South American lake paleo-records across the Pampean Region

García-Rodríguez, Felipe; Piovano, Eduardo L.; Puerto, Laura del; Inda, Hugo; Stutz, Silvina; Bracco, Roberto; Panario, Daniel; Córdoba, Francisco; Sylvestre, Florence; Ariztegui, Daniel

doi:10.22498/pages.17.3.115

Cited by 11 publications

(5 citation statements)

References 9 publications

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“…Results are consistent with previous reconstructions which analyzed the phytolith record of Negra lagoon, where a warm/wet period was also identified between 1,980 ± 40 yr BP and 930 ± 45 yr BP, although an intermediate drier/colder episode has been proposed (Bracco et al, 2005a;2005b;2010;del Puerto, 2009) Furthermore, paleolimnological studies in the southern Pampa plains of Argentina suggested that it is fairly acceptable to assume that during the middle-late Holocene, the ratio of evaporation to precipitation was higher, thus leading to salinization, low water levels and possible desiccation of lakes (Stutz et al, 2012). In the northern region of the Pampa plain, a paleolimnological record indicates brackish to saline conditions with pulses of shortperiodic freshwater conditions for 4,840 -1,200 cal.…”

Section: Stagesupporting

confidence: 92%

On the Relationship between Holocene Environmental Variability and the Diatom Composition in the Peña Lagoon, Se Uruguay

et al. 2018

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Uruguayan Southern lagoons exhibit high Holocene resolution paleoenvironmentalpaleoclimatic records for inferring long-term regional changes. The multiproxy analysis of three sediment cores allowed to recognize Holocene climatic variability from the paleolimnological record of Peña lagoon over the last 2,458 yr BP. Four main stages were identified throughout the record. The first (2,458-1,500 cal yr BP) was characterized as a shallow mesoeutrophic system with high abundances of aerophilic benthic species (i.e., Hantzschia amphioxys, Nitzschia brevissima, Frustulia sp., Luticola goeppertiana), epiphytic taxa (i.e Epithemia adnata, Eunotia spp., Rophalodia gibba) and planktonic taxa (i.e. Aulacoseira ambigua and A. granulata). The second stage showed a noticeable change in the diatom assemblage dominated by fresh-brackish benthic species Staurosira construens, but also fluctuations in the abundance of Aulacoseira ambigua and A. granulata, which indicates the occurrence of temperate to cold and semiarid climatic conditions, including intervals of high rainfall. The core chronology allowed us to ascribe this stage to the Little Ice Age (LIA). The third stage, post 390 cal yr BP, showed the highest proportion of freshwater planktonic species throughout the entire core, thus indicating the development of a eutrophic system under relatively warm and wet conditions, which were assigned to the Current Warm Period. After ca. 1962 AD, a sharp increase in the abundance of epiphytic species (i.e., Cocconeis placentula, Eunotia spp, Epithemia adnata and Encyonema minutum) highlights the onset of the fourth stage, which was characterized by littoral expansion and consequently, the proliferation of associated macrophytes due to anthropogenic impacts.

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Section: Stagesupporting

confidence: 92%

On the Relationship between Holocene Environmental Variability and the Diatom Composition in the Peña Lagoon, Se Uruguay

et al. 2018

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“…Hence, many questions regarding the natural climatic cycles and the strength of human-induced changes remain unanswered for vast regions of South America (Villalba et al 2009). This is the case for the Pampa plain, an area in which the prevailing flat geomorphology promotes the occurrence of numerous shallow lakes that contain archives of Holocene environmental changes (García-Rodríguez et al 2009). Most of these water bodies are small and shallow (< 500 ha in * E-mail: ghassan@conicet.gov.ar (Received 10 August 2012;accepted 27 September 2013) surface area and up to c. 4 m deep), and characterized by conductivity ranging from oligo-to hyperhaline, naturally high nutrient concentrations, and dense and rich macrophyte communities (Giorgi et al 2005).…”

Section: Introductionmentioning

confidence: 99%

“…Most of these water bodies are small and shallow (< 500 ha in * E-mail: ghassan@conicet.gov.ar (Received 10 August 2012;accepted 27 September 2013) surface area and up to c. 4 m deep), and characterized by conductivity ranging from oligo-to hyperhaline, naturally high nutrient concentrations, and dense and rich macrophyte communities (Giorgi et al 2005). Their dynamics are intricately linked to climatic conditions and anthropogenic activities (Fernández Cirelli & Miretzky 2004), as is evident from the pronounced hydrological variability that characterized these water bodies during the twentieth century (e.g., lake-level fluctuations, varying river discharges, extension of flooded lowlands, see García-Rodríguez et al 2009). Despite their abundance and climatic sensitivity, only one Holocene paleoenvironmental change study has used diatom analysis on these systems (Stutz et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Diatom-based reconstruction of Middle to Late Holocene paleoenvironments in Lake Lonkoy, southern Pampas, Argentina

