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We reported the presence of Peridiniopsis borgei Lemmermann in La Encantada lake (Province of Huaura) and studied the specimens using optical and scanning electron microscopical techniques. The population of P. borgei showed a variation in the number and degree of development of the marginal ridges. This is the first illustrated report of the species in Perú.

Although planktonic diatoms are one of the most abundant taxonomic groups in coastal wetlands, their assemblages have not been used to determine the environmental health of these ecosystems. Studies of ecosystem environmental health have been based on other taxonomic groups; we propose that diatom genera diversity represents a viable alternative for this purpose. Thus, our aim was to determine the alpha and beta diversities of the planktonic diatom assemblage present in Caulín Bay, Chiloé Island (41° 49’S; 73° 38’O), southern Chile, during the austral winter and spring of the years 2012 and 2014. Inasmuch Caulín Bay is an important site for aquatic bird observation and conservation, hunting is prohibited on a national scale and, internationally, the site has been declared an Important Bird and Biodiversity Area (IBA). Our results indicate different diversities between sampling stations, but not between the years studied. In total, we recorded 53 diatom genera, of which the most abundant were Coscinodiscus (21.99%) and Cocconeis (16.23%). The study area presented high genera diversity (i.e., H’(log2) >3.74) and beta diversity indicated that Caulín presents a low level of heterogeneity and is a low genera replacement environment. Consequently, we infer that Caulín Bay is productive and environmentally stable ecosystem. This leads us to conclude that diatom diversity determination is a viable alternative to establish aquatic ecosystem environmental health and we recommend that future conservation strategies be established for Caulín Bay.RESUMENSi bien las diatomeas planctónicas son uno de los grupos taxonómicos más abundantes de los humedales costeros, sus ensambles no se han utilizado para determinar el estado ambiental de estos ecosistemas. Aunque se han realizado estudios de la salud ambiental de un ecosistema utilizando otros grupos taxonómicos, nosotros proponemos que la diversidad de géneros de diatomeas representa una alternativa viable. Por lo tanto, el objetivo de este estudio fue determinar las diversidades alfa y beta del ensamble de diatomeas planctónicas presentes en la Bahía de Caulín, Isla de Chiloé (41 ° 49’S; 73 ° 38’O), sur de Chile, durante las temporadas de invierno y primavera austral de los años 2012 y 2014. Bahía Caulín es un sitio importante para la observación y conservación de aves acuáticas por lo que a nivel nacional se ha prohibido la caza y a nivel internacional fue decretada un Área Importante para la Conservación de Aves, AICA. Los resultados de este estudio indicaron diferencias en las diversidades entre las estaciones de muestreo, pero no entre los años estudiados. En total, se identificaron 53 géneros de diatomeas; los más abundantes fueron Coscinodiscus (21,99%) y Cocconeis (16,23%). El área de estudio presentó una alta diversidad de géneros (i.e., H’(log2) >3.74) y la diversidad beta indicó que Caulín presentó bajo nivel de heterogeneidad y es un entorno con bajo reemplazo de géneros. Así, inferimos que Bahía Caulín es un ecosistema productivo y ambientalmente estable, por lo cual concluimos que la determinación de las diversidades de diatomeas es una alternativa para establecer la salud ambiental de los ecosistemas acuáticos y recomendamos establecer futuras estrategias de conservación para Bahía Caulín.PALABRAS CLAVE: diatomeas, diversidades ecológicas, plancton, humedales costeros, desembocadura

In this study, the diatom Entomoneis paludosa (W. Smith) Reimer is reported for the first time from Salar de Ascotán, in the Región of Antofagasta, Chile. Only isolated valves were found, and the species is described using light and electron microscopy techniques. Comments about its morphology and ecology are also given. Till now E. paludosa had been reported only from other four Chilean localities.

