Temporal Variability of Macroinvertebrate Assemblages in a Mediterranean Coastal Stream: Implications for Bioassessment.

Macroinvertebrates from a small forest stream in central-south Chile were sampled monthly from September 2017 to August 2018 to assess temporal variability in the assemblage and the effects of that variability on ecological indicators. Higher precipitation and flows occurred in winter months, and water quality varied among months. We collected 59 macroinvertebrate taxa, finding higher taxa richness and abundances in summer months than in winter months. Four taxa demonstrated marked seasonality, being abundant in some months and then decreasing in following months (Limnoperla jaffueli (Navás), Nousia maculata (Demoulin), Smicridea sp. (McLachlan), Chironomidae spp.). The scores of the family Hilsenhoff Biotic Index (HBI), Hilsenhoff Species-level Biotic Index (HSBI), Multimetric Macroinvertebrate Index (MMI), and Chilean Biological Monitoring Working Party (ChBMWP) index varied throughout the year reflecting natural variability. However, only HBI and HSBI scores were significantly different among seasons, ranging across three water quality classes (excellent, very good, and good), showing the lowest water classes in spring, coinciding with higher abundances of tolerant species. The MMI and ChBMWP indicated good and very good site conditions throughout the year, respectively. Shannon-Weaver diversity ranged between 2.59 (April) and 1.78 (February); however, Pielou evenness had high values throughout the year (> 0.62), except in February. Changes in macroinvertebrates composition throughout the year were explained primarily by discharge, water temperature, and conductivity. Our findings indicate that natural monthly variability in macroinvertebrate assemblages influences the scores of biological indices throughout the year. Therefore, we recommend that natural stream variability be accounted for in biomonitoring programs. We also emphasize the need to use caution when interpreting biological index scores to avoid misinterpretations in stream quality classification.

Examining the influence of human stressors on benthic algae, macroinvertebrate, and fish assemblages in Mediterranean streams of Chile.

Changes in land-uses and cover are strong drivers of stream degradation worldwide. In Mediterranean ecoregions, land conversion from forest with native species to tree plantations, agricultural, and urban areas have drastically increased in recent years. Here, we examined the influence of land-use types on water quality (physical and chemical variables) and biota (benthic algae, macroinvertebrates, and fishes). We conducted field surveys between December-March 2016 (dry season) in 24 sites located across four land-use types including native vegetation (NV), tree plantation (TP), agriculture (Ag), and urban (Ur) within the Chilean Mediterranean ecoregion. We calculated metrics and multivariate statistics to assess correlations between biological and environmental variables. Significant differences between land-uses were found for environmental/physicochemical variables and the three biotic groups (i.e., benthic algae, macroinvertebrates, and fishes). We found higher chlorophyll-a biomass for TP, Ag, and Ur compared to NV streams. The macroinvertebrate diversity of sensitive taxa (i.e., Ephemeroptera, Plecoptera, and Trichoptera) and water quality were lower in land draining streams with human uses, other than NV, with the most evident impact found in Ag and Ur streams. NV and TP streams had a lower Diptera density and lower percentage of non-insect taxa. Fish richness and diversity were not affected by land-use. However, cold-water fishes (both native and introduced) were closely associated with NV and TP streams whereas warm-water fishes (mostly introduced) were closely associated with Ag and Ur streams. Multivariate analysis revealed that both local habitat and catchment-scale variables influenced each biological assemblage. Our findings suggest that benthic algae, macroinvertebrates, and fish populations are good indicators of human land-use disturbances, with Ag and Ur areas being the most detrimental for freshwater biota.

Aproximación multimétrica a la evaluación de la calidad del agua en cuencas con diferentes niveles de intervención antrópica / Multimetric approach to water quality evaluation of basins with diferent levels of antropic perturbation / Aproximação multimétrica à avaliação da qualidade da agua em bacias com diferentes níveis de intervenção antrópica

La vegetación ribereña desempeña un conjunto de funciones ecosistémicas. Tiene influencia sobre la hidrología, geomorfología, química del agua y suministro de material alóctono, por lo cual es relevante en la productividad y funcionamiento, estabilizando laderas, regulando la temperatura, filtrando y reteniendo nutrientes y otorgando hábitat a las comunidades acuáticas. Este estudio realizó una aproximación multiparamétrica en ríos mediterráneos de Chile central. Los resultados mostraron que las variables que mejor reflejan la distribución de los macroinvertebrados fueron la conductividad y los sólidos disueltos, las cuales también se correlacionaron significativamente con la calidad de ribera y del hábitat fluvial. Esta aproximación sugiere la evaluación integral del sistema fluvial como una herramienta para la conservación y restauración de la salud integral de los ecosistemas acuáticos.

The riparian zone vegetation performs several functions for the ecosystem. It influences the hydrology, geomorphology, water chemistry; and supplies of allocthonous materials; therefore, it is important for the productivity and functioning of fluvial systems, stabilizing slopes, regulating temperature, filtering and retaining nutrients, and providing habitat to aquatic communities. This study followed a multiparametric approach in Central Chile mediterranean streams. The results showed that the variables that better reflect the distribution of macroinvertebrates were conductivity and dissolved solids. These variables also correlated significantly with bank quality and stream habitat. This approximation suggests the integral evaluation of a stream system as a tool for conservation and restoration of integral health of aquatic ecosystems.

A vegetação riberenha desempenha um conjunto de funções ecossistêmicas. Tem influência sobre a hidrologia, geomorfologia, química da água e subministro de material alóctono, pelo qual é relevante na produtividade e funcionamento, estabilizando ladeiras, regulando a temperatura, filtrando e retendo nutrientes e outorgando habitat às comunidades aquáticas. Este estudo realizou uma aproximação multiparamétrica em rios mediterrâneos do Chile central. Os resultados mostraram que as variáveis que melhor refletem a distribuição dos macroinvertebrados foram a condutividade e os sólidos dissolvidos, as quais também se correlacionaram significativamente com a qualidade de ribeira e do habitat fluvial. Esta aproximação sugere a avaliação integral do sistema fluvial como uma ferramenta para a conservação e restauração da saúde integral dos ecossistemas aquáticos.

Deconstructing latitudinal species richness patterns in the ocean: does larval development hold the clue?

The consistent decrease in species richness with latitude shows several exceptions among marine organisms. We hypothesize that contrasting latitudinal diversity gradients can be explained by differences in critical life-history attributes, such as mode of larval development (MLD). We deconstructed latitudinal species richness patterns of marine benthic invertebrates according to MLD to elucidate differences in patterns of species richness and to reveal underlying processes. The patterns of species richness were remarkably similar across taxa within MLD but differed between MLD. Species richness decreased polewards in planktotrophic species and increased in direct developers. Temperature explained most of the variation in species richness. Low temperature at high latitudes may generally favour direct developing species, but, together with low chlorophyll-a concentration, limit the distribution of planktotrophic species. The contrasting influence of temperature on different MLDs might be explained by its effect on the length of planktonic life and on brooding costs.