Fossil Diatom Research Articles

Stratigraphic distribution and biostratigraphic utility of the fossil diatom Lancineis rectilatus in the central Kanto Plain, central Japan

The stratigraphic range of extinct shallow-marine diatom species Lancineis rectilatus Naya was investigated in upper Pliocene to Holocene marine strata from five sediment cores drilled on the central Kanto Plain, central Japan. The lowest occurrence of L. rectilatus in the five cores was in the marine strata between the Kd25 and Kd12-Type tephra layers, and was dated at ca 1.45 Ma. The uppermost occurrence of L. rectilatus was in marine strata deposited during marine isotope stage 17, which has an estimated age of ca 0.7 Ma. Occurrences of L. rectilatus can thus provide a useful biostratigraphic index for sediments deposited during ca 1.45–0.7 Ma in the Kanto Plain. This is the first report showing that diatom fossil is applicable as a biostratigraphic indicator for the Quaternary shallow marine strata.

Benthic fossil diatoms from the upper Ogallala Group (late Miocene) near Scotia, NE (USA)

Benthic fossil diatoms from the upper Ogallala Group (late Miocene) near Scotia, NE (USA)

Long-term and regional perspectives on recent change in lacustrine diatom communities in the tropical Andes

Understanding and managing the responses of natural systems to climate change requires knowing whether recent changes in ecosystem structure and function are within the bounds of natural variation or whether the systems are entering new states that are unprecedented. Several recent studies of the fossil diatom record of the last ~ 150 years in Andean lakes have shown changes in diatom species composition that suggest changes in lake thermal structure in response to regional climate warming. Yet these paleolimnological records are only a few hundred years in length, so it is unclear whether the systems have entered new states, with potentially severe consequences for ecosystem structure and function, or whether current trends are within the natural variability of the systems. Here, we use a recently compiled diatom database from tropical South America to explore the regional distribution and ecological controls of selected planktic diatom taxa that are associated with warming and changes in the lake thermal structure. We also review published Andean stratigraphic records that span thousands of years to characterize the long-term dynamics of relevant planktic species in response to past climate change. The contemporary data show that many planktic taxa have broad latitudinal and elevational distributions. The distributions of several taxa are correlated with surface water temperature, but most also are correlated with pH and/or conductivity. A review of existing stratigraphic data from Andean lakes demonstrates that rapid changes in diatom abundance, including abrupt increases followed by decades to centuries of near extirpation, are a common mode of population variation for some planktic taxa. Yet the majority of these published paleolimnological investigations are of lakes that are larger and differ in nutrient status and conductivity from the small dilute systems where recent species shifts have been observed. We propose that assessing the resilience of contemporary diatom communities and, by inference, lake ecosystems is best done by generating new records from Andean lakes of varied size and chemistry that span a millennium or more and hence a broader spectrum of climate conditions, coupled with new ecological and biogeographic studies that build upon ongoing research programs in the tropical Andes. (Less)

The Paleocene record of marine diatoms in deep-sea sediments

Abstract. Marine planktonic diatoms, as today's ocean main carbon and silicon exporters, are central to developing an understanding of the interplay between the evolution of marine life and climate change. The diatom fossil record extends as far as the Early Cretaceous, and the late Paleogene to Recent interval is relatively complete and well documented. Their early Paleogene record, when diatoms first expanded substantially in the marine plankton, is hampered by decreased preservation (notably an episode of intense chertification in the early Eocene) as well as by observation bias. In this article, we attempt to correct for the latter by collecting diatom data in various Paleocene samples from legacy Deep Sea Drilling Project and Ocean Drilling Program deep-sea sediment sections. The results show a different picture from what previous analyses concluded, in that the Paleocene deep-sea diatoms seem in fact to have been as diverse and abundant as in the later Eocene, while exhibiting very substantial survivorship of Cretaceous species up until the Eocene.

