68 research outputs found
Spatial Resolution of a Micromegas-TPC Using the Charge Dispersion Signal
The Time Projection Chamber (TPC) for the International Linear Collider will
need to measure about 200 track points with a resolution close to 100 m. A
Micro Pattern Gas Detector (MPGD) readout TPC could achieve the desired
resolution with existing techniques using sub-millimeter width pads at the
expense of a large increase in the detector cost and complexity. We have
recently applied a new MPGD readout concept of charge dispersion to a prototype
GEM-TPC and demonstrated the feasibility of achieving good resolution with pads
similar in width to the ones used for the proportional wire TPC. The charge
dispersion studies were repeated with a Micromegas TPC amplification stage. We
present here our first results on the Micromegas-TPC resolution with charge
dispersion. The TPC resolution with the Micromegas readout is compared to our
earlier GEM results and to the resolution expected from electron statistics and
transverse diffusion in a gaseous TPC.Comment: 5 pages, 8 figures, to appar in the Proceedings of the 2005
International Linear Collider Workshop (LCWS05), Stanford, 18-22 March 200
Near-island biological hotspots in barren ocean basins
Phytoplankton production drives marine ecosystem trophic-structure and global fisheries yields. Phytoplankton biomass is particularly influential near coral reef islands and atolls that span the oligotrophic tropical oceans. The paradoxical enhancement in phytoplankton near an island-reef ecosystemâIsland Mass Effect (IME)âwas first documented 60 years ago, yet much remains unknown about the prevalence and drivers of this ecologically important phenomenon. Here we provide the first basin-scale investigation of IME. We show that IME is a near-ubiquitous feature among a majority (91%) of coral reef ecosystems surveyed, creating near-island âhotspots' of phytoplankton biomass throughout the upper water column. Variations in IME strength are governed by geomorphic type (atoll vs island), bathymetric slope, reef area and local human impacts (for example, human-derived nutrient input). These ocean oases increase nearshore phytoplankton biomass by up to 86% over oceanic conditions, providing basal energetic resources to higher trophic levels that support subsistence-based human populations
Effects of fishery protection on biometry and genetic structure of two target sea cucumber species from the Mediterranean Sea
Sea cucumber fisheries are now occurring
in most of the tropical areas of the world, having
expanded from its origin in the central Indo-Pacific.
Due to the overexploitation of these resources and the
increasing demand from Asian countries, new target
species from Mediterranean Sea and northeastern
Atlantic Ocean are being caught. The fishery effects
on biometry and genetic structure of two target species
(Holothuria polii and H. tubulosa) from Turkey, were
assessed. The heaviest and largest individuals of H.
polii were found into the non-fishery area of Kusadasi,
also showing the highest genetic diversity. Similar
pattern was detected in H. tubulosa, but only the
weight was significantly higher in the protected area.
However, the observed differences on the fishery
effects between species, could be explained considering
the different percentage of catches (80% for H.
polii and 20% for H. tubulosa)
Being young in a changing world: how temperature and salinity changes interactively modify the performance of larval stages of the barnacle Amphibalanus improvisus
The fate of key species, such as the barnacle Amphibalanus improvisus, in the course of global change is of particular interest since any change in their abundance and/or performance may entail community-wide effects. In the fluctuating Western Baltic, species typically experience a broad range of environmental conditions, which may preselect them to better cope with climate change. In this study, we examined the sensitivity of two crucial ontogenetic phases (naupliar, cypris) of the barnacle toward a range of temperature (12, 20, and 28°C) and salinity (5, 15, and 30 psu) combinations. Under all salinity treatments, nauplii developed faster at intermediate and high temperatures. Cyprid metamorphosis success, in contrast, was interactively impacted by temperature and salinity. Survival of nauplii decreased with increasing salinity under all temperature treatments. Highest settlement rates occurred at the intermediate temperature and salinity combination, i.e., 20°C and 15 psu. Settlement success of ânaiveâ cyprids, i.e., when nauplii were raised in the absence of stress (20°C/15 psu), was less impacted by stressful temperature/salinity combinations than that of cyprids with a stress history. Here, settlement success was highest at 30 psu particularly at low and high temperatures. Surprisingly, larval survival was not highest under the conditions typical for the Kiel Fjord at the season of peak settlement (20°C/15 psu). The proportion of nauplii that ultimately transformed to attached juveniles was, however, highest under these âhomeâ conditions. Overall, only particularly stressful combinations of temperature and salinity substantially reduced larval performance and development. Given more time for adaptation, the relatively smooth climate shifts predicted will probably not dramatically affect this species
Marine fish traits follow fast-slow continuum across oceans
A fundamental challenge in ecology is to understand why species are found where they are and predict
where they are likely to occur in the future. Trait-based approaches may provide such understanding,
because it is the traits and adaptations of species that determine which environments they can inhabit.
It is therefore important to identify key traits that determine species distributions and investigate
how these traits relate to the environment. Based on scientific bottom-trawl surveys of marine fish
abundances and traits of >1,200 species, we investigate trait-environment relationships and project
the trait composition of marine fish communities across the continental shelf seas of the Northern
hemisphere. We show that traits related to growth, maturation and lifespan respond most strongly to
the environment. This is reflected by a pronounced âfast-slow continuumâ of fish life-histories, revealing
that traits vary with temperature at large spatial scales, but also with depth and seasonality at more
local scales. Our findings provide insight into the structure of marine fish communities and suggest that
global warming will favour an expansion of fast-living species. Knowledge of the global and local drivers
of trait distributions can thus be used to predict future responses of fish communities to environmental
change.Postprint2,92
Climate change impacts and adaptation of commercial marine fisheries in Australia: a review of the science
Review of the projected impacts of climate change on coastal fishes in southern Africa
The coastal zone represents one of the most economically and ecologically important ecosystems on the planet, none more so than in southern Africa. This manuscript examines the potential impacts of climate change on the coastal fishes in southern Africa and provides some of the first information for the Southern Hemisphere, outside of Australasia. It begins by describing the coastal zone in terms of its physical characteristics, climate, fish biodiversity and fisheries. The region is divided into seven biogeographical zones based on previous descriptions and interpretations by the authors. A global review of the impacts of climate change on coastal zones is then applied to make qualitative predictions on the likely impacts of climate change on migratory, resident, estuarine-dependent and catadromous fishes in each of these biogeographical zones. In many respects the southern African region represents a microcosm of climate change variability and of coastal habitats. Based on the broad range of climate change impacts and life history styles of coastal fishes, the predicted impacts on fishes will be diverse. If anything, this review reveals our lack of fundamental knowledge in this field, in particular in southern Africa. Several research priorities, including the need for process-based fundamental research programs are highlighted
Climate change effects on stream and river temperatures across the northwest U.S. from 1980â2009 and implications for salmonid fishes
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