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UVR induce optical changes and phosphorous release of lake water and macrophyte leachates in shallow Andean lakes
Marcela BASTIDAS NAVARRO,Beatriz MODENUTTI
Journal of Limnology , 2010, DOI: 10.4081/jlimnol.2010.112
Abstract: We carried out laboratory experiments in order to study the effect of ultraviolet radiation (UVR) on optical features and phosphorous release of Dissolved Organic Mater (DOM) from lake water and macrophyte leachates. Lake water samples were obtained from lakes Escondido and El Trébol, and macrophytes (Potamogeton linguatus and Schoenoplectus californicus) from their littoral zones. After UVR exposure, DOM from lake El Trébol seemed to react more quickly than that from Lake Escondido and this seems to be related with the degree of lability or aromaticity in the DOM bulk of each lake. Leachates from both macrophytes showed different absorbance spectra with differences in photochemical transformations after UVR exposure: S. californicus leachates exhibited the highest photodegradation. A significant Soluble Reactive Phosphorus (SRP) release was observed in lake water after UVR exposure. Lake El Trébol showed the highest SRP concentrations, suggesting that the release of orthophosphate was favored by low molecular weight DOM. P. linguatus leachates have more dissolved phosphorus content than S. californicus ones and after UVR exposure, P. linguatus leachate did not react to UVR while S. californicus exhibited a decrease in SRP. However both macrophyte leachates showed the higher P release in darkness. The obtained results indicated that macrophyte leachates could contribute significantly to changes in the optical characteristics and in the nutrient content in shallow Andean lakes. An increasing input of P. linguatus leachates would produce DOM of high molecular size and a higher P release than S. californicus.
Planktonic ciliates from an oligotrophic South Andean lake, Morenito Lake (Patagonia, Argentina)
MODENUTTI, B. E.;PéREZ, G. L.;
Brazilian Journal of Biology , 2001, DOI: 10.1590/S1519-69842001000300007
Abstract: in this contribution we have studied the planktonic ciliates from morenito lake, an oligotrophic lake situated in the south andes of argentina. six species that are new records for south america or argentina are described and illustrated. besides, population dynamics of the ciliate species were studied during a spring?summer period. strobilidium lacustris and balanion planctonicum were the most abundant species, showing a maximum in mid summer. paradileptus elephantinus was present all over the period while urotricha furcata was observed in late summer samples. strobilidium lacustris and s. humile were found to be occasional species during the studied period. the recorded ciliate assemblage with oligotrichs and prostomates as dominant indicate the oligotrophic condition of the lake.
Efecto de la estructuración por macrófitas y por recursos alimentarios en la distribución horizontal de tecamebas y rotíferos en un lago andino patagónico
BASTIDAS-NAVARRO,MARCELA; MODENUTTI,BEATRIZ;
Revista chilena de historia natural , 2007, DOI: 10.4067/S0716-078X2007000300008
Abstract: the presence of macrophytes in the littoral zone of lakes produces particular conditions including higher resource availability for consumers. for this reason, the littoral zone is generally the area with the highest diversity of lakes and rivers. in this work we studied the horizontal distribution of testate amoebae and rotifers in lago escondido (argentina) in relation to food resources availability. the study was carried out along a north-south transect that includes the littoral and the pelagic zone of the lake. phytoplankton and zooplankton were sampled during summer and spring (2001-2003) in five sampling stations: one pelagic and four littoral. rotifers and testate amoebae, as well as phytoplanktonic algae abundance and biomass were estimated. food resources were classified as nanoplankton (< 20 μm) and net phytoplankton (> 20 μm) and the biovolume of these fractions varied significantly within the pelagic and littoral zones of the lake. nanoplankon dominated the pelagic zone and was mainly composed by nanoflagellates while net phytoplankton prevailed in the littoral zone and was composed by diatoms, cyanophytes and chlorophytes. the highest number of species and diversity of testate amoebae and rotifers were observed in the littoral stations; nevertheless, no significant differences between the zones colonized by different macrophytes were observed. the cca analysis showed four different groups. keratella cochlearis, synchaeta spp., polyarthra vulgaris and collotheca mutabilis characterized the pelagic samples and were related with a high abundance of nanoplankton. on the other hand, rotifers like trichocerca spp., lecane spp. and euchlanis spp. and the testate amoebae dijflugia pyriformis and trinema enchelys associated with the littoral samples were related with high abundances of net phytoplankton. besides, a third group of species {lecane spp. and arcella spp.), presented in both zones, was mainly related with a decrease in abundance of net phytoplankton
