Residents
Authors: Phillips Lorraine J. , Rantz Marilyn , Petroski Gregory F.
Published: July 2010

Depression affects approximately 30% to 40% of nursing home residents but frequently goes unrecognized. Using the Missouri Minimum Data Set, we aimed to determine whether changes in clinical status, other than mood changes, were associated with new depression diagnosis in residents 65 and older without a recorded depression diagnosis. Of 127,587 potential participants, 14,371 met inclusion criteria and were not depressed at baseline (Time 0). At the next quarterly assessment (Time 1), 1,342 (9.3%) had acquired a new diagnosis of depression. Residents with new depression were significantly younger and less cognitively impaired. Nearly 30% had a decline in activities of daily living (ADL) performance. The multivariate model predicting depression showed that increased verbal aggression, urinary incontinence, increased pain, weight loss, change in care needs, cognitive decline, and ADL decline significantly increased the likelihood of new depression diagnosis. The pattern of decline identified here may provide additional clues to the presence of underlying depression.
Capsular Tension Ring in the Management of Occult Lens Zonular Dehiscence in Infantile Glaucoma
Authors: Guo Suqin , Wagner Rudolph , Forbes Brian , Tannen Bradford , Caputo Anthony
Published: July 2010

The authors present a case of bilateral zonular dehiscence in a boy with infantile glaucoma who had developed cataracts. The zonular dehiscence was noted at the beginning of cataract surgery. The cataracts were removed and capsular tension rings and intraocular lenses were safely inserted and remained well centered.
Acute Bilateral Cataract With Phacomorphic Glaucoma in a Girl With Newly Diagnosed Type 1 Diabetes Mellitus
Authors: Skrabic Veselin , Ivanisevic Milan , Stanic Robert , Unic Ivana , Bucan Kajo , Galetovic Davor
Published: July 2010

The authors present a rare case of acute bilateral cataract with phacomorphic glaucoma in a girl with newly diagnosed type 1 diabetes mellitus without a known history of ocular problems. Within 3 months after the diagnosis of diabetes mellitus, she presented with high intraocular pressure. Her visual acuity was limited to hand motions. The patient required immediate surgical intervention. Postoperatively, the intraocular pressure normalized and bilateral visual acuity was 6/6.
Personal Projects of Boys with Developmental Coordination Disorder
Authors: Poulsen Anne A. , Barker Fiona M. , Ziviani Jenny
Published: July 2010

Understanding the leisure perspectives of preadolescent boys with developmental coordination disorder (DCD) requires more than documenting time-use patterns. This study explored the use of the Personal Projects Analysis for Children (PPA-C) to improve depth of understanding about personally meaningful leisure participation for this population. Sixty boys with DCD and 113 boys without DCD completed the PPA-C. Boys with DCD reported significantly fewer personal projects involving physical activities; fewer friends with whom to complete personal projects; more solitary leisure projects; and fewer personally meaningful personal projects in total than the comparison group. The PPA-C findings provided ecologically sensitive and personally salient information about leisure time participation from the perspectives of boys with and without DCD. The low frequency of self-reported social and physical activity personal projects for boys with DCD has not been previously detailed in this way. Occupational therapists are challenged to be vigilant regarding restricted leisure portfolios and expectations about activity participation in boys with DCD, with further research and advocacy for balanced portfolios of personally meaningful leisure.
Los náufragos de nuestro mundo. El caso de los refugiados
Authors: Loewe Daniel
Published: July 2010

De acuerdo a este artículo, los argumentos más importantes contra un derecho cosmopolita a la inmigración no son transferibles legítimamente al caso de los refugiados. Interpretando el Derecho Cosmopolita kantiano, en el artículo se argumenta que el derecho de asilo debería ser entendido de un modo más extensivo que en la práctica usual de nuestros días.
Migraciones y pobreza
Authors: Pogge Thomas W.
Published: July 2010

