29 research outputs found
The role of physico-chemical interactions in the seasonality of toxic dinoflagellate cyst assemblages: The case of the NW Patagonian fjords system
Harmful algal blooms (HABs) are recurrent in the NW Patagonia fjords system and their frequency has increased over the last few decades. Outbreaks of HAB species such as Alexandrium catenella, a causal agent of paralytic shellfish poisoning, and Protoceratium reticulatum, a yessotoxins producer, have raised considerable concern due to their adverse socioeconomic consequences. Monitoring programs have mainly focused on their planktonic stages, but since these species produce benthic resting cysts, the factors influencing cyst distributions are increasingly gaining recognition as potentially important to HAB recurrence in some regions. Still, a holistic understanding of the physico-chemical conditions influencing cyst distribution in this region is lacking, especially as it relates to seasonal changes in drivers of cyst distributions as the characteristics that favor cyst preservation in the sediment may change through the seasons. In this study, we analyzed the physicoâchemical properties of the sediment (temperature, pH, redox potential) and measured the bottom dissolved oxygen levels in a âhotspotâ area of southern Chile, sampling during the spring and summer as well as the fall and winter, to determine the role these factors may play as modulators of dinoflagellate cyst distribution, and specifically for the cysts of A. catenella and P. reticulatum. A permutational analysis of variance (PERMANOVA) showed the significant effect of sediment redox conditions in explaining the differences in the cyst assemblages between spring-summer and fall-winter periods (seasonality). In a generalized linear model (GLM), sediment redox potential and pH were associated with the highest abundances of A. catenella resting cysts in the spring-summer, however it was sediment temperature that most explained the distribution of A. catenella in the fall-winter. For P. reticulatum, only spring-summer sediment redox potential and temperature explained the variation in cyst abundances. The implications of environmental physico-chemical seasonality for the resting cysts dynamics of both species are discussed.Postprint3,74
Turbulence and hypoxia contribute to dense biological scattering layers in a Patagonian fjord system
The
aggregation of plankton species along fjords can be linked to physical
properties and processes such as stratification, turbulence and oxygen
concentration. The goal of this study is to determine how water column
properties and turbulent mixing affect the horizontal and vertical
distributions of macrozooplankton along the only northern Patagonian fjord
known to date, where hypoxic conditions occur in the water column. Acoustic
Doppler current profiler moorings, scientific echo-sounder transects and
in situ plankton abundance measurements were used to study macrozooplankton
assemblages and migration patterns along Puyuhuapi Fjord and Jacaf Channel in
Chilean Patagonia. The dissipation of turbulent kinetic energy was quantified
through vertical microstructure profiles collected throughout time in areas
with high macrozooplankton concentrations. The acoustic records and in situ
macrozooplankton data revealed diel vertical migrations (DVM) of
siphonophores, chaetognaths and euphausiids. In particular, a dense
biological backscattering layer was observed along Puyuhuapi Fjord between
the surface and the top of the hypoxic boundary layer (ââŒâ100 m), which
limited the vertical distribution of most macrozooplankton and their DVM,
generating a significant reduction of habitat. Aggregations of
macrozooplankton and fishes were most abundant around a submarine sill in
Jacaf Channel. In this location macrozooplankton were distributed throughout
the water column (0 to ââŒâ200 m), with no evidence of a hypoxic boundary
due to the intense mixing near the sill. In particular, turbulence
measurements taken near the sill indicated high dissipation rates of
turbulent kinetic energy (ΔââŒâ10â5 W kgâ1) and
vertical diapycnal eddy diffusivity (KÏââŒâ10â3 m2 sâ1). The elevated vertical mixing ensures that the
water column is well oxygenated (3â6 mL Lâ1, 60 %â80 %
saturation), creating a suitable environment for macrozooplankton and fish
aggregations. Turbulence induced by tidal flow over the sill apparently
enhances the interchange of nutrients and oxygen concentrations with the
surface layer, creating a productive environment for many marine species,
where the preyâpredator relationship might be favored.</p
Identification of nurseries areas of juvenile Prochilodus lineatus (Valenciennes, 1836) (Characiformes: Prochilodontidae) by scale and otolith morphometry and microchemistry