Lithostratigraphy and diatom fossil ages of the marine Pliocene strata in the western area of the Nishikubiki Mountains, Niigata Prefecture, central Japan.

Lithostratigraphy and diatom fossil ages of the marine Pliocene strata in the western area of the Nishikubiki Mountains, Niigata Prefecture, central Japan.

Long‐term limnological changes in the Ecuadorian páramo: Comparing the ecological responses to climate warming of shallow waterbodies versus deep lakes

Abstract Páramos are high‐altitude ecosystems of grasslands and shrubs that sustain high levels of biodiversity and contain numerous lakes, ponds and wetlands that are a crucial source of water for millions. In the Andes, limnological data are rare from páramos and particularly so from shallow waterbodies that are prominent features of the landscape. Here, we analyse fossil diatom assemblages using dated sediment cores from three shallow lakes in the páramo of southern Ecuador and document their response to recent climate changes. The two shallowest sites were <0.5 m deep and contained nearly identical diatom assemblages, dominated by Achnanthidium minutissimum and other benthic taxa. The deepest study site, at 4 m depth, differed notably from its shallower counterparts in that the dominant taxa were tychoplanktonic Aulacoseira species. All three study sites showed only minor assemblage shifts over the past ˜200 years. This contrasts sharply with paleolimnological data from nearby deep lakes (Zmax > 17 m) that recorded abrupt changes in diatom phytoplankton coincident with the onset of higher temperatures, reduced wind speeds and the onset of thermal stratification in recent decades. In temperate and high‐latitude regions, an overriding factor influencing freshwater ecosystems is the duration and extent of ice cover, which itself is closely linked to climate variables. In contrast, there is no winter ice cover and the growing season is continuous year round in our equatorial Andean sites. Instead, rising temperatures are affecting deep lakes primarily by altering the physical structure of the water column resulting in greater periods of thermal stratification, which in turn drives changes in biota and other lake processes. However, this mechanism of change only affects deep lakes because shallow waterbodies are easily mixed by wind. Our data demonstrate the differential response of large, deep lakes in the páramo compared to the relative complacency of changes in shallow waterbodies, which is in marked contrast to similar sites affected by seasonal ice cover.

Late Holocene climate changes from diatom records in the historical Reservoir Gonggeomji, Korea

The paleoenvironmental history of the artificial Reservoir Gonggeomji in Sangju City, Korea, was reconstructed using fossil diatom analysis of four sediment cores: GG01, 02, 03, and 04. Accelerator mass spectrometer (AMS) radiocarbon dating results suggest that Reservoir Gonggeomji was maintained from ca. 1350 to 150 cal year BP, and the diatom record in core sediment samples revealed well-defined hydrological changes and paleoenvironmental conditions during this period. The fossil diatom assemblages were predominantly benthic freshwater diatoms. The highest diatom concentrations in all cores were in diatom zone II, in which species richness and diversity were also very high. Cymbella, Eunotia, Gomphonema, Gyrosigma, Navicula, and Pinnularia were the dominant genera in all core sediments. The long-term trend in diatom species abundance and species diversity showed a stronger relationship to temperature anomalies in the northern hemisphere during the past 2000 years with changes in precipitation. These diatom changes could have been controlled by natural climate change, despite anthropogenic activities linked to construction of the dyke in the artificial reservoir.

Fossil diatom assemblages during the last millennium in the Toberi River mouth area, Hokkaido, Japan

Fossil diatom assemblages during the last millennium in the Toberi River mouth area, Hokkaido, Japan

Cyclotella petenensis and Cyclotella cassandrae, two new fossil diatoms from Pleistocene sediments of Lake Petén-Itzá, Guatemala, Central America

While analyzing the fossil diatom flora in one of the longest paleolimnological records (core PI-6) from Lake Petén-Itzá, lowland Guatemala, we encountered Aulacoseira Thwaites, Cyclotella (Kützing) and Discostella (Cleve & Grunow) Houk & Klee species appearing successively in the record. Among them, two new species that are assigned to the genus Cyclotella are described herein. Cyclotella petenensis sp. nov. is characterised by a coarse striation marked by a shadow line and a tangentially undulate central area with an arc of central fultoportulae. Cyclotella cassandrae sp. nov. has an elliptically shaped valve, coarse striae and a scattered ring of central fultoportulae in the central area. Classification and differences to similar taxa in the genus Cyclotella are discussed.

