Variations in Benthic Macroinvertebrate Communities and Biological Quality in the Aguarico and Coca River Basins in the Ecuadorian Amazon

Adequate environmental management in tropical aquatic ecosystems is imperative. Given the lack of knowledge about functional diversity and bioassessment programs, management is missing the needed evidence on pollution and its effect on biodiversity and functional ecology. Therefore, we investigated the composition and distribution of the macroinvertebrate community along two rivers. Specifically, 15 locations were sampled in the Coca and Aguarico Rivers (Ecuadorian Amazon) and the macroinvertebrates were used to indicate water quality (WQ), expressed as the Biological Monitoring Working Party Colombia (BMWP-Col) classes. Results indicate that elevation, pH, temperature, width, and water depth played an important role in the taxa and functional feeding groups (FFG) composition. The results show that diversity of taxa and FFG were generally scarce but were more abundant in good quality sites. Collector-gathers (CG) were, in general, dominant and were particularly abundant at low WQ and downstream sites. Scrapers (SC) were the second most abundant group, dominating mostly at good WQ and upstream sites. Predators (PR) were homogeneously distributed among the sites, without clear dominance, and their abundance was slightly higher in sites with medium-low WQ and downstream sites. Lastly, both shredders (SH) and collector-filterers (CF) were almost absent and were more abundant in good quality sites. The findings of this research can be used as baseline information in the studied region since a dam was constructed two years after the sampling campaign, which has been operating since. Furthermore, the results can be used to fill the knowledge gaps related to the bioassessments of other similar systems, particularly for a tropical rainforest.

Anthropogenic impacts on aquatic bacteria: a perspective from the tropics

Bacterioplankton comprises a highly diverse group of microorganisms, which are dominant in aquatic ecosystems, and play a central role in ecosystem functioning and biogeochemical cycles. Due to their high turnover and dispersal rates, as well as high adaptability and plasticity, microbes are likely to respond quickly to environmental changes and perturbations on their ecosystems. In this opinion paper, we reviewed some studies that addressed bacterial community’s responses to anthropogenic impacts in their aquatic environments. Inorganic nutrients and organic matter inputs from the catchment areas are likely to increase due to changes in climate and land use. These changes will impact the microbial community composition and metabolism, as well the amount of energy and carbon flowing through aquatic food webs as mostly demonstrated in studies from temperate and boreal systems. However, due to the low number of studies on microbial communities in tropical ecosystems, our understanding of how they will respond to perturbations in this distinct environmental context is still limited. Research in microbial ecology in southern countries is still in its infancy and deserves more attention in the future, since tropical aquatic ecosystems are hotspots of biodiversity, host most of the world freshwater reserves, and play a key role in global biogeochemical cycles.

Methods for selection of Daphnia resting eggs: the influence of manual decapsulation and sodium hypoclorite solution on hatching rates

Cladocerans are able to produce resting eggs inside a protective resistant capsule, the ephippium, that difficults the visualization of the resting eggs, because of the dark pigmentation. Therefore, before hatching experiments, methods to verify viable resting eggs in ephippia must be considered. This study aimed to evaluate the number of eggs per ephippium of Daphnia from two tropical aquatic ecosystems and the efficiency of some methods for decapsulating resting eggs. To evaluate the influence of methods on hatching rates, three different conditions were tested: immersion in sodium hypochlorite, manually decapsulated resting eggs and intact ephippia. The immersion in hypochlorite solution could evaluate differences in numbers of resting eggs per ephippium between the ecosystems studied. The exposure to sodium hypochlorite at a concentration of 2% for 20 minutes was the most efficient method for visual evaluation and isolation of the resting eggs. Hatching rate experiments with resting eggs not isolated from ephippia were underestimated (11.1 ± 5.0%), showing the need of methods to quantify and isolate viable eggs. There were no differences between the hatching rate of resting eggs submitted to hypochlorite solution (47.2 ± 7.34%) and manually decapsulated (53.7 ± 13.24%). However, the immersion in hypochlorite was a more efficient technique, faster and not requiring manual ability.

