El Nino MvP - Academia.edu (original) (raw)

Papers by El Nino MvP

10 Africa, a continent endowed with huge water resources that sustain its agricultural activities... more 10 Africa, a continent endowed with huge water resources that sustain its agricultural activities i s 11 increasingly coming under threat from impacts of climate extremes (droughts and floods), which 12 puts the very precious water resource into jeopardy. Understanding the relationship betwe en 13 climate variability and water storage over the cont inent, therefore, is paramount in order to 14 inform future water management strategies. This study employs Gravity Recovery And Climate 15 Experiment (GRACE) satellite products and the higher order (fourth order cumu lant) statistical 16 independent component analysis (ICA) method to study the relationship between Terres trial 17 Water Storage (TWS) changes and five global climate-teleconnection indices; El Niño-Southern 18 Oscillation (ENSO), North Atlantic Oscillatio n (NAO), Madden-Julian Oscillation (MJO), 19 Quasi-Biennial Oscillation (QBO) and the Indian Ocean Dipole (IOD) over Africa for the period 2

PLoS ONE, 2013

Pheromones mediate social interactions among individuals in a wide variety of species, from yeast... more Pheromones mediate social interactions among individuals in a wide variety of species, from yeast to mammals. In social insects such as honey bees, pheromone communication systems can be extraordinarily complex and serve to coordinate behaviors among many individuals. One of the primary mediators of social behavior and organization in honey bee colonies is queen pheromone, which is produced by multiple glands. The types and quantities of chemicals produced differ significantly between virgin and mated queens, and recent studies have suggested that, in newly mated queens, insemination volume or quantity can affect pheromone production. Here, we examine the long-term impact of different factors involved during queen insemination on the chemical composition of the mandibular and Dufour's glands, two of the major sources of queen pheromone. Our results demonstrate that carbon dioxide (an anesthetic used in instrumental insemination), physical manipulation of genital tract (presumably mimicking the act of copulation), insemination substance (saline vs. semen), and insemination volume (1 vs. 8 ml) all have long-term effects on mandibular gland chemical profiles. In contrast, Dufour's gland chemical profiles were changed only upon insemination and were not influenced by exposure to carbon dioxide, manipulation, insemination substance or volume. These results suggest that the chemical contents of these two glands are regulated by different neuro-physiological mechanisms. Furthermore, workers responded differently to the different mandibular gland extracts in a choice assay. Although these studies must be validated in naturally mated queens of varying mating quality, our results suggest that while the chemical composition of Dufour's gland is associated with mating status, that of the mandibular glands is associated with both mating status and insemination success. Thus, the queen appears to be signaling both status and reproductive quality to the workers, which may impact worker behavior and physiology as well as social organization and productivity of the colony.

Paleoceanography, 2009

A fully coupled general circulation model is used to investigate the hypothesis that during Plioc... more A fully coupled general circulation model is used to investigate the hypothesis that during Pliocene times tectonic changes in the Indonesian seas modified the Indo‐Pacific heat transport and thus increased the zonal sea surface temperature gradient in the equatorial Pacific to its large, current magnitude. We find that widening the Indonesian seaway by moving the northern tip of New Guinea south of the equator leads to an increased inflow of South Pacific waters into the Indian Ocean, but because of potential vorticity constraints on cross‐equatorial flow it also leads to reductions in both the inflow of North Pacific waters and the total Indonesian throughflow transport. The reduced throughflow is matched by increased eastward transport of warm and fresh North Pacific surface waters along the equator to the central equatorial Pacific. As a result, the Intertropical Convergence Zone lies closer to the equator and the western Pacific Warm Pool expands farther east than for present‐d...

Journal of Insect Physiology, 2012

Honey bee colonies consist of tens of thousands of workers and a single reproductive queen that p... more Honey bee colonies consist of tens of thousands of workers and a single reproductive queen that produces a pheromone blend which maintains colony organization. Previous studies indicated that the insemination quantity and volume alter queen mandibular pheromone profiles. In our 11-month long field study we show that workers are more attracted to high-volume versus low-volume inseminated queens, however, there were no significant differences between treatments in the number of queen cells built by workers in preparation for supersedure. Workers exposed to low-volume inseminated queens initiated production of queen-like esters in their Dufour's glands, but there were no significant difference in the amount of methyl farnesoate and juvenile hormone in worker hemolymph. Lastly, queen overwintering survival was unexpectedly lower in high-volume inseminated queens. Our results suggest that the queen insemination volume could ultimately affect colony health and productivity.

