1,721,275 research outputs found
Experiment on Prey-Switch of Hemigrapsus takanoi towards a native and non-native gammarid species
No full textWe conducted two experiments to assess the predation of female H. takanoi (a non-native species in the Baltic) on a native gammarid (Gammarus duebeni) and a non-native analogous gammarid (Gammarus tigrinus). The experiments were conducted at the GEOMAR Helmholtz Centre for Ocean Research Kiel. Crabs were sampled in the innermost part of the Kiel Fjord, Germany (59°19'44N, 10°08'55.5E) during the summer of 2021. This experiment covered a prey-switching trial where both prey species were offered simultaneously in varying densities (2:14, 4:12, 6:10, 8:8, 10:6, 12:4, 14:2; n = 6 replicates per ratio); once again, the amount of consumed prey per species was assessed after 6 hours of feeding by H. takanoi. All remaining parameters were the same as described for Experiment No. 1
Experiment on the functional response of Hemigrapsus takanoi towards a native and non-native gammarid species
No full textWe conducted two experiments to assess the predation of female H. takanoi (a non-native species in the Baltic) on a native gammarid (Gammarus duebeni) and a non-native analogous gammarid (Gammarus tigrinus). In the first experiment, we examined the functional response of female H. takanoi to G. duebeni and G. tigrinus. The experiments were conducted at the GEOMAR Helmholtz Centre for Ocean Research Kiel. Crabs were sampled in the innermost part of the Kiel Fjord, Germany (59°19'44N, 10°08'55.5E) during the summer of 2021. The experimental design utilized a fully factorial approach. One temperature (16°C) and one salinity (10) across five prey densities (1, 2, 4, 8, 16) were used. Each combination was replicated three times, alongside three replicates of predator-free controls at each prey density to quantify background prey mortality. The crabs were starved for 48 hours ahead of the experiment and were exposed to the respective number of gammarids for a 6-hour feeding period. The number of gammarids consumed was recorded
Experiment on the functional response of non-indigenous crab Hemigrapsus takanoi across seasons and temperatures in the Baltic Sea
No full textWe examined the functional response of the Japanese brush-clawed shore crab ( Hemigrapsus takanoi ) towards blue mussels ( Mytilus sp.) across four seasons for an ambient and +6 °C future warming scenario in the Baltic Sea. The experiment was carried out as a laboratory experiment at the GEOMAR Helmholtz Centre for Ocean Research Kiel. Crabs were sampled in the innermost part of the Kiel Fjord, Germany (54°19′44.8″ N, 10°08′55.5″ E) between Summer 2021 and Spring 2023 during the respective season. The experimental design used a fully factorial approach, examining the functional response across two temperatures, two sexes, and eight prey densities (1, 2, 4, 6, 8, 16, 32, 64) across four seasons. Each crab was subjected to a pre-experiment 48-hour starvation period and then exposed to a fixed number of mussels for a 72-hour feeding trial. The number of mussels consumed was recorded, providing data on the predatory impact of H. takanoi under varying temperature scenarios and across seasons
Effects of ash from native and alien plants on phytoplankton biomass and mosquito abundances: A mesocosm experiment
No full textMENVSCDepartment of Geography and Environmental SciencesWildfires are natural or anthropogenic phenomena increasing at alarming rates globally due to land–use alterations, droughts, climatic warming, hunting and biological invasions. Whereas wildfire effects on terrestrial ecosystems are marked and relatively well–studied, ash depositions into aquatic ecosystems have often remained overlooked, but have the potential to significantly impact bottom–up processes and effects on semi–aquatic taxa such as mosquitoes. This study assessed (i) ash–water–phytoplankton biomass dynamics and (ii) post–colonization mosquito abundances using six plant species [i.e., three natives (apple leaf Philenoptera violacea, Transvaal milk plum Englerophytum magalismontanum, quinine tree Rauvolfia caffra) and three aliens (lantana Lantana camara, gum Eucalyptus camaldulensis, guava Psidium guajava)] based on a six–week mesocosm experiment with different ash concentrations (1 and 2 g L–1). We assessed concentrations of chemical elements, i.e., N, P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn and B from ash collected, and observed significant differences amongst the species. High concentrations of P, K, Mn, Fe, Cu, Zn and B were recorded from Transvaal milk plum ash and low