Algal-silica cycling and pigment diagenesis in recent alpine lake sediments: mechanisms and paleoecological implications

Hobbs, William O.; Lalonde, Stefan V.; Vinebrooke, Rolf D.; Konhauser, Kurt O.; Weidman, R. Paul; Graham, Mark D.; Wolfe, Alexander P.

doi:10.1007/s10933-010-9441-5

Cited by 20 publications

(16 citation statements)

References 34 publications

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“…3e), which corresponds to the peak LGM wet period estimated in the North Chilean Humidity index at c. 23,000 cal BP . The dissolution of biosilicates (Hobbs et al 2010) at this depth meant we did not have evidence of diatom growth in these sediments to confirm inundation of the wetland. At Rano Raraku, diatoxanthin, a diatom pigment, was preserved in the lowest Arecaceae-rich pollen zone (Dumont et al 1998) and could have come from the same moist period.…”

Section: Discussionmentioning

confidence: 96%

A plant microfossil record of Late Quaternary environments and human activity from Rano Aroi and surroundings, Easter Island

et al. 2015

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To investigate past vegetation change and human activity at the highest elevations on Easter Island, this study examines pollen, phytoliths, diatoms, starch and arthropods preserved in sediment/soil profiles from Rano Aroi crater, and another, newly described wetland in the adjacent, much smaller Rano Aroi Iti depression. A Bayesian age-depth model for Rano Aroi provides adequate certainty for the Late Pleistocene and last *1000 years, but is poorly constrained from 12,000 to 1000 cal BP. The occurrence of cf. Potamogeton and Lycopodium pollen types at this highland site (*425 m altitude), while absent or rare at lowland sites, could well be related to the cooler higher altitude conditions. Smaller quantities of Arecaceae (palm) pollen than at lowland sites indicate that this relatively high-altitude part of the island was near the altitudinal forest limit in the Late Pleistocene, with extensive Asteraceae-dominated shrubland. Arecaceae forest dominated the Holocene, for which there is evidence for a prolonged dry phase. The subsequent disappearance of charcoal and reappearance of diatoms, particularly Eunotia cf. pectinalis, suggest that the dry phase ended prior to human settlement. Polynesian activity is best constrained by abundant microscopic charcoal fragments beginning in a layer at 710 (2r: 645-797) cal BP, and suggesting a period of forest clearance and burning, culminating at 339 (2r: 177-428) cal BP. Thinner soils compared with lowland horticultural sites and 14 C dates of macroscopic Sophora charcoal suggest that the site was occupied after 1670 CE. Newly described terraces, and pollen, phytoliths and starch of cf. Broussonetia papyrifera (paper mulberry), cf. Colocasia esculenta (taro) and Musa (banana) sp. identified in this study show the value of a combined microfossil approach and provide evidence for extension of cultivation of these Polynesian-introduced cultigens to this least accessible part of the island. Rano Aroi Iti yielded a Bayesian 14 C age-depth chronology to a basal age of 1530-1314 cal BP, giving an unexpectedly old age for presumably introduced New World pollen of Sisyrinchium, which occurs throughout the core.

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Section: Discussionmentioning

confidence: 96%

A plant microfossil record of Late Quaternary environments and human activity from Rano Aroi and surroundings, Easter Island

et al. 2015

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“…In Lake PIS, SiO 2 concentrations declined by 70% over the summer. The supply from run‐off and recycling processes probably failed to compensate for consumption by diatoms, losses by diatoms sinking and/or losses by washout (Hobbs et al., ). In such conditions, our results further highlight that silica‐colimitation is likely to increase in late summer.…”

Section: Discussionmentioning

confidence: 99%

Growth rate of alpine phytoplankton assemblages from contrasting watersheds and N‐deposition regimes exposed to nitrogen and phosphorus enrichments