Insectes Sociaux, 2012

The presence of the honey bee queen reduces worker ovary activation. When the queen is healthy an... more The presence of the honey bee queen reduces worker ovary activation. When the queen is healthy and fecund, this is interpreted as an adaptive response as workers can gain fitness from helping the queen raise additional offspring, their sisters. However, when the queen is absent, workers activate their ovaries and lay unfertilized eggs that become males. Queen pheromones are recognised as a factor affecting worker ovary activation. Recent work has shown that queen mandibular pheromone composition changes with queen mating condition and workers show different behavioural responses to pheromone extracts from these queens. Here, we tested whether workers reared in colonies with queens of different mating condition varied in level of ovary activation. We also examined the changes in the chemical composition of the queen mandibular glands to determine if the pheromone blend varied among the queens. We found that the workers activated their ovaries when queens were unmated and had lower ovary activation when raised with mated queens, suggesting that workers detect and respond adaptively to queens of differing mating status. Moreover, variation in queen mandibular gland's chemical composition correlated with the levels of worker ovary activation. Although correlative, this evidence suggests that queen pheromone may act as a signal of queen mating condition for workers, in response to which they alter their level of ovary activation.

Insect Molecular Biology, 2011

Mating is a complex process causing many behavioural and physiological changes, but the factors t... more Mating is a complex process causing many behavioural and physiological changes, but the factors triggering them and the underlying molecular processes are not well characterized. In the present study we examine the effects of CO(2) (a commonly used anaesthetic in instrumental insemination that causes changes similar to those occurring after mating) and physical manipulation (which may mimic certain aspects of copulation) on the behavioural, physiological and brain transcriptional changes in honey bee queens. We show that while CO(2) causes cessation of mating flights and ovary activation, physical manipulation has additional effects on ovary activation and brain transcriptional changes. Comparisons with previous studies of honey bees and female Drosophila indicate that common molecular mechanisms may be responsible for regulating reproductive changes across different mating regimes and insect orders.

Insect Molecular Biology, 2013

Mating causes dramatic changes in female insects at the behavioural, physiological and molecular ... more Mating causes dramatic changes in female insects at the behavioural, physiological and molecular level. The factors driving these changes (e.g. seminal proteins, seminal volume) and the molecular pathways by which these factors are operating have been characterized only in a handful of insect species. In the present study, we use instrumental insemination of honey bee queens to examine the role of the insemination substance and volume in triggering post‐mating changes. We also examine differences in gene expression patterns in the fat bodies of queens with highly activated ovaries to determine if events during copulation can cause long‐term changes in gene expression. We found that the instrumental insemination procedure alone caused cessation of mating flights and triggered ovary activation, with high‐volume inseminated queens having the greatest ovary activation. Hierarchical clustering grouped queens primarily by insemination substance and then insemination volume, suggesting tha...

Insect Biochemistry and Molecular Biology, 2014

Social context is often a primary regulator of social behavior, but genes that affect or are affe... more Social context is often a primary regulator of social behavior, but genes that affect or are affected by social context have rarely been investigated. In social insects, caste specific pheromones are key modulators of social behavior, e.g., in honey bees the queen mandibular gland (MG) pheromone mediates reproductive dominance, its absence prompting ovary activation and queen pheromone production in workers. Here, we investigate the effect of social environment on genome-wide expression patterns in the MG, to determine how social context modulates expression of genes that, in turn alter social environment. We used microarrays to examine the MGs of virgin and mated queens, and queenright (QR) and queenless (QL) workers with or without activated ovaries. Approximately 2554 transcripts were significantly differentially expressed among these groups, with caste and social context being the main regulators of gene expression patterns, while physiological state (ovary activation) only minimally affecting gene expression. Thus, social context strongly regulates expression of genes, which, in turn, shape social environment. Among these, 25 genes that are putatively involved in caste selective production of the fatty-acid derived MG pheromone were differentially expressed in queens and workers. These genes whose functions correspond with enzymatic or transport processes emphasize the occurrence of disparate pheromone biosynthetic pathways for queens and workers, adding another dimension regarding the regulation of these important pheromones. Gene ontology analysis also revealed genes of different functional categories whose expression was impacted by caste or by the social environment, suggesting that the MG has broader functions than pheromone biosynthesis.

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Using the monthly extended reconstructed sea surface temperature (SST) dataset version 3 (ERSST.v... more Using the monthly extended reconstructed sea surface temperature (SST) dataset version 3 (ERSST.v3) spanning 1880-2007 and SODA ocean assimilation data spanning 1958-2001, we investigate the seasonality of the asymmetry of the El Niño-Southern Oscillation (ENSO) and its possible impacts on the tropical eastern Pacific annual cycle. Like the amplitude of ENSO, the skewness of ENSO (i.e., asymmetry of ENSO) is locked to the seasonal cycle, showing large amplitude during the winter and small amplitude during the spring except May. Furthermore, the seasonality of the asymmetry of ENSO is changing decade by decade, which is strong during 1930s, 1950s, and 1990s and weak during 1900s, 1910s, 1940s, and 1970s. These decadal changes are significantly correlated to those in the amplitude of the annual and semi-annual cycles of tropical eastern Pacific SST, suggesting that the changes in the seasonality of the asymmetry of ENSO may modify the amplitude of the annual and semi-annual cycles of the tropical eastern Pacific SST via a nonlinear process. Using the coupled general circulation model simulations, we also showed similar results to the aforementioned observed features, which overcame some deficiencies due to relatively short reliable records of the observation.

