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Search Results: 1 - 10 of 978 matches for " Cornelia Roder "
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In-Situ Effects of Simulated Overfishing and Eutrophication on Benthic Coral Reef Algae Growth, Succession, and Composition in the Central Red Sea
Christian Jessen, Cornelia Roder, Javier Felipe Villa Lizcano, Christian R. Voolstra, Christian Wild
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0066992
Abstract: Overfishing and land-derived eutrophication are major local threats to coral reefs and may affect benthic communities, moving them from coral dominated reefs to algal dominated ones. The Central Red Sea is a highly under-investigated area, where healthy coral reefs are contending against intense coastal development. This in-situ study investigated both the independent and combined effects of manipulated inorganic nutrient enrichment (simulation of eutrophication) and herbivore exclosure (simulation of overfishing) on benthic algae development. Light-exposed and shaded terracotta tiles were positioned at an offshore patch reef close to Thuwal, Saudi Arabia and sampled over a period of 4 months. Findings revealed that nutrient enrichment alone affected neither algal dry mass nor algae-derived C or N production. In contrast, herbivore exclusion significantly increased algal dry mass up to 300-fold, and in conjunction with nutrient enrichment, this total increased to 500-fold. Though the increase in dry mass led to a 7 and 8-fold increase in organic C and N content, respectively, the algal C/N ratio (18±1) was significantly lowered in the combined treatment relative to controls (26±2). Furthermore, exclusion of herbivores significantly increased the relative abundance of filamentous algae on the light-exposed tiles and reduced crustose coralline algae and non-coralline red crusts on the shaded tiles. The combination of the herbivore exclusion and nutrient enrichment treatments pronounced these effects. The results of our study suggest that herbivore reduction, particularly when coupled with nutrient enrichment, favors non-calcifying, filamentous algae growth with high biomass production, which thoroughly outcompetes the encrusting (calcifying) algae that dominates in undisturbed conditions. These results suggest that the healthy reefs of the Central Red Sea may experience rapid shifts in benthic community composition with ensuing effects for biogeochemical cycles if anthropogenic impacts, particularly overfishing, are not controlled.
Benthic Reef Primary Production in Response to Large Amplitude Internal Waves at the Similan Islands (Andaman Sea, Thailand)
Carin Jantzen, Gertraud M. Schmidt, Christian Wild, Cornelia Roder, Somkiat Khokiattiwong, Claudio Richter
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081834
Abstract: Coral reefs are facing rapidly changing environments, but implications for reef ecosystem functioning and important services, such as productivity, are difficult to predict. Comparative investigations on coral reefs that are naturally exposed to differing environmental settings can provide essential information in this context. One prevalent phenomenon regularly introducing alterations in water chemistry into coral reefs are internal waves. This study therefore investigates the effect of large amplitude internal waves (LAIW) on primary productivity in coral reefs at the Similan Islands (Andaman Sea, Thailand). The LAIW-exposed west sides of the islands are subjected to sudden drops in water temperature accompanied by enhanced inorganic nutrient concentrations compared to the sheltered east. At the central island, Ko Miang, east and west reefs are only few hundred meters apart, but feature pronounced differences. On the west lower live coral cover (-38 %) coincides with higher turf algae cover (+64 %) and growth (+54 %) compared to the east side. Turf algae and the reef sand-associated microphytobenthos displayed similar chlorophyll a contents on both island sides, but under LAIW exposure, turf algae exhibited higher net photosynthesis (+23 %), whereas the microphytobenthos displayed reduced net and gross photosynthesis (-19 % and -26 %, respectively) accompanied by lower respiration (-42 %). In contrast, the predominant coral Porites lutea showed higher chlorophyll a tissues contents (+42 %) on the LAIW-exposed west in response to lower light availability and higher inorganic nutrient concentrations, but net photosynthesis was comparable for both sides. Turf algae were the major primary producers on the west side, whereas microphytobenthos dominated on the east. The overall primary production rate (comprising all main benthic primary producers) was similar on both island sides, which indicates high primary production variability under different environmental conditions.
Captive rearing of the deep-sea coral Eguchipsammia fistula from the Red Sea demonstrates remarkable physiological plasticity
Anna Roik,Till Rthig,Cornelia Roder,Paul J. Müller,Christian R. Voolstra
PeerJ , 2015, DOI: 10.7717/peerj.734
Abstract: The presence of the cosmopolitan deep-sea coral Eguchipsammia fistula has recently been documented in the Red Sea, occurring in warm (>20 °C), oxygen- and nutrient-limited habitats. We collected colonies of this species from the central Red Sea that successfully resided in aquaria for more than one year. During this period the corals were exposed to increased oxygen levels and nutrition ad libitum unlike in their natural habitat. Specimens of long-term reared E. fistula colonies were incubated for 24 h and calcification (G) as well as respiration rates (R) were measured. In comparison to on-board measurements of G and R rates on freshly collected specimens, we found that G was increased while R was decreased. E. fistula shows extensive tissue growth and polyp proliferation in aquaculture and can be kept at conditions that notably differ from its natural habitat. Its ability to cope with rapid and prolonged changes in regard to prevailing environmental conditions indicates a wide physiological plasticity. This may explain in part the cosmopolitan distribution of this species and emphasizes its value as a deep-sea coral model to study mechanisms of acclimation and adaptation.
