Algal Microfossils Research Articles

Isolation and Analysis of the Palynomorphs from Khadro Formation Exposed at Ranikot Fort Area Sindh, Pakistan

Seventeen (17) palynomorphs were found from the Khadro Formation comprises of sandstone, shale, and limestone exposed at Ranikot Fort area Sindh, Pakistan. Palynomorphs are microfossils, possessing organic-walled microscopic organisms, their size range is from 5-500 µ (micrometers). Majority of the samples contained angiospermic and algal microfossils. Algal remains indicated the prevalence of sub-tropical to tropical climate, in which marine environmental species were Chaetomorpha akineta, Zygnema terrestre and Synechococcus aeruginosus and also including fresh water species such as, Pinnularia denticulata, Oscillatoria vizagapatensis and Genecularia sp. Arecaceae & Nymphaeaceae also indicated the fresh water vegetation. The fungal counterparts viz,; Dicellaesporites minutus inferred the deposition time of Khadro Formation and the environmental conditions was humid, hot, and with heavy rain fall. Presence of the Pteriodophytic spores (Laevigatosporites sp.) indicated that environment was deltaic, swampy and being estuarine. From Palynomorphs of different groups based on distribution pattern, confirms that during deposition time of Khadro Formation at early environmental condition was hot.

Mapping ancient sedimentary organic matter molecular structure at nanoscales using optical photothermal infrared spectroscopy

Elucidating the molecular structure of sedimentary organic matter (SOM) is key to understanding petroleum generation processes, as well as ancient sedimentary environments. SOM structure is primarily controlled by biogenic source material (e.g., marine vs. terrigenous), depositional conditions, and subsurface thermal history. Additional factors, e.g., strain, may also impact the molecular structure of SOM. Multiple spatially resolved approaches exist for in situ evaluation of SOM, including Raman and infrared spectroscopies, as well as mass spectrometric methods. While these methods have enabled increased understanding of the occurrence and distribution of SOM functional groups, they suffer from disadvantages including low spatial resolution (infrared spectroscopy), limited molecular information (Raman spectroscopy), and sample destruction (mass spectrometric methods). Recent technological advances have resulted in infrared spectrometers capable of breaking the Abbe diffraction limit, greatly increasing the spatial resolutions accessible for an infrared measurement.Here we utilize optical photothermal infrared spectroscopy (O-PTIR) to record maps of functional group distributions at 500 nm spatial resolution in Tasmanites (algal microfossils) from the Upper Devonian Ohio Shale. These data allow for discrimination between Tasmanites, adjacent SOM, and fine-grained minerals. Additionally, functional group distributions within Tasmanites were found to be generally homogenous, although slight variations exist between the body and fold apices (zones of greatest deformation) which may indicate strain-induced chemical reactions. The data presented here represent the first application of O-PTIR to study SOM, highlighting the promise of this analytical approach for future studies evaluating the molecular composition of geologic materials at sub-micron scales.

History of Mid- and Late Holocene Palaeofloods in the Yangtze Coastal Lowlands, East China: Evaluation of Non-Pollen Palynomorph Evidence, Review and Synthesis

The surface of the lowland deltaic plain around Taihu (Lake Tai), south of the Yangtze river mouth in eastern China, lies near sea level and until recent drainage and development by human societies was mostly covered by wetlands of various types. It was created by regular overbank flooding, mainly from the Yangtze, and the deposition of mostly mineral sediments over the several millennia since sea level regained its current altitude in the early mid-Holocene and progradation of the Yangtze delta began. Fluvial activity has therefore been the dominant influence on sedimentation in the Taihu lowlands, and in the lower Yangtze valley generally, and has determined the character of the mainly inorganic sediment sequences that have accumulated there, with autochthonous deposition of organic sediments within the local wetland plant communities playing a minor role. The presence of both clastic flood horizons and peat layers within the deposits of the Taihu plain attests to great variability in the magnitude of fluvial input from the Yangtze, with repeated extreme floods occurring at some periods, but with periods when the growth of peat layers shows low water tables, little exogenic sediment input and so little fluvial influence. We have examined the published evidence for these different depositional environments in the lower Yangtze and the Taihu plain during the Holocene, comparing the flood history with the middle and upper reaches of the Yangtze catchment. Discrete phases of high or low flooding influence are recognised, and these correspond with large-scale Holocene climate history. Intensified human land use in recent millennia has complicated this relationship, amplifying the flooding signal. Our palynological research shows that algal microfossil type and abundance is a useful proxy for changing water depth and quality in the aquatic environments of the Holocene Taihu wetlands, and can recognise flooding events that are not registered in the floodplain lithological sequences.