Science Priorities for Seamounts: Research Links to Conservation and Management
Seamounts shape the topography of all ocean basins and can be hotspots of biological activity in the deep sea. The Census of Marine Life on Seamounts (CenSeam) was a field program that examined seamounts as part of the global Census of Marine Life (CoML) initiative from 2005 to 2010. CenSeam progressed seamount science by collating historical data, collecting new data, undertaking regional and global analyses of seamount biodiversity, mapping species and habitat distributions, challenging established paradigms of seamount ecology, developing new hypotheses, and documenting the impacts of human activities on seamounts. However, because of the large number of seamounts globally, much about the structure, function and connectivity of seamount ecosystems remains unexplored and unknown. Continual, and potentially increasing, threats to seamount resources from fishing and seabed mining are creating a pressing demand for research to inform conservation and management strategies. To meet this need, intensive science effort in the following areas will be needed: 1) Improved physical and biological data; of particular importance is information on seamount location, physical characteristics (e.g. habitat heterogeneity and complexity), more complete and intensive biodiversity inventories, and increased understanding of seamount connectivity and faunal dispersal; 2) New human impact data; these shall encompass better studies on the effects of human activities on seamount ecosystems, as well as monitoring long-term changes in seamount assemblages following impacts (e.g. recovery); 3) Global data repositories; there is a pressing need for more comprehensive fisheries catch and effort data, especially on the high seas, and compilation or maintenance of geological and biodiversity databases that underpin regional and global analyses; 4) Application of support tools in a data-poor environment; conservation and management will have to increasingly rely on predictive modelling techniques, critical evaluation of environmental surrogates as faunal âproxiesâ, and ecological risk assessment
Posterior reversible encephalopathy syndrome â Case report
Introduction. Posterior reversible encephalopathy syndrome (PRES) is a group of clinical disorders typically manifested by
the presence of seizures, headache, impaired consciousness, nausea and focal neurological deficits. It is stated that PRES
is a result of high blood pressure which leads to impaired self-regulation and hyperperfusion causing endothelial damage
and vasogenic oedema or that excessive arteriolar vasoconstriction causes reduced blood flow, thus causing ischemia and
cytotoxic oedema.
Case Report. A 21-year-old woman was admitted to obstetrics & gynaecology department with symptoms of eclampsia.
CT of the head revelaed a holohemispheric watershed pattern. MRI confirmed the presence of vasogenicoedema in the
affected regions, typical for PRES. C-section was performed. Ten days after administering treatment, MRI showed complete
withdrawal of the lesions. The diagnosis of PRES was based on clinical symptoms and MRI, with typical cortical and subcortical
oedema without infarction
The use of fishing vessels to provide acoustic data on the distribution and abundance of Antarctic krill and other pelagic species
A fishery for Antarctic krill (Euphausia superba) has existed for over 3 decades and the Commission for Conservation of Antarctic Marine Living Resources (CCAMLR) manages this fishery using precautionary catch limits, fishery data collection and a scientific observer programme operating on the fishing vessels. A recent increase in the number of vessels fishing and the rising costs of undertaking scientific research cruises have focussed attention on being able to use fishing vessels to collect more extensive scientific data sets. In 2011, CCAMLRâs Subgroup on Acoustic Survey and Analysis Methods (SG-ASAM) was tasked with assessing the use of acoustic data collected from fishing vessels to provide qualitative and quantitative information on the distribution and relative abundance of Antarctic krill and other pelagic species. SG-ASAM conceived a proof of concept programme and implemented the first stage in 2013 to determine the current setup of acoustic equipment on participating fishing vessels and to establish whether these vessels could collect geo- and time-referenced acoustic data. To date data have been received from 7 krill fishing vessels and SG-ASAM has now focussed on the development of data collection protocols to enable fishing vessels to collect quantitative acoustic data along prescribed transects. While this development work continues, the willingness of fishing industry to participate in such studies has already been demonstrated by several fishing companies, and Norwegian- and Chinese-flagged fishing vessels are undertaking krill biomass surveys in two key fishery areas in the South Atlantic sector of the Southern Ocean
