Diel dynamic of phytoplankton functional groups in a tropical water supply, Extremoz Lake, northeastern Brazil

Abstract

Aim: This study analyzed -the diel and vertical dynamics of phytoplankton functional groups in a natural tropical lake (Extremoz Lake, northeast Brazil), to investigate and understand the driver factors of the community during a severe drought period. Methods: Sampling of the abiotic variables and phytoplankton was performed at intervals of 6 hours over 24 hours in vertical profiles, in dry and rainy seasons (according to the historical average). The phytoplankton species were grouped according to the functional groups' approach sensu Reynolds et al. (2002). Results: October/12 was considered as a dry period (18.4 mm), while March/13, due to the historical average, as a rainy season, due to the low rainfall during the study period (15.7 mm), it was called severe drought. The lake showed thermal and chemical destratification in both periods. Phytoplankton biomass was higher in the dry season and their vertical distribution was stratified in both periods. In both samplings there were less algal biomass during the night. Phytoplankton functional groups of mixed and shallow systems (S 1 , L 0 and K) were descriptors throughout the study period with higher biomass always registered in the group S 1 , represented by Planktolyngbya limnetica (Cyanobacteria) Conclusion: The lack of seasonality observed in this study, due to prolonged drought, may have influenced the pattern of homogeneous behavior in both samplings. This pattern strongly influenced the vertical distribution of phytoplankton in the two periods, with a constancy of dominance of functional descriptors groups.Keywords: shallow lake, vertical distribution, cyanobacteria, functional groups.Resumo: Objetivo: O nosso trabalho teve como objetivo avaliar a dinâmica nictemeral e vertical dos grupos funcionais fitoplanctônicos em uma lagoa natural tropical (Lagoa de Extremoz, nordeste do Brasil), para investigar e compreender os fatores direcionadores da comunidade em um período de seca severa. Métodos: As amostragens das variáveis abióticas e do fitoplâncton foram realizadas a intervalos de 6 horas ao longo de um ciclo de 24 horas em perfis verticais nas estações de seca e chuva. As espécies fitoplanctônicas foram agrupadas de acordo com a abordagem de grupos funcionais sensu Reynolds et al. (2002). Resultados: O mês de outubro/12 foi caracterizado como período seco (18,4 mm), enquanto que março/13, pela média histórica era caracterizado período chuvoso, devido a baixa precipitação no período de estudo (15,7 mm), foi denominado seca severa. A lagoa apresentou desestratificação térmica e química em ambos períodos. A biomassa do fitoplâncton foi maior na estação seca e a distribuição vertical da mesma foi estratificada em ambas os períodos. Em ambas as amostragens houve menor biomassa algal nos períodos noturnos. Grupos funcionais fitoplanctônicos típicos de ambientes rasos e misturados (S 1 , L 0 e K) foram descritores durante todo o período do estudo, com maior biomassa registrada sempre no grupo S 1 , representado pela Planktolyngbya limnetica (Cyanobac...

Assessing temporal and spatial variability of phytoplankton composition in a large reservoir in the Brazilian northeastern region under intense drought conditions

“…In the same way, another study performed in a tropical water supply reservoir (Extremoz Lake, NE Brazil) also showed the dominance of Pl. limnetica under low values of phosphate-P (Pinto and Becker, 2014), in accordance with our results.…”

Abiotic factors driving cyanobacterial biomass and composition under perennial bloom conditions in tropical latitudes

“…The biomass of Planktolyngbya, a shade-adapted filamentous cyanobacterium (Fabbro & Duivenvoorden, 2000), was related to higher concentrations of suspended solids (VSS and TSS) and shallower depth, dominating year-round in the meso-eutrophic Tabatinga lake. In agreement with previous reports, Planktolyngbya has been associated with turbid environments, with mixed layers and relatively lower values of phosphate in Brazilian semiarid lakes (Pinto and Becker 2015;Barroso et al 2018). Meanwhile, Aphanocapsa, a coccoid cyanobacterium typically found in eutrophic environments (Padisák et al, 2009), was detected under mesotrophic conditions and associated to lower suspended solids and deeper water depth (Zmax).…”

Sediment phosphorus fractionation and flux in a tropical shallow lake

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