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Detailed studies of Chironomidae fauna can yield a reliable tool to evaluate the effects of climatic change and anthropogenic disturbances over freshwater ecosystems. Using modern chironomid remains deposited in surface sediment samples of 27 lakes located in south-central Chile (37° S–41° S), we investigated the spatial distribution and diversity of chironomids in association with climatic and limnological variables. Linear methods and ordination analyses were used to select the best explanatory environmental variables that influence the diversity and distribution of chironomids among sites. We identified 52 chironomid taxa, highlighting Tanytarsini-tribe, Ablabesmyia, and Parapsectrocladius as the most common. Our results suggest air temperature as the most important and significant factor controlling the distribution of chironomids among the Araucanian lakes, followed by water temperature, and dissolved oxygen. The diversity of chironomids is negatively correlated with parameters related to lake productivity. Orthocladiinae and Podonominae subfamilies are most frequent in high-altitude lakes associated with cold temperatures, whereas Chironominae and Tanypodinae are characteristic of lowland-lakes influenced by higher temperatures. Human-induced contamination of freshwater ecosystems and the ongoing climate change in south-central Chile represent the main threat to macroinvertebrates communities, and therefore a challenge to predict the trajectories of chironomid assemblages in the near future.

Craspedacusta is a freshwater jellyfish that has been introduced to Chilean lakes. Blooms of the medusa stage of Craspedacusta were first detected in an artificial water body in Valparaiso ...

Craspedacusta sowerbii is a global invader of inland waters, but little is known on what environmental factors control its colonization success. We hypothesized that water transparency and thus, exposure to UV radiation are relevant for the colonization success of this relatively transparent invasive hydroid. Here we used field and laboratory experiments to assess the effect of natural solar radiation and artificial UV radiation on the medusa stage of C. sowerbii across natural and simulated water transparency gradients in three Chilean Patagonian lakes. Short-term exposure of the jellyfish to artificial UV radiation under low Dissolved Organic Carbon (DOC) treatments induced mortality and caused sublethal effects such as swimming anomalies and production of reactive oxygen species. Outdoor exposure of jellyfish to full solar radiation in the most transparent water (Lake Ranco; DOC = 0.6 mg l−1) resulted in almost complete mortality. However, higher DOC contents provided partial or almost complete protection against the adverse impact of UV radiation. Overall, our findings provide evidence of the role of underwater light conditions in the underlying mechanisms that may favor the invasion of this gelatinous alien species in inland waters. The results imply that under the current “brownification” of lakes, an increase in water color might provide more favorable conditions for the invasion process of this hydroid.

The microalgae Didymosphenia geminata (Lyngbye) Schmidt, commonly known as Didymo or “Rock snot” is an invasive freshwater benthic diatom, native to rivers of the Circumboreal Region of Europe. In Chile, Didymo was first found blooming in the Espolon River (around 44 °S) in Patagonia in 2010. Several years later, Didymo has expanded its range to 3000 km from 38 °S to 53 °S. Genetic information about this alga could improve the early detection and monitoring of this invasive species especially in uncontaminated rivers. Therefore, this information could help managers to make conservation decisions about places threatened by Didymo invasion. Here, a phylogenetic analysis employing two commonly used molecular markers was conducted to identify Chilean Didymo samples from different spatially distant infested rivers. The data presented herein confirm the presence of Didymo in Chile and include the first genetic account of an invasion in South America.

A new record of the freshwater jellyfish Craspedacusta sowerbii in northern Chilean Patagonia is reported. The specimens were collected from Laguna Illahuapi, an oligotrophic shallow lake (15 m maximum depth) in early austral autumn, May 2013. This water body is located in the upper zone of the Rio Bueno basin, Province of Ranco, Region de los Rios, Chile. The region is characterized by a great diversity of freshwater environments with minimal human pressure. This report confirms the presence of C. sowerbii in Chilean Patagonia and represents the southernmost range of distribution of this exotic medusa in South America. This study also contributes additional information on the limnological characterization of this water body.

