Springtime zooplankton size structure over the continental shelf of the Bay of BiscaY

Linking lower and higher trophic levels requires special focus on the essential role played by mid-trophic levels, i.e., the zooplankton. One of the most relevant pieces of information regarding zooplankton in terms of flux of energy lies in its size structure. In this study, an extensive data set of size measurements is presented, covering parts of the western European continental shelf and slope, from the Galician coast to the Ushant front, during the springs from 2005 to 2012. Zooplankton size spectra were estimated using measurements carried out in situ with the Laser Optical Plankton Counter (LOPC) and with an image analysis of WP2 net samples (200 μm mesh size) performed following the ZooScan methodology. The LOPC counts and sizes particles within 100–2000 μm of spherical equivalent diameter (ESD), whereas the WP2/ZooScan allows for counting, sizing and identification of zooplankton from ~ 400 μm ESD. The difference between the LOPC (all particles) and the WP2/ZooScan (zooplankton only) was assumed to provide the size distribution of non-living particles, whose descriptors were related to a set of explanatory variables (including physical, biological and geographic descriptors). A statistical correction based on these explanatory variables was further applied to the LOPC size distribution in order to remove the non-living particles part, and therefore estimate the size distribution of zooplankton. This extensive data set provides relevant information about the zooplankton size distribution variability, productivity and trophic transfer efficiency in the pelagic ecosystem of the Bay of Biscay at a regional and interannual scale

Laboratory Measurements of Fe XXIV L-Shell Line Emission

Recent ASCA spectra exhibit discrepancies with the relative line intensities of various Fe XXIII and XXIV L-shell emission lines predicted by standard plasma emission codes. To address this issue, we have carried out a series of high-resolution, broadband measurements of Fe XXIV line emission using an electron beam ion trap facility. X-ray lines produced in the trap are detected and resolved using Bragg crystal spectrometers. We report measurements of 3 → 2 and 4 → 2 transitions, which result primarily from electron impact excitation. Overall, good agreement is found with distorted wave calculations

Floraciones de fitoplancton y variación de la estructura comunitaria fitoplanctónica en tres lagos someros eutróficos de Chile Central

The phytoplankton community of three eutrophic shallow lakes located in the same geographical area was compared over a period of three years. Although these lakes are similar in many respects (e.g. location, origin, average depth, high concentration of nutrients, human influence) develop very different phytoplankton communities. Lo Galindo is dominated by Zygnematophyceae, Cyanophyceae and Chlorophyceae, while in Lo Méndez the groups Dinophyceae and Bacillariophyceae and in Las Tres Pascualas the Chlorophyceae, Cryptophyceae and Euglenophyceae. In Lo Mendez and Lo Galindo are frequent blooms of different groups of algae (cyanobacteria, green algae, diatoms and dinoflagellates), which generated wealth increases at different times of the year, even in winter they were presented. In Las Tres Pascualas blooms were rare. The occurrence and frequency of blooms of species representatives of the M, C,Y and Lo functional groups, and VII, VI, IV and V morphological groups, reflect the eutrophic lakes, being indicative of the degree of contamination of these systems that influence their present and future use.La comunidad fitoplanctónica de tres lagos someros eutróficos ubicados en la misma zona geográfica fue comparada durante un periodo de tres años. Aunque estos lagos son similares en muchos aspectos (p.ej. ubicación, origen, profundidad media, alta concentración de nutrientes, influencia humana) desarrollan comunidades de fitoplancton muy diferentes. En Lo Galindo dominan Zygnematophyceae, Cyanophyceae y Chlorophyceae, en Lo Méndez Dinophyceae y Bacillariophyceae y en Las Tres Pascualas Chlorophyceae, Cryptophyceae y Euglenophyceae. En Lo Méndez y Lo Galindo se presentaron frecuentes floraciones de diferentes grupos de microalgas (cianobacterias, algas verdes, diatomeas y dinoflagelados), las que generaron aumentos de abundancia en diferentes épocas del año, incluso en invierno. En Las Tres Pascualas, las floraciones fueron poco frecuentes. La ocurrencia y frecuencia de floraciones de especies representantes de los grupos funcionales M, C, Y y Lo y morfológicos VII, VI, IV y V reflejan las condiciones eutróficas de los lagos, siendo indicadoras del grado de contaminación de estos sistemas que influencia su uso actual y futuro