Background: The invasive diatom Didymosphenia geminata (Lyngbye) M. Schmidt has received considerable attention in recent years due to its rapid geographic expansion and massive proliferation, which have altered habitat availability for benthic species and triggered negative effects on stream ecosystems. We evaluated the changes in the community structure of phytobenthos caused by the temporal variation in D. geminata coverage, in addition to the environmental variables correlated with the temporal variation of this invasive microalga in the Andean sector of the Biobio River basin, Chile. Methods: Environmental parameters were measured during the austral summer of 2014-2015, when phytobenthos samples were collected and used to develop a relative abundance matrix of taxa by calculating species richness and Shannon diversity. Multivariate techniques were used to establish the relationships among environmental variables, including D. geminata coverage, and the phytobenthic community. Results: Massive proliferation of D. geminata occurs during summer (December-January). According to multiple regression analysis, electrical conductivity, temperature and total phosphorus were the variables that best explained the variation in D. geminata coverage. When D. geminata coverage was over 50%, phytobenthic species richness was significantly higher than at the uninvaded site, without a significant change in Shannon diversity. In addition, the % coverage of this invasive microalga and total phosphorus concentration were variables that differentiated phytobenthic communities among the study sites. Conclusions: Environmental factors such as conductivity, temperature and total phosphorus concentration influenced the temporal variability of D. geminata mats. In addition, the massive growth of this invasive diatom caused a higher species richness without altering Shannon diversity. Our results suggest that the spatio-temporal variability of D. geminata correlated with environmental variables will help predict the habitat suitability of this alga in other Andean rivers and allow a better understanding of ecological habitat alterations.

Se describe a Frankophila sudamericana Rivera & Cruces como una nueva especie de diatomea. El taxón se caracteriza por poseer valvas linear-elípticas, estrías (10 en 10 μm, raramente 9) formadas por tres hileras de aréolas, espinas huecas y no bifurcadas, y por su área axial plana y carente de depresiones. Se señalan las principales diferencias existentes con las restantes especies del género, especialmente con F. wayqechae Furey et al.

Naiadinium polonicum is a dinoflagellate widely distributed in lakes and reservoirs of the Northern Hemisphere, sometimes associated with fish mortality by production of toxins. During May 2013 a massive proliferation of this species was detected in Rapel Reservoir (34°10’S, 71°29’W). In the present paper a morphological study of the species was performed using light and electron microscopical techniques. This is the first record of N. polonicum for Chilean continental waters. The morphological characters of the specimens analyzed are consistent with the descriptions and illustrations found in the literature. In this study, Naiadinium polonicum was considered as a conspecific taxon to Naiadinium biscutelliforme, and we considered the species to be variable with relation to the number and relative size of the intercalary plates (1-2a). Naiadinium polonicum reached a maximum concentration of 2572 cells/mL, and since this phenomenon was observed only once we preliminary attributed the high content of nutrients (66 μgL-1 PT, 645.67 μgL-1 NT) available in the water column as the preponderant factor that probably caused the proliferation.

The freshwater diatom Didymosphenia geminata was studied from Chilean material collected in Río Espolón and Río Bío-Bío using light and electron microscopy. Its principal morphological features are described and illustrated for the first time and comments about its relationships with other closely taxa, as well as its distribution in Chile, are given.

Las diatomeas de la zona de rompiente de las olas constituyen un grupo reducido de especies que producen acumulaciones masivas sobre playas arenosas con fuerte oleaje, a menudo como unicas dominantes de la comunidad. Se unen a las burbujas generadas por el oleaje y forman masas flotantes de color marron o verde, de forma irregular, las que luego con la marea se depositan sobre la playa formando franjas largas. En mayo de 2015 una de estas acumulaciones, de color verde, fue detectada en la Bahia de Coquimbo. El analisis de las muestras mediante microscopia optica y electronica de barrido demostro la presencia de la diatomea Aulacodiscus kittonii, un taxon muy conocido por participar en este tipo de eventos. Este es el primer registro para Chile y para el Pacifico Sur Oriental, evento en el cual A. kittonii fue la especie dominante, como tambien el primer registro para Chile de A. kittonii como una especie viviente. Se entrega una descripcion de los especimenes chilenos y se comenta e ilustra la variabilidad de algunas de sus caracteristicas morfologicas.

