Relationships between Holocene sea-level variations, trophic development, and climatic change in Negra Lagoon, Southern Uruguay

Bracco, Roberto; Inda, Hugo; Puerto, Laura del; Castiñeira, Carola; Sprechmann, Peter; García-Rodríguez, Felipe

doi:10.1007/s10933-004-4934-8

Cited by 40 publications

(19 citation statements)

References 21 publications

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“…Such salinity changes were a consequence of the Holocene sea-level changes, with salinity levels higher during the Holocene transgression and lower during the Holocene regression. During the regression process, a decrease in salinity together with an increase in trophic state was observed (e.g., García-Rodríguez et al, 2004a;Bracco et al, 2005a). Gordon et al (2008) also observed a similar trophic response in relation to salinity in coastal lagoons of the South African coast.…”

Section: Opal Phytolithsmentioning

confidence: 87%

“…The Holocene transgression-regression events led to the deposition of Villa Soriano Formation (Montaña & Bossi, 1995). In addition, they moderated the trophic state development of the coastal systems of southern Uruguay, being higher during regressive than transgressive events (García-Rodríguez & Witkowski, 2003;García-Rodríguez et al, 2004a, b, c;Bracco et al, 2005a).…”

Section: The Study Areamentioning

confidence: 97%

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A multiproxy approach to inferring Holocene paleobotanical changes linked to sea-level variation, paleosalinity levels, and shallow lake alternative states in Negra Lagoon, SE Uruguay

et al. 2010

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A multiproxy analysis of diatoms, chrysophyte cysts, opal phytoliths, and palynomorphs was undertaken in Negra Lagoon, to decipher Holocene changes in paleobotanical proxies associated with sea-level changes and paleolimnological conditions. Before the Holocene transgression (7000 yr BP), a terrestrial system was inferred as no aquatic palynomorphs or biogenic silica remains were recorded. During the sea-level maximum (5200 yr BP), marine/ brackish conditions were established as indicated by diatoms, Chenopodiaceae, and a high content of cysts of Peridinioideae. The catchment consisted of grasslands and wetlands as indicated by the opal phytolith data. The Holocene transgression was followed by a sea-level decrease, which led to the onset of brackish/freshwater conditions as inferred from the co-dominance of freshwater and marine/ brackish diatoms. This is also supported not only by the concomitant increase in non-siliceous freshwater microalgae and emergent macrophytes, but also by the presence of Myriophyllum. As sea level continued to decrease during late Holocene, a freshwater system was observed because of the complete separation from the ocean. Chrysophyte cysts were consistently recorded and brackish diatoms exhibited reduced abundances. The observed limnological changes are consistent with the alternative states hypothesis of Scheffer's model (1998). That is, the clear water phases were explained because of high macrophyte abundances, low phytoplankton frequencies, high cyst to diatom ratios, and increase in frequencies of benthic diatom species. Conversely, turbid phases were likely to occur when low cyst to diatom ratios together with increase in planktonic diatoms and decrease in macrophytes values were detected. This highlights the importance of this approach to detect long-term changes in shallow lake alternative states.

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Section: Opal Phytolithsmentioning

confidence: 87%

Section: The Study Areamentioning

confidence: 97%

A multiproxy approach to inferring Holocene paleobotanical changes linked to sea-level variation, paleosalinity levels, and shallow lake alternative states in Negra Lagoon, SE Uruguay

et al. 2010

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“…These conditions are also registered by faunal assemblages from the Pampa grasslands (Tonni et al 1999) and by paleolimnological records from southern Uruguay (Bracco et al 2005b), and have been associated with the Little Ice Age, which is generally thought to have occurred between 400 and 150 cal year BP (Bradley et al 2003;Villalba et al 2005). At Nahuel Rucá Lake, however, cold and fluctuating humid-dry conditions persisted until the present.…”

Section: Paleoclimate Trendsmentioning

confidence: 90%

“…Because the grasses of southern Uruguay and eastern Argentina are similar, the reference collection of phytoliths of del Puerto et al (2006) can be used for phytolith identification in the area of Nahuel Rucá Lake. Despite such problems as multiplicity and redundancy, the Twiss classification of grass phytoliths was shown to be a reliable tool for inferring paleoclimate changes and has been tested using multi-proxy approaches (Fredlund and Tieszen 1997;Alexandre et al 1999;Baker et al 2000;Bracco et al 2005b). …”

