Chrysophycean Cysts Research Articles

The ratio between chrysophycean cysts and diatoms in temperate, mountain lakes: some recommendations for its use in paleolimnology

The ratio between chrysophycean cysts and diatom valves (CD ratio) in lake sediments has been suggested as a useful indicator of changing trophic state conditions in oligotrophic lakes. Other environmental factors, however, may influence the CD ratio because chrysophycean cysts usually reflect conditions in the planktonic environment and diatoms reflect benthic conditions. We investigated the CD ratio in 76 mountain lakes in the Pyrenees to determine the environmental drivers that influence the ratio and assess its value for paleoenvironmental inference. The lakes surveyed included a broad range with respect to bedrock type, altitude and surface area, characteristics that cover much of the variability that can be found in cold, oligotrophic mountain lakes. Lake depth and Ca2+ concentration explain most of the variation in the CD ratio. Trophic state factors (e.g. total phosphorus, TP) play a secondary role. As a predictor, CD ratio performs primarily as a lake depth indicator. The predictive models can be improved if trophic state (i.e. TP) and chemical conditions (Ca2+) are known or can be estimated independently. Use of the CD ratio for inferring Ca2+ oscillations only makes sense in lakes with Ca2+ <200 µeq/L or in those that oscillate below and above this threshold through time. Other interpretations of the CD ratio (e.g. lake trophic state changes, ice-cover duration) make sense if complementary paleolimnological evidence indicates that neither water depth nor Ca2+ concentration changed significantly. Indeed, paleolimnological interpretation of the CD ratio requires considering the particular characteristics of the lake and may vary depending on the temporal scale considered. This study provides some guidelines for evaluating critically the use of the CD ratio.

Seasonal to sub-seasonal palaeoenvironmental changes in Lake Sihetun (Lower Cretaceous Yixian Formation, NE China)

Sedimentary properties of the fossil-bearing deposits of Lake Sihetun (Yixian Formation, Lower Cretaceous) were investigated on a high-resolution, sub-millimetric scale. Data were obtained from three excavations and 50 thin-sections. Lake evolution is subdivided into four phases, of which Phases 2 and 3 provided suitable conditions for excellent fossil preservation. Six microfacies are recognized within these two phases: (1) allochthonous, siliciclastic laminae (26.1 μm thick on average), (2) chrysophycean cyst accumulations, (3) tuffaceous silt, (4) lacustrine chemical precipitates, (5) tuff and (6) normal-graded, sandy to silty siliciclastics. Phase 2 is characterized by Microfacies 1–5 and Phase 3 by Microfacies 6. Biofilms are common, and mass occurrences of framboids (pyrite pseudomorphs) are occurring in sediments of Phase 2. Varves can be verified for Microfacies 2 and 4 (179 μm thick). Thicknesses of Microfacies 2 highly fluctuate depending on the occurrence of seasonal heavier rains, which led to deposition of tuffaceous silt layers (Microfacies 3). Meromictic conditions dominated Phase 2, but recurrent mixing is demonstrated by short-lived colonization events by a benthic invertebrate fauna. The transition of Phase 2 to holomictic Phase 3 is marked by a dramatic increase in sediment yield associated with a change from dry to humid climates. Fossil preservation differs according to the diverse physical and chemical conditions during lake evolution. Phase 2 yields framboid replacement of organic tissue and excellent preservation of growth increments of clam-shrimp carapaces, which are poorly preserved in Phase 3. Conversely, though exhibiting a different mode of preservation, insect fossils are superbly preserved as dark stains sealed by silica coatings during Phase 3.

Diatom-inferred lateglacial and Holocene climatic variability in the South Carpathian Mountains (Romania)