Middle Triassic freshwater green algae and fungi of the Puesto Viejo Basin, central-western Argentina: palaeoenvironmental implications

Diverse freshwater green algal microfossils and dispersed fungal spores among rich terrestrial palynofloras were recovered from the upper part of the Quebrada de los Fósiles Formation, Puesto Viejo Group, cropping-out in the fault-bounded San Rafael Basin, Mendoza Province, Argentina. Sedimentological data suggest that the vegetation recorded from this unit grew in floodplains of high-sinuosity fluvial systems when intense episodic volcanic activity provided great quantities of ash deposits to the sites. Small and temporary shallow lake deposits and thin peat ponds were recorded at two sections, yielding palynofloras composed of variable contents of spores, pollen, freshwater algae and fungal associations. The taxa described and illustrated herein consist of representatives of colonial Chlorophyta algae (Botryococcus), a diverse group of Zygnematales zygospores represented by the genera Lecaniella, Maculatasporites, Mehlisphaeridium, Ovoidites and the incertae sedis algae Leiosphaeridia and Retirotundia as well as representatives of fungi assigned to Microsporonites and Portalites. Two new species of Ovoidites are described herein, Ovoidites tripartitus and Ovoidites circumplicatus, and the new combination Ovoidites scissus is also presented. The terrestrial and aquatic vegetation grew associated with shallow water bodies in floodplain environments developed under warm temperate, strongly seasonal climatic conditions. The environment was stressed by volcanism that probably restricted the colonization and development of the ecosystem. The occurrence of algal microfossils in the Quebrada de los Fósiles Formation suggest shallow and episodic locally restricted aquatic environments inhabited by autochthonous freshwater green algae consistent with the sedimentological evidence. A Middle Triassic age is inferred from recent radiometric dating obtained from the basal and upper ignimbrite beds of the Quebrada de los Fósiles Formation indicate an age of 243.9 ± 2.0 Ma and 235.8 ± 2.0 Ma, respectively, thus mostly constrained to the Ladinian age. The composition of the fossil flora (palynoflora and macroflora) also indicates Middle Triassic age.Ana M. Zavattieri [amz@mendoza-conicet.gob.ar], Unidad de Paleopalinología, Departamento de Paleontología, Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CCT-CONICET-Mendoza, Av. A. Ruíz Leal s/n, Parque General San Martín, M5502IRA Mendoza, Argentina; Pedro Raúl Gutiérrez [pedroraulgutierrez@gmail.com], Museo Argentino de Ciencias Naturales “B. Rivadavia”, CONICET, Sección Paleopalinología, Área Paleontología. Buenos Aires, Argentina, Av. Ángel Gallardo 470, C1405DJR Buenos Aires, Argentina; Mariana Monti [mariana.monti@ypftecnologia.com.ar], YPF Tecnología S.A. (Y-TEC), Avenida del Petróleo s/n, entre 129 y 143, B1924CKU Berisso, Argentina.

Climate variability and cultural eutrophication at Walden Pond (Massachusetts, USA) during the last 1800 years.

