A study of Hate Speech in Social Media during the COVID-19 outbreak

In pandemic situations, hate speech propagates in social media, new forms of stigmatization arise and new groups are targeted with this kind of speech. In this short article, we present work in progress on the study of hate speech in Spanish tweets related to newspaper articles about the COVID-19 pandemic. We cover two main aspects: The construction of a new corpus annotated for hate speech in Spanish tweets, and the analysis of the collected data in order to answer questions from the social field, aided by modern computational tools. Definitions and progress are presented in both aspects. For the corpus, we introduce the data collection process, the annotation schema and criteria, and the data statement. For the analysis, we present our goals and its associated questions. We also describe the definition and training of a hate speech classifier, and present preliminary results using it.Fil: Cotik, Viviana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil: Debandi, Natalia. Universidad Nacional de Río Negro; Argentina.Fil: Luque, Franco. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Luque, Franco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Miguel, Paula. Universidad de Buenos Aires; Argentina.Fil: Moro, Agustín. Universidad de Buenos Aires; Argentina.Fil: Moro, Agustín. Universidad Nacional del Centro; Argentina.Fil: Pérez, Juan Manuel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil: Serrati, Pablo. Universidad de Buenos Aires; Argentina.Fil: Zajac, Joaquín. Universidad de Buenos Aires; Argentina.Fil: Zayat, Demián. Universidad de Buenos Aires; Argentina

Assessing the impact of contextual information in hate speech detection

In recent years, hate speech has gained great relevance in social networks and other virtual media because of its intensity and its relationship with violent acts against members of protected groups. Due to the great amount of content generated by users, great effort has been made in the research and development of automatic tools to aid the analysis and moderation of this speech, at least in its most threatening forms. One of the limitations of current approaches to automatic hate speech detection is the lack of context. Most studies and resources are performed on data without context; that is, isolated messages without any type of conversational context or the topic being discussed. This restricts the available information to define if a post on a social network is hateful or not. In this work, we provide a novel corpus for contextualized hate speech detection based on user responses to news posts from media outlets on Twitter. This corpus was collected in the Rioplatense dialectal variety of Spanish and focuses on hate speech associated with the COVID-19 pandemic. Classification experiments using state-of-the-art techniques show evidence that adding contextual information improves hate speech detection performance for two proposed tasks (binary and multi-label prediction). We make our code, models, and corpus available for further research

Newly Discovered Sites and Potential Threats for the Critically Endangered Frog, Alsodes pehuenche, in Southern South America

