Biological index based on epiphytic diatom assemblages is more restrictive than the physicochemical index in water assessment on an Amazon floodplain, Brazil.

Canadian Water Quality Index (CWQI) provides protection for freshwater life promoting healthy ecosystems and safeguarding human health. Biological Diatom Index (BDI) was developed to indicate the ecological status and water quality of freshwater systems. This paper evaluates the relations between the two different indices. During rising and falling, water samples were taken in the Curuai Floodplain, Brazil. CWQI was calculated using 14 physicochemical parameters and 1 microbiological parameter. The limits were established according to freshwater quality conditions and standards based on water use classes 1 and 2 determined in CONAMA 357 legislation and British Columbia. Canadian Water Quality Index categorization ranged from "marginal" to "excellent," most sampling units were "good" (71%), followed by "fair" (12%) and "excellent" (12%) water quality. Total phosphorus (38 times), chlorophyll a (20), dissolved oxygen (10), and total organic carbon (10) were the parameters that presented the most non-compliance values. Encyonema silesiacum (14%), Gomphonema parvulum (13%), and Navicula cryptotenella (12%) were the main taxa in the rising period, while G. lagenula, E. silesiacum, and Fragilaria capucina were the main taxa during the falling period. BDI ranges from I to V water quality classes. We observed "poor" to "very good" ecological status, with most sampling units "moderate" (52%) and "good" (29%). Water quality for class 2 was better than water quality for class 1, as the limits of the parameters evaluated were more restrictive in class 1 than in class 2 and the predominant uses of water require a higher degree of water purity. The biological index based on diatoms was the most restrictive index whose water classes and categorizations have shown an ecological status that could threaten the protection of aquatic communities on the Curuai floodplain. We suggest the combined use of both indices-physicochemical and biological for water quality assessment in this type of environment.

Vertical distribution of phytoplankton communities in Tigres Lake (Goiás, Brazil) during the rainy and dry seasons - DOI: 10.4025/actascibiolsci.v30i1.1446 / Distribuição vertical da comunidade fitoplanctônica do lago dos Tigres (Goiás, Brasil) - DOI: 10.4025/actascibiolsci.v30i1.1446

Tigres Lake is a blocked valley lake, with no registered studies of phytoplankton vertical distribution for that lake type; as such, our work assumes a pioneering nature. The aim of this study was to recognize temporally and spatially the vertical patterns of phytoplankton community attributes, to detect the dominant and descriptive phytoplankton functional groups, and relate them to limnological characteristics. Tigres Lake was characterized as a warm polymictic lake, featuring occasional thermal stratification in deeper stations. The dry and early rainy seasons presented limnological (evidenced by PCA) and biological (observed by CCA) differences. The dry months presented more nutrient concentrations and greater transparency level; on those months, phytoplankton functional groups Lo, Y, N and W1 were predominant; while the rainy months featured higher temperatures and lower transparency levels, and the predominant phytoplankton functional groups were S1, T and N. By jointly evaluating limnological characteristics, biovolume and phytoplankton functional groups, it can be concluded that the vertical profile of Tigres lake is oligo-mesotrophic

O lago dos Tigres é um lago do tipo vale bloqueado, sendo que não foi registrado estudo evidenciando a distribuição vertical fitoplanctônica para esse tipo de lago; dessa forma, esta pesquisa assume um caráter pioneiro. Objetivou-se, nesse trabalho, o reconhecimento temporal e espacial dos padrões verticais de atributos da comunidade fitoplanctônica, detectar os grupos funcionais fitoplanctônicos dominantes e descritivos do sistema e relacioná-los com características limnológicas. O lago estudado foi caracterizado como polimítico quente, sendo que ocorreram eventuais estratificações térmicas nas estações de maior profundidade. Os períodos de seca e início de chuva apresentaram-se tanto limnologicamente (evidenciado pela ACP) quanto biologicamente (observado pela ACC) distintos. Os meses de seca apresentaram maiores concentrações de nutrientes e maiores transparências. Nesses meses, também foi registrado predomínio dos grupos funcionais Lo, Y , N e W1. Os meses de chuvas apresentaram maiores temperaturas e menores transparências, sendo que os grupos funcionais predominantes foram S1, T e N. Avaliando conjuntamente as características limnológicas, o biovolume e os grupos funcionais, pode-se concluir que o perfil vertical do lago dos Tigres é oligo-mesotrófico