Fossil diatoms, geochemistry, and the Anthropocene paleolimnology of Lake Huron

Abstract Sediment cores from northern (NL) and southern (SL) Lake Huron were analyzed for diatom fossils and sediment geochemistry to investigate human effects on the lake over the last two centuries. Anthropogenic activities drove two major transformations in diatom indicators of lake ecology for the NL around 1972 and 1991 and three transformations for the SL around 1921, 1964, and 1998. The synergistic effects of increased agriculture and decreased forest land coincided with a shift in the SL to a more mesotrophic condition after 1921. Population increase and attendant industry and mining pollution were apparent in sediment contaminants that increased rapidly in the 1930s. Diatom indicators of climate change appeared as early as the 1970s. Mitigation efforts resulted in water quality improvements as indicated by geochemical indicators of contamination and diatom species shifts, but these changes were concurrent with the negative impacts of invasive mussels and climate warming since the 1990s. Until these stressors are alleviated phytoplankton abundance will likely remain at the current low levels. The composition of the diatom flora will continue toward dominance by Cyclotella sensu lato, which may have implications on food web characteristics such as feeding strategies of zooplankton. Overall, these paleo-records provide evidence of human impacts, remediation, and future trajectories for lake condition, all of which are important factors for consideration by lake managers.

Accelerated diversification is related to life history and locomotion in a hyperdiverse lineage of microbial eukaryotes (Diatoms, Bacillariophyta).

Summary Patterns of species richness are commonly linked to life history strategies. In diatoms, an exceptionally diverse lineage of photosynthetic heterokonts important for global photosynthesis and burial of atmospheric carbon, lineages with different locomotory and reproductive traits differ dramatically in species richness, but any potential association between life history strategy and diversification has not been tested in a phylogenetic framework.We constructed a time‐calibrated, 11‐gene, 1151‐taxon phylogeny of diatoms – the most inclusive diatom species tree to date. We used this phylogeny, together with a comprehensive inventory of first–last occurrences of Cenozoic fossil diatoms, to estimate ranges of expected species richness, diversification and its variation through time and across lineages.Diversification rates varied with life history traits. Although anisogamous lineages diversified faster than oogamous ones, this increase was restricted to a nested clade with active motility in the vegetative cells.We propose that the evolution of motility in vegetative cells, following an earlier transition from oogamy to anisogamy, facilitated outcrossing and improved utilization of habitat complexity, ultimately leading to enhanced opportunity for adaptive divergence across a variety of novel habitats. Together, these contributed to a species radiation that gave rise to the majority of present‐day diatom diversity.

Doping of magnetite nanoparticles facilitates clean harvesting of diatom oil as biofuel for sustainable energy

Photosynthetic unicellular brown algae diatoms are considered as photobioreactors (PBRs) that synthesize and store oil in the form of lipid droplets and the much of the crude oil we use comes from fossil diatoms. The clean extraction of this crude oil from diatoms is difficult task. The construction of green chemical protocols for the clean separation of diatom oil from cells without killing or to harm the diatom cells is still in its primitive stage. In this report we would like to propose that facile doping of magnetite on diatoms can be used for clean oil separation in PBRs. We doped magnetite nanoparticles onto the surface of diatom Diadesmis confervaceae a diatom which oozes oil naturally. Doping magnetite onto diatoms can also facilitate easy separation of oil when cells are kept in an electromagnetic field. The cell wall of diatom besides having SiOH group has 281 amino acids of which 187–188 amino acids are conserved and are known for metal binding sites. The magnetite nanoparticles bind to the SiOH groups and metal binding sites of amino acids. The presence of appropriate amine functionalized linkers forming peptide aminosilane shells can further facilitate the binding of peptide/polypeptides which can be used in drug delivery. Besides this the magnetite doped diatoms have wide applications in removal of phosphates and chromium from waste water too.