Efecto de la estructuración por macrófitas y por recursos alimentarios en la distribución horizontal de tecamebas y rotíferos en un lago andino patagónico Effect of macrophytes and food resources on the horizontal distribution of testate amoebae and rotifers in an Andean-Patagonian lake
MARCELA BASTIDAS-NAVARRO,BEATRIZ MODENUTTI
Revista chilena de historia natural , 2007,
Abstract: La presencia de macrófitas en la zona litoral lacustre trae aparejada condiciones diferentes con respecto a la zona pelágica, en particular en la disponibilidad de recursos. Por esta razón, las zonas litorales pueden presentar una mayor biodiversidad. En este trabajo se analizó la distribución horizontal de tecamebas y rotíferos en el lago Escondido (Argentina), vinculándola con los recursos alimentarios presentes en las diferentes zonas. Se tomaron muestras para el estudio del fitoplancton y zooplancton durante verano y primavera (2001-2003) en cuatro estaciones litorales y una pelágica. Se realizó el recuento de rotíferos y tecamebas y se determinó la abundancia y la biomasa fitoplanctónica. Los recursos alimentarios fueron clasificados en nanoplancton (< 20 μm) y fitoplancton de red (> 20 μm). El nanoplancton estuvo compuesto por nanoflagelados y el fitoplancton de red por diatomeas, cianófitas y clorófitas. La biomasa de estas fracciones varió significativamente, observándose una predominancia del nanoplancton en la zona pelágica y del fitoplancton de red en la zona litoral. Los mayores valores de riqueza y de diversidad de tecamebas y rotíferos fueron observados en las estaciones litorales, no hallándose diferencias significativas entre las zonas con diferentes macrófitas. El análisis de ACC evidenció cuatro grupos. Por un lado, Keratella cochlearis, Synchaeta spp., Polyarthra vulgaris y Collotheca mutabilis, asociadas a las muestras pelágicas, se relacionaron con una alta abundancia de nanoplancton. Por otro lado, los rotíferos Trichocerca spp., Lecane spp. y Euchlanis spp., y las tecamebas Dijflugia pyriformis y Trinema enchelys se relacionaron con el fitoplancton de red y las muestras litorales. Además, un tercer grupo reunió a especies (Lecane spp. y Arcella spp.) presentes en ambas zonas y en relación con una baja abundancia del fitoplancton de red. Por último, el rotífero Synchaeta spp. y las muestras pelágicas de primavera se relacionaron con el aumento de la abundancia de la cianofita Coelosphaerium kuetzingianum. Las diferencias se aladas indican que los recursos alimentarios serían un factor determinante en la distribución de especies de tecamebas y rotíferos en el lago Escondido. Para estos zoopláncteres de peque o tama o las macrófitas litorales brindarían alimento al favorecer el incremento del fitoplancton de red The presence of macrophytes in the littoral zone of lakes produces particular conditions including higher resource availability for consumers. For this reason, the littoral zone is generally the area with the highest diversity
Planktonic ciliates from an oligotrophic South Andean lake, Morenito Lake (Patagonia, Argentina)
MODENUTTI B. E.,PéREZ G. L.
Brazilian Journal of Biology , 2001,
Abstract: In this contribution we have studied the planktonic ciliates from Morenito Lake, an oligotrophic lake situated in the South Andes of Argentina. Six species that are new records for South America or Argentina are described and illustrated. Besides, population dynamics of the ciliate species were studied during a spring--summer period. Strobilidium lacustris and Balanion planctonicum were the most abundant species, showing a maximum in mid summer. Paradileptus elephantinus was present all over the period while Urotricha furcata was observed in late summer samples. Strobilidium lacustris and S. humile were found to be occasional species during the studied period. The recorded ciliate assemblage with oligotrichs and prostomates as dominant indicate the oligotrophic condition of the lake.
