1,721,035 research outputs found
Growth, respiration and mortality rates of live L. pertusa under gradually amplifying acidification and warming increments and consequences for dissolution and bioerosion of dead coral framework
No full textIn a 13-months laboratory experiment conducted in 2014/2015, the interactive effects of gradually increasing temperature and pCO2 levels on survival, growth and respiration of two prominent colour morphotypes (white and orange) of the framework-forming cold-water coral Lophelia pertusa (also known as Desmophyllum pertusum), as well as bioerosion and dissolution of dead coral framework were assessed. In six-week intervals, three treatments (T1: acidification, T2: warming, T3: combined acidification and warming) were gradually increased in their respective manipulated parameters by 1°C and/or 200 µatm pCO2 after an initial two intervals under ambient (near in-situ) conditions. Each treatment consisted of 7 replicates that were manipulated over the course of the experiment and 3 control replicates that remained at ambient conditions throughout the entire duration of the experiment. Each replicate tank consisted of one live coral fragment of the white morphotype, one fragment of the orange morphotype and one dead framework fragment (naturally bioeroded framework material). Dead framework was examined with regard to attached bioeroders and calcifying organisms, the latter being removed prior to the experiment. All coral samples were collected from an inshore Norwegian cold-water coral habitat in the outer Trondheim-Fjord near Nord-Leksa (63°36.4'N, 09°22.7'E) between 150 to 230 m water depth using the manned submersible JAGO (GEOMAR, 2017; doi:10.17815/jlsrf-3-157) during RV POSEIDON (GEOMAR, 2015; doi:10.17815/jlsrf-1-62) cruise POS455 in June/July 2013. In situ conditions at the time of sampling near the corals were 7.7°C in temperature, 35.2 in salinity and ~6 mL/L oxygen concentration. Prior to the experiment, corals were kept in a closed recirculating system of 1,700 L in a climate-controlled laboratory facility at GEOMAR in Kiel at near in situ conditions of temperature and salinity (7.8 145 ± 0.2 °C and 35.8 ± 0.6) for half a year. Calcification/dissolution rates of live corals and bioerosion/dissolution rates of dead coral framework were determined using the buoyant weighing technique (Davies, 1989; doi:10.1007/BF00428135) with a high precision analytical balance (Sartorius CPA225D, readability = 0.1 mg) placed above every individual aquarium for each measurement. Respiration rates were determined via oxygen consumption measurements using an optode-based oxygen analyser (Oxy-10 mini, PreSens GmbH). Mortality was examined during every six-week interval by visual inspection of all live fragments. Dead polyp counts were calculated as percentage of total polyps counts of every individual fragment. Carbonate system parameters were calculated from the two measured parameters total alkalinity (TA) and dissolved inorganic carbon (DIC). TA and DIC samples were taken at the end of every 6-week interval and analyzed via potentiometric open-cell titration (862 Compact Titrosampler, Metrohm) in case of TA and by infrared detection of CO2 using an Automated Infra-Red Inorganic Carbon Analyzer (AIRICA with LI-COR 7000, Marianda) in case of DIC. TA and DIC were corrected against Certified Reference Material from A.G. Dickson (Scripps Institution of Oceanography) and density-corrected. The purpose of this study was to examine thresholds and optima of live corals under gradual increases of ocean acidification and warming and to quantify dissolution and bioerosion rates of dead coral framework to ultimately assess the balance between live coral calcification and degradation of dead coral framework under future ocean conditions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
FS Alkor Fahrtbericht / Cruise report AL 275: Geobiological investigations and sampling of aphotic coral reef ecosystems in the NE-Skagerrak
No full textÖkophysiologische Untersuchungen an Sepien (<em>Sepia bandensis</em> & <em>Sepia officinalis</em>)
No full textObwohl Tintenfische im marinen Nahrungsnetz eine hohe trophische Position einnehmen und sie bereits seit vielen Jahren für wisschenschaftliche und wirtschaftliche Interessen gehalten werden, sind Untersuchungen an den kritischen juvenilen Phasen äußerst selten. Die vorliegende Arbeit untersuchte im ersten Teil wissenschaftlich erstmalig das Juvenilwachstum der tropischen Stumpfdornsepie Sepia bandensis unter kontrollierten Bedingungen in einer geschlossenen Tropenkreislaufanlage. Ein enorm hoher - allerdings vermutlich auf Selektion beim Einsammeln der Eier zurückzuführender - Schlupferfog (95,5%) wurde in den ersten Wochen nach dem Schlüpfendurch eine Wachstumsrate der Paralarven von 2,23% DML/Tag abgelöst. Während der 28 tägigen Versuchsphase fand allerdings nur noch ein mäßiges Wachstum mit durchschnittlich 1,12% DML/Tag statt. Anhaltend hohe Mortalitäten führten am 28. Versuchstag zum Abbruch der Haltung unter konstanten Bedingungen. Das älteste Tier wurde 100 Tage alt und hatte eine Dorsale Mantellänge von 23 mm (Totallänge: ca. 30 mm) erreicht. In einem Teilversuch wurden 45 Sepien bei 28°C unter sonst annähernd gleichen Bedingungen wie die Tiere im Hauptversuch bei 24°C gehalten. Sowohl in den Wachstumsraten, als auch bei den Überlebensraten blieben die bei 28°C gehaltenen Tiere deutlich hinter jenen der unter 24°C gehaltenen Sepien zurück. Hungernde Sepia bandensis wiesen oft eine dunkle Pigmentierung im Kopfbereich auf ("Hungerfleck"). Zwischen dem Augenabstand und der Dorsalen Mantellänge konnte eine gute Beziehung mit einem Bestimmtheitsmaß von r2 = 0,66 entdeckt werden..