Recent shifts in the ecological condition of Walden Pond, MA, are of potentially wide interest due to the lake's importance as a cultural, historical, and recreational resource in addition to its scientific value as an indicator of local and global environmental change. Algal microfossils in six sediment cores document changes in hydroclimate and trophic status of the lake during the last 1800 years and extend two previous sediment core records of shorter length. Low percentages of planktonic diatoms in the longest cores (WAL-3, WAL-15) indicate shallowing and/or greater water clarity associated with a relatively arid interval during the Medieval Climate Anomaly, ca. A.D. 1150–1300, Cultural eutrophication of the lake since the A.D. 1920s caused diatoms in the genera Asterionella and Synedra to increase in relative abundance at the expense of Cyclotella, Discostella, and the chrysophyte alga Mallomonas allorgei. Percentages of Asterionella and Synedra have remained fairly stable since A.D. 2000 when a previous sediment core study was conducted, but scaled chrysophytes have become more numerous. These findings suggest that, although mitigation efforts have curtailed anthropogenic nutrient inputs to Walden Pond, the lake has not returned to the pre-impact condition described by Henry David Thoreau and may become increasingly vulnerable to further changes in water quality in a warmer and possibly wetter future.

Natural and anthropogenic forcing of Holocene lake ecosystem development at Lake Uddelermeer (The Netherlands)

Lake Uddelermeer (The Netherlands) is characterized by turbid conditions and annual blooms of toxic cyanobacteria, which are supposed to be the result of increased agricultural activity in the twentieth century AD. We applied a combination of classic palaeoecological proxies and novel geochemical proxies to the Holocene sediment record of Lake Uddelermeer (The Netherlands) in order to reconstruct the natural variability of the lake ecosystem and to identify the drivers of the change to the turbid conditions that currently characterize this lake. We show that the lake ecosystem was characterized by a mix of aquatic macrophytes and abundant phytoplankton between 11,500 and 6000 cal year BP. A transition to a lake ecosystem with clear-water conditions and relatively high abundances of ‘isoetids’ coincides with the first signs of human impact on the landscape around Lake Uddelermeer during the Early Neolithic (ca. 6000 cal year BP). An abrupt and dramatic ecosystem shift can be seen at ca. 1030 cal year BP when increases in the abundance of algal microfossils and concentrations of sedimentary pigments indicate a transition to a turbid phytoplankton-dominated state. Finally, a strong increase in concentrations of plant and faecal biomarkers is observed around 1950 AD. Canonical Correspondence Analysis suggests that reconstructed lake ecosystem changes are best explained by environmental drivers that show long-term gradual changes (sediment age, water depth). These combined results document the long-term anthropogenic impact on the ecosystem of Lake Uddelermeer and provide evidence for pre-Industrial Era signs of eutrophication.

The EdiacaranAspidella-type impressions in the Jinxian successions of Liaoning Province, northeastern China

Macroscopic impression fossils from the Xingmincun Formation of the Jinxian Group, Liaoning Province of northeastern China, are identified as members of the Aspidella plexus of Ediacaran age. This is the first recognition of the taxon in the Liaoning Province, although such fossils have been previously recorded in the succession, but were referred to as new species and relegated to an earlier Neoproterozoic age. A revision of the taxonomic interpretation and relative age estimation of the previous record is provided, as well as an evaluation of abiotic vs. biotic processes that could produce similar structures to studied impressions. The mode of preservation of the fossils is considered from a biochemical point of view and along with the properties of organic matter in the integument of soft-bodied metazoans. The selective preservation of the Ediacaran organisms, including metazoans, as impressions (moulds and casts) against the organically preserved contemporaneous cyanobacterial and algal microfossils, and an exceptionally small number of terminal Ediacaran metazoan fossils (Sabellidites, Conotubus and Shaanxilithes), demonstrates the non-resistant characteristics and the very different biochemical constitution of the Ediacaran metazoans compared with those that evolved in the Cambrian and after. The refractory biomacromolecules in cell walls of photosynthesizing microbiota (bacterans, cutans, algaenan and sporopollenin groups) and in the chitinous body walls of Sabellidites contrast sharply with the labile biopolymers in Ediacaran metazoans known only from impressions. The newly emerging biosynthesis of resistant biopolymers in metazoans (chitin and collagen groups) initiated by the annelids at the end of Ediacaran and fully evolved in Cambrian metazoans, considered with the ability to biomineralize, made their body preservation possible. The Chengjiang and Burgess Shale metazoans show evidence of this new biochemistry in body walls and cuticles, and not only because of the specific taphonomic window that enhanced their preservation.