Climatic and environmental changes were studied using siliceous algae (diatoms and chrysophycean cysts) analyses in a mountain lake in the South Carpathian Mountains for the lateglacial and Holocene. Lake Brazi (1740 a.s.l.) is a small, shallow lake in the Retezat Mountains. According to the basal radiocarbon dating of the core, the lake was formed around 15,750 cal BP and sediment accumulation has been continuous ever since. High resolution diatom analyses were carried out together with loss-on-ignition and biogenic silica measurements. Total epilimnetic phosphorus (TP) concentrations and pH were reconstructed quantitatively. Ten statistically significant zones were distinguished, six of which appeared in the lateglacial and Early Holocene suggesting the instability of diatom assemblages after deglaciation. The uppermost zone covered six thousand years, which suggests that diatom assemblages remained quite stable during the second half of the Holocene. High lake level occurred between 9500 and 9000 cal BP. After 6300 cal BP the lake level gradually increased again until 5800 cal BP. A further increase was detected at 3000 cal BP, while after 1500 cal BP water level decreased. Although there is limited knowledge regarding the environmental constraints of several diatom taxa present in the sequence (e.g. Aulacoseira laevissima), which makes the precise environmental interpretation of the diatom record more difficult, the available data provide an important new insight into the environmental history of Lake Brazi and the Carpathian Mountains. The most remarkable changes in the aquatic ecosystem were observed at 6000 cal BP in the Holocene and 12,800 cal BP, at the onset of the Younger Dryas. Marked changes were also detected at 10,500–10,300; 9800; 9500–9000; 8900–8800; 8300; 6300–5800 and 3100–3000 cal BP.

Lacustrine particle dynamics in high-altitude Estany Redó (Spain) - a high resolution sediment trap study

Particle fluxes were measured from 2000 to 2001 with 3 integrating open traps (O-traps) and a sequencing trap (S-trap) in the 73-m deep, oligotrophic, high-mountain Estany (Lake) Redo (2240 m a.s.l.) over a period of 558 days. O-traps were deployed at 26, 46, and 66 m water depth to measure overall sedimentation rates, while the S-trap was deployed at 66 m water depth to detect dynamics of seasonal particle fluxes with a resolution of 4 days (during ice break-up, summer, ice formation) to 21 days (during ice cover). Our results show a high degree of seasonal variability in particle dynamics. Total particle fluxes vary from almost zero to more than 600 mg m-2 d-1. The highest fluxes occur during short time windows after ice-break-up (minerogenic particles), during spring (planktonic biomass), and during fall overturn (chrysophycean cysts). Particle fluxes also differed markedly from year to year in absolute values (2000: 644 mg m-2 d-1, 2001: 370 mg m-2 d-1) as well as in average values (2000: 76 mg m-2 d-1, 2001: 44 mg m-2 d-1). Annual and seasonal meteorological changes and events have a clear influence on the lake system and on the amount and composition of particles. C/N ratios during April and May increased significantly from 2000 (6-14) to 2001 (>28), reflecting the more intense soil erosion and transport of terrestrial plant remains into the lake caused by heavy precipitation in 2001. Air temperature strongly influences the timing of the occurrence of the main bio-productivity peak. Strong wind events shorten the period of ice cover. Our investigation shows that sediment trap studies lasting more than one limnological cycle are useful in studying the effects of short-term meteorological changes and weather events on high mountain lakes. However, long-term particle flux measurements would be necessary to determine amplitudes of natural seasonal cycles and for the interpretation of the decadal-scale environmental changes occurring in such lakes.

History of Mine Drainage Impact on Lake Orijärvi Algal Communities, SW Finland

The Cu (Pb, Zn) mine of Orijarvi (1757–1956) was the first mining operation in Finland where flotation techniques (1911–1955) were used to enrich ore. Large quantities of tailings were produced. The impacts of past mining activities on the aquatic ecosystem of nearby Lake Orijarvi were studied using a combination of paleolimnological methods (analysis of sedimentary diatom frustules, chrysophycean cysts, metal concentrations and radiometric datings). The acid mine drainage (AMD) – derived metal impact to the lake was found to be the strongest thus far recorded in Finland. Concentrations of Cu, Pb and Zn in sediments are two to three orders of magnitude higher than background values. During the most severe loading phase, there were practically no algae in the lake. Achnanthes minutissima was the hardiest species able to tolerate increased metal contents. The metal load has changed the properties of sediments in such a way that chrysophycean cysts were impossible to identify because of coating and corrosion. Lake water still has elevated heavy metal concentrations, indicating that the impact from the tailings area continues to affect the lake. It has low productivity, and the planktic diatom community is still not developed. The study demonstrates that unremediated mining areas form a major risk to the environment. The damage to aquatic ecosystem can remain severe for decades after the mining activities have ceased.