Especímenes de Craspedostauros indubitabilis (Lange-Bertalot & Genkal) E.J. Cox provenientes de una muestra recolectada en Bahía Salada, Caldera, Chile (27°38'S-71°00'W) fueron oxidados y examinados mediante técnicas de microscopía fotónica y electrónica. El género y la especie son señalados por primera vez para las aguas marinas costeras de Chile. Craspedostauros fue descrito por Cox en 1999 para reunir algunas diatomeas marinas birrafidales, ubicadas hasta esa fecha en los géneros Stauroneis Ehrenberg y Stauronella Mereschkowsky. El género puede ser reconocido por sus aréolas provistas de cribra, un estauro angosto, numerosas bandas en el cingulum y dos cloroplastos en forma de H con una peculiar disposición en la zona central. De acuerdo con el material chileno, Craspedostauros indubitabilis se caracteriza por poseer valvas linear-elípticas a lanceoladas con extremos generalmente redondeados, las estrías (22-30 en 10 μπι) son paralelas en el centro de la valva y levemente convergentes cerca de los extremos, las aréolas adyacentes al rafe son de mayor tamaño que las restantes, cada aréola está ocluida por 3 a 13 poros, y un engrosamiento de sílice separa los extremos proximales internos del rafe. Se provee una diagnosis de este taxón basado en las características observadas en el material chileno. Las fotomicrografías que se presentan entregan información acerca de sus principales características morfológicas.

Several lakes in Chile are near important volcanic areas where eruption impacts can limit the quality of lacustrine sediments for reconstructing past enviro nmental changes. In this study, we report changes i n diatoms, pollen, and chironomids assemblages after a tephra deposition in Lake Galletue (Chilean Andes). A sedi ment core obtained from Lake Galletue (40 m water depth) was sliced in 1 cm intervals and subsamples were t aken to analyze each proxy. 210 Pb and 137 Cs activities were measured to obtain the geochrono logy and mineralogical analyses were performed to determine the mineral co mposition of the tephra. Diatom species composition and productivity were modified when the lake received t he tephra; Aulacoseira granulata decreased and was later replaced by Cyclotella af. glomerata. After the tephra input, Aulacoseira granulata abundance increased to predisturbance levels and Cyclotella af. glomerata decreased. These changes seem to suggest a momentary increase in lake nutrient levels after the tephra deposition . Chironomid assemblages also decreased in head capsules just after the tephra deposition, but the most important change was the replacement of Ablabesmyia by Parakiefferiella, probably due to the sedimentological changes produced by the input of coarse tephra grains. Furthermore, unlike other studies, chironomid assem blages in Lake Galletue did not show a decrease dra stically in diversity within the tephra layer. The pollen an alysis indicated that, prior to the volcanic event, the vegetal community was dominated by Nothofagus sp., Araucaria araucaria, and Blechnum sp.-type. After the tephra deposition, the same taxa are dominant, indicating that the volcanic event seems not produce changes i n the vegetation. Nevertheless, within the tephra layer i t is possible to see an increase in Poaceae, which represent due to the percolation process - the effect of erup tion on the vegetation. According to our results, d iatoms were the most sensitive proxy for describing the changes produced by tephra deposition into the aquatic eco system and, despite the noticeable changes in its sediment ological properties; the lake seems to have a high resilience capacity, allowing it to return to pre-tephra input conditions.

Stephanodiscus kuetzingii Klee & Casper, described from a Pleistocene deposit in the Luneburger Heide, Lower Saxony, Germany (Kutzing type material for Cyclotella minutula), was found living in Rapel Reservoir, Central Chile. There are no published records of living material for this species. Its valve morphology was studied using light and scanning electron microscopy. The morphological features of the Chilean specimens are in good agreement with those of S. kuetzingii described by Klee and Casper. The present study provides additional information on rimoportula structure, in which a long external tube was observed, as well as on the presence of a narrow circumferential hyaline area at the valve face/mantle junction of convex valves. The similarities and differences between S. kuetzingii and other closely related Stephanodiscus species are discussed.