Pattern recognition using binary masks based on the fractional Fourier transform

This paper presents two new methodologies for pattern recognition invariant to position and rotation. The two methods use the correlation of signatures obtained using a binary rings mask created from the fractional Fourier transform (FRFT). An analysis of fragmented information was performed with 21 images of fossil diatom species. The methodologies were applied to 30 species of phytoplankton to test the performance when rotation distortion is present in a target. Also, a noise analysis was performed. Higher signature correlation values are achieved by working outside the Fourier plane by changing the order of the FRFT.

Transparent Exopolymeric Particles (TEP) Selectively Increase Biogenic Silica Dissolution From Fossil Diatoms as Compared to Fresh Diatoms

Diatom production is mainly supported by the dissolution of biogenic silica (bSiO2) within the first 200 meters of the water column. The upper oceanic layer is enriched in dissolved and/or colloidal organic matter, such as exopolymeric polysaccharides (EPS) and transparent exopolymeric particles (TEP) excreted by phytoplankton in large amounts, especially at the end of a bloom. In this study we explored for the first time the direct influence of TEP-enriched diatom excretions on bSiO2 dissolution. Twelve dissolution experiments on fresh and fossil diatom frustules were carried out on seawater containing different concentrations of TEP extracted from diatom cultures. Fresh diatom frustules were cleaned from the organic matter by low ash temperature, and fossil diatoms were made from diatomite powder. Results confirm that newly formed bSiO2 dissolved at a faster rate than fossil diatoms due to a lower aluminium (Al) content. Diatom excretions have no effect on the dissolution of the newly formed bSiO2 from Chaetoceros neogracile. Reversely, the diatomite specific dissolution rate constant and solubility of the bSiO2 were positively correlated to TEP concentrations, suggesting that diatom excretion may provide an alternative source of dSi when limitations arise.

Evidence of Holocene water level changes inferred from diatoms and the evolution of the Honghe Peatland on the Sanjiang Plain of Northeast China

Diatom-inferred changes in past water levels and the evolution of peatlands during the Holocene period are investigated in the Honghe National Natural Reserve (HNNR), which is located on the Sanjiang Plain of Northeast China. This investigation began with analyses of fossil diatoms and the corresponding water environments from the surface sediments of peatlands. The detrended correspondence analysis (DCA) and redundancy analysis (RDA) methods show that the water level is one of the major factors that drives the distribution of diatom assemblages in the peatlands of the HNNR. A diatom-based inference model is developed, and the Holocene water levels are reconstructed based on the inference model. Applied to a one-component weighted averaging partial least squares (WAPLS) model, the jackknife statistical test yields a relatively high correlation coefficient and a low root-mean-squared error of prediction (R2jack = 0.220; RMSEPjack = 0.2339) compared with a series of models. The peatland water level was relatively high from 6.5 to 2.8 ka (1 ka = 1000 cal yr BP), and species that prefer deep water, such as Aulacoseira crenulata (Ehrenberg) Krammer and Navicula cuspidata Kützing, were dominant at that time. The water level also increased markedly from 2.8 to 2.5 ka and subsequently declined from 2.5 ka to the present. A clear reciprocal shift is noted between an assemblage of deep-water species that includes A. crenulata and species that prefer sphagnum bogs, including Nitzschia perminuta (Grunow) Peragallo. This evidence suggests that the water level of the HNNR peatland became shallower, implying the presence of a paleolake in the early or middle Holocene that was followed by the development of the peatland, which is a result of paludification, up to the present time. These results strengthen the potential for paleo-reconstructions of the hydrology of the peatlands of Northeast China using multiple proxies.

