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No dia 25 de agosto de 2023, por meio de videoconfer\u00eancia Renata Aparecida Costa aluna de doutorado do Programa de P\u00f3s-gradua\u00e7\u00e3o em Biodiversidade Vegetal e Meio Ambiente do Instituto de Pesquisas Ambientais (IPA), bolsista FAPESP (processo n\u00ba 2018\/26686-0), defendeu sua tese de doutorado intitulada: \u201cAvalia\u00e7\u00e3o das respostas do fitopl\u00e2ncton e do epip\u00e9lon submetidos \u00e0 diferentes t\u00e9cnicas de restaura\u00e7\u00e3o de ecossistemas eutr\u00f3ficos\u201d.<\/p>\n
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A banca examinadora foi presidida pela sua orientadora Profa. Dra. Carla Ferragut (Instituto de Pesquisas Ambientais – IPA), tendo como membros Profa. Dra. Luciane Oliveira Crossetti (Universidade Federal do Rio Grande do Sul – UFRGS), Prof. Dr. St\u00e9fano Zorzal de Almeida (Universidade Federal do Esp\u00edrito Santo – UFES), Prof. Dr. Jo\u00e3o Alexandre Saviolo Osti (Universidade Guarulhos, Univeritas – UNG) e Prof. Dr. Raoul Henry (Universidade Estadual Paulista \u201cJ\u00falio de Mesquita Filho\u201d – UNESP).<\/p>\n
Lagos e reservat\u00f3rios distribu\u00eddos no mundo est\u00e3o sendo prejudicados com a eutrofiza\u00e7\u00e3o. A busca pela restaura\u00e7\u00e3o de ecossistemas aqu\u00e1ticos eutrofizados \u00e9 fundamental para o presente e futuro do meio ambiente em equil\u00edbrio e de toda sua biodiversidade, assim como para a humanidade que necessita da \u00e1gua para m\u00faltiplos usos. O presente estudo teve como objetivo avaliar as respostas do fitopl\u00e2ncton e epip\u00e9lon frente \u00e0 quatro t\u00e9cnicas de restaura\u00e7\u00e3o em reservat\u00f3rio eutr\u00f3fico. Para atingir esse objetivo, foram realizados dois experimentos in situ<\/em> em mesocosmos de fundo aberto na regi\u00e3o litor\u00e2nea do reservat\u00f3rio Lago das Gar\u00e7as. O experimento I aplicou quatro t\u00e9cnicas de restaura\u00e7\u00e3o isoladamente e o experimento II combinou duas t\u00e9cnicas. O experimento I<\/strong> consistiu na aplica\u00e7\u00e3o das t\u00e9cnicas isoladas de aera\u00e7\u00e3o de fundo, floculante natural, macr\u00f3fitas flutuantes e biorreator de perif\u00edton. Cada t\u00e9cnica foi comparada ao controle, que apenas isolou a coluna d\u2019\u00e1gua. Amostras da \u00e1gua, fitopl\u00e2ncton e epip\u00e9lon foram coletadas aos 3, 10, 17, 27 e 60 dias no per\u00edodo do ver\u00e3o. Manejos nas t\u00e9cnicas do biorreator de perif\u00edton e macr\u00f3fitas foram realizados. No experimento II<\/strong>, duas t\u00e9cnicas foram selecionadas com base no experimento anterior, principalmente, visando as respostas de redu\u00e7\u00e3o do f\u00f3sforo da \u00e1gua e aumento do crescimento do epip\u00e9lon fototr\u00f3fico. As t\u00e9cnicas aplicadas em conjunto foram a aera\u00e7\u00e3o de fundo e o biorreator de perif\u00edton. As amostras da \u00e1gua, fitopl\u00e2ncton e epip\u00e9lon foram coletadas aos 2, 9, 16, 28 e 59 dias, no per\u00edodo do ver\u00e3o. Em rela\u00e7\u00e3o aos resultados da aplica\u00e7\u00e3o das t\u00e9cnicas isoladas, o \u00fanico tratamento a apresentar redu\u00e7\u00e3o significativa do f\u00f3sforo da \u00e1gua foi a aera\u00e7\u00e3o de fundo, que tamb\u00e9m reduziu a biomassa do fitopl\u00e2ncton no per\u00edodo experimental. O tratamento biorreator de perif\u00edton aumentou o epip\u00e9lon fototr\u00f3fico. Aumento do epip\u00e9lon fototr\u00f3fico tamb\u00e9m foi detectado no tratamento floculante, mas o efeito de arraste do fitopl\u00e2ncton realizado pelo floculante contribuiu para esse resultado