Phytoplankton Functional Groups Driven by Alternative States in a Tropical Floodplain Lake (Pantanal, Brazil)

Abstract

The flood pulse associated with local factors is the main drivers of the phytoplankton functional groups. The aim of this study was to evaluate the dynamics of the phytoplankton community and the Reynolds Functional Groups (RFG) and their relationships with the alternative states in a Pantanal floodplain lake. The Coqueiro Lake (municipality of Poconé, state of Mato Grosso, Brazil) was sampled monthly at three sites from April 2002 to May 2003. Three periods were identified: i) period I (first receding) with colonization of Egeria najas (Alismatales, Hydrocharitaceae), reduced depths and clear waters, characterized by the lowest species richness (mean = 23 taxa/sample) and reduced phytoplankton biomass (mean = 1.0 mg L-1); ii) periods II (low waters and rising) without Egeria najas, with lowest influence from the river, lowest depths, turbid waters, highest phytoplankton biomass (mean = 9.8 mg L-1) and species richness (mean = 29 taxa/sample); iii) periods III (high waters and beginning of the second receding) with Egeria najas and high influence from the river, greater depths, clear waters, with intermediate species richness (mean = 26 taxa/sample) and lowest phytoplankton biomass (mean = 0.7 mg L-1). Phytoplankton was composed mainly of nanoplanktonic algae with greatest contributions in the low waters without Egeria najas and was represented by 16 RFG, with reduced variability between the three periods and sites. The functional groups K, P, F, J, H1 and H2 were important in this shallow flood lake governed by natural mechanisms of alternation of clear water regime with reduced phytoplankton biomass to a new state of turbid water dominated by phytoplankton. The variations in the phytoplankton functional groups were related to the physical and chemical regime of the lake and the hydrodynamics of the flood system, which acts as a continuous renewal of the habitat conditions in the different alternative states the lake.

Ecological attributes of aquatic invertebrates in two water turbidity scenarios in a lake of the Pantanal, Brazil

“…annulata and Chironomus strenzkei. The transition conditions in turbid waters are structural and functional elements that contribute to the spatio-temporal dynamics of wetlands, exclusively as in the Sinhá Mariana Lake (Loverde-Oliveira & Huszar, 2007).…”

“…In the Sinhá Mariana Lake, research has been conducted to understand the temporal distribution patterns of phytoplankton (Loverde-Oliveira & Huszar, 2007), the morphological characteristics and their implications on the limnology of lakes (Fantin-Cruz et al, 2008), and the composition and structure of fish communities (Galina & Hahn, 2009;Pacheco & Da-Silva, 2009). Other studies evaluated the presence of macrophytes (Nunes & Da-Silva, 2009) and the species richness of aquatic invertebrates in different habitats (Wantzen et al, 2011).…”

“…The Sinhá Mariana Lake (Fig. 1) is an extension of the Mutum River in the Pantanal (16°14′S, 55°58′W, state of Mato Grosso, Central Brazil) and situated on the left bank of the Cuiabá River, a tributary of the Paraguay River (Loverde-Oliveira & Huszar, 2007).…”

“…Changes in the aquatic system of Pantanal during the rain and drought regime increase the discharge of sediments in rivers, streams, and lakes, resulting in silting processes and decreased water transparency, with increased turbidity (Wantzen et al, 2008). Lakes have also been shown to change from low turbidity to high turbidity as a result of heavy rains (Loverde-Oliveira & Huszar, 2007) in periods of instability. Some lakes show recurrent shifts between a clear and a turbid state in a periodic multi-year pattern that appears to be driven by a combination of internal processes and forcing by weather-related cycles in nutrient load (Loverde-Oliveira et al, 2009).…”