Grazing impact on autotrophic picoplankton in two south Andean lakes (Patagonia, Argentina) with different light:nutrient ratios
BALSEIRO,ESTEBAN G.; QUEIMALI?OS,CLAUDIA P.; MODENUTTI,BEATRIZ E.;
Revista chilena de historia natural , 2004, DOI: 10.4067/S0716-078X2004000100007
Abstract: andean ultraoligotrophic lakes are environments with high light:nutrient ratios. in these lakes a particular planktonic food web has been noticed, constituted by large mixotrophic ciliates which share and compete for food resources with nanoflagellates and cladocerans. clearance rates on autotrophic picoplankton of nanoflagellates, the ciliate ophrydium naumanni and cladocerans were compared through grazing experiments in lakes moreno oeste and rivadavia. the lakes exhibited significant differences in the light:nutrient ratio and had different crustacean and zooplankton compositions. in lake moreno oeste the metalimnion was included in the euphotic zone resulting in an illuminated layer where deep chlorophyll maxima developed. on the contrary, in lake rivadavia the illuminated layers were restricted to the epilimnion and no deep chlorophyll maxima were observed. in lake moreno oeste, the contribution to total bacterivory of the ciliate o. naumanni and the cladoceran ceriodaphnia dubia was observed to increase at 30 m depth, due mainly to the vertical distribution of both species. on the contrary, the grazing rates of the nanoflagellate assemblage, dominated by the mixotrophic chrysochromulina parva, did not change along the water column and were considerably high (one order of magnitude higher than those obtained for o. naumanni and c. dubia). in lake rivadavia, nanoflagellate grazing rates were lower and the relative impact of the nanoflagellate assemblage was comparable to those of o. naumanni and daphnia cf .commutata. the observed difference in clearance rates of the nanoflagellate assemblage probably would reflect an increase in the phagotrophy where light energy is higher relative to phosphorus. in lake moreno oeste where light is not limiting, the observed increase of the phagotrophy by protists may be due to a higher requirement of limiting elements
Impacto del pastoreo sobre picoplancton autotrófico en dos lagos andinos (Patagonia, Argentina) con diferentes relaciones luz:nutrientes Grazing impact on autotrophic picoplankton in two south Andean lakes (Patagonia, Argentina) with different light:nutrient ratios
ESTEBAN G. BALSEIRO,CLAUDIA P. QUEIMALI?OS,BEATRIZ E. MODENUTTI
Revista chilena de historia natural , 2004,
Abstract: Los lagos andino-patagónicos son ambientes con una alta relación luz:nutrientes. En estos lagos se ha descrito una red trófica particular constituida por grandes ciliados mixotróficos que comparten y compiten por recursos alimentarios con nanoflagelados y cladóceros. A través de experimentos de pastoreo se compararon las tasas de limpieza sobre picoplancton autotrófico de nanoflagelados; el ciliado Ophrydium naumanni y cladóceros de los lagos Moreno Oeste y Rivadavia. Estos lagos presentan diferencias significativas en cuanto a su relación luz:nutrientes y tienen también una composición de crustáceos del zooplancton diferente. En el lago Moreno Oeste, el metalimnion está incluido dentro de la zona eufótica, determinando un estrato iluminado en el que se desarrolla un máximo de clorofila en profundidad. En el lago Rivadavia, en cambio, los estratos iluminados están restringidos al epilimnion y no se observó ningún máximo de clorofila en profundidad. En el lago Moreno se observó que a 30 m de profundidad se producía un incremento en la proporción de la bacterivoría ejercida por el ciliado O. naumanni y el cladócero Ceriodaphnia dubia debido fundamentalmente a la distribución vertical de ambas especies. Por el contrario, las tasas de limpieza del conjunto de nanoflagelados, dominado por la especie mixótrofa Chrysochromulina parva, no presentaron cambios a lo largo de la columna de agua y fueron un orden de magnitud mayores que aquellas de O. naumanni y C. dubia. En el lago Rivadavia, las tasas de pastoreo de los nanoflagelados fueron menores y comparables con las obtenidas para O. naumanni y Daphnia cf. commutata. Las diferencias observadas en las tasas de limpieza de nanoflagelados probablemente reflejan un incremento de la fagotrofía donde la energía lumínica es alta en relación con el fósforo. De esta manera, en el lago Moreno Oeste, donde la luz no es limitante, el aumento observado en la bacterivoría de los protistas podría deberse a un mayor requerimiento de nutrientes limitantes Andean ultraoligotrophic lakes are environments with high light:nutrient ratios. In these lakes a particular planktonic food web has been noticed, constituted by large mixotrophic ciliates which share and compete for food resources with nanoflagellates and cladocerans. Clearance rates on autotrophic picoplankton of nanoflagellates, the ciliate Ophrydium naumanni and cladocerans were compared through grazing experiments in lakes Moreno Oeste and Rivadavia. The lakes exhibited significant differences in the light:nutrient ratio and had different crustacean and zooplankton compo