e, ainda, ocasionou polui\u00e7\u00e3o secund\u00e1ria. No tratamento macr\u00f3fitas, verificou-se a redu\u00e7\u00e3o da biomassa fitoplanct\u00f4nica e f\u00f3sforo da \u00e1gua no in\u00edcio do per\u00edodo experimental, mas esse efeito foi perdido por conta, principalmente, da senesc\u00eancia das ra\u00edzes das plantas aqu\u00e1ticas. Necessidade de melhora nos manejos realizados, e principalmente na determina\u00e7\u00e3o da periodicidade, foi evidenciada nos tratamentos isolados de biorreator de perif\u00edton e macr\u00f3fitas. Em rela\u00e7\u00e3o ao efeito temporal na composi\u00e7\u00e3o das esp\u00e9cies descritoras do fitopl\u00e2ncton, as quatro t\u00e9cnicas isoladas apresentaram mudan\u00e7as na estrutura da comunidade ao longo do per\u00edodo experimental. Apesar da redu\u00e7\u00e3o da biomassa fitoplanct\u00f4nica, esp\u00e9cies vinculadas a ambientes enriquecidos persistiram na comunidade nos quatro tratamentos. Em rela\u00e7\u00e3o aos resultados do experimento II, aplica\u00e7\u00e3o de duas t\u00e9cnicas simult\u00e2neas, melhora na redu\u00e7\u00e3o do f\u00f3sforo da \u00e1gua e biomassa do fitopl\u00e2ncton, assim como o aumento do epip\u00e9lon fototr\u00f3fico foi verificado at\u00e9 os 16 dias. As t\u00e9cnicas combinadas contribu\u00edram significativamente com o aumento de f\u00f3sforo nos sedimentos. Considera\u00e7\u00f5es sobre o aumento da efici\u00eancia na aplica\u00e7\u00e3o da aera\u00e7\u00e3o e biorreator de perif\u00edton simultaneamente foram levantadas, como a aplica\u00e7\u00e3o das t\u00e9cnicas em conjunto no per\u00edodo do inverno, ou a aplica\u00e7\u00e3o das t\u00e9cnicas separadas e em uma sequ\u00eancia, pois existe a possibilidade de uma t\u00e9cnica reduzir o efeito positivo da outra. Diante dos achados do presente estudo, conclui-se que as respostas encontradas poder\u00e3o subsidiar aperfei\u00e7oamentos em manejos e tomadas de decis\u00f5es que dizem respeito a restaura\u00e7\u00e3o de ambientes l\u00eanticos, principalmente em locais de clima sub\/tropical, no qual ainda existem poucos estudos em rela\u00e7\u00e3o \u00e0 restaura\u00e7\u00e3o de lagos e reservat\u00f3rios. Por fim, os achados em ambos os experimentos mostram que as t\u00e9cnicas frequentemente estudadas em locais de clima temperado t\u00eam efeitos positivos em locais que sofrem com a influ\u00eancia de maiores temperaturas ao longo do ano. Mas, que os manejos devem ser mais constantes, e a resist\u00eancia ao processo de oligotrofiza\u00e7\u00e3o \u00e9 um fator agravante, por conta dos efeitos das maiores temperaturas.<\/p>\n Palavras-chave: <\/strong>f\u00f3sforo, algas planct\u00f4nicas, algas bent\u00f4nicas, experimento mesocosmos<\/p>\n Lakes and reservoirs distributed around the world are being harmed by eutrophication. The restoration of eutrophic aquatic ecosystems is fundamental for the present and future of the environment in balance and all its biodiversity, as well as for humanity that needs water for multiple uses. The present study aimed to evaluate the responses of phytoplankton and epipelon to four restoration techniques in a eutrophic reservoir. To achieve this objective, two in situ experiments were carried out in open-bottom mesocosms in the littoral region of the Gar\u00e7as reservoir. Experiment I applied four restoration techniques separately, and Experiment II combined two techniques. Experiment I consisted of applying the isolated techniques of aeration, natural flocculant, floating macrophytes, and periphyton bioreactor. Each technique was compared to the control, which only isolated the water column. Water, phytoplankton, and