Hassan

2013

Diatom Research

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Diatoms recovered from shallow Lake Lonkoy sediment core in southern Pampas, Argentina, were studied in order to assess past environmental conditions. A total of 47 samples were selected from a 1.42-m long core that spans the last 4840 cal. years. Diatoms were extracted by chemical cleaning and studied under light and scanning electron microscopy. A total of 89 diatom taxa were recorded, including 36 taxa that reached > 2% relative abundance and were used in statistical analyses. A cluster analysis allowed five significant diatom association zones (DAZ) to be defined. DAZ I (142-92 cm) was dominated by Cyclotella meneghiniana Kützing, Cocconeis placentula Ehrenberg and Nitzschia hustedtiana Salah, and a low abundance of aerophilic taxa, indicating brackish water conditions probably related to the Holocene sea-level high stand. DAZ II (90-48.5 cm) was dominated by C. meneghiniana and Aulacoseira granulata (Ehrenberg) Simonsen, representing a period of high nutrient loading and turbid conditions in the lake, associated with higher water levels and lower salinities than the environmental conditions in DAZ I. The upper 50 cm of the core (DAZ III to V) showed an increase in the dominance of brackish epiphytic and hypereutrophic benthic taxa, indicating an increase in nutrient concentrations associated with agricultural human impacts in the basin. Overall, diatoms allowed major paleoenvironmental changes to be inferred for the lake during the Holocene.

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“…Because diatom preservation is strongly linked to pH, temperature, ionic strength, sediment reworking, and resuspension (e.g., Lewin 1961; Flower and Nicholson 1987; Flower 1993; Barker 1992; Ryves et al 2006), different physico-chemical conditions may lead to different patterns of live-dead agreement. This work focused on diatoms from alkaline, fresh- to brackish eutrophic shallow lakes, which are numerous in the South American Pampas and constitute the primary source of paleoenvironmental information and, consequently, of modern-analogue data sets (García-Rodriguez et al 2009). Hence, whether the results or conclusions apply to a wider range of lakes of different physical and chemical characteristics requires further study.…”

Section: Discussionmentioning

confidence: 99%

On the benefits of being redundant: low compositional fidelity of diatom death assemblages does not hamper the preservation of environmental gradients in shallow lakes

Hassan¹

2015

Paleobiology

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Comparisons between death assemblages and their source living communities are among the most common actualistic methods of evaluating the preservation of compositional and environmental information in fossil assemblages. Although live-dead studies have commonly focused on marine mollusks, the potential of diatoms to preserve ecological information in continental settings has been overlooked. Thus, little is known about the nature and magnitude of the taphonomic biases affecting live-dead agreement of diatom assemblages, despite their extensive application as modern and fossil bioindicators in paleoecological and paleoenvironmental reconstructions. In this study, I analyzed three live-dead data sets in order to evaluate the compositional and environmental fidelity exhibited by diatom death assemblages in shallow lakes. I find that diatom death assemblages (DAs) do differ significantly in their taxonomic composition from living assemblages (LAs), mainly as a consequence of (1) differences in the temporal resolution between time-averaged DAs and non-averaged LAs, and (2) differential preservation of diatom taxa related to the intrinsic properties of their valves. Despite compositional dissimilarities, DAs were able to capture the same environmental gradients as LAs, with high significance. This decoupling between live-dead agreement in community composition and community response to gradients can be related to the existence of at least two mutually exclusive subsets of species that significantly captured compositional dissimilarities based on the full set of the species in the three lakes. This functional redundancy implies that the between-sample relationships of living assemblages can be significantly preserved by DAs even if some taxa are removed by taphonomic processes. The preservation of environmental gradients thus does not require good preservation of all living taxa. Structural redundancy compensates for the loss of compositional fidelity caused by postmortem processes in the diatom data set.

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South American lake paleo-records across the Pampean Region

Cited by 11 publications

References 9 publications

On the Relationship between Holocene Environmental Variability and the Diatom Composition in the Peña Lagoon, Se Uruguay

On the Relationship between Holocene Environmental Variability and the Diatom Composition in the Peña Lagoon, Se Uruguay

Diatom-based reconstruction of Middle to Late Holocene paleoenvironments in Lake Lonkoy, southern Pampas, Argentina

On the benefits of being redundant: low compositional fidelity of diatom death assemblages does not hamper the preservation of environmental gradients in shallow lakes

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