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For macroinvertebrates inhabiting lentic systems, quantity and availability of various substrates are important for the establishment and development of different assemblages, also, the biome reflects macroinvertebrates system production. In this study, the diversity was estimated from the biomass present in the four substrates: macrophyte ( Myriophyllum aquaticum ), rock, sediments and organic matter, it was analyzed the seasonal variation of biomass and abundance considering three hydrological periods. It was collected 2.957 individuals grouped in 17 genera and 11 orders. Helobdella was the dominant taxon, it contributes to 90% of the total biomass of the community; Hyalella , Tanytarsus and Centrocorisa were important too. Electric conductivity, sulfates and the water temperature were determined for the biomass. The dominance of macroinvertebrates was higher in macrophyta (0,99). In the rest of the substrates, diversity was larger (iŸƒ = 1,5 nats.ind-1) and the evenness minor (iŸƒ = 0,24). There are significant differences in the registers of biomass among the substrates but not among the campaigns. In conclusion, macrophyte was the substrate and the habitat most used by macroinvertebrates and it contains more individuals; however, the macrophyte was not the most diversity substrates because, when it was compared with other three substrates the diversity is higher.

The aim of this work was to characterize the sediment toxicity of a zone of the River Uruguay through a battery of bioassays. The samples were extracted from an area of influence of domestic wastewater discharges and pulp mill effluents (Fray Bentos), a touristic town downstream (Las Canas), and another one, upstream, isolated from those discharges (Nuevo Berlin). The bioassays: Photobacterium leiognathi toxicity screen, Ceriodaphnia dubia reproduction and embryo-larval teratogenicity and lethality with Pimephales promelas were applied to the sediment elutriates, while the Hyalella curvispina sub-lethal growth test was performed using whole sediment. To assess bioavailability and toxicity pathways, the sediment-water partitioning of 2,4,5-triclorofenol among phases was determined as: 63% dissolved, 27% suspended and the rest settled. Toxicity to organics and metals using P. leioghnati was observed in all sampled sites. The frequency of P. promelas vertebral malformations was 3.3% only to Fray Bentos elutriate, but the C. dubia reproduction bioassay showed effects only in those from Nuevo Berlin and Las Canas. The growth test with H. curvispina evidenced effects for all samples. The toxicity pathways could be ingestion of dissolved and particulate contaminants, possibly associated to higher clay and silt contents and contaminant input. The cause-effect relationships will be subject to further research.

Se realiza una revisión de las especies de anfípodos del género Hyalella en aguas continentales de la Patagonia, isla Tierra del Fuego, Reserva de la Biosfera de Cabo de Hornos e islas adyacentes (38-54°S). Esta zona austral presenta numerosos tipos de ambientes acuáticos continentales como lagos, humedales y arroyos, y las principales especies en ambientes bentónicos corresponden a anfípodos del género Hyalella. La bibliografía menciona la presencia de H. costera, H. chiloensis, H. falklandensis, H. franciscae, H. neonoma, H. patagónica, H. rionegrina y H. simplex. La distribución de estas especies concuerda con estudios biogeográficos sobre la presencia de especies endémicas y de amplia distribución en el sur de la Patagonia y zona subantárticas. A pesar de la presencia de especies depredadoras introducidas, sobre la base de la literatura, los anfípodos serían más abundantes debido a la presencia de materia orgánica particulada. This study reviews the amphipod species of the genus Hyalella in the inland waters of Patagonia, Tierra del Fuego Island, Cape Horn Biosphere Reserve, and adjacent islands (38-54°S). This southern zone has numerous kinds of continental water bodies such as lakes, wetlands, and streams, and the main species in benthic assemblages are amphipods of the genus Hyalella. The literature mentions the presence of H. costera, H. chiloensis, H. falklaidensis, H. franciscae, H. neonoma, H. patagonica, H. rionegrina, and H. simplex. The distribution of these species agrees with biogeographical studies about the presence of widespread, endemic species in southern Patagonia and the sub-Antarctic zone. In spite of the presence of introduced predatory species, the literature indicates that the amphipods are more abundant due to the presence of particulated organic matter.

Se realiza una revisión de las especies de anfípodos del género Hyalella en aguas continentales de la Patagonia, isla Tierra del Fuego, Reserva de la Biosfera de Cabo de Hornos e islas adyacentes (38-54°S). Esta zona austral presenta numerosos tipos de ambientes acuáticos continentales como lagos, humedales y arroyos, y las principales especies en ambientes bentónicos corresponden a anfípodos del género Hyalella. La bibliografía menciona la presencia de H. costera, H. chiloensis, H. falklandensis, H. franciscae, H. neonoma, H. patagónica, H. rionegrina y H. simplex. La distribución de estas especies concuerda con estudios biogeográficos sobre la presencia de especies endémicas y de amplia distribución en el sur de la Patagonia y zona subantárticas. A pesar de la presencia de especies depredadoras introducidas, sobre la base de la literatura, los anfípodos serían más abundantes debido a la presencia de materia orgánica particulada.