RAPID : research on automated plankton identification

Author Posting. © Oceanography Society, 2007. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 20, 2 (2007): 172-187.When Victor Hensen deployed the first true plankton1 net in 1887, he and his colleagues were attempting to answer three fundamental questions: What planktonic organisms are present in the ocean? How many of each type are present? How does the plankton’s composition change over time? Although answering these questions has remained a central goal of oceanographers, the sophisticated tools available to enumerate planktonic organisms today offer capabilities that Hensen probably could never have imagined.This material is based upon work supported by the National Science Foundation under Grants OCE-0325018, OCE-0324937, OCE-0325167 and OCE-9423471, and the European Union under grants Q5CR-2002-71699, MAS3-ct98-0188, and MAS2-ct92-0015

Penning-trap Q-value determination of the Ga-71(v, e(-))Ge-71 reaction using threshold charge breeding of on-line produced isotopes

<p>We present a first direct Q-value measurement of the Ga-71(v, e(-))Ge-71 reaction using the TITAN mass-measurement facility at ISAC/TRIUMF. The measurements were performed in a Penning trap on neon-like Ga-71(21+) and Ge-71(22+) using isobar separation of the on-line produced mother and daughter nuclei through threshold charge breeding in an electron-beam ion trap. In addition, isoionic samples of Ga-71(21+) and Ge-71(21+) were stored concurrently in the Penning trap and provided a separate Q-value measurement. Both independent measurements result in a combined Q-value of 233.5 +/- 1.2 keV, which is in agreement with the previously accepted Q-value for the v cross-section calculations. Together with a recent measurement of the v-response from the excited states in Ge-71, we conclude that there are no further uncertainties in the nuclear structure, which could remove the persistent discrepancy between the SAGE and GALLEX calibration measurements performed with neutrinos from reactor-produced Cr-51 and Ar-37 sources and the theoretical expectation. (c) 2013 Elsevier B.V. All rights reserved.</p>

Measuring the stability of fundamental constants with a network of clocks

The detection of variations of fundamental constants of the Standard Model would provide us with compelling evidence of new physics, and could lift the veil on the nature of dark matter and dark energy. In this work, we discuss how a network of atomic and molecular clocks can be used to look for such variations with unprecedented sensitivity over a wide range of time scales. This is precisely the goal of the recently launched QSNET project: A network of clocks for measuring the stability of fundamental constants. QSNET will include state-of-the-art atomic clocks, but will also develop next-generation molecular and highly charged ion clocks with enhanced sensitivity to variations of fundamental constants. We describe the technological and scientific aims of QSNET and evaluate its expected performance. We show that in the range of parameters probed by QSNET, either we will discover new physics, or we will impose new constraints on violations of fundamental symmetries and a range of theories beyond the Standard Model, including dark matter and dark energy models

The Astropy Problem

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Despite this, the project has always been and remains to this day effectively unfunded. Further, contributors receive little or no formal recognition for creating and supporting what is now critical software. This paper explores the problem in detail, outlines possible solutions to correct this, and presents a few suggestions on how to address the sustainability of general purpose astronomical software

Clam feeding plasticity reduces herbivore vulnerability to ocean warming and acidification

Ocean warming and acidification affect species populations, but how interactions within communities are affected and how this translates into ecosystem functioning and resilience remain poorly understood. Here we demonstrate that experimental ocean warming and acidification significantly alters the interaction network among porewater nutrients, primary producers, herbivores and burrowing invertebrates in a seafloor sediment community, and is linked to behavioural plasticity in the clam Scrobicularia plana. Warming and acidification induced a shift in the clam's feeding mode from predominantly suspension feeding under ambient conditions to deposit feeding with cascading effects on nutrient supply to primary producers. Surface-dwelling invertebrates were more tolerant to warming and acidification in the presence of S. plana, most probably due to the stimulatory effect of the clam on their microalgal food resources. This study demonstrates that predictions of population resilience to climate change require consideration of non-lethal effects such as behavioural changes of key species. Changes in ocean temperature and pH will impact on species, as well as impacting on community interactions. Here warming and acidification cause a clam species to change their feeding mode, with cascading effects for the marine sedimentary food web

Warming and Resource Availability Shift Food Web Structure and Metabolism

Experimental warming of a marine food web suggests that ocean warming can lead to greater consumer abundance but reduced overall biomass, providing a potentially species-independent response to environmental warming