Fossil zygospores of Zygnemataceae and other microremains of freshwater algae from two Miocene palaeosinkholes in the Opole region, SW Poland

ABSTRACTAlgal microremains were encountered during palynological investigation of deposits filling two Miocene palaeosinkholes excavated in the Tarnów Opolski and Górażdże quarries. Algal microfossils of 40 species were identified, most of which are frequent non-pollen palynomorphs occurring in Neogene deposits. The microfossils most frequently found in all studied samples belong to the genera Sigmopollis and Botryococcus. Both algal assemblages contain a significant proportion of resting cells (zygospores = hypnozygotes) such as Cycloovoidites, Diagonalites, Megatetrapidites, Ovoidites, Stigmozygodites, and Tetrapidites, probably fossil zygospores of members of the Zygnemataceae family (Mougeotia, Spirogyra, Zygnema). Some specimens probably related to desmid zygospores (Closteritetrapidites, Monopunctites, Planctonites), freshwater dinoflagellate cysts, and Prasinophyceae (Leiosphaeridia) were found. Most of the identified fossilised remains of algae are often seen in sediments indicating meso- to eutrophic conditions and are characteristic for stagnant or slowly flowing shallow waters. Fossil algae of Pediastrum and Tetraedron genera were recorded in samples from the Górażdże palaeosinkhole, suggesting small differences in the aquatic habitat (e.g. water depth) between ponds in the sinkholes. Three new fossil species related to zygospores of the Zygnemataceae are described: Ovoidites vangeelii sp. nov., Tetrapidites grandis sp. nov., and Tetrapidites opolensis sp. nov

Bacterial, fungal, and algal microfossils in the Lower Proterozoic Baikal region of Siberia (Udokan and Sayany Mountains)

Microfossils from metamorphized Lower Proterozoic deposits of the Udokan Mountains (Naminga Formation) and Sayany Region (Daldarma Formation) are investigated in preparations and petrographic thin sections. They include leucoxenized and ferruginous threads varying in size (50–500 μm) and thread accumulations, which are compared to cyanobacteria. Mineralized thalli probably belong to algae. Small, rounded forms from carbonaceous beds are treated as iron and chemolithotrophic bacteria of stagnant zones of paleobasins. Round or pear-shaped nontransparent forms with projections or several fused forms are described from preparations and identified as fungal microfossils. Similar forms have been recorded in the Lower Proterozoic of Karelia.

Paleoenvironmental and taphonomic implications of trace fossils in Ordovician kukersites

Abstract In an examination of the trace fossils of the Upper Ordovician Yeoman Formation of southeastern Saskatchewan, close relationships were observed between dispersed organic matter (DOM) or macerals (kerogen) and biogenic sedimentary structures. Macerals in these sediments are dominantly composed of the microfossil, Gloeocapsomorpha prisca alginite. To date, no agreement has been reached concerning the life habit of this organism, or the mechanism for accumulation of beds rich in G. prisca. The more popular view is that G. prisca was a non-photosynthetic, prokaryotic, benthic algal mat; others believe it was a photosynthetic, eukaryotic or prokaryotic, planktonic organism, which bloomed episodically throughout the Ordovician. Differing evidence and conclusions may be explained by the fact that the alga was preserved at various stages in its life cycle; i.e. it could be either planktonic or benthic. Depending on the nature of G. prisca, these algal microfossils were consumed and processed differently by burrowing infauna. Fluctuations in abundance of G. prisca are represented by fluctuations in feeding habits represented by the trace fossils and by fluctuating abundance of G. prisca preserved in the sediment. Periods of lowered G. prisca availability are represented by early life cycle, small disseminated type A G. prisca thinly lining the burrows of suspension-feeders. When conditions shifted and G. prisca was more abundant, larger, vegetative, disseminated type B G. prisca are also found in the burrow linings and fills. At maximum blooms, kukersites (beds rich in disseminated type B G. prisca) were preserved. In all phases of the bloom, G. prisca is absent from the fill of deposit-feeding Planolites, but occurs in the linings of suspension-feeding Palaeophycus. Based on the distribution of G. prisca within trace fossils in the Yeoman Formation, a planktonic nature for this microfossil better explains the accumulation of kukersite beds rich in G. prisca that occur in southeastern Saskatchewan. Although conditions causing these blooms and the scale of cyclicity need to be further examined, a restriction of the sea-floor is suggested by the limited trace fossil suite as well as dominance of a single species of phytoplankton, G. prisca.