La ranita del Pehuenche Alsodes pehuenche es un anfibio acuático de hábitos nocturnos que habita pequeños arroyos y mallines en la Cordillera Central, próximos al límite entre Argentina y Chile. La Unión Internacional para la Conservación de la Naturaleza (UICN) clasificó a la especie como En Peligro Crítico debido a su restringida extensión de ocurrencia y área de ocupación, así como a la disminución continua en la calidad del hábitat y número de individuos maduros debido a la pavimentación de una ruta, presencia de ganado y presencia de peces exóticos. En esta contribución reportamos el descubrimiento de tres nuevas poblaciones en territorio argentino, extendiendo el rango geográfico 6 km al sudeste y 19 km al noreste de las poblaciones conocidas. Encontramos individuos positivos para el hongo quitridio tanto en las nuevas poblaciones como en las previamente conocidas. También registramos truchas en arroyos habitados y no habitados por la especie y en una ocasión observamos una trucha marrón Salmo trutta depredando sobre larvas de A. pehuenche. Las nuevas poblaciones encontradas enfrentan las mismas amenazas que las poblaciones previamente conocidas, excepto aquellas relacionadas a las obras de pavimentación, lo que implica una necesidad urgente de realizar acciones que aseguren la supervivencia de la especie.The Pehuenche Spiny-chest Frog (Alsodes pehuenche) is a nocturnal aquatic frog that inhabits small streams and wetlands in the Central Andean Cordillera near the border between Argentina and Chile. The International Union for Conservation of Nature (IUCN) classified it as Critically Endangered (CR) due to its small extent of occurrence (EOO) and area of occupancy (AOO), as well as the continuing decline in the number of mature individuals and habitat quality due to road paving, livestock activities, and nonnative predatory fish. From March 2017 to February 2020, we conducted 11 d of research during five field trips to search for tadpoles and adults on the Argentine side of the border. We used information from local communities and satellite imagery to identify potential habitats. We found A. pehuenche individuals in 12 of the 26 sampled streams, which we grouped into three populations. These new populations extend the geographic range 6 km to the southeast and 19 km to the northeast. This increased the EOO fivefold, from 95 km2 to 497.9 km2 . Nevertheless, the AOO remains small at 4.84 km2 . We found individuals positive for Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) in both new and previously known populations. We discovered salmonid fish in streams with and without frogs, and at one location we observed a Brown Trout (Salmo trutta) preying on tadpoles. The newly discovered populations face the same threats as those identified for previously known populations, except for road paving, which suggests that rapid responses are necessary to ensure the survival of the species.Fil: Corbalán, Valeria Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina. Asociación para la Conservación de la Diversidad Biológica Argentina; ArgentinaFil: Debandi, Guillermo. Asociación para la Conservación de la Diversidad Biológica Argentina; ArgentinaFil: Literas, Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina. Asociación para la Conservación de la Diversidad Biológica Argentina; ArgentinaFil: Alvarez Guerrero, Leandro Manuel. Asociación para la Conservación de la Diversidad Biológica Argentina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Rivera, Juan Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Veterinarias. Departamento de Ciencias Biológicas; ArgentinaFil: Dopazo, Judit Elisabet. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Zarco, Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina. Asociación para la Conservación de la Diversidad Biológica Argentina; ArgentinaFil: Cornejo, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Blotto Acuña, Boris Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Faivovich, Julián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Masiel, Daniela. Asociación para la Conservación de la Diversidad Biológica Argentina; Argentin

Honey Locust (Gleditsia triacanthos L. (Fabaceae)) Invasion Effect on Temperature, Light and Metabolism of a Pampean Stream

El asentamiento de especies invasoras en una región generalmente produce cambios en los ecosistemas en los que se introducen. En este caso se analiza el efecto producido por una invasión de Gleditsia triacanthos, la acacia negra, sobre un arroyo pampeano. Esta especie modifica el clima térmico y lumínico del tramo. La amplitud térmica se reduce significativamente en el tramo invadido aunque la temperatura promedio en ambos tramos es similar. La irradiación se reduce entre un 85 y un 95 % bajo el dosel arbóreo. Estas modificaciones disminuyen la producción primaria bruta de 2,7 a 1,7 g O2/m2 en primavera y de 25 a 20 g O2/m2 en verano. La respiración se reduce a la mitad en los tramos invadidos, tanto en primavera como en verano, siendo el metabolismo neto similar en ambos tramos y estaciones del año. Por otro lado, el tramo invadido por acacia tiene muy escasas macrófitas. Se postula que la invasión de acacias además de disminuir la biodiversidad por reducción de las macrófitas y de los organismos asociados a ella reduce la producción primaria provocando cambios en la red trófica.The establishment of invader species in a region generally modifies the ecosystems where they are introduced. In this study we analyze the effect produced by a Gleditsia triacanthos (honey locust) invasion on a pampean stream. This organism modifies the temperature and the light reaching the stream. Thermal range shows significant differences between reaches but mean temperatures are similar in both reaches. Radiation diminished between 85 and 95 % down the trees. These modifications reduce the primary gross production of 2.7 to 1.7 g O2. m-2 at spring and of 25 to 20 g O2. m-2 at summer. Respiration in spring and summer is halved at invaded reaches, but net ecosystem metabolism is similar in both reach and seasons. Moreover, the reach invaded by honey locust show scarce macrophytes. We argue that the honey locust reduces the diversity by reduction of macrophytes and their associated organisms but also reduce the primary production causing changes in the food web.Fil: Giorgi, Adonis David Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján; ArgentinaFil: Vilches, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas. Programa Ecología de Protistas; ArgentinaFil: Rodríguez Castro, María Carolina. Universidad Nacional de Luján. Departamento de Ciencias Básicas. Programa Ecología de Protistas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zunino, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Debandi, Juan. Universidad Nacional de Luján. Departamento de Ciencias Básicas. Programa Ecología de Protistas; ArgentinaFil: Kravetz, Sebastián. Universidad Nacional de Luján. Departamento de Ciencias Básicas. Programa Ecología de Protistas; ArgentinaFil: Torremorell, Ana María. Universidad Nacional de Luján. Departamento de Ciencias Básicas. Programa Ecología de Protistas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Efecto de la invasión de acacia negra (Gleditsia triacanthos L.) sobre arroyos pampeanos

