The role of aerial dispersal in shaping patterns of biodiversity remains poorly understood, mainly due to a lack of coordinated efforts in gathering data at appropriate temporal and spatial scales. It has been long known that the rate of dispersal to an ecosystem can significantly influence ecosystem dynamics, and that aerial transport has been identified as an important source of biological input to remote locations. With the considerable effort devoted in recent decades to understanding atmospheric circulation in the south-polar region, a unique opportunity has emerged to investigate the atmospheric ecology of Antarctica, from regional to continental scales. This concept note identifies key questions in Antarctic microbial biogeography and the need for standardized sampling and analysis protocols to address such questions. A consortium of polar aerobiologists is established to bring together researchers with a common interest in the airborne dispersion of microbes and other propagules in the Antarctic, with opportunities for comparative studies in the Arctic.

This study provides new length-weight relationship information for 21 neotropical fish species. Specimens were collected between 2004 and 2005 from the lower section of the Santa Lucı´a river basin (Uruguay). Presented are also the first reference on weight-length relationships for these 21 species, and new maximum sizes for six of these species.

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Sediment constitutes an important sink of endocrine disruptor compounds; however, the potential of sediments to act as a source of endocrine disruptors should be more extensively investigated. The main objective of this study was to determine whether exposure of immature common carp to Uruguay River sediments undergo physiological and endocrine alterations. The lower Uruguay River watershed supports intensive agricultural and forest production, receives municipal sewage discharge and industrial effluent, and a new large pulp mill was constructed in 2006. A 30-day semi-static assay was performed using sediments from four sites along the Uruguay River and compared with an unexposed group in dechlorinated water as a negative control. We focused on two upstream and two downstream sites of a new elemental chlorine free pulp mill. The results showed that plasma vitellogenin levels increased in fish along the river and significant differences were found between the exposed and unexposed groups. Condition factor and gonadosomatic index were not different; however, a significant difference in hepatosomatic index was observed in fish exposed to sediment from an industrial site. A significant reduction in primary spermatocyte accumulation was observed in the exposed group compared with that in the control group, and some individuals exposed to sediments from industrial sites presented with testis-ova. Our results suggest that Uruguay River sediments act as an important source of estrogenic compounds that could be responsible for the alterations observed. Future studies are needed to identify the causal agents and determine exposure routes.

Pesticides used in agriculture are among the most important environmental pollutants. Organophosphate and carbamate insecticides, intensely used in deciduous fruit-trees, may be transported to aquatic ecosystems by runoff. Northwest rural Montevideo possesses zones of fruit-tree farms, where azinphos-methyl is currently the most used pesticide. Despite the well-known neurotoxic properties of this agrochemical, studies of its effects on aquatic organisms are scarce in Uruguay. The main goal of this study was to evaluate effects on brain cholinesterases and erythrocyte micronuclei in Astyanax fasciatus exposed to azinphos-methyl in laboratory and field conditions. Dose-response curves showed concentration-dependent brain cholinesterase inhibitions and a LC 50 (48-hour) of 2.31 mg L-1 for azinphos-methyl. Fishes exposed for 48 hours to toxicant and then transferred to clear water recovered 80% of brain cholinesterase activity in 10 days. Field study indicated that A. fasciatus from a watershed with low contamination showed a brain cholinesterase specific activity of 62.2±5.1 Units mg-1 protein (22ºC) 97.7 % of which was acetylcholinesterase. Specimens from a basin with intense fruticulture exhibited a spatial gradient, those collected downstream to the farms showed brain acetylcholinesterase activities 32% lower than fishes captured upstream. In conclusion, our data suggest that A. fasciatus is a suitable species for ecotoxicological biomonitoring.

The Uruguay river basin supports intensive agricultural and forest production, and receives municipal sewage discharge and industrial effluent. Therefore, the river receives xenobiotic compounds which can be distributed in sediments, biota, water and particulate matter. There is evidence of the ability of several of these compounds to interfere with the endocrine system and the sediments are an important source. The aim of this study was to determine whether exposure of immature Cyprinus carpio to Uruguay river sediments undergo physiological and endocrine alterations. A 30-day semi-static assay was performed using sediments from four sites along the Uruguay river and compared with an unexposed group in dechlorinated water as a negative control. The results showed that plasma vitellogenin levels increased along the river, and significant differences were found in exposed fish. Significant difference in hepatosomatic index was observed in fish exposed to sediment from an industrial site. In the histological analysis, only reproductive stage of males showed differences, where the number of primary spermatocyte accumulations was lower in exposed ones, and some exposed individuals from industrial sites presented with testis-ova. Our results suggest that the Uruguay river sediments are a source of endocrine-disrupting compounds available to the aquatic organisms.

Prevalence and intensity of black-spot disease in a fish community from a subtropical stream (Santa Lucía river basin, Uruguay)The objective of the present study was to identify fish species susceptible to black spot disease, the temporal variation in intensity prevalence and abundance of black spot, and its correlation with environmental and host parameters. In order to do so, several sampling campaigns were conducted bimonthly during one year, along the main course of an agricultural watershed. A total of twenty-seven fish species were collected, out of which only two, Astyanax aff. fasciatus ("mojarra") and Oligosarcus jenynsii ("dientudo") presented black spot disease. In A. aff. fasciatus, 63 % of black spot prevalence was registered and did not show significant seasonal changes during the sampling period, nor did the abundance and intensity. Regarding possible relations between the disease and environmental and host parameters, a higher intensity of black spot infection was observed in the ventral region of the fish and allometric coefficient (W T − L S , relationship) values did not differ significantly between parasitized and non-parasitized fish groups.

Summary This work is the first report on length–weight relationships for 15 fish species from the Lower Uruguay freshwater ecoregion. Fishes were collected between 2008 and 2010 in eight streams (Cañada del Sauce, San Luis, Don Esteban Chico and Grande, de la Palmita, Lencina, del Sauce and del Totoral), all tributaries to the Negro River (Uruguay). A standardized fishing effort (50 electric pulses along 100 m) with an electrofishing device (Type IG600T, Hans Grassl GmbH, Schönau am Königssee, Germany) was conducted in each wadeable stream reach. New maximal standard lengths and total weight are given for five and 13 fish species, respectively.