Modern humans in Sarawak, Malaysian Borneo, during Oxygen Isotope Stage 3: palaeoenvironmental evidence from the Great Cave of Niah

During recent reinvestigations in the Great Cave of Niah in Borneo, the ‘Hell Trench’ sedimentary sequence seen by earlier excavators was re-exposed. Early excavations here yielded the earliest anatomically-modern human remains in island Southeast Asia. Calibrated radiocarbon dates, pollen, algal microfossils, palynofacies, granulometry and geochemistry of the ‘Hell Trench’ sequence provide information about environmental and vegetational changes, elements of geomorphic history and information about human activity. The ‘Hell’ sediments were laid down episodically in an ephemeral stream or pool. The pollen suggests cyclically changing vegetation with forest habitats alternating with more open environments; indicating that phases with both temperatures and precipitation reduced compared with the present. These events can be correlated with global climate change sequences to produce a provisional dating framework. During some forest phases, high counts of Justicia, a plant which today colonises recently burnt forest areas, point to fire in the landscape. This may be evidence for biomass burning by humans, presumably to maintain forest-edge habitats. There is evidence from palynofacies for fire on the cave floor in the ‘Hell’ area. Since the area sampled is beyond the limit of plant growth, this is evidence for human activity. The first such evidence is during an episode with significant grassland indicators, suggesting that people may have reached the site during a climatic phase characterised by relatively open habitats ∼50 ka. Thereafter, people were able to maintain a relatively consistent presence at Niah. The human use of the ‘Hell’ area seems to have intensified through time, probably because changes in the local hydrological regime made the area dryer and more suitable for human use.

Estimating historical in-lake alkalinity generation from sulfate reduction and its relationship to lake chemistry as inferred from algal microfossils

Sediment cores were used to estimate in-lake alkalinity generation resulting from sulfate reduction relative to inferred changes in lakewater pH and trophic status over the last century in three Connecticut lakes. Despite being situated in geological settings with crystalline bedrock and thin, poorly buffered soils, and being impacted with high rates of acidic precipitation, none of the study lakes have declined in inferred pH based on scaled chrysophyte and diatom remains. In fact, the pH of one of the lakes, Coventry Lake, has significantly increased over the last century. Over the last 44 to 69 years the amount of sulfur stored in the sediments from each lake increased from ~two to three times resulting in mean rates of alkalinity generation ranging from 78 to 145 meq m−2 yr−1, significantly higher than the 45 to 48 meq m−2 yr−1 of hydrogen ions falling directly on the lake surfaces. In-lake alkalinity generation resulting from sulfate reduction has been sufficient to neutralize all of the acid falling directly onto the lake surfaces, as well as between 9% and 25% of the acid deposited onto the surrounding watersheds. Despite the increased importance of in-lake alkalinity generation, our findings support the hypothesis that significant amounts of alkalinity are also being generated in the catchments of the study lakes. The bulk of the increases in stored sulfur in all three lakes were as Fe sulfides and not in the form of organic sulfur, suggesting that the increases were the result of dissimilatory bacterial reduction of sulfate. As a result of the large increases in storage of Fe sulfides the ratio of total iron to chromium reducible sulfur (Fe:CRS) has declined in all cores over time. Despite the overall decline in Fe:CRS in recent sediments, values are still largely above 3 in more recent sediments of two of the lakes. However, values of Fe:CRS have dropped below 1 in surface sediments of Uncas Lake, suggesting that in-lake loading of phosphorus may be responsible for a recent shift in the algal flora towards a slightly more eutrophic condition.

