Vertical and temporal variation in phytoplankton assemblages correlated with environmental conditions in the Mundaú reservoir, semi-arid northeastern Brazil

Abstract

The goal of this study was to analyse the vertical structure of the phytoplankton community at the Mundaú reservoir, located in the semi-arid region of northeastern Brazil, and to correlate it to environmental conditions over two distinct seasons, dry and rainy. Samples were collected bimonthly at eight depths in the dry and rainy season for analyses of the physical and chemical variables of the water, as well as density, abundance, dominance, species diversity index and equitability of the community. Analysis of variance (ANOVA-two way) was used to analyse the vertical and seasonal differences, and Canonical Correspondence Analysis (CCA) was used to assess associations between phytoplankton and environmental variables Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju was the only dominant species and Geitlerinema amphibium (C. Agardh) Anagnostidis, Merismopedia punctata Meyen and Synedra rumpens Kützing. Others six taxa were abundant in at least one of the samples. Distinct vertical distribution patterns were observed for the abundant taxa between depths and seasons. The cyanobacteria, with the exception of C. raciborskii, showed similar seasonal patterns, with higher densities in the dry season. The CCA showed a strong correlation between the density of the phytoplanktonic species and abiotic variables. The vertical changes in abundant taxa revealed distinct patterns regulated by the variation in the environmental factors that were directly linked to seasonality, with the success of one or more species being dependent on their life strategies and ecological needs. The present study restates the importance of environmental and seasonal factors for phytoplankton composition and distribution in a freshwater tropical reservoir through a vertical gradient.Keywords: freshwater, microalgae, seasonality, spatial dynamics, tropical region Variações vertical e temporal nas assembleias fitoplanctônicas correlacionadas com condições ambientais no reservatório Mundaú, semiárido do nordeste do BrasilResumo O objetivo deste estudo foi avaliar a estrutura vertical da comunidade fitoplanctônica no reservatório Mundaú localizado na região semiárida do nordeste do Brasil e correlacioná-la com as condições ambientais durante dois períodos sazonais distintos, seca e chuva. Amostras foram coletadas bimensalmente em oito profundidades em duas estações climáticas, seca e chuvosa para análises de variáveis físicas e químicas da água, bem como, da densidade, abundância, dominância, índice de diversidade especifica e equitabilidade da comunidade. Análise de variância (ANOVA -dois critérios) foi usada para avaliar as diferenças vertical e sazonal e Análise de Correspondência Canônica (CCA) as associações entre o fitoplâncton e variáveis ambientais. Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju foi a única espécie dominante e Geitlerinema amphibium (C. Agardh) Anagnostidis, Merismopedia punctata Meyen e Synedra rumpens Kützing, foram abundantes em ambas as estações. Outros seis táxons foram ...

Environmental factors driving phytoplankton biomass and diversity in a tropical reservoir

“…Nevertheless, in this study neither the biomass nor the diversity showed dependence on biotic factors, probably due to the occurrence of mixing and transport processes, favored by inflow and outflow and wind, which could cause the homogeneous distribution of phytoplankton by keeping organisms in suspension by means of advective transport processes, important mechanisms of horizontal transport of particles. A very different result from those found in other studies (Webster, 1990, Lira, et al, 2014, Soares-Vieria, et al, 2015, López-Muñoz, 2015, even in this same reservoir (Aguirre -Ramírez, et al, 2007). In this study, along the photic zone, as it was reported by Soares-Vieria, et al (2015), it was observed a gradient in the expression of temperature, pH and dissolved oxygen related to photosynthetic activity, a process that allows CO 2 removal, oxygen production and therefore pH increase.…”

Composition of the phytoplankton community in the first stages of the Quimbo dam life cycle in Huila - Colombia

“…August to the rainy season, precipitation levels in May and August were much higher (136 mm, 145 mm) than June and July (66mm, 50mm), according to the closest meteorological station (located in Garzón -Huila at 02° 11 ' 24.3" N, 75° 36' 18.2W). For tropical reservoirs, precipitation is one the main factors that promote changes in phytoplankton composition and dynamics (Chellappa and Costa, 2003;Jöhnk et al, 2008;Delpla et al, 2009;and Gast et al, 2014), in this study, the dominance of CYANOPHYCEAE persisted during the rainy season and CONJUGATOPHYCEAE during dry season. As for the stations, we can see that Garzon River has the highest abundance of DINOPHYCEAE and CYANOPPHYCEAE which relates to the fact that, once again, this is the most polluted station and as it has been well studied, these two classes of algae can proliferate very well under these conditions (Spector, 1984;Bittencourt-Oliveira et al, 2012), and with time they could bloom triggering all the consequences that blooms imply (Anderson et al, 2002;Allen et al, 2008;Havens 2008).…”

Cyanobacterial blooms in freshwaters bodies in a semiarid region, northeastern Brazil: A review

“…Extreme climatic events are already being observed in Northeast Brazil, causing changes in the phytoplankton community, especially in the dominance of cyanobacteria (e.g., Lira et al, 2014;Câmara et al, 2015;Brasil et al, 2016;Costa et al, 2016). Bouvy et al (2000) made one of the most important reports on cyanoHABs (in almost 40 reservoirs in the Northeast) associated with climate change, when the severe drought of 1998 (a consequence of the El Niño in 1997) made the environment favourable for cyanobacteria proliferation, specially Cylindrospermopsis raciborskii.…”