Seasonal ecosystem variability in remote mountain lakes: implications for detecting climatic signals in sediment records

Weather variation and climate fluctuations are the main sources of ecosystem variability in remote mountain lakes. Here we describe the main patterns of seasonal variability in the ecosystems of nine lakes in Europe, and discuss the implications for recording climatic features in their sediments. Despite the diversity in latitude and size, the lakes showed a number of common features. They were ice-covered between 5–9 months, and all but one were dimictic. This particular lake was long and shallow, and wind action episodically mixed the water column throughout the ice-free period. All lakes showed characteristic oxygen depletion during the ice-covered-period, which was greater in the most productive lakes. Two types of lakes were distinguished according to the number of production peaks during the ice-free season. Lakes with longer summer stratification tended to have two productive periods: one at the onset of stratification, and the other during the autumn overturn. Lakes with shorter stratification had a single peak during the ice-free period. All lakes presented deep chlorophyll maxima during summer stratification, and subsurface chlorophyll maxima beneath the ice. Phosphorus limitation was common to all lakes, since nitrogen compounds were significantly more abundant than the requirements for the primary production observed. The major chemical components present in the lakes showed a short but extreme dilution during thawing. Certain lake features may favour the recording of particular climatic fluctuations, for instance: lakes with two distinct productive periods, climatic fluctuations in spring or autumn (e.g., through chrysophycean cysts); lakes with higher oxygen consumption, climatic factors affecting the duration of the ice-cover (e.g., through low-oxygen tolerant chironomids); lakes with higher water retention time; changes in atmospheric deposition (e.g., through carbon or pigment burial); lakes with longer stratification, air temperature changes during summer and autumn (e.g., through all epilimnetic species).

Chrysophycean cysts (stomatocysts) from Lake Baikal and Irkutsk Reservoir, Siberia

Chrysophycean cysts (stomatocysts, statospores) from Lake Baikal and Irkutsk Reservoir, Siberia, Russia have been investigated by means of scanning electron microscopy for the first time. The paper contains descriptions and illustrations of 7 particularly distinctive forms. Five of the cyst types described here are new to the literature. Two are very similar to cysts previously described from lake sediments in North America, but differ in details of surface ornamentation and cyst collar construction.

Pliocene Chrysophycean Stomatocysts from the Sonoma Volcanics, Napa County, California

Pliocene Chrysophycean Stomatocysts from the Sonoma Volcanics, Napa County, California

Chrysophycean cyst assemblages and their relationship to water chemistry in 71 Adirondack Park (New York, USA) lakes mssub: 1994-09-12 msacc: 1995-02-28

Chrysophycean cysts were identified and enumerated from the surface sediments of 71 lakes in Adirondack Park, New York, and their relationships with measured limnological variables were examined with canonical ordination (redundancy analysis). Gradients in the cyst distributions were most strongly related to conductivity, dissolved organic carbon, Secchi depth, and aluminum. Lesser amounts of variance in the cyst data were explained by pH, acid neutralizing capacity (ANC), maximum depth, and altitude. We derived predictive models for 13 environmental variables based on the cyst assemblages using partial least squares (PLS) regression. The best models, in terms of regression coefficients (r 2 ) and root mean square errors of prediction (RMSEP), were obtained for pH and ANC (r 2 = 0.64 ; RMSEP = 0.59 and 0.46 ln (μeq/L+41)), respectively, followed by [Mg] (r 2 = 0.53, RMSEP = 0.36 In (μeq/L+1)), total aluminum (r 2 = 0.48, RMSEP = 0.86 In (μg/L+1)), conductivity (r 2 = 0.46, RMSEP = 0.19 ln (μS/cm+1)), and monomeric aluminum (r 2 =0.35, RMSEP = 0.66 ln (μM+1)). These models can be used to infer historical levels of these variables in paleolimnological studies.

The relationship of chrysophycean stomatocysts to environmental variables in freshwater lakes in British Columbia

