Planktic Diatoms Research Articles

The diatom flora in the ultra-oligotrophic Lake El'gygytgyn, Chukotka

Lake El'gygytgyn, an impact crater lake in northeastern Siberia, was analysed based on water-column characteristics and the modern and sub-recent diatom flora. Vertical temperature, conductivity and oxygen profiles, as well as ionic concentrations in the lake water, reveal that Lake El'gygytgyn is a clear, cold-monomictic, ultra-oligotrophic high-Arctic lake with high light-penetration depth. We identified 113 diatom taxa, of which only 2 species are planktic diatoms. Cyclotella ocellata is the only quantitatively significant diatom present in the modern phytoplankton community, and is also predominant in a short sediment core, which probably reflects the mid- and late-Holocene environmental history of Lake El'gygytgyn. Pliocaenicus costatus var. sibiricus is also common but of minor importance. This is the first evidence of P. costatus var. sibiricus outside the Lake Baikal region.

Limnologic history of Lago de Pátzcuaro, Michoacán, Mexico for the past 48,000 years: impacts of climate and man

Lago de Pátzcuaro lies at an elevation of 2035 m (19° 36′ N 101° 39′ W) on the west part of the volcanic Meseta Central of Mexico, about 50 km east-southeast of Morelia. Pollen, diatom, and geochemical records from a 15 m core taken in 6 m of water continuously track vegetation and limnological changes in the Pátzcuaro basin for the past 48 ky (calendar years). Pine, oak, and alder pollen dominate both the Wisconsin and Holocene vegetation record, and indicate that this region did not witness strongly arid climates during that time. Before the Holocene, Juniperus-type and Artemisia pollen document cooler climates of more effective moisture at least seasonally. Isoetes characterizes the full and late glacial interval (25–13 ka) and implies, along with the diatoms Aulacoseira and Stephanodiscus, cool, deep, freshwater conditions at Lago de Pátzcuaro.The freshest and deepest lacustrine phase in the lake occurred 38 to 25 ka. During this time, Lago de Pátzcuaro may have drained into the Lerma River system. Between 30 and 10 ka, diatom species that bloom in the winter and early spring imply moisture during those seasons. Evaluation of contemporaneous marine and terrestrial records west and east of Lago de Pátzcuaro suggests that this moisture probably originated from westerly storm tracks shifted south by the Laurentide ice sheet.After 10 ka, Lago de Pátzcuaro became shallower and more eutrophic. Rooted aquatic plants prospered under a climate regime of negative hydrologic budgets, increased seasonality, and moisture arriving during the summer as it does today. The lake became alkaline enough by the mid-Holocene to deposit ostracode-rich marls at the core site for the first time in the past 48 ky. Indigenous agriculture in the Pátzcuaro drainage and around the lake appears about 4 ka, with the appearance of Zea and Chenopodiineae pollen. Iron and potassium track increased soil erosion, and planktic diatoms ( Cyclostephanos) record nutrients flushed into the lake from the drainage basin.

Merkmalsvariabilität bei planktischen Diatomeen in Berlin-Brandenburger Gewässern

Merkmalsvariabilität bei planktischen Diatomeen in Berlin-Brandenburger Gewässern

A diatom record of climate and hydrology for the past 200 ka from owens lake, california with comparison to other great basin records

Diatoms from lake sediments beneath Owens Lake playa, Inyo County, California, document a nearly continuous paleolimnological record of climate and hydrologic change since the penultimate glacial-interglacial cycle based on a chronology established by radiocarbon, tephrochronology, and paleomagnetic control. Freshwater planktic diatoms (especially species of Stephanodiscus), plagioclase feldspar-rich sediments with high magnetic susceptibility, and Juniperus-type pollen characterized the penultimate glaciation at Owens Lake. Saline diatoms dominated in the following interglacial period, and there are several episodes during which freshwater planktic diatoms became abundant between 100 and 50 ka that may represent interstadial climatic conditions. Saline diatoms fell to low values after 50 ka, but warm-season Aulacoseira species indicate episodes of significant summer precipitation in the hydrologic balance of Owens Lake prior to the last glacial maximum. By 25 ka, glacial environments were again characterized by abundant Juniperus, plagioclase feldspar, and Stephanodiscus species. Generally arid Holocene climates were recorded in Owens Lake by short-term fluctuations of saline and freshwater diatoms, desiccation, and oolitic sediments barren of diatoms. Comparison to paleoclimate records both north and south of Owens Lake suggest a southerly displacement of storm tracks originating from the Aleutian Low during glacial episodes.