In-situ Effects of Eutrophication and Overfishing on Physiology and Bacterial Diversity of the Red Sea Coral Acropora hemprichii
Christian Jessen, Javier Felipe Villa Lizcano, Till Bayer, Cornelia Roder, Manuel Aranda, Christian Wild, Christian R Voolstra
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062091
Abstract: Coral reefs of the Central Red Sea display a high degree of endemism, and are increasingly threatened by anthropogenic effects due to intense local coastal development measures. Overfishing and eutrophication are among the most significant local pressures on these reefs, but there is no information available about their potential effects on the associated microbial community. Therefore, we compared holobiont physiology and 16S-based bacterial communities of tissue and mucus of the hard coral Acropora hemprichii after 1 and 16 weeks of in-situ inorganic nutrient enrichment (via fertilizer diffusion) and/or herbivore exclusion (via caging) in an offshore reef of the Central Red Sea. Simulated eutrophication and/or overfishing treatments did not affect coral physiology with respect to coral respiration rates, chlorophyll a content, zooxanthellae abundance, or δ 15N isotopic signatures. The bacterial community of A. hemprichii was rich and uneven, and diversity increased over time in all treatments. While distinct bacterial species were identified as a consequence of eutrophication, overfishing, or both, two bacterial species that could be classified to the genus Endozoicomonas were consistently abundant and constituted two thirds of bacteria in the coral. Several nitrogen-fixing and denitrifying bacteria were found in the coral specimens that were exposed to experimentally increased nutrients. However, no particular bacterial species was consistently associated with the coral under a given treatment and the single effects of manipulated eutrophication and overfishing could not predict the combined effect. Our data underlines the importance of conducting field studies in a holobiont framework, taking both, physiological and molecular measures into account.
Grazing Management of Temperate Grasslands and Fallows
Walter Roder
Journal of Bhutan Studies , 2002,
Abstract: The paper provides a general overview of fodder resources andtheir management in temperate Bhutan (altitude range of1500-3000m). The terms are used as defined by RC-Jakar(RNR-RC-Jakar, 1996). As per these definitions, temperatepasture can include any kind of land used for grazing. Whenreferring to registered grassland or tsamdro, only the termtsamdrog is used. Where possible, the term pasture isreplaced with more specific or more appropriate terms.
Selfconsistent calculations of sigma-meson properties at finite temperature
Dirk Roder
Physics , 2005,
Abstract: I study the properties of the scalar sigma-meson [also referred to as f_0(600)] at nonzero temperature in the O(N)-model in the framework of the Cornwall-Jackiw-Tomboulis formalism. In the standard Hartree (or large-N) approximation one only takes into account the double-bubble diagrams in the effective potential. I improve this approximation by additionally taking into account the sunset diagrams, which lead to 4-momentum dependent real and imaginary parts of the Dyson-Schwinger equations. By solving these and the equation for the chiral condensate selfconsistently, one obtains the decay width and the spectral density of the sigma-meson. I compare the results in the case with explicit chiral symmetry breaking with the chiral limit. I found that the 4-momentum dependent real part of the selfenergy does not lead to major qualitative changes in the spectral density.
Rupturas e continuidades no padr?o organizacional e decisório do Ministério das Rela??es Exteriores
Figueira, Ariane Roder;
Revista Brasileira de Política Internacional , 2010, DOI: 10.1590/S0034-73292010000200001
Abstract: the aim of this article is to understand how the decision process in brazil's foreign policy is structured, with an emphasis on the inter-bureaucratic dynamics during 20 years (1988-2007), marked out by the time restrictions of the research. therefore, indicators were established, which allow investigation of the conclusions as to whether decision-making is centralized or horizontalized in its intra-bureaucratic structure, whether it is insulated from or open to dialogue with other government agencies.
On the Reliability of kNN Classification
Maxim Tsypin,Heinrich Roder
Lecture Notes in Engineering and Computer Science , 2007,
Rela es diplomáticas Brasil- Paraguai e o problema do crime organizado transfronteiri o
Ariane Cristine Roder Figueira
Meridiano 47 : Boletim de Análise de Conjuntura em Rela??es Internacionais , 2010,
Abstract: O objetivo do artigo é compreender a atual conjuntura política paraguaia no que se refere a recente instala o do estado de exce o na regi o fronteiri a com o Brasil a partir de uma vis o estrutural da problemática do crime organizado que assola as estruturas do país vizinho ao longo de sua história e provoca sérios impactos a estrutura econ mica e de seguran a na regi o
“I Am Getting Healthier”. Perceptions of Urban Aboriginal and Torres Strait Islander People in a Chronic Disease Self-Management and Rehabilitation Program  [PDF]
Alison Nelson, Kyly Mills, Samara Dargan, Chantel Roder
Health (Health) , 2016, DOI: 10.4236/health.2016.86057
Abstract: Chronic disease is a main contributor to the disproportionately high burden of illness experienced by Aboriginal and Torres Strait Islander Australians. However, there are very few programs addressing chronic disease self-management and rehabilitation which are designed specifically for urban Aboriginal and Torres Strait Islander people. This paper aims to explore client and staff perceptions of the Work It out Program, a chronic disease rehabilitation and self-management program designed for urban Aboriginal and Torres Strait Islander people. The study used a mixed methods approach to explore the success, barriers and self-reported outcomes of the program. Quantitative data were collected through a structured survey, comprising social and demographic data. Qualitative data were collected through interviews using Most Significant Change theory. Twenty-eight participants were recruited, 6 staff and 22 clients (M = 7, F = 21) with an age range between 21 and 79 years of age (Mean = 59.00, SD = 17.63). Interviews were completed in 2013 across four Work It out locations in Southeast Queensland. Semi-structured interviews were conducted either individually or in groups of two or three, depending on the participants’ preference. Thematic analysis of the data revealed six main themes; physical changes, lifestyle improvements, social and emotional well-being, perceptions about the successful features of the program, perceived barriers to the program and changes for the future. This exploratory study found that clients and staff involved in the Work It out Program perceived it as an effective self-management and rehabilitation program for urban Aboriginal and Torres Strait Islander Australians. Further evaluation with a larger sample size is warranted in order to establish further outcomes of the program.
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