Abiotic variability among different aquatic systems of the central Amazon floodplain during drought and flood events

Abstract

This paper examines water properties from lakes, (depression lakes, sensu Junk et al., 2012), channels (scroll lakes with high connectivity, sensu Junk et al., 2012) and paleo-channels (scroll lakes with low connectivity-sensu Junk et al., 2012, locally called ressacas) located in Mamirauá Sustainable Development Reserve, in Central Amazon floodplain, Amazonas, Brazil. We analysed surface temperature, conductivity, pH, dissolved oxygen, turbidity, transparency, suspended inorganic and organic matter, chlorophyll-a, pheophytin, total nitrogen, total phosphorus, organic and inorganic carbon in 2009 high water phase, 2009 and 2010 low water phases. Multivariate statistical analyses of 24 aquatic systems (6 ressacas, 12 lakes and 6 channels, 142 samples) were applied to the variables in order to: 1) quantify differences among aquatic system types; 2) assess how those differences are affected in the different phases of the hydrological year. First, we analysed the entire set of variables to test for differences among phases of the hydrological year and types of aquatic systems using a PERMANOVA two-way crossed design. The results showed that the all measured limnological variables are distinct regarding both factors: types of aquatic systems and hydrological phases. In general, the magnitude and amplitude of all variables were higher in the low water phase than in the high water phase, except for water transparency in all aquatic system's types. PERMANOVA showed that the differences between aquatic system's types and hydrological phases of all variables were highly significant for both main factors (type and phase) and for the type x phase interaction. Limnological patterns of Amazon floodplain aquatic systems are highly dynamic, dependent on the surrounding environment, flood pulse, main river input and system type. These patterns show how undisturbed systems respond to natural variability in such a diverse environment, and how distinct are those aquatic systems, especially during the low water phase. Aquatic systems in Mamirauá floodplain represent limnological patterns of almost undisturbed areas and can be used as future reference for comparison with disturbed areas, such as those of the Lower Amazon, and as a baseline for studies on the effects of anthropogenic influences and climate change and on Amazon aquatic ecosystem. Keywords

Assessment of Atmospheric Correction Methods for Sentinel-2 MSI Images Applied to Amazon Floodplain Lakes

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Riverine mixing at the molecular scale – An ultrahigh-resolution mass spectrometry study on dissolved organic matter and selected metals in the Amazon confluence zone (Manaus, Brazil)

“…Second, the Amazon system can be regarded as a relatively a No biotic factors included; e.g., increased respiration or exudation of DOM. unperturbed river system and is thus especially suited for in situ studies (Furch and Junk, 1997;Devol and Hedges, 2001;Junk et al, 2011;Affonso et al, 2015). Third, intensified biogeochemical processes are expected in the confluence zone due to strong chemical gradients of pH (5-7.5), dissolved organic carbon (3-11 mg/L) and suspended particulate matter (<10-230 mg/L).…”

Morphology-based functional groups as the best tool to characterize shallow lake-dwelling phytoplankton on an Amazonian floodplain

“…and low water), and leads to high spatio-temporal heterogeneity in the aquatic communities (Ward and Stanford, 1995;Ward et al, 1999). The physical and chemical properties of Amazonian floodplain lakes vary widely depending on the seasonal water level fluctuation (Affonso et al, 2015), soil type, vegetation cover, climate conditions (Junk, 2013;Junk et al, 2015), and human land use and occupation (Junk and Cunha, 2012) and can cause increased nutrients leading to high levels of phytoplankton blooms.…”