En este artículo se argumenta que los esfuerzos políticos hacia la erradicación de la pobreza en los países en vías de desarrollo deberían ser preferentes frente a los esfuerzos dirigidos a ampliar el número de personas pobres y oprimidas admitidas en nuestras sociedades ricas. Ambos tipos de esfuerzos son objetivos morales, pero el primero parece ser más efectivo que el segundo.
Differential Toxicity of DNA Adducts of Mitomycin C
Authors: Bargonetti Jill , Champeil Elise , Tomasz Maria
Published: July 2010

The clinically used antitumor agent mitomycin C (MC) alkylates DNA upon reductive activation, forming six covalent DNA adducts in this process. This review focuses on differential biological effects of individual adducts in various mammalian cell cultures, observed in the authors′ laboratories. Evidence is reviewed that various adducts are capable of inducing different cell death pathways in cancer cells.This evidence is derived from a parallel study of MC and its derivatives 2,7‐diaminomitosene (2,7‐DAM) which is the main metabolite of MC and forms two mono‐adducts with DNA, and decarbamoyl mitomycin C (DMC), which alkylates and cross‐links DNA, predominantly with a chirality opposite to that of the DNA adducts of MC. 2,7‐DAM is not cytotoxic and does not activate the p53 pathway while MC and DMC are cytotoxic and able to activate the p53 pathway. DMC is more cytotoxic than MC and can also kill p53‐deficient cells by inducing degradation of Checkpoint 1 protein, which is not seen with MC treatment of the p53‐deficient cells. This difference in the cell death pathways activated by the MC and DMC is attributed to differential signaling by the DNA adducts of DMC. We hypothesize that the different chirality of the adduct‐to‐DNA linkage has a modulating influence on the choice of pathway.
Variation in colloidal chromophoric dissolved organic matter in the Damariscotta Estuary, Maine
Authors: Floge Sheri A. , Wells Mark L.
Published: July 2010

The relationship between chromophoric dissolved organic matter (CDOM), colloidal DOM (.1 kDa), and phytoplankton biomass in marine waters of the Damariscotta estuary, Maine, was studied using flow field‐flow fractionation (flow FFF). The goal was to determine whether temporal variability in CDOM in this region is due in part to rapid cycling of marine colloids. CDOM absorption of filtered (0.2 µm) seawater correlated positively with colloidal absorbance (r2 = 0.772, p = 0.021). We observed changes in colloidal size spectra and CDOM optical properties associated with phytoplankton biomass. In particular, a significant positive correlation was found between the < 18 kDa colloidal fraction and chlorophyll a (Chl a) (r2 = 0.819, p = 0.013). While we did not find significant relationships between Chl a and either CDOM absorption or the spectral slope of filtered seawater (r2 and p values of 0.079, 0.590 and 0.111, 0.519, respectively), we did observe patterns of higher CDOM absorption and spectral slopes following periods of increased phytoplankton biomass. The spectral slope of colloidal material often was significantly lower than that of filtered seawater and normally varied significantly with colloidal size. These findings show that colloidal processes can contribute to CDOM optical signatures in coastal waters.
Different coupling of dissolved amino acid, protein, and carbohydrate turnover to heterotrophic picoplankton production in the Southern Ocean in austral summer and fall
Authors: Simon Meinhard , Rosenstock Bernd
Published: July 2010

