Palaeolimnology

Recent environmental evolution of the lake Issik-Kul: its natural environment

by Santiago Riera

Giralt, S.; Riera-Mora, S.; Julià, R.; Klerkx, J.; Lignier, V.; Beck, C.; De Batist, M.; Kalugin, I. (2002). In: J. Klerkx & D. Mamatchkanov (eds.), The Issik-Kul Lake: evaluation of the environmental state and its remedation. NATO ARW: NATO Sci. & Environm Affairs Div. Kluwer Acad. Publishers: 125-145.

Paleolimnological study based on ostracods (Crustacea) in Late-glacial and Holocene deposits of Lake Krakower See (Mecklenburg-Vorpommern, NE …

by Finn Viehberg

Viehberg, F.A., 2004. Paleolimnological study based on ostracods (Crustacea) in Late-glacial and Holocene deposits of Lake Krakower See in Mecklenburg-Vorpommern, NE Germany. Studia Quaternaria 21, 109-115.

Two cores were taken from the southern lake basin to record the lake development from the Allerød until today. The... more Two cores were taken from the southern lake basin to record the lake development from the Allerød until today. The Late Glacial and Holocene deposits of Lake Krakower See (Mecklenburg-Vorpommern, NE Germany) revealed changing water levels of the lake. Subfossil freshwater ostracods were used to interpret signals in terms of hydrological changes, eutrophication and temperature. A diverse ostracod fauna of 24 species was found in the examined sediment samples. For the first time the development of Late-Glacial and Post-Glacial freshwater ostracod assemblage could be recorded in the study area.

Key words: freshwater-ostracoda, water level changes, Cytherissa lacustris, Metacypris cordata, paleolimnology,
Mecklenburg West Pomerania

Organic inclusions in lacustrine diatom frustules as a host for carbon and nitrogen isotopes.

by Jonathan Grey

Verh Int Verein Limnol 2006

Back to the future: using palaeolimnology to infer long‐term changes in shallow lake food webs

by Jonathan Grey

Freshwater Biology 2010

1. Shallow lakes are often cited as classic examples of systems that exhibit trophic cascades but, whilst they provide... more 1. Shallow lakes are often cited as classic examples of systems that exhibit trophic cascades but, whilst they provide good model systems with which to test general ecological theory and to assess long-term community change, their food web linkages have rarely been resolved, so changes associated with the structure and dynamics of the ecological network as a whole are still poorly understood.
2. We sought to redress this, and to demonstrate the potential benefits of integrating palaeolimnological and contemporary data, by constructing highly resolved food webs and stable isotope derived measures of trophic interactions and niche space, for the extant communities of two shallow U.K. lakes from different positions along a gradient of eutrophication. The contemporary surface sediment cladoceran and submerged macrophyte assemblages in the less enriched site, Selbrigg Pond, matched the palaeolimnological assemblages of the more enriched site, Felbrigg Hall Lake, in its more pristine state during the 1920s. Thus, Selbrigg was a temporal analogue for
Felbrigg, from which the consequences of long-term eutrophication on food web structure could be inferred. These data represent the first steps towards reconstructing not only past assemblages (i.e. nodes within a food web), but also past interactions (i.e. links within a food web): a significant departure from much of the previous research in palaeolimnology.
3. The more eutrophic food web had far fewer nodes and links, and thus a less reticulate network, than was the case for the more pristine system. In isotopic terms, there was vertical compression in d15N range (NR) and subsequent increased overlap in isotopic niche space, indicating increased trophic redundancy within Felbrigg. This structural change, which was associated with a greater channelling of energy through a smaller
number of nodes as alternative feeding pathways disappear, could lead to reduced dynamic stability, pushing the network towards further simplification. These changes reflected a general shift from a benthic-dominated towards a more pelagic system, as the plant-associated subweb eroded.
4. Although these data are among the first of their kind, the palaeo-analogue approach used here demonstrates the huge potential for applying food web theory to understand how and why these ecological networks change during eutrophication. Furthermore because of the rich biological record preserved in their sediments, shallow lakes represent potentially important models for examining long-term intergenerational dynamics, thereby providing a means by which models and data can be integrated on meaningful timescales – a goal that has long proved elusive in food web ecology.