Beta diversity as a tool for determining priority streams for management actions

Beta diversity has become essential for understanding ecosystem functioning and for determining biodiversity-conservation priority areas. However, the beta diversity patterns of invertebrates in tropical aquatic ecosystems are not well known, particularly in streams. Using data from low-order streams located in southern Brazil, we evaluated the beta diversity of Chironomidae. We tested the hypothesis that increased environmental heterogeneity increases beta diversity. The streams were grouped into two categories, rural and urban, according to the percentage of urbanization in their micro-basins. Our results showed that the heterogeneity of environmental variables can determine the beta diversity of Chironomidae, and the increased environmental heterogeneity caused by differences in the intensity of urbanization impacts can increase the beta diversity in urban streams. Therefore, the intensified impacts of anthropogenic activities in aquatic ecosystems can also increase beta diversity. Finally, we suggested that beta diversity can be an effective tool for not only designing measures and determining priority conservation areas, but also accurately identifying potentially degraded and priority sites that require water management plans.

SUCESIÓN DE MICROALGAS PERIFÍTICAS EN TRIBUTARIOS DEL RÍO GAIRA SIERRA NEVADA DE SANTA MARTA-COLOMBIA

<p class="Body">En ecosistemas acuáticos tropicales con altos niveles de intervención antrópica como algunos ríos de la Sierra Nevada de Santa Marta (SNSM) es de vital importancia la determinación del tipo de variables que permiten ponderar el buen estado o por el contrario, el nivel de impacto sufrido en estos ambientes con importancia ecológica y con vocación para ofrecer servicios de abastecimiento. Para este estudio se seleccionaron tributarios de la cuenca media del río Gaira (SNSM), se evaluó el proceso sucesional de microalgas perifíticas, desde enero hasta abril de 2012, mediante el análisis de la comunidad asociada a sustratos artificiales. El propósito del estudio fue analizar la variación en la estructura de la comunidad de microalgas perifíticas durante el proceso de sucesión y evaluar los factores ambientales que determinan esta variación en un rio tropical. Los resultados destacan el caudal, la luz y el oxígeno disuelto los cuales presentaron los valores más altos para el tributario C (Jabalí); el pH fue ligeramente básico para todos los sitios, la temperatura y conductividad presentaron valores más altos en el tributario A (Honduras). El análisis biológico mostró que durante las primeras semanas de exposición del sustrato <em>Melosira varians</em> y <em>Lyngbya </em>sp. fueron dominantes para los tributarios A y B (La Picúa), mientras que para el tributario C se registró una dominancia de <em>Fragilaria </em>sp, <em>Nitzschia</em> sp y <em>Melosira varians</em>. Semanalmente se evaluó la diversidad y riqueza de especies, los mayores valores se registraron después de la cuarta semana de colecta. En el estudio fueron más notorios los cambios en la densidad que en la composición de especies, a pesar de esto el proceso de sucesión fue completo y se evidenció la presencia de especies pioneras (<em>Lyngbya </em>sp, <em>Nitzschia</em> sp), intermedias (<em>Melosira varians</em>, <em>Cocconeis placentula</em>) y tardías (<em>Surirella </em>sp); al igual que la desaparición de especies como <em>Lyngbya </em>sp., proceso mediado por la consecuente aparición de algas tardías de mayor tamaño (<em>Surirella </em>sp).</p><p class="Body"><strong>ABSTRACT</strong></p><p class="Body">In tropical aquatic ecosystems with high levels of human intervention as some rivers in the Sierra Nevada de Santa Marta (SNSM) is vital to determine the type of variables that weigh the good condition or otherwise, the level of impact suffered these environments ecological importance and vocation to offer catering services. For this study were selected tributaries of the middle basin of Gaira (SNSM) River, the successional process periphytic microalgae was evaluated, from January to April 2012, by analyzing the community associated with artificial substrates. The purpose of the study was to analyze the variation in community structure of periphytic microalgae during the succession process and assess environmental factors that determine this variation in a tropical river. The results showed that the discharge, light and dissolved oxygen showed the highest values for the tax C (Jabalí Stream) the pH was slightly basic for all sites, temperature and conductivity showed the highest values for tax A (Honduras Stream). Biological analysis showed during the first weeks of substrate exposure that <em>Lyngbya</em> sp., and <em>Melosira varians</em> were dominant from A and B streams (Honduras and La Picúa), while for the tax C be a dominance of <em>Fragilaria</em> sp. was recorded, <em>Nitzschia</em> sp and <em>Melosira varians</em>. The highest values of diversity and richness were registered after the fourth week of collection. Changes in density were most noticeable than species composition. The successional process was complete and showed the presence of pioneer species (<em>Lyngbya</em> sp., <em>Nitzschia</em> sp), intermediate (<em>Melosira varians,</em> <em>Cocconeis placentula</em>) and late (<em>Surirella</em> sp.), as well as the disappearance of species Lyngbya sp. a process mediated by the consequent occurrence of late larger mycroalgae (<em>Surirella</em> sp.).</p><p class="Body"> </p>