Paleolimnological proxies reveal continued eutrophication issues in the St. Lawrence River Area of Concern

Abstract Recent surface-water surveys suggest that high nutrient concentrations and nuisance algae remain issues in the St. Lawrence River Area of Concern (AOC) at Cornwall, Ontario, specifically in the tributaries and nearshore zones of Lake St. Francis (LSF). In particular, it is unclear whether management actions designed to reduce nutrient inputs, first implemented in the 1990s as part of the Remedial Action Plan for the AOC, have reduced algal production or influenced assemblage composition. To address this issue, a paleolimnological approach was used to provide a historical context for the present-day nutrient concentrations and to quantify the extent of change in water quality in LSF since the early 1990s. A sediment core was collected near the north shore of LSF and was examined for changes in the concentrations and compositions of fossil diatoms and pigments, as well as stable isotope (δ15N and δ13C) values. Analyses of diatom and pigment concentrations indicated that overall algal abundance has risen in the last few decades, including trends of increasing occurrences of potentially toxic cyanobacteria, despite ongoing remediation efforts. Temporal patterns of stable isotope signatures in the core suggest a steady increase in nutrient influx since the mid-20th century, with the post-1990 increase in algal production likely attributable to recent inputs associated with land-use changes in local contributing watersheds. These patterns suggest that the AOC delisting goals for the LSF tributaries will not be reached without a drastic change in land management practices.

New Mesozoic and Cenozoic fossils from Ecuador: Invertebrates, vertebrates, plants, and microfossils

Ecuador is well known for its extensive extant biodiversity, however, its paleobiodiversity is still poorly explored. Here we report seven new Mesozoic and Cenozoic fossil localities from the Pacific coast, inter-Andean depression and Napo basin of Ecuador, including vertebrates, invertebrates, plants, and microfossils. The first of these localities is called El Refugio, located near the small town of Chota, Imbabura Province, from where we report several morphotypes of fossil leaves and a mycetopodid freshwater mussel of the Upper Miocene Chota Formation. A second site is also located near the town of Chota, corresponding to potentially Pleistocene to Holocene lake deposits from which we report the occurrence of leaves and fossil diatoms. A third locality is at the Pacific coast of the country, near Rocafuerte, a town in Esmeraldas Province, from which we report a late Miocene palm leaf. We also report the first partially articulated skull with teeth from a Miocene scombridid (Mackerels) fish from El Cruce locality, and completely preserved seeds from La Pila locality, both sites from Manabí Province. Two late Cretaceous fossil sites from the Napo Province, one near Puerto Napo showing a good record of fossil shrimps and a second near the town of Loreto shows the occurrence of granular amber and small gymnosperms seeds and cuticles. All these new sites and fossils show the high potential of the sedimentary sequences and basins of Ecuador for paleontological studies and for a better understanding of the fossil record of the country and northern South America.

Abundance of Diadesmis confervacea Kützing and Eunotia camelus Ehrenberg indicates the historical water level variation in a marsh

Water level fluctuations result in changes in available habitat, affecting communities of algae and freshwater diatoms. Paleolimnological approaches assist in understanding the effects of hydrological regimes on communities over time. Therefore, the aim of this study was to identify the variation in water level due to the abundance of two diatom species, Diadesmis confervacea Kutzing and Eunotia camelus Ehrenberg. Diadesmis confervacea has a periphytic habit and occurs primarily in shallow, marshy environments with high temperatures. Eunotia camelus has a planktonic habit and is mainly found in deeper environments. We analyzed the diatom fossils from sediment collected from a marsh located on Mutum Island, in the Upper Parana River floodplain. The sediment core of 2 m was divided into layers of 2.5 cm and was dated to 830 PB using 14C isotope. The relative abundances of the two species were obtained through quantitative analysis. The results showed a shift in the abundance of each species to the geomorphological changes and periods. The ratio of the opposing values of abundances of the two species might have been caused by changes in water levels due to ecological preferences. Competition for light between planktonic and periphytic communities also might affect algae abundance. Thus, we observed that D. confervacea and E. camelus are good indicators of hydrological changes. Therefore, our study contributes to better understand the effects of variation in water level and hydrological regime in the diatom species.