Pampean fluvial ecosystems of low order usually lack of riparian vegetation. In recent years the invasion of honey locust (Gleditsia triacanthos L.) has caused changes in landscape composition. The aim of this study was to evaluate the effect of honey locust invasion on pampean streams. Three reaches with different degree of invasion were selected and compared with three control reaches with no canopy. In order to evaluate the effect of invasion, nutrients (soluble reactive phosphorus, ammonium and nitrates), biomass of producers (seston, macrophytes, periphyton and phytobenthos) and net production in each reach were determined. Significant differences were observed for all of variables estimated between reaches with and without canopy, but not in all cases. The amount of variables with significant differences between both reaches rises following a gradient of increasing invasion levels. Furthermore, differences are more pronounced with increasing percentage of honey locust coverage on the stream. We conclude that sustained invasion of honey locust modifies the concentration of nutrients in water, the biomass of some communities and the production of these communities. This effect could be avoided with early management of the invasion of honey locust.Los ecosistemas fluviales pampeanos de orden bajo suelen carecer de vegetación ribereña. En los últimos años, la invasión de la langosta de la miel (Gleditsia triacanthos L.) ha causado cambios en la composición del paisaje. El objetivo de este estudio fue evaluar el efecto de la invasión de la acacia negra en los arroyos pampeanos. Se seleccionaron tres tramos con diferente grado de invasión y se compararon con tres sectores de control sin dosel. Para evaluar el efecto de la invasión, se determinaron los nutrientes (fósforo reactivo soluble, amonio y nitratos), la biomasa de los productores (seston, macrofitos, perifitón y fitobentos) y la producción neta en cada sector. Se observaron diferencias significativas para todas las variables estimadas entre tramos con y sin dosel, pero no en todos los casos. La cantidad de variables con diferencias significativas entre ambas situaciones aumenta luego de un gradiente de niveles crecientes de invasión. Además, las diferencias son más pronunciadas con el aumento del porcentaje de cobertura de la acacia negra en el arroyo. Concluimos que la invasión sostenida de la acacia negra modifica la concentración de nutrientes en el agua, la biomasa de algunas comunidades y la producción de estas comunidades. Este efecto podría evitarse con el manejo temprano de la invasión de la acacia negra

Fortalecimiento de las capacidades de diagnóstico e investigación del Laboratorio de Salud Pública de Ciencias Exactas (UNLP) integrado a la Red de Diagnóstico SARS-Cov2 de la Provincia de Buenos Aires

En el marco de la pandemia declarada en 2020 se gestan diversos grupos de trabajo e investigación en la Facultad de Ciencias Exactas de la UNLP. En esta videopresentación se relatan las experiencias de algunos de ellos, vinculados a la temática del COVID-19.Facultad de Ciencias Exacta

Efectos del calentamiento climatico y el pastoreo sobre una comunidad de algas marinas bentonicas Antarcticas, en etapas tempranas de sucesion