epipelon samples were collected at 3, 10, 17, 27, and 60 days in the summer period. Management in periphyton bioreactor and macrophyte techniques were performed. In experiment II, two techniques were selected based on the previous experiment, mainly targeting the responses of reduced phosphorus in water and increased growth of the phototrophic epipelon. The techniques applied together were aeration and the periphyton bioreactor. Water, phytoplankton, and epipelon samples were collected at 2, 9, 16, 28, and 59 days, in the summer period. Regarding the results of the application of isolated techniques, the only treatment to present a significant reduction of phosphorus in the water was aeration, which also reduced the phytoplankton biomass in the experimental period. The periphyton bioreactor treatment increased the phototrophic epipelon. An increase in the phototrophic epipelon was also detected in the flocculant treatment, but the phytoplankton drag effect carried out by the flocculant contributed to this result and also caused secondary pollution. In the macrophyte treatment, there was a reduction in phytoplankton biomass and water phosphorus at the beginning of the experimental period, but this effect was lost mainly due to the senescence of the roots of aquatic plants. The need for improvement in the management carried out, and especially in determining the periodicity, was evidenced in the isolated treatments of periphyton bioreactor and macrophytes. Regarding the temporal effect on the phytoplankton species composition, the four isolated techniques showed changes in the community structure throughout the experimental period. Despite the reduction of phytoplanktonic biomass, species linked to enriched environments persisted in the community in the four treatments. Regarding the results of experiment II, the application of two simultaneous techniques, improvement in the reduction of phosphorus in water and phytoplankton biomass, as well as an increase in phototrophic epipelon was observed up to 16 days. The combined techniques contributed significantly to the increase of phosphorus in the sediments. Considerations about increasing efficiency in the application of aeration and periphyton bioreactor simultaneously were raised, such as the application of techniques together in the winter period, or the application of separate techniques and in a sequence, since there is a possibility that one technique could reduce the positive effect of the other. In view of the findings of the present study, it is concluded that the answers found may support improvements in management and decision-making regarding the restoration of lentic environments, mainly in sub\/tropical climates, where there are still few studies regarding the restoration of lakes and reservoirs. Finally, the findings in both experiments show that the techniques often studied in temperate climates have positive effects in places that suffer from the influence of higher temperatures throughout the year. However, management must be more constant, and resistance to the oligotrophication process is an aggravating factor, due to the effects of higher temperatures.<\/p>\n Keywords:<\/strong> phosphorus, planktonic algae, benthic algae, mesocosms experiment<\/p>\nABSTRACT<\/strong><\/h4>\n
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<\/a>Renata Aparecida Costa<\/strong><\/a>
\nAvalia\u00e7\u00e3o das respostas do fitopl\u00e2ncton e do epip\u00e9lon submetidos \u00e0 diferentes t\u00e9cnicas de restaura\u00e7\u00e3o de ecossistemas eutr\u00f3ficos<\/a><\/p>\n
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