Deficiencies in the diatom evidence for a Pliocene reduction of the East Antarctic Ice Sheet

Evidence for Pliocene reduction of the East Antarctic Ice Sheet (EAIS) has been inferred from the presence of Pliocene planktic marine diatoms in tills of the Sirius Group now exposed along the slopes of the Transantarctic Mountains. We highlight deficiencies in this diatom evidence for a Pliocene reduction of the EAIS. First, we examine what diatom habitats are left behind by a retreating ice sheet, in this case the Fennoscandian Ice Sheet (FIS), and find that diatoms should occur in planktic and benthic marine, brackish water, freshwater, and terrestrial habitats. We expect that during former reexpansions, these diverse diatom assemblages were picked up by the advancing FIS and deposited in tills. This is shown to be the case, and diatoms found in tills from Sweden and Finland reflect the many habitats over which the FIS passed. If there was a reduction of the EAIS during the Pliocene followed by renewed glaciation, diatoms from many different habitats should be found in the resulting tills of the Sirius Group. This is not the case. Only marine planktic diatoms and a few freshwater forms are reported. Similarly, vertical (downsection) distribution of diatoms in Sirius Group and Fennoscandian tills differ. While in the Sirius Group, diatoms appear restricted to surface and near‐surface sediments, in Fennoscandia they are found throughout the tills. Such data do not support a Pliocene reduction model for the EAIS.

Five new species of the nanoflagellatePirsonia in the German Bight, North Sea, feeding on planktic diatoms

The structure, development, and host range of five newly detected species of the phagotrophic nanoflagellatePirsonia are described. They feed on planktic diatoms common in the North Sea:P. verrucosa sp. nov. (onRhizosolenia delicatula), P. formosa sp. nov. (onRhizosolenia setigera), P. diadema sp. nov. (onCoscinodiscus granii andC. wailesii), P. eucampiae (onEucampia zodiacus) andP. mucosa sp. nov. (onRhizosolenia shrubsolei). The occurrence of resting cysts inPirsonia guinardiae is reported. The impact ofPirsonia on phytoplankton communities is discussed.

Factors influencing the share of planktic diatoms in lakes

Factors influencing the share of planktic diatoms in lakes

Competition ability of two planktic diatoms under different vertical light gradients, mixing-depth and -frequencies: An experimental approach

Competition ability of two planktic diatoms under different vertical light gradients, mixing-depth and -frequencies: An experimental approach

Iterative evolution in the diatom genus Rhizosolenia Ehrenberg

Sorhannus, U., Fenster, E. J., Hoffman, A. & Burckle, L. 1991 01 15: Iterative evolution in the diatom genus Rhizosolenia Ehrenberg. Lethaia, Vol. 24, pp. 39–44. Oslo. ISSN 0024–1164. Two late Pliocene planktic diatom lineages, Rhizosolenia sigmoida Sörhannus and Rhizosolenia praebergonii Mukhina, originated consecutively from Rhizosolenia bergonii Peragallo in the eastern equatorial Pacific Ocean. This morphological iteration is closely associated with two successive shifts in the oxygen isotope record (18O/16O) at approximately 3.3 Ma and 2.9 Ma. suggesting that palcoenvironmental factors may have been directly or indirectly involved in initiating these events. Iterative evolution, pseudoextinction. diatom, oxygen isotope record.

Punctuated morphological change in a Neogene diatom lineage: “Local” evolution or migration?

A biometric analysis of the morphology of a late Pliocene planktic diatom lineage, Rhizosolenia praebergonii Mukhina indicates that it appeared abruptly in the fossil record in the Indian Ocean at 2.9 Ma after which it remained virtually unchanged. The observed pattern can be explained by “local”; evolution from the ancestral form Rhizosolenia bergonii, Peragallo or by migration from thecentral Pacific Ocean, where it originated gradually, in conjunction with an accelerated rate of evolution. At present time, it is not possible to conclude which one of the two hypotheses is more likely.