Fossil chironomid δ 13 C as a proxy for past methanogenic contribution to benthic food webs in lakes?

by Jonathan Grey

Journal of Palaeolimnology 2010

We used a series of experiments to determine whether stable carbon isotope analysis of modern and fossil larval head... more We used a series of experiments to determine whether stable carbon isotope analysis of modern and fossil larval head capsules of chironomids allowed identification of their dietary carbon source. Our main focus was to assess whether carbon from naturally 13C-depleted methane-oxidizing bacteria (MOB) can be traced in chironomid cuticles using stable carbon isotope analysis. We first showed that a minimum sample weight of *20 lg was required for our equipment to determine head capsule d13C with a standard deviation of 0.5%. Such a small minimum
sample weight allows taxon-specific d13C analyses at a precision sufficient to differentiate whether head capsules consist mainly of carbon derived from MOB or from other food sources commonly encountered in lake ecosystems. We then tested the effect of different chemical pre-treatments that are commonly used for sediment processing on d13C measurements on head capsules. Processing with 10% KOH (2 h), 10% HCl (2 h), or 40% HF (18 h) showed no detectable effect
on d13C, whereas a combination of boiling, accelerated solvent extraction and heavy chemical oxidation resulted in a small (0.2%) but statistically significant decrease in d13C values. Using culturing experiments with MOB grown on 13C-labelled methane, we demonstrated that methanogenic carbon is transferred not only into the larval tissue, but also into chironomid head capsules. Taxon-specific d13C of fossil chironomid head capsules from different lake sediments was analyzed. d13C of head capsules generally ranged from -28 to -25.8%, but in some instances we observed d13C values as low as -36.9 to -31.5%, suggesting that carbon from MOB is traceable in fossil and subfossil chironomid remains. We
demonstrate that stable carbon isotope analyses of fossil chironomid head capsules can give insights into dietary links and carbon cycling in benthic food webs in the past and that the method has the potential to reconstruct the importance of MOB in the palaeo-diet of chironomid larvae and, indirectly, to infer past changes in methane flux at the sediment water interface in lakes.

Reconstruction of late Pleistocene climate in the Valsequillo Basin (Central Mexico) through isotopic analysis of terrestrial and freshwater snails

by Rhiannon Stevens

Climatic and land use changes on the NW of Iberian Peninsula recorded in a 1500-year record from Lake Sanabria

by Santiago Riera

R. Julià1*, J.A. Luque, S. Riera, and J.A. Alejandro

CONTRIBUTIONS to SCIENCE, 3 (3): 355–369 (2007)
Institut d’Estudis Catalans, Barcelona
DOI: 10.2436/20.7010.01.13 ISSN: 1575-6343 www.cat-science.cat

This multi-proxy paleoenvironmental study from Lake Sanabria (NW Iberian Peninsula), based on pollen, diatom, and... more This multi-proxy paleoenvironmental study from Lake Sanabria (NW Iberian Peninsula), based on pollen, diatom, and sedimentology, provides evidences of climatic oscillations attributed to the Late Roman and Medieval Warm Periods as well as the Little Ice Age (LIA). From 440 to 950 AD, the climate was characterized by mild temperatures and a Mediterranean rainfall regime, although climatic cold periods were recorded at ca. 530 and 700. Evidence from pollen indicators of land-use suggests that grazing and farming were widespread activities. This period corresponds to the end of the Roman Warm Period and the Medieval Warm Period. The onset of new climate conditions occurred between 950 and 1100 AD, as minimum values of organic matter, arboreal pollen, diatom concentration, total nitrogen (TN), and grain size indicate low temperatures and a more regular rainfall regime. This period corresponds to the LIA and ended at 1590 AD, when lake productivity tended to recover to previous values in spite of the occurrence of cool events. Total organic carbon, TN, and diatom content covary with the temperature index for the NW Iberia, suggesting that Lake Sanabria was mainly controlled by climate before the industrial period. Since 1920 AD, lake productivity has been mainly influenced by human activity.

Recent environmental evolution of the lake Issik-Kul: its natural environment

by Santiago Riera

Giralt, S.; Riera-Mora, S.; Julià, R.; Klerkx, J.; Lignier, V.; Beck, C.; De Batist, M.; Kalugin, I. (2002). In: J. Klerkx & D. Mamatchkanov (eds.), The Issik-Kul Lake: evaluation of the environmental state and its remedation. NATO ARW: NATO Sci. & Environm Affairs Div. Kluwer Acad. Publishers: 125-145.

1,000-year environmental history of Lake Issyk-Kul

by Santiago Riera

Lake Issyk-Kul constitutes one of the most important economic resources in the Republic of Kyrgyzstan, with more than... more Lake Issyk-Kul constitutes one of the most important economic resources in the Republic of Kyrgyzstan, with more than 100 recreational centers along its shore. Some 370,000 holidaymakers visit the lake annually, and this number is expected to increase in the near future given the growing interest in natural environments (Romanovsky, 1990; Savvaitova and Petr, 1992). Thus, a fuller understanding of the past and present evolution of this ecosystem is essential for promoting and sustaining this natural habitat.