The taxonomie position of Cyclotella andina Theriot, Carney et Richerson, a tropical freshwater planktonic diatom originally identified from Lake Titicaca, is modified based on morphological characters. The presence of striae arranged in discrete fascicles on the valve- face, coupled with the placing of fiilto- and rimoportulae on the same internal costa below the position of external spines (or on the valve face/mantle region in spineless individuals), form the basis to transfer this species from the genus Cyclotella Kutzing to the genus Cyclostephanos Round. Morphometric analyses of 350 valves from seven populations from three Andean lakes demonstrate a morphological continuum in fossil and modern assemblages. Principal Component Analysis (PCA) shows that three main factors characterize most of the variability in morphology. PCI (λ1 = 71.7%) is a size-related component (e.g. valve diameter); PC2 (λ2 = 23.9%) is a size-free component that relates the length of biseriate to uniseriate areolae, and PC3 (λ3...

Lioloma elongatum is the only species of the genus recorded for the South Pacific Ocean off the coast of Chile. Although it has been reported between 22°S and 29°S, we found the species widely distributed in the region. We provide a description and illustrate the morphology of the Chilean individuals for the first time, and also comment on the variability of some characteristics of the frustule.

The marine small diatoms Nitzschia amabilis, Nitzschia elegantula and Chaetoceros muelleri var. subsalsum are reported for the first time from Chilean coastal waters. A short diagnosis is included for each taxon, and photomicrographs provide information about the main morphological characteristics.

Durante el analisis de cepas provenientes de muestras de fitoplancton marino se observo que una de ellas contenia celulas muy pequenas, aisladas o formando cortas cadenas de 2-4 individuos. Observaciones realizadas con microscopia electronica revelaron la presencia de Extubocellulus spinifer (Hargraves & Guillard) Hasle, Stosch & Syvertsen, una diminuta especie no senalada hasta ahora para el Pacifico Suroriental. En el presente trabajo se describen las caracteristicas de las celulas chilenas, se comenta acerca de la variabilidad de algunas de sus caracteristicas morfologicas, y se discute sobre las diferencias entre las dos especies conocidas del genero.

En este estudio se senala la presencia de la diatomea Stephanodiscus minutulus (Kutzing) Cleve & Moller por primera vez para aguas continentales de Chile; es un taxon muy comun en diversos sistemas acuaticos de Europa y Norteamerica, y para Sudamerica solo existen escasos registros en Argentina. La especie fue encontrada en un perfl sedimentario colectado en el Lago Laja (Cordillera de los Andes), Chile central. Se describen las principales caracteristicas morfologicas de S. minutulus y se entregan comentarios sobre su relacion con otras especies cercanas.

A sediment core encompassing the last 2000 years was extracted from Lake Laja, Chile, (36°54′S, 71°05′W) using an Uwitec drilling platform. The sediment was subsampled for loss on ignition, nutrients, biogenic silica, and biological proxies (diatoms, chironomids, pollen). The sedimentary profile was characterized by several coarse volcanic layers. Loss on ignition, nutrients, and biogenic silica showed an increasing trend that suggests a recent shift to a higher trophic status. Diatom assemblages also suggested higher nutrient content with increased abundances of Aulacoseira granulata, A. distans, and Asterionella formosa. At the same time, a marked change in the benthic and facultative planktonic taxa may be associated with cooling. This period of change coincides with the European Little Ice Age (LIA). The chironomid profile showed four key zones distinguished largely by changes in the abundance of Tanytarsini, Parachironomus, and Macropelopia. Like diatoms, chironomids also seemed to reflect a shift to higher trophic conditions in the upper part reflected by increasing abundance of taxa such as Tribelos/Phaenopsectra, Cricotopus/Orthocladius, and Ablabesmyia. The most striking feature in the chironomid assemblage is the abundance of Podonominae, Parapsectrocladius, and Limnophyes/Compterosmittia, which could be associated with a cold-dry period between 1500 and 1900 AD in Lake Laja (the period of the European LIA). Pollen assemblages indicated fluctuations in humidity through changes in Nothofagus dombeyi-type, Poaceae, and Ephedra, and we inferred a strong human impact over the last 100 years from the appearance of Plantago and increased levels of Poaceae and Asteraceae subf. Cichorioidae. Finally, the three proxies showed the occurrence of a cold-dry event in Lake Laja (~1550–1900 AD), which roughly coincides with the European LIA. However the data from this research, does not prove neither rejects the existence of the occurrence of the MWP in the central Andes.