Paleolimnological Study of Willard and Russell Ponds in New Hampshire

ABSTRACT Long-term environmental trends in Willard and Russell ponds in New Hampshire were assessed using paleolimnological techniques. Algal microfossils (diatom valves and chrysophyte scales) and pollen remains were analyzed from sediment cores representing the depositional environment of the last 200–300 years. Sediment characteristics and geochemical data were also studied to assess past limnological and watershed changes. The export of ions from the watershed has increased in both ponds and trace metal concentrations in sediments have increased over the post-industrial period. Pollen data suggest that the terrestrial vegetation in the watershed had changed in the past. Stratigraphic changes in diatom and chrysophyte taxa indicated lakewater quality changes in Willard and Russell ponds in the past. Diatom assemblages were quantified to infer past total phosphorus (TP), pH, and chloride (CI) concentrations, using diatom-based inference models that have been developed for the lakes in the northeastern USA. Past inferred TP concentrations remained relatively unchanged and both water bodies can be categorized as oligotrophic for the past 200–300 years. However, inferred pH and CI levels have changed in the study ponds. Although changes in inferred CI are most likely related to watershed disturbances, the recent decline in inferred pH is most likely due to increased acidic precipitation. The study shows the usefulness of a paleolimnological approach in determining long-term water quality monitoring trends. These long-term data would be useful in developing effective lake management and restoration plans in New Hampshire.

Biomineralization in the La' erma Gold Deposit of the Western Qinling Mountains

Abstract Geological and geochemical studies and experiments on mineralization indicate that the source bed of the La' erma gold deposit in the south subbelt of the western Qinling Mountains is hydrothermal cherts in the Cambrian Taiyangding Group. Organic geochemical study of the cherts shows that the organic precursors intimately associated with gold are marine bacteria and algae. The gold content in chert is positively correlated with the amount of bacterial and algal microfossils, and simulation experiments on biomineralization of modern bacteria and algae indicate that bacteria and algae played an important role in the formation of the La' erma gold deposit.

A paleolimnological study of eutrophied Lake Arendsee (Germany)

To study the algal microfossil assemblages of eutrophic Lake Arendsee (Germany) prior to the beginning of a restoration project, a 47-cm long freeze core, dating back to ca 1800, was taken from the deepest area of the lake. Based on the CRS modeled 210Pb and 137Cs profiles from the core, 1948 is around 15 cm and the sedimentation rate has increased from ∼ 21.2 mg cm-2 yr-1 in 1900 to ∼ 56.6 mg cm-2 yr-1 in 1986. The sediments were dominated by three centric diatoms. Stephanodiscus binatus, a species associated with eutrophic environments, dominated the upper 19 cm of the core. Cyclotella rossii, a species commonly found in less productive freshwater systems, was found to dominate the lower portion of the core and was absent above 16 cm. S. agassizensis was found throughout the core. In addition to the centric diatoms, three penate diatoms were found to be abundant. Fragilaria crotonensis was found throughout the core, but was most abundant from 19 cm to 16 cm. Asterionella formosa was prevalent below 15 cm, while Diatoma elongatum was found to be common from 17 cm to the surface. The abundances of algal remains of cyanobacteria, chlorophytes, cryptophytes and dinoflagellates decrease dramatically below 25 cm. Zooplankton remains were most abundant around 20 cm, with copepod spermatophores, fecal pellets and protozoa remains most common in the lower portion of the core. The major species shifts observed in the core from Lake Arendsee occur in a transition zone between 20 cm and 15 cm (1920–1940), a time when agricultural production was being increase with the use of inorganic fertilizer.

Structural Comparison of Algal Microfossils with Extant Algaenans Using Ruthenium Tetroxide Degradation

Algaenans are non-hydrolysable biopolymers present in the cell walls of specific freshwater and marine microalgae. As a consequence of their high resistance algaenans are selectively preserved upon sedimentation and burial in the sediments. Upon chemical analysis of algaenan isolated from some green microalgae it was shown that most algaenans share the same chemical features i. e. highly aliphatic and probably cross-linked by ether linkages. Analysis of the Ru04 product mixtures derived from the sediments and comparison with the Ru0₄ degradation products from algaenans isolated from cultured algae showed that the algaenans present in these sediments are virtually identical to those from cultured algae and did not undergo severe alterations upon sedimentation and subsequent burial in the sediments. The differences between the sedimentary material and algaenans are probably mainly caused by the presence of other micrafossils and because manomers that are only ester-linked to the polymer matrix in the case of T. minimum and P. botyanum algaenan are removed from the algaenan during diagenesis. These findings clearly illustrate that selective preservation of resistant algaenans can be an important process in the preservation of sedimentary organic matter in lacustrine sediments.