Metabolic response of the cold-water coral Lophelia pertusa to variations in ambient temperature and pH - an ecophysiological case study
No full textInfluence of Anthropogenic Climate Change on the Ecophysiology of the Cold Water Coral Lophelia pertusa = Einfluss des anthropogenen Klimawandels auf die Ökophysiologie der Kaltwasserkoralle Lophelia pertusa
No full textThe scleractinian coral Lophelia pertusa (Caryophylliidae) is the most common frameworkforming cold-water coral with a global distribution. L. pertusa bioherms are hot-spots of biodiversity because their three-dimensional framework provides niches and nursery grounds for a variety of species, including commercially important fish species. In contrast to shallowwater corals from the tropics, very little is known about the ecophysiology of cold-water corals such as L. pertusa and their sensitivity towards climate change. The present study intends to start filling this knowledge gap by examining a variety of L. pertusa’s ecophysiological responses (e.g. food uptake, respiration, growth, fitness, behaviour) under present-day (in the following referred as “ambient”) and experimentally manipulated environmental conditions. Living specimens of L. pertusa from two Norwegian cold-water coral locations (Oslofjord and Sula Reef Complex) were collected during two research cruises with the aid of the manned submersible JAGO and transferred into a newly established closed recirculating system at IFM-GEOMAR. Long-term analyses (>3 years) of dissolved inorganic nutrients revealed the high tolerance of L. pertusa to rising concentrations of nitrate and phosphate. However, for the main toxic compound - ammonium - it could be demonstrated that the corals’ polyp behaviour alters if concentrations are increased to > 17 μmol L-1. Food availability is thought to be one of the most important factors determining cold-water coral distribution and growth. This study provides feeding rates for three live food organisms encompassing different sizes and qualities. It also describes the food uptake mechanism for mesozooplankton based on the first video documentation of the whole feeding process. The effect of rising temperatures (ocean warming) on the oxygen consumption, fitness, and behaviour was investigated through a combination of short-term and long-term aquarium experiments. This study shows that at ambient conditions of 7.5 °C L. pertusa exhibits low respiration rates of ~ 0.3 μmol O2 g-1 h-1 which may increase up to 58 % after a relatively small temperature change (+ 3.5 °C). High Q10 values of 3.7 ± 0.7 in these corals and significantly depressed RNA/DNA ratios in coral polyps maintained for 2 weeks under elevated temperatures (11°C) revealed that L. pertusa is sensitive to small temperature changes even though analyses of their behaviour may suggest some acclimatisation. L. pertusa exhibits relatively low bulk calcification rates that vary over time and applied measurement methods. On average calcification amounts to 8.7 x 10-3 % d-1 which is intermediate in the broad range of reported L. pertusa growth rates. Interestingly, corals fed under nearby ad libitum conditions showed no relationship between food quality/quantity and growth. This indicates a degree of regulation in the feeding mechanism and may suggest that calcification is rather dependent on a basic metabolic rate than on specific food supply. The impact of increasing concentrations of CO2 (ocean acidification) on L. pertusa growth rates and fitness was examined in a short-term (one week) and a long-term (8 months) experiment. This study shows for the first time that - when kept under long-term exposure to elevated CO2 levels - L. pertusa is capable to compensate for adverse effects as experienced during short-term incubations. Net growth is sustained even in waters undersaturated with respect to aragonite (ΩAr < 1). These results suggest that cold-water coral reefs, the majority of which will be exposed to undersaturated waters before the end of this century, may not suffer immediate wide-spread extinction as previously projected. However, the fact that even a temperature increase of about 3 °C seems to be of higher relevance in respect to fitness than a doubling of the pCO2 emphasises the problem of synergistic impacts between ocean warming and ocean acidification and the need for further long-term incubation experiments
Seawater carbonate chemistry and live coral performance vs. framework dissolution and bioerosion
No full textPhysiological sensitivity of cold-water corals to ocean change is far less understood than of tropical corals and very little is known about the impacts of ocean acidification and warming on degradative processes of dead coral framework. In a 13-month laboratory experiment, we examined the interactive effects of gradually increasing temperature and pCO2 levels on survival, growth, and respiration of two prominent color morphotypes (colormorphs) of the framework-forming cold-water coral Lophelia pertusa, as well as bioerosion and dissolution of dead framework. Calcification rates tended to increase with warming, showing temperature optima at ~ 14°C (white colormorph) and 10–12°C (orange colormorph) and decreased with increasing pCO2. Net dissolution occurred at aragonite undersaturation (ΩAr < 1) at ~ 1000 μatm pCO2. Under combined warming and acidification, the negative effects of acidification on growth were initially mitigated, but at ~ 1600 μatm dissolution prevailed. Respiration rates increased with warming, more strongly in orange corals, while acidification slightly suppressed respiration. Calcification and respiration rates as well as polyp mortality were consistently higher in orange corals. Mortality increased considerably at 14–15°C in both colormorphs. Bioerosion/dissolution of dead framework was not affected by warming alone but was significantly enhanced by acidification. While live corals may cope with intermediate levels of elevated pCO2 and temperature, long-term impacts beyond levels projected for the end of this century will likely lead to skeletal dissolution and increased mortality. Our findings further suggest that acidification causes accelerated degradation of dead framework even at aragonite saturated conditions, which will eventually compromise the structural integrity of cold-water coral reefs
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