We assessed growth dynamics of heterotrophic picoplankton and concentrations and turnover of dissolved protein, amino acids, and neutral monosaccharides in the Atlantic sector of the Southern Ocean in austral summer (December‐January) and fall (March‐May). Phytoplankton biomass (chlorophyll a) and biomass production of heterotrophic picoplankton in summer was twice as high as in fall. This difference was also reflected in protein turnover rate constants and in concentrations of dissolved combined neutral polysaccharides (DCCHO). Turnover rate constants of dissolved free amino acids (DFAA) were in the same range in both seasons, but turnover rate constants of glucose were higher in fall as compared to summer. In summer, dissolved protein was the major substrate for growth of heterotrophic picoplankton, followed by DFAA and dissolved free neutral monosaccharides (DFCHO). During summer, heterotrophic picoplankton production was closely correlated to concentrations and incorporation of dissolved protein. In fall, heterotrophic picoplankton production was only significantly correlated to glucose turnover rate constants. The latter were also inversely correlated to DCCHO concentrations in fall. The reduced supply of organic substrates by phytoplankton in fall not only resulted in an equal reduction of heterotrophic picoplankton production but also in a shift of the supply in dissolved protein, DFAA, and DFCHO to heterotrophic picoplankton. Dissolved protein was the major substrate for heterotrophic picoplankton growth in summer, but in fall, when supply of dissolved protein was reduced, DFAA and DFCHO were relatively more important substrates.
High‐resolution profiles and nitrogen isotope tracing reveal a dominant source of nitrous oxide and multiple pathways of nitrogen gas formation in the central Arabian Sea
Authors: Nicholls Joanna Claire , Davies Christian Andrew , Trimmer Mark
Published: July 2010

The oxygen minimum zone (OMZ) of the Arabian Sea is a significant source of nitrous oxide (N2O), yet the metabolism responsible for N2O production is unclear. High‐resolution profiles identified peaks and troughs of N2O and NO2‐ in the top 500 m of the water column. The first peak in N2O was not in the oxycline, but deeper at the oxic‐suboxic interface. Peaks and troughs were targeted with a suite of 15N incubations (15NO3‐, 15NO2‐, 15NH4+) to identify pathways of N2O and N2 formation. With 15NO2‐, 15N‐N2O was produced at all depths with a binomial distribution with respect to the NO2‐ pool. With 15NO3‐, the 15N was not binomially distributed. NO3‐ is first reduced to NO2‐ before reduction to N2O, and NO2‐ → N2O is the dominant metabolism responsible for N2O production. The N2O produced from 15NH4+ represented 2‐5% of that from 15NO2‐ at the top of the OMZ. In addition, the production of 45N2O, but no 46N2O, at some depths with 15NH4+, suggested a novel source akin to Nitrosomonas spp. under O2 limitation. Unlike N2O, the production of N2 with 15NO2‐ or 15NO3‐ was not binomially distributed and therefore was not entirely derived from the same source as N2O. Although indicative of an alternative N2 source to denitrification, the lack of significant production of labeled N2 with 15NH4+ discounts anaerobic ammonium oxidation (anammox), as we understand it. Dissolved organic nitrogen or nitrate/nitrite reduction to ammonium are suggested as the additional sources of N in N2 production.
North to Alaska: Evidence for conveyor belt transport of Dungeness crab larvae along the west coast of the United States and Canada
Authors: Park Wongyu , Douglas David C. , Shirley Thomas C.
Published: July 2010

We propose and evaluate the hypothesis that Dungeness crab (Cancer magister) larvae from the northwestern coast of the United States and Canada can be transported northward to southeastern Alaska. Larvae collected in southeastern Alaska during May and June 1997–2004 had abundances and stages that varied seasonally, interannually, and spatially. An unexpected presence of late‐stage larvae in spring raises a question regarding their origin, and the most plausible explanation is that they hatched off the northern Washington and British Columbia coasts and were transported to southeastern Alaska. Buoy drift tracks support the hypothesis that larvae released off the northern Washington and British Columbia coasts during the peak hatching season can be physically transported to southeastern Alaska, arriving as late‐stage larvae in May and June, when local larvae are only beginning to hatch. A northward spring progression of monthly mean 7°C SST isotherms and phytoplankton blooms provide further evidence that environmental conditions are conducive for larval growth and metabolism during the transport period. The proposed larval transport suggests possible unidirectional gene flow between southern and northern populations of Dungeness crabs in southeastern Alaska.
Eutrophication of ancient Lake Ohrid: Global warming amplifies detrimental effects of increased nutrient inputs
Authors: Matzinger Andreas , Schmid Martin , Veljanoska-Sarafiloska Elizabeta , Patceva Suzana , Guseska Dafina , Wagner Bernd , Müller Beat , Sturm Michael , Wüest Alfred
Published: July 2010

