Nitrogen and phosphorus present in sewage can be used for microalgae growth, possibiliting cost reduction in the production of microalgae at the same time that it decreases the eutrophication potential of the effluent. This research aimed at monitoring the native community of microalgae and coliform bacteria in a secondary effluent from anaerobic municipal sewage treatment. Two treatments (aerated and non-aerated) were performed to grow microalgae under semi-controlled conditions in semi-closed photobioreactors in a greenhouse. The results showed no significant pH and coliforms (total and Escherichia coli ) variation between treatments. Nutrient concentrations were reduced supporting microalgae growth up to 10 7 cells.mL −1 independent of aeration. Exponential growth was obtained from the first day for the non-aerated, but a 5 day lag phase of growth was obtained for the aerated. Chlorella vulgaris was the dominant microalgae (99.9%) in both treatments. In the aerated, 5 algae classes were detected (Chlorophyceae, Cyanophyceae, Chrysophyceae, Bacillariophyceae and Euglenophyceae), with 12 taxa, whereas in the non-aerated, 2 classes were identified (Chlorophyceae and Cyanophyceae), with 5 taxa. We concluded that effluent is viable for microalgae growth, especially Chlorella vulgaris, at the same time that the eutrophication potential and coliforms are decreased, contributing for better quality of the final effluent.

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Mixotrophy is a metabolic strategy in which an organism is autotrophic and heterotrophic simultaneously. Considering that the aquatic environment provides several organic sources of carbon, it is probably common for microalgae to perform mixotrophy and not only photoautotrophy, but little is known about microalgae mixotrophy. The present work aimed at investigating the growth, photosynthetic activity, morphology, and biochemical composition of the microalga Chlorella sorokiniana in mixotrophic and photo-mixotrophic conditions, comparing it with photoautotrophy. The results showed pH changes after glucose addition, reaching pH 11.62 in mixotrophic and 10.47 in sequential photo-mixotrophic cultures, which limited the microalgal growth. Highest biomass was obtained in the mixotrophic culture in comparison with the sequential photo-mixotrophic one. Rapid light saturation curves showed that α (photosynthetic efficiency, 1.69) and relative electron transport rate (rETR; 565.61) were higher in the mixotrophic cultures, whereas the highest I (irradiance saturation, 386.68) was obtained in the photoautotrophic ones. In the sequential photo-mixotrophic cultures, photosynthetic activity varied during glucose consumption, decreasing the maximum quantum yield F/F after glucose addition, indicating change in metabolism, from photoautotrophy to mixotrophy by the microalga. The results showed that the mixotrophic cultures had higher production of chlorophyll a (6.26 mg mL), cell density (6.62 × 10 cell mL), and lipids (0.06 pg μm). Sequential photo-mixotrophic cultures showed the highest biovolume (360.5 μm cell) and total carbohydrates (0.026 pg μm). The protein concentration was 3.2 and 2.4 times higher in photoautotrophy and photo-mixotrophic growth, respectively, than in mixotrophy, but lipids were three times higher under mixotrophy. The biochemical changes we observed indicate that the microalga's plasticity in face of new environmental characteristics, such as the presence of organic carbon, can change the flow of energy through natural ecosystems.

INTRODUÇÃOO uso de organismos biológicos como bioindicadores em estudos se dá devido à grande relação das suas funções vitais com o ambiente em que vivem e por responderem de diversas maneiras as modificações sofridas nesse ambiente (Hepp et al, 2007). Essas respostas estão relacionadas com a sensibilidade às variações físicas e químicas em corpos hídricos; características morfofisiológicas; abundância e riqueza; ciclo de vida longo; fácil visualização e identificação; serem bioacumuladores e cosmopolitas (Fonseca, 2021).Em ecossistemas aquáticos, a presença de macrófitas oferecem diversas condições para o estabelecimento de organismos como os macroinvertebrados (Diniz et al, 2018). Elas são importantes para a ciclagem de nutrientes, locais de reprodução, formação de habitats, fontes de alimento e refúgio para diversas espécies (Dias et al, 2012).Esse grupo de plantas aumenta a complexidade dos ambientes bentônicos alterando os habitats por enriquecerem o substrato ao fornecer massas radiculares e materiais em decomposição, gerando um substrato mais firme, heterogêneo e estável, possibilitando a abundância da comunidade de macroinvertebrados (Schramm, 1989).Os macroinvertebrados bentônicos apresentam uma diversa atuação ecológica nos ecossistemas aquáticos, englobando o maior número de indivíduos, espécies e biomassa, habitando ecossistemas com substratos orgânicos ou inorgânicos (Carvalho et al, 2018). São bioindicadores de qualidade de água, com classificação em intolerantes, tolerantes e resistentes conforme a capacidade de suportar níveis de alterações ou poluição sofridas em determinada região (Esteves, 2011). Dessa forma, o seguinte projeto tem o objetivo de avaliar como a distribuição espacial de macroinvertebrados aquáticos é influenciada pela presença das macrófitas aquáticas, verificando como fatores bióticos e abióticos contribuem nos efeitos das macrófitas sobre a distribuição de macroinvertebrados bentônicos. MATERIAIS E MÉTODOS Foramverificadas, in situ, as seguintes variáveis abióticas: pH, condutividade elétrica, temperatura, concentração de oxigênio e oxigênio dissolvido e salinidade. Esses parâmetros foram mensurados utilizando uma sonda multiparâmetros.As amostras de macroinvertebrados bentônicos foram coletadas no sedimento próximo e/ou na presença de macrófitas aquáticas, por um coletor do tipo core. Em cada ponto foram realizadas