Algal microfossils provide high temporal resolution of environmental trends

Sedimentary chrysophytes and diatoms from Baby Lake (Sudbury, Canada) were analyzed to assess lakewater trends associated with (i) the commencement of metal mining and smelting activity at the Coniston Smelter in 1913, and (ii) the closure of the smelter in 1972. We reconstructed several environmental variables (i.e. pH, total [Al], and [Ni]) by applying weighted-averaging regression and calibration models to our paleolimnological data. As a result of emissions from the Coniston Smelter, the lake started to acidify from a high pH of about 6.5 in 1940 to a low pH of 4.2 in 1975. During this period, inferred lakewater [Al] and [Ni] also increased dramatically. Following the closure of the smelter in 1972, inferred lakewater pH and metal concentrations recovered close to pre-industrial levels. The inferred pH recovery corresponds closely to the known lakewater pH recovery (a difference of about 0.4 and 0.6 of a pH unit was observed between measured pH, and chrysophyte and diatominferred pH, respectively). Our study demonstrates that algal microfossils can provide high resolution inferences of past environmental trends. This approach holds great potential for documenting a lake's response to decreased loadings of sulphate and metals, and in helping to establish and implement emission standards.

A simple, inexpensive piston corer for collecting undisturbed sediment/water interface profiles

Paleolimnological techniques are invaluable for assessing recent environmental changes, espe- cially in circumstances where long-term ecologi- cal data are unavailable. Paleoecological recon- structions rely on multiple lines of stratigraphic evidence that may require measurement of nu- merous sediment properties, including density, percent dry weight, organic matter and nutrient content, mineralogy, inorganic chemistry, pig- ments, pollen, animal and algal microfossils, and radionuclide activities (i.e. 2l~ and 137Cs). A large-volume sediment/water interface corer that is capable of retrieving substantial amounts of mud is required to provide sufficient material for multiple analyses. Several corers are commer- cially available (e.g. KB

Scaled Chrysophytes (Chrysophyceae) as Indicators of pH in Sudbury, Ontario, Lakes

Surface sediment chrysophytes (Chrysophyceae) of 30 Sudbury, Ontario, lakes were analyzed to investigate the relationship of these algal microfossils with the limnological characteristics of the study lakes. The distribution of the majority of common chrysophyte taxa is correlated closely with lake water pH, pH-related factors, or both. Chrysodidymus synuroideus, Synura echinulata, Mallomonas hamata, M. acaroides var. muskokana, and Chrysosphaerella longispina appear to be indicators of strongly to moderately acidic waters whereas M. pseudocoronata and M. caudata are indicators of circumneutral to alkaline waters. Using multiple regression of pH indicator chrysophyte assemblages against the measured lake pH, a calibration equation was developed to compute chrysophyte-inferred pH. Chrysophyte-inferred pH values were closely related with measured lake water pH (r2 = 0.74). The study indicates that in the absence of historical pH data, stratigraphic analysis of scaled chrysophytes would provide useful information about the history of lake acidification in the Sudbury area. There is some indication that high metal concentrations, in addition to pH, may influence chrysophycean species distribution in acidic lakes.

Chrysophyte scales in lake sediments provide evidence of recent acidification in two Quebec (Canada) lakes

Several lake surveys have indicated that many lakes in Quebec are sensitive to acidification, but no historical data are available to provide conclusive evidence of lake acidification. Paleolimnological studies can provide such evidence. Chrysophycean algal microfossils were analyzed from the sediments of Lake Bonneville and Lake Truite Rouge in Quebec. The chrysophyte flora in the study lakes was stable until 40 yr ago, but since then the taxa characteristic of acidic or slightly acidic waters increased in abundance. The study provides evidence of recent lake acidification in Quebec.