Lake Ohrid in southeastern Europe is one of the few ancient, long‐lived lakes of the world, and contains more than 200 endemic species. On the basis of integrated monitoring of internal and external nutrient fluxes, a progressing eutrophication was detected (~3.5‐fold increase in phosphorus (P) concentration in the lake over the past century). The lake is fortunately still oligotrophic, with high concentrations of dissolved oxygen (DO) in the deep water that are requisite for the unique endemic bottom fauna. Hypolimnetic DO is not only very sensitive to changes in anthropogenic P load—via mineralization of organic material—but also to global warming via decrease of vertical mixing and less frequent complete deep convection. Moreover, these two human effects amplify each other. To keep DO from falling below currently observed minimal levels—given the predicted atmospheric warming of 0.04°C yr−1—the P load must be decreased by 50% in coming decades. However, even with such a reduction in P load, anoxia is still expected toward the end of the century if the rate of warming follows predictions.
Behavioral response as a predictor of seasonal depth distribution and vertical niche separation in freshwater phytoplanktonic flagellates
Authors: Clegg Mark R. , Maberly Stephen C. , Jones Roger I.
Published: July 2010

The distribution of phytoplanktonic flagellates in aquatic ecosystems has been widely attributed to a number of driving factors. In this study, we evaluated the influence of behavior on the daytime, seasonal depth distribution and vertical niche separation of five phylogenetically contrasting species of freshwater flagellates. A model predicting distribution was formulated using the dominant behavioral preferences for light, oxygen, and carbon dioxide, previously quantified in laboratory experiments, and was subsequently applied to the physical and chemical conditions measured in a small, strongly stratifying, hypertrophic lake. This model predicted the daytime depth distributions of natural populations of flagellates well, with an average areal fit of above 56% for all species; above 74% for Ceratium furcoides, Chlamydomonas sp., and Dinobryon sertularia; and of up to 93% during stratification. Regression analyses showed no significant variation from a 1 : 1 relationship between the predicted and observed average depths of species in the water column. The model also predicted the constriction into discrete vertical niches upon stratification and delineated the progression from Plagioselmis nannoplanctica in surface waters, through C. furcoides and D. sertularia, to Chlamydomonas sp. and Euglena gracilis deeper in the water column. Changes in observed distributions could not be directly correlated with other members of the plankton community or explained by the segregation of nutrients. The model's wider, transferable applicability suggested that behavioral response to environmental gradients may predict many patterns of distribution, particularly during stratification. In addition to known physiological and biochemical influences, this investigation emphasized the importance of behavioral response in the functional ecology of phytoplanktonic flagellates.
Do zooplankton contribute to an ultraviolet clear‐water phase in lakes?
Authors: Williamson Craig E. , De Lange Hendrika J. , Leech Dina M.
Published: July 2010