Palaeoenvironmental Reconstruction of the Early to Middle Miocene Sequence in West Central Sinai, Egypt, as Revealed from Fossil Diatoms

AbstractA detailed analysis of the diatoms from the sedimentary sequence exposed in Abu Qada basin, west central Sinai, was used to determine the palaeoenvironmental changes during the Lower to Middle Miocene. A total of 85 diatom species and varieties belonging to 37 genera were identified from 154 samples collected throughout the stratigraphic succession. The lithological characters of the studied samples varied between sandstone, silty interbeds, sandy shales, shales, and terminated with anhydrite and limestones. These rock units are included in two lithostratigraphic formations (Rudies and Kareem), which are separated by a marked unconformity. The distribution and preservation of fossil diatoms in the sedimentary record are examined with the aim of outlining the temporal and spatial variation in the composition of the diatom assemblages, in order to estimate the changes in depositional environments during the Lower to Middle Miocene. The distributional pattern of the recorded diatom taxa distinguished four diatom eco‐zones. The environment of each eco‐zone is deduced and a proposed paleobathymetric change and depositional history of the Miocene sediments in the studied area are given.

Climate drivers of diatom distribution in shallow subarctic lakes

Abstract Global warming can induce profound changes to the functioning of northern freshwater ecosystems. Diatom (Bacillariophyceae) communities often provide early warning signs of associated ecological regime shifts, responding sensitively to alterations in underwater light climate, nutrient regimes, habitat availability and lake water acid–base balance. The underlying mechanisms are manifold and may be mediated via direct climate impact on the physical and chemical properties of lakes or via changes in the terrestrial environment and catchment‐lake coupling. To address catchment‐mediated climate effects on diatom community composition, spatial diatom distribution in the surface sediments of 31 subarctic treeline lakes displaying a broad gradient in terrestrial dissolved organic matter (tDOM) was contrasted with limnological indices of light climate, nutrient availability and lake water pH. To evaluate direct and indirect climate impacts on the long‐term development of benthic phototrophic communities at the subarctic treeline, fossil diatom assemblages in the sediments of a shallow oligotrophic lake were examined against established temperature variability and inferences of terrestrial influence over the past 600 years. The regional lake set was used to test local calibration models for reconstructing dissolved organic carbon as well as lake water pH that is a fundamental environmental determinant for diatom distribution and may echo temperature variability in dilute lakes. Across the treeline, lake water pH imposed primary control over the benthic‐dominated surface sediment diatom communities. The pH influence was connected to catchment geomorphology, soils and vegetation cover and, together with habitat controls, largely superseded tDOM impact on underwater light attenuation and nutrient levels. Similarly, temporal changes in diatom distribution in the sediment core appeared to be relatively little affected by tDOM variability. The species shifts were subtle yet occurred in distinct synchrony with centennial temperature fluctuations, attributed to changing length of the ice cover period and associated effects on lake water chemistry, nutrient regimes and physical habitats. Our results suggest that diatom flora in shallow lakes at the subarctic Fennoscandian treeline may be comparatively resilient towards climate‐driven changes in terrestrial carbon and nutrient fluxes. Diatom communities in poorly buffered lakes may, however, be susceptible to catchment greening and changes in hydrology through effects on lake water acid–base balance. While diatom responses in the sediment sequence were subtle, the palaeolimnological record indicates that periphytic diatom communities in shallow oligotrophic subarctic lakes may be sensitive to the effects of global warming.