Cladogenetic and anagenetic changes in the morphology ofRhizosolenia praebergoniiMukhina

Biometric analysis of a late Pliocene planktic diatom morphospecies, Rhizosolenia praebergonii Mukhina, from the equatorial Pacific Ocean indicates that it represents a lineage which underwent relatively rapid change in morphology after its first appearance (3–1–2–7 Ma) followed by a period of time where the rate (as expressed as a slope) of morphological change was not significantly different from zero (2–7–1–7 Ma). Based on criteria for identifying ancestral‐descendant relationships (Prothero and Lazarus, 1980), we conclude that R. praebergonii evolved from R. bergonii Peragallo via a cladogenetic event. The observed pattern of evolution conforms to the shifting balance model of evolution, rather than to a punctuated model. Isotopic evidence suggests that paleoclimatic events may have played a role in the onset of the period of stasis.

Marine planktic diatom correlation of lower Messinian deposits in the western Mediterranean

Samples from late Neogene Mediterranean outcrops were analysed for diatom content. The presence of certain species in the Tripoli Formation (Caltanissetta Basin, Sicily) and in the Beida Formation (Cheliff Basin, NW Algeria) permits correlation between these sections and the paleomagnetic reversal record. The occurrence of Thalassiosira praeconvexa, Thalassiosira miocenica, Thalassiosira convexa var. aspinosa and Asterolampra acutiloba indicates that the Tripoli and Beida formations were deposited over an interval ranging from the upper half of Paleomagnetic Epoch 6 into the lower half of Epoch 5 (5.6 to 5.9 Ma). Previous diatom correlations were too young. The occurrence of Nitzschia reinholdii and Asterolampra acutiloba in pre-evaporitic diatomites from the upper Turre Formation (SE Spanish Sorbas Basin) is used to place deposits at this site tentatively in Paleomagnetic Epoch 5 or 6.

Evolution in a pelagic planktic system: A paleobiologic test of models of multispecies evolution

Two rival models of evolution in multispecies systems are tested against empirical species-level data. The two models are the Red Queen model of Van Valen as reformulated by Stenseth and Maynard Smith, which assumes that evolution is driven principally by biotic interactions, and the Stationary model of Stenseth and Maynard Smith, which assumes that evolution is propelled primarily by abiotic factors and will cease in the absence of changes in abiotic parameters. Testing refers to the models' predictions regarding the behavior of extinction and origination rates, and assumptions regarding equilibrium diversity and a constant effective environment. The data set includes the dates of origination and extinction for all coccolith, planktic foraminifer, and radiolarian species recorded in the Oligocene through Holocene, and all planktic diatom and silicoflagellate and ebridian species recorded in the Middle Miocene through Holocene in 111 DSDP sites of the low- to mid-latitude Pacific Ocean.The condition of stable specific age distribution over geologic time is met, which allows one to perform survivorship analysis on extinction rates. The best fit survivorship curve is a decreasing function of age for both coccolith and foraminifer species, and an increasing function of age for radiolarian species. Neither model predicts age dependence of the probability of extinction. The small disparity between these curves and age-independent curves for each group indicates, however, that an age-independent interpretation of extinction probability is a reasonable first approximation. Rates of origination are analyzed in terms of species accretion, introduced to represent the cumulative origination of species within a higher taxon as a function of the age or duration of the community. Accretion analysis indicates that the probability of accretion is both diversity-dependent and absolute time-dependent.The assumption of a constant effective environment is tested by polycohort analysis and nonparametric logistic regression analysis of true species cohorts. Both techniques indicate considerable variation in extinction probability over geologic time. When the predictions of the two evolutionary models are adjusted to take this variation into account, the results of both survivorship and accretion analysis seem to conform more closely to the predictions of the Red Queen than to the Stationary model. However, as the speed with which the effective environment changes is increased relative to speciation-extinction rates, it becomes increasingly difficult to differentiate patterns predicted by the two models. The assumption of equilibrium diversity can be neither corroborated nor rejected, since the species-level data are compatible with both an equilibrium and a nonequilibrium view of diversity behavior. Reservations concerning the basic assumptions of both models indicate an ultimate test requires that both models be reformulated to make precise and distinctive predictions under a varying effective environment.

System Analysis of Silica‐Diatom Interaction

AbstractThe prediction of and measures to prevent planktic diatom blooms in shallow lakes and slowly flowing rivers are major problems specific to water quality management. In this paper methods of mathematical systems analysis, computer simulation, and parameter identification are used to analyse a simple system consisting only of a population of planktic diatoms and dissolved silica in a shallow lake.