This note reports the first finding of Haloroundia speciosa (Hustedt) Diaz et Maidana (Bacillariophyceae) in a sample collected from the Salar de Aguas Calientes, Loa Province, northern Chile (23°30'S; 67°33'W). This species is restricted to the Andes Mountains. Comments about its morphological features and geographical distribution in north Andean areas are given.

En este trabajo se analizo la estructura comunitaria de diatomeas depositadas en los sedimentos superficiales de ocho lagos andinos chilenos ubicados entre los 32°49' y 38°48' S. Se encontro un total de 99 taxa de diatomeas, distribuidos en 48 generos. Del total de taxa, 74 fueron identificados a nivel de especie siendo todos ellos cosmopolitas a excepcion de Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis y Pinnularia acidicola, entre otras, que estan descritos solo para el Hemisferio Sur. Por otro lado, las muestras analizadas presentaron distinta composicion floristica de diatomeas. De esta manera, en los ensambles diatomologicos depositados en los sedimentos de las lagunas de altura Ocho, Huifa, Ensueno y Negra ubicadas sobre los 2.860 m del nivel del mar, abundaron especies bentonicas, tipicas de aguas oligotroficas y acidas como Achnanthidium exiguum, Achnanthidium minutissimum, Encyonema minutum, Pinnularia acidicola y Planothidium lanceolatum. En los ensambles diatomologicos de los lagos Galletue, Icalma y Laja, ubicados bajo los 1.360 m del nivel del mar, abundaron diatomeas planctonicas, caracteristicas de aguas alcalinas y mesotroficas como Asterionella formosa, Aulacoseira distans, Aulacoseira granulata, Cyclotella stelligera y Rhopalodia gibba

Past ice lobe behaviour at Laguna San Rafael is described in documents provided by Spanish and then Chilean explorers from the late seventeenth to the early twentieth centuries. These records begin in AD 1675, when temperate conditions, probably similar to those at present, prevailed. At that point, the glacier was confined within its valley, not penetrating the Laguna. The glacier advanced noticeably during the nineteenth century and probably reached a maximum position for the `Little Ice Age' around AD 1875. The historical sources suggest a slight retreat in AD 1904 in relation to the conditions prevailing 29 years earlier. The historical data show that the eighteenth to nineteenth century cooling period at San Rafael glacier was within the temporal window of the European `Little Ice Age'. This work provides independent, direct historical evidence for the occurrence of this event in southern Chile.