concentrations of P, K, Ca, Mg, Cu and Zn were recorded from apple leaf. An increase in phytoplankton biomass (using chlorophyll–a [chl-a] concentration as a proxy) for all treatments i.e., 1 and 2 g L–1 for all plant species ash was observed a week after, followed by decreases in the following weeks, with the exception of 2 g L–1 for lantana, gum and control. Silicate concentrations (i.e., used as a proxy for diatom abundance) showed increasing patterns among all ash treatments, with exception of controls. However, no clear patterns were observed between native and alien plant ash on both chlorophyll-a (chl–a) and silicate concentrations. We found that ash has notable effects on water
chemistry, particularly nitrate, which increased throughout the weeks, whereas, pH and conductivity were high at lower ash concentrations. The impacts of ash on water chemistry, chl–a and silicate concentrations varied with individual species and the amount of ash deposited into the system. Overall, there was no statistically clear difference in colonization between ash from native and alien species. We recorded colonization by two mosquito genera (i.e., Culex spp., Anopheles spp.), with Culex generally much more abundant than Anopheles. Few differences were identified among the plants, with statistically clear effects of ash type and concentration on larval and pupal stages. High Culex egg and larval abundances were shown in lantana and apple leaf treatments compared to controls, and milkplum versus controls for pupae of both genera. Further research is required to elucidate the influence of nutrient inputs from different ash species on vector mosquito population and phytoplankton dynamics.NR
Assessing environmental factors structuring populations and movement dynamics of the invasive snail Tarebia granifera in a subtropical Austral reservoir
No full textMENVSCDepartment of Geography and Environmental SciencesInvasive alien species continue to spread and proliferate in waterways worldwide, but environmental drivers of invasion dynamics lack assessment. Understanding alien species ability to self-disperse via locomotion following arrival to new environments is also critical for prediction of invasion success. The study assessed: (i) the distribution and abundance of Tarebia granifera and the potential drivers of population structure in Nandoni reservoir; and (ii) compared movement traits between two widespread invasive alien snails, T. granifera and Physa acuta, to assess their net distance and velocity and determine dispersal potential. Tarebia granifera was widespread at sites invaded, with abundances exceeding 500 individuals m-2 at impacted areas. Tarebia granifera was significantly associated with sediment (i.e., chlorophyll-a, Mn, sediment organic carbon (SOC) and organic matter (SOM)) and water (i.e., pH, conductivity, total dissolved solids (TDS)) variables. Tarebia granifera seemed to exhibit two recruitment peaks in November and March, identified via size-based stock assessment. Tarebia granifera displayed a significantly greater velocity and covered a significantly larger net distance than Physa acuta. The exploratory behaviour (i.e., mean, or absolute turning angles and straightness index) did not differ significantly between the two alien species; both species showed a slight tendency to turn counter clockwise. Overall, the study shows that there was higher snail abundance during the summer season, furthermore, sediment and water variables were found to be important in structuring T. granifera populations. The present study suggests a more rapid capacity to self-disperse in T. granifera than P. acuta, but a similar level of exploratory behaviour between the two species. The study provided autecological information and insights on the distribution and extent of spread of T. granifera, given the often-overlooked role of animal behaviour in promoting invasion, this information can help inform and predict the invasion pattern of invasive alien freshwater
snail. This information can also help in the development of invasive alien snail management action plans within the region and elsewhere.NR
Alien species lists for regions: Great Lakes-St. Lawrence River, North and Baltic Seas, and Chesapeake Bay
No full textUnderlying established alien species lists for three recipeint regions: Great Lakes-St. Lawrence River (GLSL), North and Baltic Seas (NBS), and Chesapeake Bay (CB). Each species entry is recorded against its taxonomic grouping and geographic origin
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
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