Seasonal increases in the ultraviolet (UV) transparency of the surface waters of an oligotrophic lake in Pennsylvania suggest that clear‐water phase (CWP) events similar to those previously observed for visible light also exist for the potentially damaging UV wavelengths. Seasonal increases in zooplankton grazers indicate that they play a role in these changes in UV that is similar to the role that zooplankton play in CWP events involving longer‐wavelength visible, or photosynthetically active radiation (PAR, 400‐700 nm). The potential role of zooplankton and incident UV in generating UV CWP events was investigated with a set of in situ microcosm experiments that manipulated UV and zooplankton, and followed changes in particulate and dissolved absorbance in the UV (320 nm) and PAR wavelength ranges over an 8‐d period in April. Nutrients were also manipulated independently to examine the potential role of nutrient regeneration by zooplankton grazing in altering water transparency. Photobleaching by incident solar UV led to a strong and significant decrease in dissolved UV and PAR absorbance. The presence of zooplankton grazers also significantly decreased dissolved UV absorbance but increased dissolved PAR absorbance. Neither zooplankton nor UV had any significant effects on UV or PAR absorbance by particulates. In contrast, nutrient additions significantly increased dissolved absorbance in both the UV and PAR wavelength ranges, indicating that regeneration of nutrients by zooplankton offsets decreases in UV absorbance and enhances increases in PAR absorbance due to grazing. While photobleaching by UV radiation is likely to make a consistent strong contribution to UV CWP events in lakes, the net effects of zooplankton on UV transparency in a given lake will depend upon multiple factors including zooplankton density and a balance between the edibility and extent of nutrient limitation of the phytoplankton.
A combined approach to understand trophic interactions between Cercopagis pengoi (Cladocera: Onychopoda) and mysids in the Gulf of Finland
Authors: Gorokhova Elena , Lehtiniemi Maiju
Published: July 2010

We use molecular markers, feeding experiments, and stable isotopes to understand trophic interactions between native mysids, Mysis mixta and Mysis relicta, and a recent invader to the Baltic Sea, the cladoceran Cercopagis pengoi. In feeding experiments, both mysid species ingested C. pengoi at a maximum of 16 prey mysid‐1 d‐1 and a specific consumption rate of 0.15 d‐1, similar to rates reported for predation on other prey species. The frequency of predation on C. pengoi assayed by molecular diet analysis of field‐collected mysids varied between 5% and 43% depending on mysid size and species. Surprisingly, it was consistently higher in juveniles than in adults and in M. mixta than in M. relicta. The results of stable isotope analysis corroborate those of feeding experiments and molecular analysis and indicate a higher contribution of C. pengoi to the nutrition of juveniles and M. mixta. These ontogenetic and interspecific differences in mysid predation on C. pengoi are likely to reflect differences related to their different migratory behavior. Thus, despite its low relative abundance, C. pengoi is readily consumed by mysids; this may impact lower food web interactions and the nutrition of mysids in the invaded ecosystems.
Consequences of fish predation, migration, and juvenile ontogeny on zooplankton spring dynamics
Authors: Hansson Lars-Anders , Nicolle Alice , Brodersen Jakob , Romare Pia , Anders Nilsson P. , Brönmark Christer , Skov Christian
Published: July 2010

In order to disentangle if and when resource supply and adult and young‐of‐the‐year (0+) fish predation affect zooplankton dynamics during spring, we monitored zooplankton during three consecutive years in a lake in southern Sweden. We also experimentally assessed 0+ fish predation rates and estimated changes in predation rates of adult fish on zooplankton. Decline in abundances of large‐sized zooplankters in early spring was not caused by 0+ fish predation. Instead, this decline was most likely a combined result of size‐selective predation from adult fish (stationary in the lake and from those returning from surrounding streams) and competition for diminishing algal food resources. On the other hand, the decline in medium‐sized zooplankton in the lake during spring was strongly affected by 0+ fish. Hence, during spring, zooplankton are facing predation both from adult fish selecting large prey and from 0+ fish, which start feeding on small‐sized prey and eventually switch to larger. Neither predation by different ontogenetic stages of fish (adult and 0+) nor resource supply shape the zooplankton spring dynamics, but rather they affect the timing and strength of these events. 0+ cyprinids tend to have stronger effect on zooplankton dynamics than other taxa of 0+ fish. A combination of predation from adult and 0+ fish during spring is the main mechanism behind the crash of the zooplankton community, which in many lakes leads to the termination of the clear‐water phase.
The presence of ladderane lipids in the oxygen minimum zone of the Arabian Sea indicates nitrogen loss through anammox
Authors: Jaeschke Andrea , Hopmans Ellen C. , Wakeham Stuart G. , Schouten Stefan , Sinninghe Damsté Jaap S.
Published: July 2010