Section: Laboratory Methodsmentioning

confidence: 99%

Late Holocene climate and environment of the SE Pampa grasslands, Argentina, inferred from biological indicators in shallow, freshwater Lake Nahuel Rucá

et al. 2010

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We analyzed pollen, non-pollen palynomorphs (NPPs), calcareous microfossils, plant macrofossils, diatoms, chrysophyte cysts, opal phytoliths and organic matter content in a 123-cm sediment sequence from Nahuel Rucá Lake, a shallow, freshwater system in the southeastern Pampa grasslands, Argentina. Three stages in the lake evolution were identified. Before 3,680 cal year BP, only pollen, NPPs (dinoflagellate cysts and acritarchs) and ostracods were recovered, suggesting brackish/saline conditions in the lake and nearby areas. Freshwater conditions are, however, indicated by Myriophyllum, Pediastrum and Zygnemataceae. The brackish/saline conditions could have been caused by marine influence during a Holocene sea level high stand that affected the area ca. 6,000 year BP. Between 3,680 and 390 cal year BP, macrophyte pollen and plant macrofossils indicate increasingly freshwater conditions in the lake and the adjacent area. Diatom and ostracod assemblages, however, suggest brackish and oligotrophic conditions, giving way to freshwater and meso-eutrophic conditions toward the end of this period. The relationship between submersed macrophytes (Myriophyllum, Potamogeton, Ceratophyllum, Chara) and planktonic algae (Chlorophyta and diatoms), suggests a shift in the lake from a clear to a turbid state. This turbid state is more evident after 390 cal year BP. High values of Pediastrum, Scenedesmus and diatoms (Cyclotella meneghiniana, Aulacoseira granulata, Paleolimnol (2010) 44:761-775 DOI 10.1007 A. muzzanensis) observed during this stage could have reduced light penetration, with consequent loss of submersed plants. Pollen and plant macrofossils in the uppermost 20 cm indicate a shallow, freshwater lake similar to present, though an increase in brackish/ freshwater diatoms suggests an increase in salinity, perhaps related to periodic droughts. Opal phytoliths yield a regional paleoclimatic reconstruction that agrees closely with inferences made using pollen, mammals and sediment characteristics.

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“…These fragilarioid species mentioned above occur, sometimes in high relative abundance, at such distant sites as Baltic Sea coastal waters (e.g. Busse & Snoeijs, 2002;Weckström & Juggins, 2005), coastal plains of the North Sea (Denys, 1990), western coast of Iberian Peninsula (Bao et al, 2007), Brazil (Sylvestre et al, 2005), Uruguay (Bracco et al, 2005), Argentina (Hassan et al, 2006) or South-Eastern Australia lagoons and saline lakes (Fluin et al, 2007;Saunders et al, 2008). The reasons for dominance of fragilarioid taxa in unstable conditions (such as contact zones between marine and freshwater environments) were discussed by, e.g.…”

Section: Introductionmentioning

confidence: 99%

Diatoms as a proxy in reconstructing the Holocene environmental changes in the south-western Baltic Sea: the lower Rega River Valley sedimentary record

et al. 2009

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This study focuses on diatom assemblages occurring in cores of Late-glacial and Holocene deposits retrieved from the mouth of the lower Rega River valley, of the southern coast of the Baltic Sea. Sediment samples from four cores were the subject of the present study. Diatom-inferred environmental characteristics, e.g., water level; water salinity (conductivity), trophic status and pH, within each core are presented. Diatom assemblage zones (DAZ) were distinguished, based on differences in the distribution of particular ecological groups. Each DAZ appears to be related to environmental changes during the deposition of a given sediment interval. The Lateglacial (Allerød) sediments originated in a shallow lake with increasing concentrations of solutes and nutrients. The Holocene record begins in the early Atlantic Chronozone and the diatoms point to weakly brackish-water sediments deposited in a shallow water environment. During the period of 8,500-5,800 cal year BP sedimentation took place in a shallow embayment and/or lagoon. From ca. 5,800 cal year BP onwards sedimentation took place in a peat bog environment alternating with Aeolian deposition. Changes in diatom community structure imply a close relationship with the climate-controlled eustatic rise of the ocean level and its consequence Littorina transgression. As with other southern Baltic Sea localities, brackish-water diatoms appear in the sediments, signaling the onset of marine transgression somewhat earlier than previously accepted. Differences and similarities in diatom assemblages and the palaeogeographic development of nearby regions within the Baltic Sea basin and lagoons (coastal areas) from different geographic regions, are also discussed.

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Relationships between Holocene sea-level variations, trophic development, and climatic change in Negra Lagoon, Southern Uruguay

Cited by 40 publications

References 21 publications

A multiproxy approach to inferring Holocene paleobotanical changes linked to sea-level variation, paleosalinity levels, and shallow lake alternative states in Negra Lagoon, SE Uruguay

A multiproxy approach to inferring Holocene paleobotanical changes linked to sea-level variation, paleosalinity levels, and shallow lake alternative states in Negra Lagoon, SE Uruguay

Late Holocene climate and environment of the SE Pampa grasslands, Argentina, inferred from biological indicators in shallow, freshwater Lake Nahuel Rucá

Diatoms as a proxy in reconstructing the Holocene environmental changes in the south-western Baltic Sea: the lower Rega River Valley sedimentary record

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