The aim of this study was to determine the community structure of freshwater macroinvertebrates and characterize trophic functional groups in the Lluta river basin located in the Atacama Desert. To this was sampled with Surber sampling in 12 stations, in extension from the source to its mouth on the coast during November 2011. In this study 66 taxa of macroinvertebrates were recorded, corresponding mostly insect larvae (46). The groups with the greatest wealth were Diptera (20 taxa), Coleoptera and Trichoptera (both with 7 taxa). On abundance, Chironomidae was the most abundant family of the study area. The group of collectors-gatherers was the most representative in 10 of the 12 stations, while the group of browsers dominated the two closest stations to the mouth. Our results are the first to describe the fauna of macroinvertebrates dulceacuáticos in extreme northern Chile basin, containing a much higher than other rich fauna desert basins. Besides the great representative of the collectors-gatherers that feed on organic fragments under 1 mm deposited on the bottom, showing the importance of this food source in the Atacama desert rivers.

El objetivo de este estudio fue determinar la estructura comunitaria de macroinvertebrados dulceacuícolas y caracterizar los grupos funcionales tróficos en la cuenca del río Lluta ubicado en el desierto de Atacama. Para esto se muestreó con una red Surber en 12 estaciones, abarcando desde la cabecera del río hasta su desembocadura en la costa marítima durante noviembre de 2011. En este estudio se registraron 66 taxa de macroinvertebrados, correspondiendo en su mayoría a larvas de insectos (46). Los grupos con mayor riqueza fueron Diptera (20 taxa), Coleoptera y Trichoptera (ambos con 7 taxa). Respecto de la abundancia, Chironomidae fue la familia más abundante del área de estudio. El grupo de los colectores-recolectores fue el más representativo en 10 de las 12 estaciones, mientras que el grupo de los ramoneadores dominaron en las dos estaciones más cercanas a la desembocadura. Nuestros resultados son los primeros en describir la fauna de macroinvertebrados dulceacuáticos en la cuenca más extrema del norte de Chile, conteniendo una riqueza faunística mucho mayor que otras cuencas desérticas. Además la gran representatividad de los colectores-recolectores que se alimentan de fragmentos orgánicos menores a 1 mm depositados en el fondo, demuestran la importancia de este recurso alimentario en ríos del desierto de Atacama.

Hábitats bênticos estão ligados por processos físicos e são elementos essenciais na avaliação da dinâmica de distribuição de insetos dípteros Chironomidae e seu papel em ecossistemas aquáticos. Este trabalho apresenta os resultados dos padrões de distribuição de larvas de Chironomidae em 38 locais que são abundantes na área de estudo, habitando o substrato do canal principal do rio, cachoeiras, córregos tributários, lagoas de planície de inundação, e reservatórios ao longo do Rio Sepotuba de sua desembocadura ao Rio Paraguai e na região de cabeceira. Um total de 1,247 larvas foi registrada. O táxons mais abundantes foram Polypedilum (Tripodura) sp. (25.2%), Cricotopus sp.3 (23.0%) e Tanytarsus sp. (15.0%). Fissimentum desiccatum foi encontrado somente no reservatório; Fissimentum sp.2 e Tanytarsus cf. T. obiriciae sp.2 nas lagoas de planície de inundação, e Goeldichironomus sp. no canal principal. A baixa diversidade dos locais S06 e S35 foi causada pela exclusiva presença da espécie Cricotopus sp.3, sozinha ou junta com um ou outro táxon (Tanytarsus sp., Djalmabatista sp.3). Coletores-filtradores representaram 16%, coletores-catadores 15%, predadores 11% e raspadores somente 1%. Os predadores dominaram no canal secundário (±88 ind/m2), correspondendo a 40% do total deste grupo. Cryptochironomus sp.2 (34%) e Ablasbemyia gr. annulata (26%) foram os mais abundantes entre os predadores. As diferenças ao longo do curso do rio foram decisivas para a formação de comunidades distintas e descontínuas e os limites tornam óbvios pertinentes às interrelações entre as populações na comunidade, como por exemplo, competição por alimento e hábitat.

Benthic habitats are linked by physical processes and are essential elements in assessing of the distribution dynamics of Chironomidae dipteran insects and their role in aquatic ecosystems. This work presents results of distribution patterns of chironomids larvae in 38 sites that are abundant in the study site, inhabiting the substrate of the main river channel, rapids, tributary brook, floodplain lakes and reservoir along the Sepotuba River from its mouth at the Paraguay River to the headwater region. A total of 1,247 larvae was registered. The most abundant taxa were Polypedilum (Tripodura) sp. (25.2%), Cricotopus sp.3 (23.0%) and Tanytarsus sp. (15.0%). Fissimentum desiccatum were found only in the reservoir; Fissimentum sp.2 and Tanytarsus cf. T. obiriciae sp.2 in floodplain lakes, and Goeldichironomus sp. in the main channel. The low diversity of the sites S06 and S35 is caused by the near-exclusive presence of the species Cricotopus sp.3, alone or together with one or another taxon (Tanytarsus sp., Djalmabatista sp.3). Collectors-filterers represent 16%, collectors-gatherers 15%, predators 11% and scrapers only 1%. The predators dominated in the secondary channel (±88 ind/m2), corresponding to 40% of the total of this group. Cryptochironomus sp.2 (34%) and Ablasbemyia gr. annulata (26%) were the most abundant among the predators. The differences along the river course are decisive for the formation of distinct or discontinuous communities and the limits become obvious though the interrelations between the populations in the community, as for instance, competition for food and habitats.

Aquatic macroinvertebrates are involved in numerous processes within aquatic ecosystems. They often have important effects on ecosystem processes such as primary production (via grazing), detritus breakdown, and nutrient mineralization and downstream spiraling. The functional feeding groups (FFG) classification was developed as a tool to facilitate the incorporation of macroinvertebrates in studies of aquatic ecosystems. This classification has the advantage of combining morphological characteristics (e.g., mouth part specialization) and behavioral mechanisms (e.g., way of feeding) used by macroinvertebrates when consuming resources. Although recent efforts have greatly advanced our ability to identify aquatic macroinvertebrates, there is limited information on FFG assignment. Furthermore, there has been some variation in the use of the FFG classification, in part due to an emphasis on using gut content analysis to assign FFG, which is more appropriate for assigning trophic guilds. Thus, the main goals of this study are to (1) provide an overview of the value of using the FFG classification, (2) make an initial attempt to summarize available information on FFG for aquatic insects in Latin America, and (3) provide general guidelines on how to assign organisms to their FFGs. FFGs are intended to reflect the potential effects of organisms in their ecosystems and the way they consume resources. Groups include scrapers that consume resources that grow attached to the substrate by removing them with their mouth parts; shredders that cut or chew pieces of living or dead plant material, including all plant parts like leaves and wood; collectors-gatherers that use modified mouth parts to sieve or collect small particles (<1mm) accumulated on the stream bottom; filterers that have special adaptations to remove particles directly from the water column; and predators that consume other organisms using different strategies to capture them. In addition, we provide details on piercers that feed on vascular plants by cutting or piercing the tissue using sharp or chewing mouth parts and consume plant liquids. We also provide a list of families of aquatic insects in Latin America, with an initial assignment to FFGs. We recommended caution when assigning FFGs based on gut contents, as it can provide misleading information. Overall, FFG is a very useful tool to understand the role of aquatic macroinvertebrates in stream ecosystems and comparisons among studies will benefit from consistency in their use. Rev. Biol. Trop. 62 (Suppl. 2): 155-167. Epub 2014 April 01.