Laguna Teno (2549 m a.s.l.) is a high elevation oligo-mesotrophic lake located in the area of influence of the active Volcanic Complex Planchon-Peteroa (VCPP) in the central Chilean Andes. The most recent eruption of VCPP was in September 2010. This study compares limnological data registered in Laguna Teno during the summers of 2009 and 2011, preand post-eruptive periods of the VCPP activity respectively. In particular remarkable post-eruption changes of conductivity and slight changes for pH values in the water column of Laguna Teno were detected. In contrast no major variations of trophic parameters of water quality and plankton attributes were observed between the two summer periods. Phytoplankton was mainly represented by the biomass and chlorophylls attributable to diatoms, dinophytes and chlorophytes, with distinctive patterns of vertical segregation. Zooplankton was constituted by a very simple community comprising the copepod Boeckella gibbosa, the cladoceran Daphnia gr. pulex and a population of rotifers of the Hexarthra genus. This study represents the first limnological characterization of Laguna Teno and the first biogeographical report of a melanized population of the Daphnia pulex complex living in a deep high altitude Chilean lake. The limnological attributes of Laguna Teno, particularly the noticeable presence of large sized pigmented Daphnia in summer allow us to: i) infer the biological responses of Daphnia to extreme conditions; ii) support the hypothesis that Teno is currently a fishless lake. The latter presumption is consistent with the lethal effects on fish registered on the watershed of Teno and Claro rivers after the eruption of VCPP in 1991. Key-words: Boeckella gibbosa, Daphnia pulex complex, Hexarthra, volcanic lake, Andes. Fundam. Appl. Limnol. Vol. 183/4 (2013), 323–335 Article Stuttgart, December 2013 © 2013 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany www.schweizerbart.de DOI: 10.1127/1863-9135/2013/0551 1863-9135/13/0551 $ 3.25 Introduction Chile is part of the geographical zone known as the ‘Pacific Ring of Fire’. This area boasts over 2000 eruptive centers of which more than 500 are geologically active, and at least 60 of them have presented some kind of important eruptive activity in the last 450 years (Gonzalez-Ferran 1995). Along the country, from north to south, an important number of large lakes of glacial origin, distributed between 0 to 4000 m above the sea level (a.s.l.), are located at the foot of volcanoes. Unlike the large North Patagonian lakes of Chile (Thomasson 1963), generally there is scant knowledge on the limnological features of the volcanic lakes of the country. In addition the effects of active volcanism on the physical-chemical features and the ecology of limnic systems have been poorly studied. Many volcanic eruptions of different intensities and durations

Among the topics covered by Hutchinson’s Santa Rosalia article, the question of the shortening and lengthening of food webs occupies a central role. As Hutchinson realized, at the time scales of ecological studies, the impact of invader species on established food webs is the fastest shortcut to the shortening or lengthening of the food webs. The construction of thousands of dams in Spain during the last century has offered ecologists a good opportunity to test the effects of invader fish species on the plankton dynamics of these systems. In this article, a series of data related to the food web structure of Sau Reservoir is analyzed for the period 1997–2005. Parameters such as Secchi depth and chlorophyll concentration, as well as abundance and size structure of zooplankton, have been matched to the zooplankton dynamics in the reservoir. Most of the changes detected within this period are attributed to the introduction of zooplanktivorous fish in the reservoir. The Secchi depth measurements have showed a progressive diminution in the clear-water phase during recent years. These changes have been related to the decrease in the abundance of Daphnia and to the reduction of the size of zooplankton, which help to explain concomitant increases in the chlorophyll concentration in the same period. Other observed changes in the composition of the zooplankton community have been the substitution of Daphnia by Bosmina and the increase in the abundance of rotifers. Thus, the annual average abundance of Bosmina in 1997 was 70% of cladocerans, while in 2005 it reached 98%. In parallel, the percentage occurrence of individual rotifers was 40% of total zooplankton numbers but had risen to 85% at the end of the period. All these changes are attributed to the artificial expansion of the food web through stocking of the reservoir with zooplanktivorous fish (Rutilus rutilus and Alburnus alburnus). This study improves our understanding of the trophic relationships in the food web prior to the introduction of the fish.

