Lago Pellegrini. Caracteristicas limnologicas

Este trabajo trata el estudio biológico del lago Pellegrini y las características limnológicas del ambiente desde el punto de vista pesquero y turístico en el lapso 1980-1998. Se realizaron monitoreos quincenales de calidad de agua y mensuales de plancton, plaguicidas, bacteriológicos, etc. en estaciones de muestreo situadas en el lago propiamente dicho, en el afluente y alrededores. Se analizan los problemas de eutrofización presentes, en la búsqueda de ensayos que disminuyan el deterioro del ecosistema. Los resultados comprueban un proceso de eutrofización natural, agravado por la actividad humana, con florecimientos de algas cianobacterias (Géneros Microcystis y Anabaena) y una disminución de la productividad secundaria y en la población íctica.

Efectos de la eutrofizacion sobre la pesca en el lago Pellegrini.

Por los problemas ocasionados en el deterioro del lago, en la pesca comercial y deportiva, se planteó como objetivo el estudio de las características limnológicas del ambiente relacionando la situación actual con la de años anteriores y además con los aportes exógenos que recibe el ecosistema. Se realizaron monitoreos de calidad físico-química del agua, nutrientes y plancton del lago y su influencia sobre el recurso pesquero, relacionando las capturas reales con los altos rendimientos pesqueros teóricos determinados en base a parámetros químicos, biológicos y morfoedáficos. Los resultados comprueban una disminución de la productividad secundaria y la población de peces, entre otros problemas de eutrofización. Se estudian distintas posibilidades para revertir esta tendencia del lago y recuperar e impulsar la pesquería comercial y deportiva.

Worsening water quality conditions at Inner Puno Bay, Lake Titicaca, Peru, and their effect on Lemna spp. biomass

Although there have been a number of studies on aquatic conditions and the flora and fauna of Lake Titicaca over many decades, most of this work has been centred on the offshore regions of the main lake. Water quality there has been degrading and abundant growth of Lemna spp. has been developing. Lemna spp., commonly called floating duck-weed or ‘lenteja de agua’ in Puno, occurs perennially in most parts of the inner Puno Bay shore-line. In this article, the authors compare water quality changes over recent decades in shore-line regions of Inner Puno Bay and their possible effects on the distribution, abundance and biomass of Lemna spp..

Ichthyological ecoregions of Argentina

The Argentine Republic is situated in the southernmost portion of the American continent, occupying over 2,785,600 km2 not including the Antarctic territory. The country ranges from subtropical areas (21º46’S) to subantarctic regions (55º03’S), extending latitudinally over about 4,000 km. It possesses significant latitudinal and altitudinal variation (33º of latitudinal range, and heights from Bajo de San Julián in Santa Cruz province at 105 m below sea level, up to Mt. Aconcagua, 6,959 m over sea level), as well as two gradients of physical variability, extending in north-south and east-west directions. Owing to these features, the country presents a wide range of climates and soil types, being one of the countries with greatest diversity of biogeographical units (Lean et al., 1990, In: Bertonatti & Corcuera, 2000). There are four main hydrographic systems: Río de la Plata basin, the Atlantic and Pacific drainages, and several endorrheic systems. Within these basins, the ichthyofaunistic assemblage is well represented, with different magnitude in accordance with the different taxonomic groupings and regions considered. From an ichthyogeographic standpoint, and according to the works of Ringuelet (1975) and Arratia et al. (1983), Argentina is included in the Brasilic and Austral Subregions. The first of these is represented by two domains: the Andean Domain, comprising the southernmost portion of Titicaca Province, and the Paranensean Domain, including part of Alto Paraná and Paranoplatensean Provinces. The Austral Subregion is represented in Argentina by the Subandean-Cuyan and Patagonian Provinces. The present survey indicates that there are about 441 fish species in Argentina, distributed throughout the country; this number represents less than 10% of the total fish species occurring in the Neotropical Region. There is a recognizable trend of faunal impoverishment, both in North-South and East-West direction, reaching its maximum expression in the provinces of Tierra del Fuego (situated at approximately 52º30’S to 55ºS, and 65ºS to 68º50’W) and San Juan (approximately 28º50’S and 67ºW to 70º45’W), which have 4 and 5 fish species respectively. In north-south direction, one of the regional indicators of this phenomenon is the Salado river basin in Buenos Aires province, which constitutes the southern distributional boundary for the majority of the paranoplatensean ichthyofauna; 12 of the families occurring in the Paraná-Plata system are absent from this pauperized paranensean ichthyofaunal assemblage. Most of the continental fish fauna of Argentina belongs to the primary division of Myers (1949), while some elements are included in the secondary division and others in an amphibiotic or ‘marine penetration’ category. This ichthyofaunistic scope encompasses a wide range of morphological, biological, ecological and ethological types (benthic and pelagic, migrating and sedentary, haematophagous or parasites, annual species, inhabitants of plains or heights, estivation-adapted, etc.) inhabiting different regions within the national territory.

Consideraciones sobre las percas (Percichthys colhuapiensis y P.trucha) de la Patagonia norte - Años 1955 a 1957. Comparaciones con material de años recientes.

Este trabajo se basa en los muestreos sobre las percas (Percichthys sp) realizado entre los años 1955 a 1957 por María Luisa Fuster de Plaza y Enrique E. Boschi, ambos investigadores se desempañaban en el Departamento de Investigaciones Pesqueras de la Dirección Nacional de Pesca, dependiente del Ministerio de Agricultura y Ganadería de la Nación de entonces. Las tareas se llevaron a cabo principalmente en varios cuerpos de agua léntica y lóticas de la región de la Patagonia Norte (Provincias de Río Negro, Neuquen y Chubut), y en la provincia de Mendoza. Consisten en datos morfométricos, desarrollo gonadal, fecundidad, contenidos alimenticios, planillas, dibujos, etc. de 80 ejemplares de percas. La autora tuvo a su cargo el análisis de los datos de esos muestreos y las comparaciones con estudios de material más reciente, correspondiente al lago Pellegrini, a partir de 1981.

The aquatic biota of the now extinct lacustrine complex of the Mexico basin

The commonest organisms of the original Mexico lake complex are listed, including those that exist today in the Lago Viejo. In addition, a brief hydraulic history of this endorheic basin is given.

Megacylops viridis Jurine, abyssal form in Lake Maggiore. [Translation of: Memorie dell'Istituto Italiano di Idrobiologia Dott.Marco de Marchi 17 57-79, 1964]

Megacyclops viridis Jurine, noticed in Lago Maggiore in 1912 by De Marchi from the littoral vegetation of Pallanza, is a normal member of the littoral plankton of the lake. The subgenus Megacyclops, created by Kiefer in his revision of the viridis-vernalis group, contains european and american species some of which are today considered as varieties of the species viridis. This paper examines morphology and of the distribution of the Italian viridis in Lake Maggiore.

Paleoenvironmental records from the Quelccaya ice cap, Peru and preliminary results from the Dunde ice cap, China [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The 1000 year records of particulate deposition (soluble and insoluble), oxygen isotopic ratios, and net accumulation from the Quelccaya ice cap are presented. The net accumulation record from Quelccaya is shown to serve as a reasonable proxy for the water levels in Lake Titicaca. ... The ice core record from the Dunde ice cap offers the potential to reconstruct a very detailed history of environmental conditions on the Tibetan Plateau for the last 3000 years.