Argentine Institute of Oceanography

Bahía Blanca, Argentina

Argentine Institute of Oceanography

Bahía Blanca, Argentina
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Neogi S.B.,Osaka Prefecture University | Neogi S.B.,International Center for Diarrhoeal Disease Research | Koch B.P.,Alfred Wegener Institute for Polar and Marine Research | Koch B.P.,Bremerhaven University of Applied Sciences | And 6 more authors.
Biogeosciences | Year: 2011

Little is known about bacterial dynamics in the oligotrophic ocean, particularly about cultivable bacteria. We examined the abundance of total and cultivable bacteria in relation to changes in biogeochemical conditions in the eastern Atlantic Ocean with special regard to Vibrio spp., a group of bacteria that can cause diseases in human and aquatic organisms. Surface, deep water and plankton (<20 μm, 20-55 μm and >55 μm) samples were collected between 50°N and 24°S. Chlorophyll-a was very low (<0.3 μg l -1) in most areas of the nutrient-poor Atlantic, except at a few locations near upwelling regions. In surface water, dissolved organic carbon (DOC) and nitrogen (DON) concentrations were 64-95 μM C and 2-10 μM N accounting for ≥90 % and ≥76 % of total organic C and N, respectively. DOC and DON gradually decreased to ∼45 μM C and <5 μM N in the bottom water. In the surface layer, culture independent total bacteria and other prokaryotes represented by 4′-6-diamidino-2-phenylindole (DAPI) counts, ranged mostly between 107 and 108 cells l -1, while cultivable bacterial counts (CBC) and Vibrio spp. were found at concentrations of 104-107 and 102-105 colony forming units (CFU) l -1, respectively. Most bacteria (>99 %) were found in the nanoplankton fraction (<20 μm), however, bacterial abundance did not correlate with suspended particulates (chlorophyll-a, particulate organic C [POC] and N [PON]). Instead, we found a highly significant correlation between bacterial abundance and temperature (p < 0.001) and a significant correlation with DOC and DON (p < 0.005 and <0.01, respectively). In comparison to CBC and DAPI-stained prokaryotes, cultivable Vibrio showed a stronger and highly significant correlation with DOC and DON (p < 0.0005 and p < 0.005, respectively). In cold waters of the mesopelagic and abyssal zones, CBC was 50 to 100-times lower than in the surface layer; however, cultivable Vibrio spp. could be isolated from the bathypelagic zone and even near the seafloor (average ∼10 CFU l -1). The depth-wise decrease in CBC and Vibrio coincided with the decrease in both DOC and POC. Our study indicates that Vibrio and other bacteria may largely depend on dissolved organic matter to survive in nutrient-poor oceanic habitats. © 2011 Author(s).

Serrano M.E.,National University of San Juan | Scaglia G.J.E.,National University of San Juan | Mut V.,National University of San Juan | Ortiz O.A.,National University of San Juan | Jordan M.,Argentine Institute of Oceanography
Control Engineering and Applied Informatics | Year: 2013

The main difficulty in the control of an underactuated system is that the system has more outputs to be controlled than the number of independent inputs. In this paper a novel trajectory tracking controller designed originally for robotic systems is applied for underactuated surface ships. A simple approach is proposed to track trajectories, knowing the desired state, a value for the control action needed to force the system to go from its current state to a desired one can be obtained. Its main advantage is that the condition for the tracking error tends to zero and the calculation of control actions, are obtained solving a system of linear equations. In addition, the convergence to zero of tracking errors and simulation results are included in this article.

Mookerjee S.,Indian National Institute of Cholera and Enteric Diseases | Jaiswal A.,Indian National Institute of Cholera and Enteric Diseases | Batabyal P.,Indian National Institute of Cholera and Enteric Diseases | Einsporn M.H.,Leibniz Center for Tropical Marine Ecology | And 6 more authors.
Environmental Monitoring and Assessment | Year: 2014