This article was published in an Elsevier journal. The attached copy is furnished to the author f... more This article was published in an Elsevier journal. The attached copy is furnished to the author for non-commercial research and education use, including for instruction at the author’s institution, sharing with colleagues and providing to institution administration. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit:

El Nino is only one phase of a larger ocean-atmosphere circulation termed the Southern Oscillatio... more El Nino is only one phase of a larger ocean-atmosphere circulation termed the Southern Oscillation (SO). A complementary phase of El Nino known as La Nina or El Viejo constitutes the other phase of the SO. The SO is the dominant mode of interannual variability in the tropics. Several parameters exhibit interannual variability and all have a center region in which the SO accounts for the major portion of the parameter's variance (Philander 1990). Surface pressure, sea surface temperatures and convective zones are such parameters. Interannual fluctuations in the sea surface temperature (SST) are noted to be a maximum between 10 degrees north and south in the central and eastern equatorial Pacific. An EI Nino event, or warm anomaly, is referred to as a low SO. Meanwhile, a high SO, knoWn also as a cold anomaly, constitutes La Nina. This phase is characterized by lower than normal SST due to intense trade winds which upwell cold water to the surface in the eastern tropical Pacific (...

The Southern Oscillation, a natural mode of oscillation of the coupled ocean-atmosphere system, a... more The Southern Oscillation, a natural mode of oscillation of the coupled ocean-atmosphere system, at times appears to be self-sustaining and hence relatively easy to predict. The 1980s seem to have been such a period; El Nino of 1982183 was the start of two complete cycles of the Southern Oscillation. At other times the oscillation seems to be a damped mode that is present for a cycle at most, after being excited by random disturbances. Disturbances that very effectively can excite El Niiio, because their surface winds have a spatial structure that coincides with those of the Southern Oscillation, are certain brief convective activities that are associated with two-week bursts of westerly winds over the western equatorial Pacific. (These convective activities do not involve ocean-atmosphere interactions that characterise the Southern Oscillation.) This type of disturbance was influential in initiating El Nifio of 1997198. That event followed El Nifio of 1992 which persisted for a surp...

The upper temperature tolerance of 10 commercially important South American bivalve species (Gari... more The upper temperature tolerance of 10 commercially important South American bivalve species (Gari solida, Semele solida, Semele corrugata, Protothaca thaca, Venus antiqua. Tagelus dombeii, Ensis macha, Aulacomya ater, Choromytilus chorus and Argopecten purpura tus) off Peru and Chile was determined and compared in order to study some of the effects of El Nino. Due to higher habitat temperatures in Peru, LTs0 (lethal temperatures for 50% of an experimental population) are higher than in Chile. In Chile LTs0 for 6 of 8 species studied varied only by 1.2"C. This might be explained by the similar temperatures and living conditions in the habitats of these species. Especially for Peru, observed differences in LTSo could be related to different geographical distributions. For all species temperature increases recorded during the strongest El Nino of this century (1982-83) did not exceed the temperature tolerance interval, TT1 (difference between after 24 h and mean annual water tempe...

Una publication del Area de Preparativos para Situaciones de Emergencia y Socorro en Casos de Des... more Una publication del Area de Preparativos para Situaciones de Emergencia y Socorro en Casos de Desastre, de la Organizacion Panamericana de la Salud/Organizacion Mundial de la Salud en colaboration con el Banco Mundial. Las opiniones expresadas, recomendaciones formuladas y denominaciones empleadas en esta publication no reflejan neccsariamente los criterios ni la politica de la Organizacion Panamericana de la Salud. La Organizacion Panamericana de la Salud dara consideration favorable a las solicitudes de autorizacion para reproducir o traducir, total o parcialmente, esta publication, siempre que no sea con fines de lucro. Las solicitudes pueden dirigirse al:

We investigate the modulation of ENSO location and amplitude by spiciness anomalies in the tropic... more We investigate the modulation of ENSO location and amplitude by spiciness anomalies in the tropical thermocline. First, Argo observations constrain the size of observed spiciness anomalies. Realistic perturbations are then used to investigate the impact on an intermediate El Nino model. This shows that spiciness anomalies can increase the thermocline feedback and thus enhance the Bjerknes feedback and ENSO amplitudes. Experiments with coupled general circulation model are conducted to investigate the impact on the character of El Nino.