The chemical characteristics of the waters of Lake Budi (IX Region, Chile), in winter and summer were analysed in order to establish seasonal variations and determine their influence on the various phytoplankton components. On the basis of the results it was possible to indicate that the chemical parameters found in the water body under examination vary in time and space, giving rise to different algal communities. The strong influence of salinity on the phytoplankton communities in both study periods appears to result principally from the influence of the sea, resulting from the intrusion of salt water during certain periods of the year. The predominant chemical characteristic in summer indicates a slight reduction in water quality, due to a rise in temperature and a reduction in the oxygen concentration. Keywords: Lake Budi, salinity, phytoplankton, water quality.INTRODUCTIONPhytoplankton constitutes the most important primary producer, and is a fundamental food source for consumers in many continental aquatic systems [1-2-3]. However the wide spectrum of organisms of which it is made up and the limnological characteristics which may be encountered in each individual system have hindered understanding of the processes involved in population dynamics [4]. In general, it has been established that the determining factors for the structure of phytoplankton communities in lakes result from the relationship which exists between the physical, chemical and biological parameters present in a water body [5]. Several studies carried out in freshwater environments have established that the growth of phytoplankton may be controlled to a large degree by the limitation of nutrients [6-7], the availability of light [8] and the composition and abundance of zooplankton [9]. It has also been determined that in coastal lakes which are subject to marine influence during some period of the year, salinity may also be a factor affecting the growth and distribution of phytoplankton [10-11]. The above is a consequence of the problems in osmotic regulation produced by the intrusion of sea-water, both for freshwater and marine organisms [12]. Under natural conditions, it has been determined that phytoplankton respond in a regular manner to the variations in their environment which occur in an annual cycle [13-14]. This is largely a consequence of changes to the physical characteristics and the stability of the water column. As a result, the varying algal components of the phytoplankton in a lake are a clear indicator of its environmental state. In this respect, an analysis of the composition and presence of species, their abundance and biomass, can provide the information needed to evaluate the ecological state of lacustrine systems. However, phytoplankton communities do not respond only to natural changes into the lakes, but may also present variations as a consequence of human interventions affecting the water body, either directly or through activities carried on in the basin as a whole. These influences affecting the lakes result in modifications to the structure and composition of the phytoplankton, which may take the form of changes in the taxa of which the algal associations are composed, in the abundance of each taxa, the richness and diversity of the associations, and other community parameters. Finally, due to the interdependence existing between the different organisms of which systems are composed, these variations in the phytoplankton communities translate into changes to the trophic chain and the productivity of the lakes [15]. Lake Budi constitutes a coastal lacustrine system where there is a strong marine influence due to the intrusion of salt water during certain periods of the year. Moreover, in recent decades there has been considerable human intervention in the basin. These two characteristics are indubitably determining factors in the physical and chemical conditions of the water column in the lake.As proposed, the aim of this study was to establish the physical and chemical parameters of the water which have the greatest influence, and which determine the algal associations present in the phytoplankton of Lake Budi.EXPERIMENTALArea of the study and sample collectionLake Budi (38o 52’ S; 73o 18’ W) is a coastal lake which is connected sporadically to the sea. Different bio-types may be recognized in the composition of its surroundings: banks, either covered with vegetation or bare; mud-sand beaches; and sediments with a high content of organic material derived from aquatic plants [16].Based on the special characteristics of Lake Budi and the contribution of its principal tributaries (Budi, Temo, Allipen, Comue, Bolleco and Botapulli), nine sampling stations were established: Rio Budi, Temo, Allipen, Comue, Bolleco, Botapulli, Deume 1, Deume 2 and Deume 3 (Fig. 1). To account for the marine influence present in Lake Budi, samples were taken at two times of year, the first in July 2004, representing the state of the lake in winter, and the second in January 2005, reflecting summer conditions. Two samples were taken at each sampling station: a surface sample (20cm) and a deep sample (1 m), with the exception of the Rio Budi station, where only surface samples were taken due to the shallowness of the water at the time of sampling. Chemical Analysis Eight physical and chemical parameters for water quality were established for this study: temperature, pH, salinity, oxygen in solution (OS), biochemical oxygen demand (BOD), total suspended solids (TSS), organic suspended solids (OSS) and nitrates. These were determined by extracting water samples using a Ruttner bottle, with each sample taken in duplicate. Consideration was given to conditions at sampling, the type of container, preservation and the maximum time-lapse between the taking and the analysis of the sample [17-18].e-mail: jtapia@utalca.cl

This paper describes lake sediment spheroidal carbonaceous particle (SCP) profiles from Laguna Chica San Pedro, located in the Biobío Region, Chile (36 degrees 51' S, 73 degrees 05' W). The earliest presence of SCPs was found at 16 cm depth, corresponding to the 1915-1937 period, at the very onset of industrial activities in the study area. No SCPs were found at lower depths. SCP concentrations in Laguna Chica San Pedro lake sediments were directly related to local industrial activities. Moreover, no SCPs were found in Galletué lake (38 degrees 41' S, 71 degrees 17.5' W), a pristine high mountain water body used here as a reference site, suggesting that contribution from long distance atmospheric transport could be neglected, unlike published data from remote Northern Hemisphere lakes. These results are the first SCP sediment profiles from Chile, showing a direct relationship with fossil fuel consumption in the region. Cores were dated using the 210Pb technique.