Susceptibility of bacterioplankton to nutrient enrichment of oligotrophic and ultraoligotrophic lake waters
Roberto BERTONI,Cristiana CALLIERI,Esteban BALSEIRO,Beatriz MODENUTTI
Journal of Limnology , 2008, DOI: 10.4081/jlimnol.2008.120
Abstract: We carried out laboratory experiments in one ultraoligotrophic pristine Andean lake (Lake Gutiérrez, Argentina) and in one subalpine lake that is now at the edge of the oligo- to mesotrophic condition (Lake Maggiore, Italy). Lake water was amended with phosphorus (+P), organic carbon (+C), alone or in combination (+CP), to test for short-term changes (48 hours) in bacteria activity and community structure (CARD FISH). Experiments were carried out in spring and summer. Results showed that bacterial production increased in the +CP treatment in both lakes, and in the +P treatment in the ultroligotrophic lake. In both lakes the bacterial activity increased more rapidly in summer (within 24 hours). Bacteria composition changed in both seasons in all the treatments. At the beginning of the experiments the subclass of β-Proteobacteria dominated both lakes, while γ-Proteobacteria showed higher percentage in spring in Lake Maggiore and in summer in Lake Gutiérrez. After incubation, in spring and in particular in the +CP treatment, we observed an increase in the relative importance of γ-Proteobacteria in both lakes, whereas in Lake Maggiore this group declined in the summer experiments following an increase in β-Proteobacteria. All our results indicate the different response of bacterioplankton in systems at the edges of the oligotrophic range.
Leachates and elemental ratios of macrophytes and benthic algae of an Andean high altitude wetland
Florencia CUASSOLO,Marcela BASTIDAS NAVARRO,Esteban BALSEIRO,Beatriz MODENUTTI
Journal of Limnology , 2011, DOI: 10.4081/jlimnol.2011.168
Abstract: In wetlands, macrophytes and filamentous algae constitute an important carbon source for the total content of Dissolved Organic Matter (DOM) of the environment. Mallín wetland meadows are highly diverse and rare habitats in Patagonia, that can be characterized as wet meadows with a dense cover mainly dominated by herbaceous plants. We carried out a field study comparing elemental composition (C:N:P) of benthic algae (Spirogyra sp. and Zygnema sp.) and the submerged macrophyte (Myriophyllum quitense) from a high latitude wetland (local name: mallín). Besides we performed laboratory experiments in order to study the effect of ultraviolet radiation (UVR) on the optical properties and nutrient release of DOM from leachates of these benthic algae and submerged macrophyte. The obtained results indicated that macrophyte leachates could contribute significantly to changes in the optical characteristics of the wetlands while benthic algae contribute with leachates with low photoreactivity. Finally, nutrient release differs among plant species and season: benthic algae leachates release more P in spring, while M. quitense releases more of this nutrient in autumn. These results suggested that the different colonization may contribute differentially to the chemical environment of the wetland.
Rapid Enzymatic Response to Compensate UV Radiation in Copepods
María Sol Souza, Lars-Anders Hansson, Samuel Hylander, Beatriz Modenutti, Esteban Balseiro
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032046
Abstract: Ultraviolet radiation (UVR) causes physical damage to DNA, carboxylation of proteins and peroxidation of lipids in copepod crustaceans, ubiquitous and abundant secondary producers in most aquatic ecosystems. Copepod adaptations for long duration exposures include changes in behaviour, changes in pigmentation and ultimately changes in morphology. Adaptations to short-term exposures are little studied. Here we show that short-duration exposure to UVR causes the freshwater calanoid copepod, Eudiaptomus gracilis, to rapidly activate production of enzymes that prevent widespread collateral peroxidation (glutathione S-transferase, GST), that regulate apoptosis cell death (Caspase-3, Casp-3), and that facilitate neurotransmissions (cholinesterase-ChE). None of these enzyme systems is alone sufficient, but they act in concert to reduce the stress level of the organism. The interplay among enzymatic responses provides useful information on how organisms respond to environmental stressors acting on short time scales.
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