Distribution of spring phytoplankton (mainly diatoms) in the upper 50 m of the Southwestern Atlantic Ocean (30-61°S)

This is the first study on diatom spatial patterns in relation to major oceanographic features along a megascale transect in the Southwestern Atlantic Ocean and provides a comparison with diatom distribution in surface sediments. Absolute abundances of diatoms, silicoflagellates and dinoflagellates (>10-μm fraction) were assessed in 80 bottle samples from 5 to 50 m, retrieved in November 1993 at 20 stations (30-61°S) along 53°W. Siliceous phytoplankton were scarce in the northern half of the transect and in the south of 57°S (100-150 cells L-1), with a strong peak in the vicinity of the Polar Front (∼200 000 cells L-1), whereas dinoflagellates were more abundant at the northern stations (up to 24 000 cells L-1). In the south of 50°S phytoplanktonic cell densities were loosely (but significantly, r = 0.54, P < 0.01) associated with chlorophyll a, whereas in the north of this latitude, this relationship disappeared (r = 0.018, P > 0.1). In total, 191 diatoms and 4 silicoflagellates were recorded. Changes in diatom assemblage compositions along the transect allowed identification of five discrete areas: Subtropical (29°S), Northern Transitional (34-41°S), Southern Transitional (43-48°S), Subantarctic (49-54°S) and Antarctic (55-59°S), each characterized by a set of typical species. Diversity changed little with latitude, but numbers of species were higher in the north of 40°S. Comparison of diatom assemblage makeup in the plankton and in the surface sediments shows very strong disagreements, whereby cold water species are very significantly over-represented in the sedimentary record, suggesting enhanced preservation and strong subsurface equatorward advection of the cold water taxa. © The Author 2006. Published by Oxford University Press. All rights reserved.Fil:Olguín, H.F. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Boltovskoy, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Lange, C.B. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

"Breathing" rogue wave observed in numerical experiment

Numerical simulations of the recently derived fully nonlinear equations of motion for weakly three-dimensional water waves [V.P. Ruban, Phys. Rev. E {\bf 71}, 055303(R) (2005)] with quasi-random initial conditions are reported, which show the spontaneous formation of a single extreme wave on the deep water. This rogue wave behaves in an oscillating manner and exists for a relatively long time (many wave periods) without significant change of its maximal amplitude.Comment: 6 pages, 12 figure

Freely decaying weak turbulence for sea surface gravity waves

We study numerically the generation of power laws in the framework of weak turbulence theory for surface gravity waves in deep water. Starting from a random wave field, we let the system evolve numerically according to the nonlinear Euler equations for gravity waves in infinitely deep water. In agreement with the theory of Zakharov and Filonenko, we find the formation of a power spectrum characterized by a power law of the form of $|{\bf k}|^{-2.5}$.Comment: 4 pages, 3 figure

Spinal cord compression in cattle after the use of an oily vaccine

An outbreak of compressive myelopathy in cattle associated with the improper use of an oil vaccine is described. Neurological signs were observed in 25 out of 3,000 cattle after 60 days of being vaccinated against foot and mouth disease. The clinical picture was characterized by progressive paralysis of the hind limbs, difficulty in standing up, and sternal recumbency during the course of 2-5 months. A filling defect between the L1 and L3 vertebrae was seen through myelography performed in one of the affected animals. A yellow-gray, granular and irregular mass was observed in four necropsied animals involving the spinal nerve roots and epidural space of the lumbar (L1-L4) spinal cord; the mass was associated with a whitish oily fluid. This fluid was also found in association with necrosis of the longissimus dorsi muscle. Microscopic changes in the epidural space, nerve roots, and spinal musculature were similar and consisted of granulomas or pyogranulomas around circular unstained spaces (vacuoles). These spaces were located between areas of severe diffuse hyaline necrosis of muscle fibers and resembled the drops of oil present in the vaccine

Wind speed and mesoscale features drive net autotrophy in the South Atlantic Ocean