The Gangetic delta is a century-old cholera endemic belt where the role of riverine-estuarine ecosystem in cholera transmission has never been elucidated. Seasonality, distribution, and abundance of environmental Vibrio cholerae O1/O139 and vibriophage in Hooghly riverine-estuarine environment and their correlation with cholera incidence pattern in West Bengal, India, have been analyzed for the first time across summer, monsoon, and winter months. A total of 146 water samples collected from two sites of the Hooghly River (Howrah and Diamond Harbour) were analyzed physicochemically along with cultivable Vibrio count (CVC), V. cholerae O1/O139, and vibriophages. V. cholerae O1 was detected in 56 (38.3 %) samples, while 66 (45.2 %) were positive for V. cholerae O1 phages. Flood tide, water temperature (31 ± 1.6 °C), and turbidity (≥250 nephelometric turbidity unit (NTU)) significantly stimulated V. cholerae and vibriophage abundance in riverine ecosystem. Solitary existence of V. cholerae O1 and phages (p < 0.0001) in aquatic environment divulges the dominance of either of the entity (V. cholerae O1 or V. cholerae O1 Φ) on the other. Significant association (p < 0.05) between Kolkata cholera cases and V. cholerae O1 in aquatic environment implies the role of riverine-estuarine ecosystem in cholera transmission. A "biomonitoring tool" of physicochemical stimulants, tidal, and climatic variants has been proposed collating V. cholerae and phage dynamics that can forewarn any impending cholera outbreak. © 2014 Springer International Publishing Switzerland.

Neogi S.B.,Osaka Prefecture University | Neogi S.B.,International Center for Diarrhoeal Disease Research | Yamasaki S.,Osaka Prefecture University | Alam M.,International Center for Diarrhoeal Disease Research | And 2 more authors.
Wetlands Ecology and Management | Year: 2014

The increasing loads of anthropogenic pollutants, compounded with climate change events, are likely to induce environmental changes in many wetlands with impacts on the native microinvertebrates and pathogens causing increased occurrence of water-borne diseases, which affect millions of people each year. In wetlands bacterial pathogens are actively preyed on by many protozoa and filter-feeding organisms but this predation can be compensated by the nourishment and protection offered by certain microinvertebrates, acting as hosts, e.g., chitinous rotifers, copepods and cladocerans. The complex interactions of ecological, biological, and genetic components mediate disease-causing organisms to exploit microinvertebrate hosts to occupy diverse niches, obtain nutrition, and withstand physico-chemical stresses. The persistence of the human pathogens in wetlands is often enabled by their association with microinvertebrates and also depends on their quorum sensing mediated colonization, biofilm formation, switching into dormant stage, and horizontal transfer of adaptive genes. The symbiosis with microinvertebrates is facilitated by the pathogen's immune evasion and fitness factors, e.g., Type-IV pili, capsular-polysaccharides, nutrient transportation, virulence and binding proteins, proteases, chitinases, and secretion systems. Spatio-temporal variation in the population of copepods and aquatic eggs/larvae of mosquitoes and midge flies, which act as vectors, can influence the outbreaks of cholera, diarrhea, malaria, dengue, filariasis and drucunculiasis. Changes in climatic factors (temperature, salinity, cyclones, rainfall, etc.) and anthropogenic pollutions (sewage, fertilizer and insecticide) may modify the abundance and biodiversity of microinvertebrates, and thus possibly exacerbate the persistence and dispersal of water-borne pathogens. Thus there is a need to adopt ecohydrological and eco-friendly interventions for managing wetlands while conserving them. © 2014 Springer Science+Business Media Dordrecht.

Neogi S.B.,Osaka Prefecture University | Neogi S.B.,International Center for Diarrhoeal Disease Research | Islam M.S.,International Center for Diarrhoeal Disease Research | Nair G.B.,Indian National Institute of Cholera and Enteric Diseases | And 3 more authors.
Wetlands Ecology and Management | Year: 2012

Cholera epidemics are thought to be influenced by changes in populations of estuarine Vibrio cholerae. We investigated the abundance and distribution of this bacterium, as "free-living" (<20 μm fraction) and associated with microphytoplankton (>20 μm) or zooplankton (>60 μm), in the Karnaphuli estuary of Bangladesh during pre- and post-monsoon seasons. Cultivable Vibrio populations were ~10 2-10 4 colony forming units (CFU) ml -1 in the high saline zone (19-23 practical salinity unit, PSU) and declined in freshwater (<10 1 CFU ml -1). Culture independent detection of toxigenic V. cholerae O1 and O139 serogroups revealed a higher abundance of "free-living" (10 4-10 5 cells l -1) than those attached to plankton (10 1-10 3 cells l -1). However, "free-living" O1 and O139 cells were sometimes absent in the medium saline and freshwater areas (0. 0-11 practical salinity unit [PSU]). In contrast, plankton samples always harbored these serogroups despite changes in salinity and other physico-chemical properties. Microphytoplankton and zooplankton were dominated by diatoms and blue-green algae, and copepods and rotifers, respectively. Toxigenic V. cholerae abundance did not correlate with plankton abundance or species but had a positive correlation with chitin in the <20 μm fraction, where suspended particulate matter (SPM), V. cholerae and chitin concentrations were highest. C:N ratios indicated that organic matter in SPM originated predominantly from plankton. The differential occurrence of "free-living" and attached V. cholerae suggests a pivotal function of plankton in V. cholerae spreading into freshwater areas. The probable association of this pathogen with organisms and particles in the nanoplankton (<20 μm) fraction requires validation of the concept of the "free living" state of V. cholerae in aquatic habitats. © 2012 Springer Science+Business Media B.V.