The Antarctic Peninsula is one of the regions most seriously affected by climate warming. Rising temperatures are considered a stress factor for the rather stenothermal benthic algae inhabiting in this region. Furthermore, it has also been associated to glacier retreat, which causes increased freshwater inflow and sedimentation into the water column, which consist of environmental changes that impose stress conditions for benthic organisms. Besides abiotic factors, grazing is one of the most important drivers of benthic algal communities, particularly at early stages of succession. The objective of the present study was to evaluate experimentally the effects of environmental perturbations ssociated to climate warming in the Antarctic region- such as increased temperature and sedimentation- and grazing, on benthic algal communities at early stages of succession. Artificial substrates (ceramic tiles, 25 cm2) were installed at a subtidal site in Potter Cove (25 de Mayo/King George Island, South Shetland Islands, Antarctica) and, after eleven months of colonization, a trifactorial experiment was performed to test the effects of temperature (2 °C and 6 °C), sediment load (with and without added sediment) and grazing by the gastropod Nacella concinna (ungrazed and grazed) on eveloped communities. Samplings were performed after 12, 14 and 36 days. Species composition and abundance of juveniles (>1mm) and early stages (>0.02mm) of macroalgae, the structure of diatom assemblages (taxonomic composition, density and ecological indexes), biomass and photosynthetic efficiency were assessed. Tiles were dominated by juvenile thalli of Palmaria decipiens and early stages of P. decipiens, Monostroma hariotii and Adenocystis utricularis, which are typical macroalgal species in early stages of succession at the Antarctic benthos. Nineteen diatom taxa were identified, mostly pennate and typically benthic forms. Increased temperature did not exert any effects on macroalgal cover nor on diatoms density. However, higher temperatures caused higher diversity and evenness in diatom assemblages probably due to changes in the relative abundance of species that are not sensitive to this factor. Sedimentation exerted positive or neutral effects on macroalgal cover and seems to protect the communities at short term, when early stages are more sensitive to high irradiance conditions. However, it negatively affected diatom evenness. Grazing by N. concinna controls diatom assemblages by reducing their density. These consumers can potentially counteract positive (or negative) sedimentation effects by removing the sediment cover. Over longer time scales, higher temperature and sedimentation may limit the photosynthetic efficiency of marine benthic algal communities in Antarctica. Early stages of succession are subject to complex interactions between abiotic and biotic factors in the Antarctic benthos. In a climate change context, the action of multiple changing factors can introduce alterations in the structure and functioning of the communities of Antarctic benthic algae, which play a central role in this system

Effects of the pruning intensity and tree size on multi-stemmed Prosopis flexuosa trees in the Central Monte, Argentina

Forestry use in Prosopis flexuosa woodlands in the Central Monte is limited by low wood productivity and by most of the trees being multi-stemmed. Desert inhabitants have turned pruning into a common practice to get some forest products, increase wood production and improve tree shape. In this study we tested pruning practices used by locals on trees of different diameter classes and different pruning intensities in the aeolian plains of the Central Monte Desert. Two trials were conducted: (a) we tested the effects of pruning on three types of trees: adult multi-stemmed trees (7.5–15 cm basal diameter; n = 12 for pruned trees and 10 for control), young trees (3–7.5 cm basal diameter; n = 20 for pruned trees and 18 for control), and saplings (<3 cm basal diameter; n = 15 for pruned trees and 18 for control); (b) we compared the effects of different pruning intensities: heavy pruning (50% of crown removed and n = 10), intermediate pruning (25% of crown removed; n = 10), and unpruned individuals (n = 10). Basal diameters of all stems, total tree height, largest and smallest crown diameters were measured yearly. We estimated the equivalent basal diameter (EBD) and crown volume. Linear mixed models (LMM), in continuous variables, and general linear mixed models (GLMM), in discrete variables, were used for evaluating the effects of the treatments on the different variables. The response observed in pruned trees was an increased length of branches, which in both trials translated into increased crown diameter and volume. No initial response was recorded in basal diameter growth of the remaining stem. In adult trees, an increase in basal diameter was detected five years after pruning. A greater response of crown growth was found in individuals subjected to heavy pruning vs. individuals under intermediate pruning. Results suggested that pruning could improve the shape of Prosopis in the short run, and increase stem diameter growth in the long run, as observed for other tree species of Prosopis that received pruning throughout the world. This suggests that this practice could be potentially used to obtain poles and firewood without a decrease in wood productivity but with an increase in branch growth, and, in consequence, it could be included in silvicultural management of woodlands dominated by multi-stemmed trees and in models of sustainable management at local scale.Fil: Alvarez, Juan Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales; Argentina; Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias; Argentina;Fil: Villagra, Pablo Eugenio. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales; Argentina; Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias; Argentina;Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico - Conicet - Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias. Ambientales; Argentina;Fil: Debandi, Guillermo. Asociación para la conservaciòn de la diversidad biológica argentina; Argentina