What is a land grab? Exploring green grabs, conservation, and private protected areas in southern Chile
Discussions of land grabs for various purposes, including environmental ends, have expanded in recent years, yet land grabbing remains inconsistently defined and poorly understood. Our ability to assess the extent to which land grabs are occurring, and to identify the mixture of factors driving land and resource acquisition, is limited. This paper assesses whether a land grab for conservation is happening in southern Chile, and identifies the various driving forces that combine to drive land acquisitions in the region, based on a detailed exploration of the recent massive growth in privately owned protected areas in the region. This paper finds that the various dominant definitions of land grabs each apply only partially to southern Chile, that land grabs for conservation need to be understood as the latest stage in a longer process by which the region's natural resources are incorporated into the Chilean and the global economy, and that green grabs interact in various ways with broader resource grabs, particularly for forestry and hydroelectricity. This case study demonstrates the limitations of some definitions of land grabs, particularly their focus on capitalist accumulation within land grabs, their international nature and their emphasis on legal processes
Partial migration and early size of southern hake Merluccius australis : a journey between estuarine and oceanic habitats off Northwest Patagonia
Partial migration is a key adaptive strategy, increasingly observed across multiple taxa. To investigate partial migration and life-cycle diversity of Merluccius australis in northwestern Patagonia, we analysed isotopic (delta C-13, delta O-18) and elemental (B-11, Na-23, Mg-24, Mn-55, Sr-86, Ba-138) compositions of otoliths from juveniles, sub-adults, and adults to identify nursery origins, habitats used, and migratory behaviours of multiple cohorts (1990-2005). Influence of early size upon migration was assessed by comparing back-calculated sizes at demersal recruitment between resident and migratory adults. Although partial migration occurred at both estuarine and oceanic nursery habitats, migratory behaviour was more frequent in fish of estuarine origin (59%) than in fish of oceanic origin (17%). Adults of estuarine origin dominated both estuarine (92%) and oceanic (77%) sampling areas. Although we found no significant differences in size at demersal recruitment between oceanic-resident and oceanic-migratory fish, a strong relationship between size at demersal recruitment and migratory behaviour appeared in fish of estuarine origin, whose probability of migration increased from 5% to 95% as demersal recruitment size increased from 18.8 to 23.6cm. Further research on M. australis life cycle is required to incorporate sub-population processes into the stock assessment and management models being used for this overexploited species
Markets, nature, neoliberalism and conservation through private protected areas in southern Chile.
A vibrant literature has emerged in recent years exploring moves towards neoliberal forms of conservation, with a reduced role for the state and an enhanced role for markets and private and civil society actors. Yet there is a need for studies which explore how and why this trend has emerged, and what impact this has on both people and nature. This paper is a detailed examination of private protected areas, which are often associated with neoliberal approaches to conservation, in Chile, a country which has had a long and deep engagement with neoliberalism. It finds that private protected areas demonstrate a broad range of attitudes towards the use of markets in conservation, from enthusiasm to hostility. Yet all have been made possible, indeed incentivised, by Chileâs liberalised property markets and individualistic political culture, products of earlier neoliberal reforms within Chileâs society and economy. As such, they provide only a limited challenge to the social and environmental consequence of the integration of southern Chileâs natural resources into global neoliberal economic chains. It emphasises the importance of considering how broader neoliberal economic, political and social reforms have allowed certain forms of conservation to emerge and thrive