This is the final version. Available on open access from Elsevier via the DOI in this recordA comprehensive in situ dataset of chlorophyll a (Chl a; N = 18,001), net primary production (NPP; N = 165) and net community production (NCP; N = 95), were used to evaluate the performance of Moderate Resolution Imaging Spectroradiometer on Aqua (MODIS-A) algorithms for these parameters, in the South Atlantic Ocean, to facilitate the accurate generation of satellite NCP time series. For Chl a, five algorithms were tested using MODIS-A data, and OC3-CI performed best, which was subsequently used to compute NPP. Of three NPP algorithms tested, a Wavelength Resolved Model (WRM) was the most accurate, and was therefore used to estimate NCP with an empirical relationship between NCP with NPP and sea surface temperature (SST). A perturbation analysis was deployed to quantify the range of uncertainties introduced in satellite NCP from input parameters. The largest reductions in the uncertainty of satellite NCP came from MODIS-A derived NPP using the WRM (40%) and MODIS-A Chl a using OC3-CI (22%). The most accurate NCP algorithm, was used to generate a 16 year time series (2002 to 2018) from MODIS-A to assess climate and environmental drivers of NCP across the South Atlantic basin. Positive correlations between wind speed anomalies and NCP anomalies were observed in the central South Atlantic Gyre (SATL), and the Benguela Upwelling (BENG), indicating that autotrophic conditions may be fuelled by local wind-induced nutrient inputs to the mixed layer. Sea Level Height Anomalies (SLHA), used as an indicator of mesoscale eddies, were negatively correlated with NCP anomalies offshore of the BENG upwelling fronts into the SATL, suggesting autotrophic conditions are driven by mesoscale features. The Agulhas bank and Brazil-Malvinas confluence regions also had a strong negative correlation between SLHA and NCP anomalies, similarly indicating that NCP is forced by mesoscale eddy generation in this region. Positive correlations between SST anomalies and the Multivariate ENSO Index (MEI) in the SATL, indicated the influence of El Niño events on the South Atlantic Ocean, however the plankton community response was less clear.Natural Environment Research Council (NERC)European Space Agency (ESA)P&D ANP/BRASOILOceanographic Institute of the University of São Paulo (IOUSP

Coastal high-frequency radars in the Mediterranean - Part 1: Status of operations and a framework for future development

Due to the semi-enclosed nature of the Mediterranean Sea, natural disasters and anthropogenic activities impose stronger pressures on its coastal ecosystems than in any other sea of the world. With the aim of responding adequately to science priorities and societal challenges, littoral waters must be effectively monitored with high-frequency radar (HFR) systems. This land-based remote sensing technology can provide, in near-real time, fine-resolution maps of the surface circulation over broad coastal areas, along with reliable directional wave and wind information. The main goal of this work is to showcase the current status of the Mediterranean HFR network and the future roadmap for orchestrated actions. Ongoing collaborative efforts and recent progress of this regional alliance are not only described but also connected with other European initiatives and global frameworks, highlighting the advantages of this cost-effective instrument for the multi-parameter monitoring of the sea state. Coordinated endeavors between HFR operators from different multi-disciplinary institutions are mandatory to reach a mature stage at both national and regional levels, striving to do the following: (i) harmonize deployment and maintenance practices; (ii) standardize data, metadata, and quality control procedures; (iii) centralize data management, visualization, and access platforms; and (iv) develop practical applications of societal benefit that can be used for strategic planning and informed decision-making in the Mediterranean marine environment. Such fit-for-purpose applications can serve for search and rescue operations, safe vessel navigation, tracking of marine pollutants, the monitoring of extreme events, the investigation of transport processes, and the connectivity between offshore waters and coastal ecosystems. Finally, future prospects within the Mediterranean framework are discussed along with a wealth of socioeconomic, technical, and scientific challenges to be faced during the implementation of this integrated HFR regional network

Coastal high-frequency radars in the Mediterranean - Part 2: Applications in support of science priorities and societal needs

The Mediterranean Sea is a prominent climate-change hot spot, with many socioeconomically vital coastal areas being the most vulnerable targets for maritime safety, diverse met-ocean hazards and marine pollution. Providing an unprecedented spatial and temporal resolution at wide coastal areas, high-frequency radars (HFRs) have been steadily gaining recognition as an effective land-based remote sensing technology for continuous monitoring of the surface circulation, increasingly waves and occasionally winds. HFR measurements have boosted the thorough scientific knowledge of coastal processes, also fostering a broad range of applications, which has promoted their integration in coastal ocean observing systems worldwide, with more than half of the European sites located in the Mediterranean coastal areas. In this work, we present a review of existing HFR data multidisciplinary science-based applications in the Mediterranean Sea, primarily focused on meeting end-user and science-driven requirements, addressing regional challenges in three main topics: (i) maritime safety, (ii) extreme hazards and (iii) environmental transport process. Additionally, the HFR observing and monitoring regional capabilities in the Mediterranean coastal areas required to underpin the underlying science and the further development of applications are also analyzed. The outcome of this assessment has allowed us to provide a set of recommendations for future improvement prospects to maximize the contribution to extending science-based HFR products into societally relevant downstream services to support blue growth in the Mediterranean coastal areas, helping to meet the UN's Decade of Ocean Science for Sustainable Development and the EU's Green Deal goals