BRYNTRN: A baryon transport model

The development of an interaction data base and a numerical solution to the transport of baryons through an arbitrary shield material based on a straight ahead approximation of the Boltzmann equation are described. The code is most accurate for continuous energy boundary values, but gives reasonable results for discrete spectra at the boundary using even a relatively coarse energy grid (30 points) and large spatial increments (1 cm in H2O). The resulting computer code is self-contained, efficient and ready to use. The code requires only a very small fraction of the computer resources required for Monte Carlo codes

Natural variability of surface oceanographic conditions in the offshore Gulf of Mexico

AbstractThis work characterizes patterns of temporal variability in surface waters of the central Gulf of Mexico. We examine remote-sensing based observations of sea surface temperature (SST), wind speed, sea surface height anomaly (SSHA), chlorophyll-a concentration (Chl-a) and Net Primary Production (NPP), along with model predictions of mixed layer depth (MLD), to determine seasonal changes and long-term trends in the central Gulf of Mexico between the early 1980s and 2012. Specifically, we examine variability in four quadrants of the Gulf of Mexico (water depth >1000m). All variables show strong seasonality. Chl-a and NPP show positive anomalies in response to short-term increases in wind speed and to cold temperature events. The depth of the mixed layer (MLD) directly and significantly affects primary productivity throughout the region. This relationship is sufficiently robust to enable real-time estimates of MLD based on satellite-based estimates of NPP. Over the past 15–20years, SST, wind speed, and SSHA show a statistically significant, gradual increase. However, Chl-a and NPP show no significant trends over this period. There has also been no trend in the MLD in the Gulf of Mexico interior. The positive long-term trend in wind speed and SST anomalies is consistent with the warming phase of the Atlantic Multidecadal Oscillation (AMO) that started in the mid-90s. This also coincides with a negative trend in the El Niño/Southern Oscillation Multivariate ENSO Index (MEI) related to an increase in the frequency of cooler ENSO events since 1999–2000. The results suggest that over decadal scales, increasing temperature, wind speed, and mesoscale ocean activity have offsetting effects on the MLD. The lack of a trend in MLD anomalies over the past 20years explains the lack of long-term changes in chlorophyll concentration and productivity over this period in the Gulf. Understanding the background of seasonal and long-term variability in these ocean characteristics is important to interpret changes in ocean health due to episodic natural and anthropogenic events and long term climate changes or development activities. With this analysis we provide a baseline against which such changes can be measured

LARVAL BLUEFIN TUNA (THUNNUS THYNNUS) TROPHODYNAMICS FROM BALEARIC SEA (WM) AND GULF OF MEXICO SPAWNING ECOSYSTEMS BY STABLE ISOTOPE

The present study uses stable isotopes of nitrogen and carbon (δ15N and δ13C) as trophic indicators for Atlantic bluefin tuna larvae (BFT) (6-10 mm SL) in the highly contrasting environmental conditions of the Gulf of Mexico (GOM) and the Balearic Sea (MED). The study analyzes ontogenetic changes in the food sources and trophic levels (TL) of BFT larvae from each spawning habitat. The results discuss differences in the ontogenic dietary shifts observed in the BFT larvae from the GOM and MED as well as trophodynamic differences in relation to the microzooplanktonic baselines used for estimating trophic enrichment. Significant trophic differences between the GOM and MED larvae were observed in relation to δ15N signatures in favour of the MED larvae, which may have important implications in their early life growth strategy.Versión de edito

Trophic Ecology of Atlantic Bluefin Tuna (Thunnus thynnus) Larvae from the Gulf of Mexico and NW Mediterranean Spawning Grounds: A Comparative Stable Isotope Study

The present study uses stable isotopes of nitrogen and carbon (δ15Nandδ13C) as trophic indicators for Atlantic bluefin tuna larvae (BFT) (6–10mm standard length) in the highly contrasting environmental conditions of the Gulf of Mexico (GOM) and the Balearic Sea (MED). These regions are differentiated by their temperature regime and relative productivity, with the GOM being significantly warmer and more productive. MED BFT larvae showed the highest δ15N signatures, implying an elevated trophic position above the underlyingmicrozooplankton baseline. Ontogenetic dietary shifts were observed in the BFT larvae from the GOM and MED which indicates early life trophodynamics differences between these spawning habitats. Significant trophic differences between the GOM and MED larvae were observed in relation to δ15N signatures in favour of the MED larvae, which may have important implications in their growth during their early life stages. These low δ15N levels in the zooplankton from the GOM may be an indication of a shifting isotopic baseline in pelagic food webs due to diatrophic inputs by cyanobacteria. Lack of enrichment for δ15N in BFT larvae compared to zooplankton implies an alternative grazing pathway from the traditional food chain of phytoplankton— zooplankton—larval fish. Results provide insight for a comparative characterization of the trophic pathways variability of the two main spawning grounds for BFT larvaeVersión del editor4,411

Reporting Recommendations for Tumor Marker Prognostic Studies (REMARK): Explanation and Elaboration

The REMARK “elaboration and explanation” guideline, by Doug Altman and colleagues, provides a detailed reference for authors on important issues to consider when designing, conducting, and analyzing tumor marker prognostic studies

A Comparison of Sampling Methods for Larvae of Medium and Large Epipelagic Fish Species during Spring Seamap Ichthyoplankton Surveys in the Gulf of Mexico

