Sponge spicule and phytolith evidence for Late Quaternary environmental changes in the tropical Pantanal wetlands of western Brazil

Long-term impacts of mid-Holocene drier climatic conditions on Bolivian tropical dry forests

“…10). This fits with the timing of the mid-Holocene drier climatic period in Andean palaeoclimate records such as Laguna Titicaca (Baker et al, 2001) and Laguna Pumachoca (Bird et al, 2011) as well as lowland Pantanal records such as Jaraguá Cave (Novello et al, 2017), Laguna Negra (Rasbold et al, 2019), and Laguna La Gaiba (Whitney et al, 2011(Whitney et al, , 2014McGlue et al, 2012;Whitney and Mayle, 2012;Metcalfe et al, 2014;Fornace et al, 2016;Fig. 11).…”

“…Pollen records from Lagunas Chaplin and Bella Vista in eastern Bolivia confirm that the mid-Holocene drier period extended to the lowlands (Burbridge et al, 2004). In the Pantanal lowlands, this period is confirmed by a speleothem record from Jaraguá Cave (Novello et al, 2017); phytolith and sponge spicule records from Laguna Negra (Rasbold et al, 2019); and pollen, geochemical, sedimentary, and Pediastrum records from Laguna La Gaiba at the eastern margin of the Chiquitano dry forest (Whitney et al, 2011; McGlue et al, 2012; Whitney and Mayle, 2012; Metcalfe et al, 2014).…”

“…As the record from Yuguarú only covers the last 6000 yr, it does not span the full duration of the mid-Holocene drier period, and therefore precludes thorough investigation of the impacts of this period on the dry forest vegetation at this site. The sponge spicule and phytolith record from Laguna Negra spans the Pleistocene to the present, providing an environmental reconstruction of flooding in the Pantanal, but not a vegetation reconstruction for the dry forest (Rasbold et al, 2019). Laguna La Gaiba is the only palaeoecological record in the Chiquitano dry forest region that spans the onset and termination of the mid-Holocene drier period.…”

“…The responses of tropical dry forests and upland savannahs to the mid-Holocene drier period are not well understood, partly due to the lack of sufficiently old, permanent lakes within the dry forest biome from which palaeo-vegetation records can be drawn. In the Chiquitano dry forest of Bolivia, there are only three lake sites for which palaeo-vegetation records for the Holocene have been published—Laguna Yuguarú in the central lowlands of Bolivia (Taylor et al, 2010) and Lagunas Negra and La Gaiba at the eastern edge of the Chiquitano forest on the Bolivian–Brazilian border (Whitney et al, 2011; Rasbold et al, 2019). As the record from Yuguarú only covers the last 6000 yr, it does not span the full duration of the mid-Holocene drier period, and therefore precludes thorough investigation of the impacts of this period on the dry forest vegetation at this site.…”

Table 1: The number of records obtained through Google Scholar and PubMed using the search terms “sponge spicules”, “glass ramp”, “spiculite” and “spongillite”.

“…Even though the authors recognized the presence of three sponge species in their assemblage, they did not explore whether their occurrence is indicative of an important environmental information (water pH, conductivity). The most comprehensive assessment of the use of freshwater sponge spicules for paleoenvironmental reconstructions was conducted in riverine and lentic systems in Caatinga (Santos et al, 2016) and Pantanal wetlands ecosystems (McGlue et al, 2012;Kuerten et al, 2013;Rasbold et al, 2019b) in Brazil. Parolin, Volkmer-Ribeiro & Stevaux (2007, Guerreiro et al (2013) and Zviejkovski et al (2017) focused mostly on reconstructing the history of lake sediments on colluvial-alluvial terraces in the Upper Paraná River, while Rasbold et al (2019a) investigated the history of island deposits.…”