Bordetella pertussis targets the basolateral membrane of polarized respiratory epithelial cells, gets internalized, and survives in intracellular locations

The airway epithelial barrier is a continuous highly organized cell layer that separates the exterior from the underlying mucosal tissue, preventing pathogen invasion. Several respiratory pathogens have evolved mechanisms to compromise this barrier, invade and even reside alive within the epithelium. Bordetella pertussis is a persistent pathogen that infects the human airway epithelium, causing whooping cough. Previous studies have shown that B. pertussis survives inside phagocytic and nonphagocytic cells, suggesting that there might be an intracellular stage involved in the bacterial infectious process and/or in the pathogen persistence inside the host. In this study we found evidence that B. pertussis is able to survive inside respiratory epithelial cells. According to our results, this pathogen preferentially attaches near or on top of the tight junctions in polarized human bronchial epithelial cells and disrupts these structures in an adenylate cyclase-dependent manner, exposing their basolateral membrane. We further found that the bacterial internalization is significantly higher in cells exposing this membrane compared with cells only exposing the apical membrane. Once internalized, B. pertussis mainly remains in nondegradative phagosomes with access to nutrients. Taken together, these results point at the respiratory epithelial cells as a potential niche of persistence.Fil: Baroli, Carlos Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; ArgentinaFil: Gorgojo, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; ArgentinaFil: Blancá, Bruno Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; ArgentinaFil: Debandi, Martina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; ArgentinaFil: Rodriguez, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; Argentin

The impact of a changing environment on young macroalgal stages and communities

The Western Antarctic Peninsula (WAP) is a hotspot for changes caused by humans. The total column ozone is not expected to increase in the next several decades leading to an increased UVB radiation at the earth’s surface and, hence, on polar organisms. Global warming is accelerated at the WAP in comparison with the global mean and in some areas water temperatures have risen by 2°C in the last 50 years. Seaweeds are an essential part of the polar coastal ecosystem showing a high level of endemism. Little is known how these communities react on stressors such as UV radiation, light intensity, increasing temperatures and sedimentation and decreased salinity (from the melt water run-off from the glaciers). A variety of field and laboratory experiments on seaweed communities and young developmental stages (spores) were performed over the last ten years in order to tackle this question. A focus was lying on the interactive effects of various variables such as UV and grazing or temperature, sedimentation and grazing and the effect of light and temperature among others. We also performed long term colonization experiments over 4 years to elucidate the general patterns of polar seaweed succession. Interactive effects occurred for example between grazing and UV radiation in field experiments and between temperature and light intensity in laboratory experiments. Other data are currently analyzed. Our results showed that juvenile stages are especially vulnerable to environmental perturbations and that the degree of susceptibility is species-specific. Shift in community structure as a response to environmental change are likely to occur with yet unknown consequences for the associated heterotrophic organisms