Climate change and human impact in central Spain during Roman times: High-resolution multi-proxy analysis of a tufa lake record (Somolinos, 1280 m asl)

by Santiago Riera

A. Currás, L. Zamora, J.M. Reed, E. García-Soto, S. Ferrero, X. Armengol, F. Mezquita-Joanes, M.A. Marqués, S. Riera, R. Julià
CATENA, Volume 89, Issue 1, February 2012, Pages 31-53

Highlights
► High-resolution multi-proxy study of a tufa lake record from Pre-Roman to Early Medieval times. ►... more Highlights
► High-resolution multi-proxy study of a tufa lake record from Pre-Roman to Early Medieval times. ► Environmental changes resulted from the interaction of different driving factors. ► Dry conditions during Roman and Visigothic times and moister phases during Iron Age and Late Roman. ► Wide human impact started at 80 yr BC, one century after the climate change towards drier conditions.

Vegetation, climate and fire in the eastern Andes (Bolivia) during the last 18,000 years

by Joseph Williams

Joseph J Williams, William D Gosling, Stephen J Brooks, Angela L Coe and Sheng Xu. 2011, Palaeogeography, Palaeoclimatology, Palaeoecology. 312(1-2). pp.115-126.

A c. 18 ka cal BP long sediment record from Laguna Khomer Kocha Upper (4153 m asl), Bolivia, shows that fire regime,... more A c. 18 ka cal BP long sediment record from Laguna Khomer Kocha Upper (4153 m asl), Bolivia, shows that fire regime, governed by climatic variation, has long been a transformative agent in the eastern Andes. Before c. 14.5 ka cal BP, warming and relatively moist conditions free from fire, facilitated the expansion of high Andean Polylepis woodland. Fire onset at c. 14.5.ka cal BP, quickly transformed the local vegetation and the woodlands became restricted to areas protected from fire. A major increase in burning, c. 10.1 − 6.4 ka cal BP removed Polylepis woodland locally and this coincided with a region-wide Holocene dry event (HDE) which caused falling lake levels and allowed fire intensification. A decline in burning at c. 6.4 ka cal BP and an increase in marsh-woodland (Alnus) marked the termination of the HDE and a return to wetter conditions. As well as recording the environmental history of local vegetation dynamics, long-distance pollen transport provides evidence of changes in the Yungas montane forests, highlighting their sensitivity to climate and burning regimes. Simultaneous adjustments in both Andean and Yungas montane taxa suggests that vegetation dynamics in the two environments are linked to a common climatic driver. There is no evidence to indicate that human activity had any impact on the local landscape.

Highlights
► Fossil pollen, charcoal and spores provided an 18 ka year record of climate change. ► Charcoal revealed that fire was a transformative agent in the eastern Andes. ► A major increase in burning occurred in the early Holocene (10.1 ka cal BP). ► Pollen and charcoal indicated a shift to wetter conditions at 6.4 ka cal BP. ► The sensitivity of Polylepis woodland to fire is confirmed.

Keywords: Fossil pollen; Fossil charcoal; Deglaciation; Holocene dry event (HDE); Polylepis woodland; Temperature; Precipitation

Nutrients exert a stronger control than climate on recent diatom communities in Esthwaite Water: evidence from monitoring and palaeolimnological records

by Xuhui Dong

Pollen, diatom and plant macrofossil assemblages indicate a low water level phase of Lake Peipsi at the beginning of the Holocene

by Volli Kalm

Four thousand years of environmental change and human activity in the Cochabamba Basin, Bolivia.

by Joseph Williams

Williams, J.J., Gosling, W.D., Coe, A.L., Brooks, S.J. and Gulliver, P. 2011. Quaternary Research, 76, 58-68.

The Cochabamba Basin (Bolivia) is on the ancient road network connecting Andean and lowland areas. Little is known... more The Cochabamba Basin (Bolivia) is on the ancient road network connecting Andean and lowland areas. Little is known about the longevity of this trade route or how people responded to past environmental changes. The eastern end of the Cochabamba valley system constricts at the Vacas Lake District, constraining the road network and providing an ideal location in which to examine past human–environmental interactions. Multi-proxy analysis of sediment from Lake Challacaba has allowed a c. 4000 year environmental history to be reconstructed. Fluctuations in drought tolerant pollen taxa and calcium carbonate indicate two periods of reduced moisture availability (c. 4000–3370 and c. 2190–1020 cal yr BP) compared to adjacent wetter episodes (c. 3370–2190 and c. 1020 cal yr BP–present). The moisture fluctuations broadly correlate to El Niño/ Southern Oscillation variations reported elsewhere. High charcoal abundance from c. 4000 to 2000 yr ago indicates continuous use of the ancient road network. A decline in charcoal and an increase in dung fungus (Sporormiella) c. 1340–1210 cal yr BP, suggests that cultural changes were a major factor in shaping the modern landscape. Despite undisputable impacts of human populations on the Polylepis woodlands today, we see no evidence of woodland clearance in the Challacaba record.


Keywords:
Charcoal
El Niño/Southern Oscillation
Fire
Fossil pollen
Holocene
Human impact
Inca
Polylepis
Sporormiella
Tiwanaku