The control of phytoplankton growth is mainly related to the availability of light and nutrients. Both may select phytoplankton species, but only if they occur in limiting amounts. During the last decade, the functional groups approach, based on the physiological, morphological and ecological attributes of the species, has proved to be a more efficient way to analyze seasonal changes in phytoplankton biomass. We analysed the dynamics of the phytoplankton functional groups sensu Reynolds, recognising the driving forces (light, mixing regime, and nutrients) in the Sau Reservoir, based on a one-year cycle (monthly surface-water sampling). The Sau Reservoir is a Mediterranean water-supply reservoir with a canyon-shaped basin and a clear and mixed epilimnion layer. The long stratification period and high light availability led to high phytoplankton biomass (110.8 fresh-weight mg L(-1)) in the epilimnion during summer. The reservoir showed P-limitation for phytoplankton growth in this period. All functional groups included one or more species (X2-Rhodomonas spp.; Y-Cryptomonas spp.; F-Oocystis lacustris; K-Aphanocapsa spp.) selected by resources, especially phosphorus. Species of Cryptomonas (group Y) dominated during the mixing period (winter season) in conditions of low light and relatively high availability of dissolved nutrients. Increases in water-column stability during spring stratification led to phytoplankton biomass increases due to the dominance of small flagellate functional groups (X2 and X3, chrysophyceans). The colonial chlorophycean O. lacustris (group F) peaked during the mid-summer stratification, when the mixed epilimnion was clearly depleted in nutrients, especially SRP. High temperature and increases in nutrient concentration during the end-summer and mid-autumn resulted in a decrease of green algae (group F) and increase of Aphanocapsa spp. (cyanobacteria, group K) and dinoflagellates (group L(o)). The study also revealed the important role of physical processes in the seasonal gradient, in selecting phytoplankton functional groups, and consequently in the assessment of ecological status. The Q index (assemblage index) based on functional groups indicated the overall good ecological status of the Sau Reservoir, which varied as a function of the mixing regime. This is the first application of the Assemblage Index to a European water-supply reservoir.

During summer 2001, zebra mussels (Dreissena polymorpha Pallas) were found (500 adults m−2) in the coupled reservoir system composed by Mequinenza, Riba-Roja and Flix (Ebro River, Northeast Spain). Two years later, mussels achieved densities of 4000 adults m−2, representing the first record of successful colonization by zebra mussels in the Iberian Peninsula. An August 2003 study investigated the environmental conditions that support the successful settlement of the zebra mussel populations during the stratification period. Flow patterns in the whole system and mussel populations near the dam were characterized. Chemical characteristics of water inputs, not the usual thermal stratification, determine the deep circulation of the Ebro River along the Riba-Roja reservoir, whereas water input from one tributary into Riba-Roja flows along the top of the water. Physico-chemical stratification of the water column seems to control the observed vertical distribution of zebra mussel biomass. Larger biomass...

Durante 2010 varias proliferaciones masivas de salpa subantartica, Ihlea magalhanica, fueron registrados en el mar interior de Chiloe (MICh, sur de Chile), que afecto la abundancia de fitoplancton y a los productores de salmon al causar altas mortalidades de peces. Las primeras proliferaciones se registraron en febrero de 2010, cuando la abundancia de I. magalhanica alcanzo 654.000 ind m-3 cerca de las balsas jaulas en isla Maillen. Proliferaciones consecutivas fueron posteriormente registradas durante marzo y de octubre a noviembre de 2010. Un mes antes de los registros de las primeras proliferaciones, la region oceanica adyacente y el MICh evidenciaron un fuerte descenso en la temperatura superficial del mar de ca. 1°C y un patron atipico de las corrientes oceanicas superficiales, cambiando desde una circulacion predominantemente meridional (norte) a zonal (hacia el este), probablemente causando el ingreso de una parcela de agua subantartica al mar interior de Chiloe. Durante las proliferaciones, la concentracion de clorofila (Clor-a) superficial disminuyo de una media historica de 13,8 a menos de 4 mg Clor-a m-3, manteniendose bajo los promedios historicos durante todo ano 2010. Resultados similares se observaron tambien en la abundancia de fitoplancton. La abundancia de las concentraciones de salpas fueron mayores cerca de las balsas jaulas de salmon, que actuan como barreras fisicas, concentrando los organismos y posiblemente favoreciendo el exito reproductivo y la persistencia de estas proliferaciones durante el 2010. Se discute el posible impacto de estas proliferaciones en la calidad y cantidad de fitoplancton, asi como los posibles escenarios para el desarrollo de nuevos eventos.