Jacquemin¹,

Bertrand²,

Oursel³

et al. 2018

Freshwater Biology

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High mountain lakes are a network of sentinels, sensitive to any events occurring within their waterbodies, their surrounding catchments and their airsheds. By modifying nutrient balance and availability in water, both local and global changes are expected to alter primary productivity and to trigger strong ecological impacts in these ecosystems. Predicting ecological trajectories under future change is a key challenge for both scientists and conservation managers. French alpine lakes, in the most southern and western part of the European Alps, have received surprisingly little attention to date. In this article, we address how variations in nitrogen (N) and phosphorus (P) supply are likely to impact the area's phytoplankton growth. We performed N and/or P enrichment microcosm experiments under controlled conditions on 12 phytoplankton assemblages sampled during the summer 2016 in four French alpine lakes with contrasting catchments and N‐deposition regimes. The nutrients limiting phytoplankton growth varied according to the nutrient stoichiometry of the lake water. In the lakes exposed to high N‐deposition rates (≈700 kg N km–2 year–1), the water contained more N than P and phytoplankton growth in microcosms was either limited by P or not limited by either N or P. In the lakes exposed to low N‐deposition rates (≈500 kg N km–2 year–1), N availability relative to P was lower in the lake with vegetated catchment than in the lake with rocky catchment, resulting in a switch from P to NP colimitation of the phytoplankton in microcosms. Our data clearly indicate that French alpine lakes do not host the same diversity and structure of phytoplankton communities and that phytoplankton composition influenced phytoplankton growth in microcosms. First, we show that nonmotile colonial chlorophytes appeared in late summer assemblages, with lower growth rates but P‐storage abilities. Second, our findings indicate that the growth of phytoplankton assemblages dominated by diatoms was increasingly limited by silica (SiO2) throughout the summer, along with a 70% decrease in SiO2 concentration in lake water. The forecast global changes in the French Alps should increase phytoplankton growth in most high mountain lakes where P is the main limiting nutrient, before NP colimitation. These changes are likely to be of lesser extent in lakes with large vegetated catchments in the northern area with lower N‐deposition rates and of greater extent in the southern area with higher N‐deposition rates and future P‐deposition rates. By investigating the relationship between nutrient availability, phytoplankton composition and phytoplankton growth rate, this experimental laboratory microcosm study will help interpret current multifactorial data from in situ monitoring networks in the Alps. It will also be helpful to develop models to better predict the sentinel lake responses to local and global changes.

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“…Another important issue is quantification. Some authors calculated pigment concentrations from a calibration curve using HPLC analyses of standards, 6,24,27 others used a method based on additional spectrophotometric measurements of the same but diluted solution as that analysed by HPLC and literature extinction coefficients of particular pigments. 9,11,28 The aim of this paper was to develop an analytical procedure (sample preparation, HPLC analysis and quantification method) for determining carotenoids that could be applied to organic-rich sediments, and to indicate the problems to be overcome during the development of this method.…”

Section: Introductionmentioning

confidence: 99%

“…Some authors have based their calculations on HPLC standard calibration curves, 6,14,27 others have used a method based on an additional spectrophotometric measurement of the same solution as that analysed by HPLC and literature extinction coefficients of particular pigments. 9,11,28 The different calculation methods are compared in Fig.…”

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confidence: 99%

Carotenoid determination in recent marine sediments - practical problems during sample preparation and HPLC analysis

Krajewska¹,

Szymczak‐Żyła²,

Kowalewska³

2017

10.5267/j.ccl

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An analytical procedure for the analysis of carotenoids in marine sediments rich in organic matter has been developed. Analysis of these compounds is difficult; the application of methods used by other authors required optimization for the samples studied here. The analytical procedure involved multiple ultrasound-assisted extraction with acetone followed by liquid-liquid extraction (acetone extract:benzene:water -15:1:10 v/v/v) and HPLC analysis. The influence of column temperature on pigment separation and the quantification method were investigated -a temperature of 5 °C was selected for the Lichrospher 100 RP-18e column. The pigments in the sediment extract were quantified using a method based on HPLC analysis (at 450 nm) and spectrophotometric measurements (at 450 nm), and extinction coefficients were determined for standard solutions at this wavelength. It is very important to use the value of the extinction coefficient appropriate to the wavelength at which the detection of carotenoids was carried out.

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Algal-silica cycling and pigment diagenesis in recent alpine lake sediments: mechanisms and paleoecological implications

Cited by 20 publications

References 34 publications

A plant microfossil record of Late Quaternary environments and human activity from Rano Aroi and surroundings, Easter Island

A plant microfossil record of Late Quaternary environments and human activity from Rano Aroi and surroundings, Easter Island

Growth rate of alpine phytoplankton assemblages from contrasting watersheds and N‐deposition regimes exposed to nitrogen and phosphorus enrichments

Carotenoid determination in recent marine sediments - practical problems during sample preparation and HPLC analysis

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