Morphometry and mixing regime of a tropical lake: Lake Nova (Southeastern Brazil)

Abstract

Lake Nova (15.5 km 2 ) is the second largest lake in the Lower Doce River Valley (Southeastern Brazil). A better understanding of ecosystem structure and functioning requires knowledge about lake morphometry, given that lake basin form influences water column stratification. The present study aims to contribute to the understanding of relationship between morphometry and mixing patterns of deep tropical lakes in Brazil. Water column profiles of temperature and dissolved oxygen were taken on four sampling sites along the lake major axis during 2011, 2012 and 2013. The bathymetric survey was carried out in July 2011, along 131.7 km of hydrographic tracks yield 51,692 depth points. Morphometric features of lake size and form factors describe the relative deep subrectangular elongated basin with maximum length of 15.7 km, shoreline development index 5.0, volume of 0.23 km 3 , volume development of 1.3, and maximum, mean and relative depths of 33.9 m, 14.7 m and 0.7 %, respectively. The deep basin induces a monomictic pattern, with thermal stratification during the wet/warm season associated with anoxic bottom waters (1/3 of lake volume), and mixing during dry and cool season. Based on in situ measurements of tributary river discharges, theoretical retention time (RT) has been estimated in 13.4 years. The morphometry of Lake Nova promote long water RT and the warm monomictic mixing pattern, which is in accordance to the deep tropical lakes in Brazil.

Controlling Factors of Methane in Tropical Lakes of Different Depths

“…This implies that lake mixing and its direct drivers in this study, such as air temperature and air pressure, are more important in controlling CH 4 concentrations in the water column at our study sites. In the future, further documenting each lake's bathymetry would provide better explanation to the relationship of stored CH 4 concentrations and climate parameters since lake basin morphometry is also very crucial to mixing (Gonçalves et al., 2016; Kling, 1988). Regardless, our finding supports the importance of extreme changes in weather to CH 4 dynamics under the Southeast Asian monsoon climate.…”

Deep lakes support higher zooplankton functional diversity than shallow lakes: A case study in lacustrine environments affected by mining tailings (lower Doce River basin, Brazil)

“…Deep lakes can provide horizontal (limnetic and littoral) and vertical (epi, meta and hypolimnion water mass) environmental conditions that allow differentiation of niches (Basińska et al, 2014;Boehrer & Schultze, 2008), favouring greater functional diversity of zooplankton. Lakes from the alluvial valley at LDRV are considered deeper than other Brazilian natural lakes, with a high relative theoretical retention time (>13 years), as detected in Lake Nova by Gonçalves et al (2016) and Palmas Lake (Barroso et al, 2014). A holomitic-monomitic mixing pattern, with strong chemical stratification of the water column during the warm season, has been described for the deep lakes at LDRV, including Nova and Juparanã lakes (Barroso et al, 2014;Bozelli et al, 1992;Gonçalves et al, 2016).…”

“…Lakes from the alluvial valley at LDRV are considered deeper than other Brazilian natural lakes, with a high relative theoretical retention time (>13 years), as detected in Lake Nova by Gonçalves et al (2016) and Palmas Lake (Barroso et al, 2014). A holomitic-monomitic mixing pattern, with strong chemical stratification of the water column during the warm season, has been described for the deep lakes at LDRV, including Nova and Juparanã lakes (Barroso et al, 2014;Bozelli et al, 1992;Gonçalves et al, 2016). In these lakes, the deep morphology is a determinant for higher potential of the water column's resistance to mixing, according to Barroso et al (2014).…”