Annual ichthyoplankton surveys have been conducted in the Gulf of Mexico during spring since 1982 by the National Oceanic and Atmospheric Administration (NOAA) National Marine Fisheries Service (NMFS) Southeast Area Monitoring and Assessment Program (SEAMAP). Historically, ichthyoplankton has been assessed using bongo and surface neuston nets. A new sampling gear, the S-10 net, was tested between 2009 and 2011. This is a 1 × 2 m frame fitted with a 0.505 mm mesh net, towed in a yo-yo fashion between the surface and 10 m. Sampling effectiveness of the three gears was compared by examining the abundance and length of larvae of bluefin tuna (Thunnus thynnus) and seven co-occurring pelagic taxa (Auxis spp., Euthynnus alleteratus, Coryphaena spp., Katsuwonus pelamis, other Thunnus spp., family Istiophoridae, and Xiphias gladius) and vertical distributions of scombrid taxa were examined using MOCNESS samples. Permutational multivariate analysis of variance (PERMANOVA) of net type and time of sampling (day/night) indicated that net type was a significant factor in assessing abundance and length for all taxa. Highest abundances for seven of eight taxa were in S-10 samples, and MOCNESS samples confirm highest scombrid abundance between the surface and 20 m. Our results show sampling effectiveness strongly depends on the depth fished by the net and that the S-10 net was more effective than standard SEAMAP bongo and neuston nets. Thus, future sampling with the S-10 net may improve the annual index of larval abundance for the western population of Atlantic bluefin tuna, traditionally based on abundance from bongo samples

Potential Impact of Climate Change on the Intra-Americas Sea: Part-1. a Dynamic Downscaling of the Cmip5 Model Projections

This study examines the potential impact of anthropogenic greenhouse warming on the Intra-Americas Sea (IAS, Caribbean Sea and Gulf of Mexico) by downscaling the Coupled Model Intercomparison Project phase-5 (CMIP5) model simulations under historical and two future emission scenarios using an eddy-resolving resolution regional ocean model. The simulated volume transport by the western boundary current system in the IAS, including the Caribbean Current, Yucatan Current and Loop Current (LC), is reduced by 20-25% during the 21st century, consistent with a similar rate of reduction in the Atlantic Meridional Overturning Circulation (AMOC). The effect of the LC in the present climate is to warm the Gulf of Mexico (GoM). Therefore, the reduced LC and the associated weakening of the warm transient LC eddies have a cooling impact in the GoM, particularly during boreal spring in the northern deep basin, in agreement with an earlier dynamic downscaling study. In contrast to the reduced warming in the northern deep GoM, the downscaled model predicts an intense warming in the shallow (≤. 200. m) northeastern shelf of the GoM especially during boreal summer since there is no effective mechanism to dissipate the increased surface heating. Potential implications of the regionally distinctive warming trend pattern in the GoM on the marine ecosystems and hurricane intensifications during landfall are discussed. This study also explores the effects of 20th century warming and climate variability in the IAS using the regional ocean model forced with observed surface flux fields. The main modes of sea surface temperature variability in the IAS are linked to the Atlantic Multidecadal Oscillation and a meridional dipole pattern between the GoM and Caribbean Sea. It is also shown that variability of the IAS western boundary current system in the 20th century is largely driven by wind stress curl in the Sverdrup interior and the AMOC

Projections of Future Habitat Use by Atlantic Bluefin Tuna: Mechanistic Vs. Correlative Distribution Models

Climate change is likely to drive complex shifts in the distribution and ecology of marine species. Projections of future changes may vary, however, depending on the biological impact model used. In this study, we compared a correlative species distribution model and a simple mechanistic oxygen balance model for Atlantic bluefin tuna (Thunnus thynnus: ABFT) in the North Atlantic Ocean. Both models gave similar results for the recent historical time period, and suggested that ABFT generally occupy favourable metabolic habitats. Projections from an earth system model showed largely temperature-induced reductions in ABFT habitat in the tropical and sub-Tropical Atlantic by 2100. However, the oxygen balance model showed more optimistic results in parts of the subpolar North Atlantic. This was partially due to an inherent ability to extrapolate beyond conditions currently encountered by pelagic longline fishing fleets. Projections included considerable uncertainty due to the simplicity of the biological models, and the coarse spatiotemporal resolution of the analyses. Despite these limitations, our results suggest that climate change is likely to increase metabolic stress on ABFT in sub-Tropical habitats, but may improve habitat suitability in subpolar habitats, with implications for spawning and migratory behaviours, and availability to fishing fleets

Potential Impact of Climate Change on the Intra-Americas Sea: Part 2. Implications for Atlantic Bluefin Tuna and Skipjack Tuna Adult and Larval Habitats

Increasing water temperatures due to climate change will likely have significant impacts on distributions and life histories of Atlantic tunas. In this study, we combined predictive habitat models with a downscaled climate model to examine potential impacts on adults and larvae of Atlantic bluefin tuna (. Thunnus thynnus) and skipjack tuna (. Katsuwonus pelamis) in the Intra-Americas Sea (IAS). An additional downscaled model covering the 20th century was used to compare habitat fluctuations from natural variability to predicted future changes under two climate change scenarios: Representative Concentration Pathway (RCP) 4.5 (medium-low) and RCP 8.5 (high). Results showed marked temperature-induced habitat losses for both adult and larval bluefin tuna on their northern Gulf of Mexico spawning grounds. In contrast, habitat suitability for skipjack tuna increased as temperatures warmed. Model error was highest for the two skipjack tuna models, particularly at higher temperatures. This work suggests that influences of climate change on highly migratory Atlantic tuna species are likely to be substantial, but strongly species-specific. While impacts on fish populations remain uncertain, these changes in habitat suitability will likely alter the spatial and temporal availability of species to fishing fleets, and challenge equilibrium assumptions of environmental stability, upon which fisheries management benchmarks are based