Galletue Lake (38° 41'S; 71° 17'W,IX Region-Chile) is located in an area that is highly influenced by eruptive activity of the Lonquimay and Llaima volcanoes. As a consequence, during the last century tephra was deposited into the lake. Sedimentary diatom assemblages were reconstructed in order to establish the tephra effect on their composition and productivity. This was done by taking a sediment core from Galletue Lake at 40m depth and sectioning it in 1 cm intervals. The core age was obtained with 210 Pb and 137 Cs activities and the mineral composition of the tephra was determined with mineralogical analyses. Furthermore, sedimentological analyses were performed and total organic matter was determined in the profile. The diatom assemblages were analysed using light and electronic microscopy. The results showed that the diatom stratigraphy can be separated in three zones recognizing the periods before and after tephra input. Aulacoseira granulata decreased during the tephra influx and was replaced by Cyclotella aff. glomerata. When the tephra disappeared from the sedimentary record, A. granulata returned to pre-volcanic event levels. At the same time, Cyclotella aff. glomerata decreased within the assemblages. Asterionella formosa and Urosolenia eriensis increased after the tephra input, with values surpassing earlier ones. These results indicate that, after the tephra input, the lake recovered its previous nutrient levels, which agrees with the organic matter content in the sedimentary matrix. Finally, the results reveal that the volcanic disturbance changed the structure and productivity of diatom assemblages in Galletue Lake.

We report the first finding of Thalassiothrix spathulata in the marine phytoplankton of Chile. The species was common in samples collected between 18o16'S and 28o06'S. Principal morphological features are described and illustrated

This note reports the finding of Thalassionema pseudonitzschioides (Schuette & Schrader) Hasle in samples collected in Iquique Bay (20°12'S, 70°10'W), in northern Chile. This is the first record of the species for the region. The taxon has been associated mainly with subtropical to temperate waters

La familia Hemiaulaceae comprende cuatro géneros, señalados previamente para las aguas chilenas con las siguientes especies: Cerataulina pelagica (Cleve) Hendey, Hemiaulus sinensis Greville, H. membranaceus Cleve, Climacodium biconcavum Cleve, Eucampia antarctica (Castracane) Mangin, E. cornuta (Cleve) Grunow y E. zodiacus Ehrenberg. Sin embargo, el análisis con microscopía fotónica y electrónica de muestras recolectadas en aguas marinas chilenas que contenían representantes de esta familia (incluyendo la mayoría de aquellas estudiadas anteriormente por otros investigadores nacionales) reveló que (1) el género Cerataulina está representado por C. pelagica, distribuida a lo largo de la costa chilena entre Arica por el norte y el Estrecho de Magallanes por el sur, (2) el género Eucampia está representado por cuatro taxa: E. zodiacus f. cylindrocornis Syvertsen (señalada en trabajos anteriores como E. zodiacus f. zodiacus), E. zodiacus f. recta Rivera. Avaria & Cruces f. nov. (descrita aquí), E. cornuta y E. antarctica. Los primeros tres taxa se distribuyen en la zona central y norte de Chile, mientras que E. antarctica es propia de las aguas antárticas desde el Estrecho de Magallanes al sur, (3) las citas anteriores de Hemiaulus sinensis, H. membranaceus y Climacodium biconcavum para las aguas chilenas corresponden a determinaciones erróneas de Eucampia zodiacus f. recta, f. nov. Se entregan descripciones de los taxa encontrados y fotografías obtenidas con los microscopios fotónico y electrónicos que ilustran sus principales características morfológicas