Distributions of ladderane lipids, which are characteristic of membranes of bacteria performing anaerobic ammonium oxidation (anammox), were determined in the northwestern Arabian Sea with respect to season, depth, and distance to the coast of Oman. Ladderane lipids were detected and quantified in suspended particulate matter (SPM) obtained from various water depths along a northwest‐to‐southeast transect during the spring intermonsoon period. Maximum concentrations of 5‐8 pg L−1 generally occurred at 500 m in the upper part of the oxygen minimum zone (OMZ). Fluxes of ladderane lipids obtained from sediment trap material sampled at 500‐m water depth ~350 km off the coast reveal a strong seasonal pattern apparently related to the annual monsoon cycle in the northern Arabian Sea, with highest fluxes of 125 ng m−2 d−1 observed during the southwest monsoon. This fourfold increase in flux during the SW monsoon compared to the spring intermonsoon period may indicate higher anammox bacterial productivity or enhanced export of ladderanes during a period of high particulate matter flux or both. Anammox, in addition to denitrification, seems to be responsible for a significant loss of nutrient nitrogen from OMZ waters in the Arabian Sea.
Habitat selection during settlement of three Caribbean coral reef fishes: Indications for directed settlement to seagrass beds and mangroves
Authors: Pollux B. J. A. , Verberk W. C. E. P. , Dorenbosch M. , de la Morinière E. Cocheret , Nagelkerken I. , van der Velde G.
Published: July 2010

We studied the settlement patterns of three Caribbean coral reef fishes in three different habitat types: mangroves, seagrass beds, and coral reefs. The settlement patterns of the three species were not random and could best be explained by active habitat selection during settlement. Acanthurus bahianus preferentially settled on the shallow reef flat and in adjacent seagrass beds, Lutjanus apodus settled exclusively into mangroves, and Ocyurus chrysurus, settled into both mangroves and seagrass beds. The settlement patterns of these three species reflect their habitat utilization during later juvenile stages. This study, therefore, suggests that the higher juvenile densities in mangroves and seagrass beds are determined by habitat selection during settlement rather than by post‐settlement processes. This habitat selection during settlement is in accordance with the assumed importance of mangroves and seagrass beds as juvenile habitats of coral reef fishes and underlines the pressing need for their conservation.
The influence of climate variation on eastern oyster (Crassostrea virginica) juvenile abundance in Chesapeake Bay
Authors: Kimmel David G. , Newell Roger I. E.
Published: July 2010

There has been a significant downward trend in the annual abundance (= spatfall) of 0‐age eastern oysters (Crassostrea virginica) measured in the autumn since 1940 in the Maryland portion of Chesapeake Bay. We developed a multiple linear regression model to predict spatfall from environmental conditions and the magnitude of the previous year’s oyster harvest. The model explained 57% of the variance in spatfall from 1940 through 1976. We used the model to predict spatfall using data from 1977 to 2004 and found poor fit for the years after 1985. We suggest that this predictive relation was lost because an epizootic of the protistan parasite Haplosporidium nelsoni in 1985 and 1986 killed large numbers of oysters in the Maryland portion of Chesapeake Bay. This event disrupted the tight relation between oyster harvest and spatfall. Using the same variables as in our initial model, we constructed a second multiple linear regression model for all data after 1977. This new model explained 53% of the variance in spatfall, although there was a reduced relation between oyster harvest in the previous year and a strong relation between July salinity and spatfall. Hindcasting spatfall from 1940 to 1976, this model explained 49% of the variance. We suggest that the overall downward trend in oyster spatfall since records began in 1940 is driven by the loss of adult oysters in the spawning stock. Superimposed on this trend is large interannual variability in oyster spatfall that is strongly related to climate‐driven changes in environmental conditions during the summer period of larval development and settlement.