Batabyal P.,Indian National Institute of Cholera and Enteric Diseases | Mookerjee S.,Indian National Institute of Cholera and Enteric Diseases | Einsporn M.H.,Leibniz Center for Tropical Marine Ecology | Lara R.J.,Leibniz Center for Tropical Marine Ecology | And 2 more authors.
Ecological Indicators | Year: 2016

Gangetic delta is considered as the homeland of cholera, which is thought to be influenced by changes in populations of estuarine Vibrio cholerae. We aim to identify the environmental, biotic and abiotic driving forces influencing the V. cholerae dynamics in riverine-estuarine environment of southern deltaic Bengal. Cultivable Vibrio count (CVC) ranged between 1 and 103 colony forming units (CFU)/mL at a salinity gradient of 1.9-30 practical salinity unit (PSU). Increased water temperatrure during summer influences the higher CVC followed by a sudden fall along with the onset of monsoon upto winter. While summer V. cholerae O1 peak (50-100 CFU/mL) can be associated with higher water temperature (P < 0.05) and higher turbidity (P < 0.005); sharp fall during monsoon (15-45 CFU/mL) is attributed to reduced salinity (25-2.5 PSU). Plankton attached V. cholerae O1 varied between 10 and 1000 CFU/mL with a highest peak at winter followed by summer and monsoon. Prevalence of toxigenic V. cholerae O1 in low salinity (2-7.5 PSU) during monsoon identifies that high water temperature (>25 °C), higher turbidity (>100 NTU) and lower salinity plays the pivotal role in toxicity acquisition. Present investigation establishes the role of Sundarban mangrove, where V. cholerae exist in an avirulent condition. During migration towards low saline inland system, V. cholerae pool possibly acquires toxin genes under the influence of environmental factors. Planktonic attachment is possibly a survival strategy at adverse condition, when they do not acquire any toxin gene. Seasonal V. cholerae dynamics has been thoroughly established in environmental settings of high saline mangrove and brackish water flowing to inland low saline condition. © 2016 Elsevier Ltd. All rights reserved.

Da Cruz C.C.,Federal University of Pará | Mendoza U.N.,Federal University of Fluminense | Queiroz J.B.,Federal University of Pará | Berredo J.F.,Goeldi Museum | And 3 more authors.
Plant and Soil | Year: 2013

Background and aims: The Bragança Peninsula, in northern Brazil is characterized by macrotides (4 m) and specific edaphic conditions, which determine the local mangrove forest's development. This study, conducted during the dry season evaluated the spatial patterns of Rhizophora mangle and Avicennia germinans species across an inundation gradient. Methods: Along a transect of 700 m, measurements of structure forest, soil moisture, porewater salinity, extractable phosphorus (extr.-P) in sediments, and phosphorus in the leaves (leaf-P) were conducted. Result: The A. germinans (100 %) occurred in high intertidal (HI) zone. A. germinans (59 %) and R. mangle (41 %) co-occurred in mid intertidal (MI) zone, while R. mangle (58 %) predominated in low intertidal (LI) zone, followed by A. germinans (37 %) and Laguncularia racemosa (5 %). Covariance analysis (ANCOVA) indicated that salinity and soil moisture means are significantly different between the mangrove forests, but do not correlate with inundation frequency (IF). The means of extr.-P were significantly different in mangrove forests and correlated with IF and leaf-P. Conclusion: The inundation frequency, the availability of P in the sediments, phosphorus in the leaves and interstitial salinity are all important factors contributing to the distribution of the mangrove tree species A. germinans and R. mangle on the Bragança Peninsula. © 2013 Springer Science+Business Media Dordrecht.

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