Diversity of phytoplankton community in different urban aquatic ecosystems in metropolitan João Pessoa, state of Paraíba, Brazil

AIM: The aim of the present study was to identify which environmental factors affect the seasonal phytoplankton structure in different types of tropical aquatic ecosystems. Phytoplankton sampling was performed bi-monthly from August 2009 to June 2110 at three sites in the Solon de Lucena Lake, Jaguaribe River and Águas Minerais reservoir. METHODS: The environmental variables were water temperature, transparency, depth, degree of infestation of aquatic macrophytes, air temperature, wind speed, solar radiation and precipitation. The phytoplankton community was studied in terms of richness, density, diversity and evenness. The data were treated with analysis of variance and canonical correspondence analysis. RESULTS: Spatial variations in the data only occurred between ecosystems (p < 0.05). The reservoir and river exhibited typical phytoplankton of lotic environments, with a greater richness of Bacillariophyta (52.8% and 47.8%, respectively). The lake exhibited the typical richness lentic environments, with the greatest contribution from Chlorophyta (52.8%). This ecosystem was characterized by an absence of macrophytes, a low degree of water transparency (0.3 ± 0 m) and high algal density (89,903 ± 38,542 ind. mL-1), with a dominance of Aphanocapsa nubilum. In the river environment, the lesser diversity (0.64 ± 0.24 bit.ind-1 ) was associated to lesser richness (2.4 ± 0.5 spp.) and lesser evenness (0.39 ± 0.19) in comparison to the other ecosystems. The influence of macrophytes in the river and reservoir contributed toward the introduction of metaphytes and epiphytes in the phytoplankton, which was explained by the direct relationship between the density of these species and macrophytes. CONCLUSION: Thus, water transparency and macrophytes were the main factors related to fluctuations between the different aquatic ecosystems studied.

Virus-Bacterium Coupling Driven by both Turbidity and Hydrodynamics in an Amazonian Floodplain Lake

ABSTRACT The importance of viruses in aquatic ecosystem functioning has been widely described. However, few studies have examined tropical aquatic ecosystems. Here, we evaluated for the first time viruses and their relationship with other planktonic communities in an Amazonian freshwater ecosystem. Coupling between viruses and bacteria was studied, focusing both on hydrologic dynamics and anthropogenic forced turbidity in the system (Lake Batata). Samples were taken during four hydrologic seasons at both natural and impacted sites to count virus-like particles (VLP) and bacteria. In parallel, virus-infected bacteria were identified and quantified by transmission electron microscopy (TEM). Viral abundance ranged from 0.5 × 107 ± 0.2 × 107 VLP ml−1 (high-water season, impacted site) to 1.7 × 107 ± 0.4 × 107 VLP ml−1 (low-water season, natural site). These data were strongly correlated with the bacterial abundance (r 2 = 0.84; P < 0.05), which ranged from 1.0 × 106 ± 0.5 × 106 cells ml−1 (high water, impacted site) to 3.4 × 106 ± 0.7 × 106 cells ml−1 (low water, natural site). Moreover, the viral abundance was weakly correlated with chlorophyll a, suggesting that most viruses were bacteriophages. TEM quantitative analyses revealed that the frequency of visibly infected cells was 20%, with 10 ± 3 phages per cell section. In general, we found a low virus-bacterium ratio (<7). Both the close coupling between the viral and bacterial abundances and the low virus-bacterium ratio suggest that viral abundance tends to be driven by the reduction of hosts for viral infection. Our results demonstrate that viruses are controlled by biological substrates, whereas in addition to grazing, bacteria are regulated by physical processes caused by turbidity, which affect underwater light distribution and dissolved organic carbon availability.