Responses of testate amoebae assemblages (Amoebozoa: Arcellinida) to recent volcanic eruptions, inferred from the sediment record in Laguna Verde, southern Patagonia, Argentina

Abstract

There is little knowledge about testate amoebae in lakes and their responses to volcanic eruptions. To address this knowledge gap, we studied the paleoecology of these protists in a sediment record from Laguna Verde, a lake located east of the southern Patagonian Ice Field, in Santa Cruz Province, Argentina. The lake is under the influence of volcanic eruptions from Lautaro Volcano, Chile, * 42 km WNW of Laguna Verde. We evaluated the response of 11 testate amoeba morphospecies in the lake to the last four Lautaro eruptions, using a 61-cm sediment core. Calcium (Ca), a major element of volcanic ash, was the most important variable explaining testate amoeba variability in the three zones determined by detretended correspondence analysis. We identified four declines in testate amoeba abundance and diversity associated with tephra deposition. Poisson regression analysis revealed that Difflugia immanata, D. bidens, and D. glans strain ''glans'' decrease after deposition of tephra layers. In contrast, Centropyxis constricta strain ''constricta,'' C. aculeata strain ''aculeata'' and Zivkovicia compressa respond positively to ash deposition. Our findings suggest a high resilience of testate

Imprints of the Little Ice Age and the severe earthquake of AD 2001 on the aquatic ecosystem of a tropical maar lake in El Salvador

“…On the other hand, the low number of ostracods and testate amoebae indicate unfavourable conditions for their development or their poor preservation (likely associated with anoxic conditions due to decomposition of organic matter in the deeper part of the water column). The species assemblage of testate amoebae suggests persistent stressful environmental conditions, related to deep water conditions, oxygen availability, limited vegetation and low organic matter content throughout the whole time spanning the core (Charqueño-Celis et al, 2022).…”

Climate and environmental history of Laguna Polo, Santa Cruz, Southern Patagonia (49 °S) since 1300 AD

“…For the testate amoebae analyses, a volume of 1 cm 3 of sediment was washed using a 53-µm meshsieve to extract tests under a stereomicroscope (5x), which were counted and slided-mounted in semipermanent preparation with glycerine. Taxonomic identi cation was carried out with the help of an optical microscope (Carl Zeiss Primo Star iLed) at CENAC and a scanning electron microscope (Phillips SEM 515) at CNEA at Bariloche, and by using literature specialized on the group down to genus level (Kumar and Dalby 1998;Sigala et al 2016) and on regional species (Burdman et al 2021;Charqueño-Celis et al 2022). As lacustrine testate amoebae species can display a wide range of eco-phenotypically controlled morphological variations, it is common to assign informal infra-subspeci c "strain" names to eco-phenotypes, which helps to avoid inadvertent and unwarranted descriptions of new species, although the International Code of Zoological Nomenclature stipulates that infra-subspeci c level designation have no status (ICZN 1990).…”