The relationships between the distributions of 82 chrysophycean cyst morphotypes and measured environmental variables in freshwater lakes in British Columbia were examined using ordination and regression statistics. After removal of unusual samples, 60 lakes were included in the analyses. Indirect and direct gradient analysis explained 23.2 and 14.0% of the variance in the cyst distribution data, and 31.4 and 53.7% of the variance in the cyst–environment relationship, respectively. Watershed area, Secchi depth and [Mg] were identified as the variables with the greatest contributions to the first ordination axis. Maximum depth contributed most strongly to axis 2. Constrained redundancy analyses were used to test the ability of individual environmental variables to explain the variance in the cyst data; no one variable was shown to have an overriding effect on cyst distributions. Five groups of cysts were identified using the ordination diagrams and the correlations between each cyst and each environmental variable. Partial least squares regression was used to construct inference models that quantified the relationship between the cyst distributions and four environmental variables (pH, [Mg], total phosphorus, and Secchi depth). For each variable, the best model included only those cysts which were significantly correlated with that variable. The inference model for pH yielded the strongest relationship (r2 = 0.51) and best predictive ability (root mean square error of prediction = 0.32). All the inference models showed a strong trend in the residuals, such that inferences at the low end of the observed gradient tended to be overestimates and inferences at the high end tended to be underestimates. Thus, paleolimnological inferences of past environmental conditions using these models will tend to underestimate the degree of change. Key words: British Columbia, phytoplankton, Chrysophyceae, stomatocysts, paleolimnology, eutrophication.

Paleolimnological significance of observed distribution patterns of chrysophyte cysts in arctic pond environments

In a survey of 35 high arctic ponds, chrysophycean cysts were relatively more common in moss periphyton and epilithon habitats, than in surface sediment samples. The highest percentages of cysts relative to diatoms were found in the semi-aquatic mosses. Although chrysophytes are generally considered to be planktonic, periphytic taxa may be common in high latitudes. The ratio of diatom frustules to chrysophyte cysts in arctic sediment cores may be tracking different environmental variables than paleolimnologists may intuitively expect based on observations from more temperate regions.

Palaeoecological significance of chrysophycean stomatocysts: a statistical approach

The statistical relationship between chrysophycean cyst abundances and ecologically known factors, derived from multivariate analyses, is proposed as a useful way to derive palaeoecological information of non-identified cysts. The method is applied to a case-study from the Spanish Pyrenees, and encouraging results are obtained for some of the morphotypes found.

Sedimentary chrysophycean cyst assemblages as paleoindicators in acid sensitive lakes

Relationships between surface sediment cyst assemblages and lakewater characteristics were studies in 50 lakes located in central Ontario. The main purposes of the study were to identify the environmental factors most strongly controlling the distribution of chrysophycean cysts and to develop indices and equations to infer lake water pH from cyst assemblages. Principal components analysis indicates that alkalinity and associated TDS as well as elements related to trophic status are the factors most strongly correlated with the distribution of chrysophycean cysts. There are significant differences in the relative importance of these factors among the lakes. The transfer functions developed provide good prediction of pH values. This report also provides a descriptive analysis of the ‘fossil’ chrysophycean cyst flora of Ontario lakes. The descriptions include representative SEM micrographs and detailed characterization of each morphotype in consideration of the morphological variation observed among specimens of the same morphotype. Special attention has been paid to the anatomy of the collar complex and to the nature of the cyst surface ornamentation. One hundred and thirty seven morphotypes are described.

Ultrastructural studies of the flagellate and cyst stages ofPseudopedinella tricostata(Pedinellales, Chrysophyceae)

During the winter of 1985 the uppermost part of the water column of the ice-covered Danish fjord, Isefjorden, was coloured yellowish brown by a growth of the small flagellate Pseudopedinella tricostata (ca. 75 × 106 cells 1-1). The species differs from others of the genus by having three chloroplasts only, each with an embedded pyrenoid. In March a distinct yellowish band was found in the lower part of the ice which electron microscopical examination showed to be due to the presence of millions of cysts of P. tricostata. The P. tricostata cyst has a continuous three-layered wall, thus differing markedly from the typical bipartite chrysophycean cyst. The outermost wall-layer contains a significant amount of iron.

Fossil chrysophycean cyst flora in a small meromictic lake in southern Ontario, and its paleoecological interpretation

Fossil chrysophycean cysts were identified and counted from the laminated sediment core from Crawford Lake. Thirty-two morphotypes have been described, most of them for the first time. The detailed description of the cysts is presented, including scanning electron photomicrographs. The abundance of certain morphotypes appears to be related to lake paleoproductivity. On this basis, fossil cyst flora have been divided into three characteristic groups: eutrophic–, mesotrophic–, and oligotrophic–meromictic forms. Our data demonstrate that chrysophycean cyst distribution can reflect lake conditions and, therefore, are potentially useful in paleoecological studies.

Fossil chrysophycean cyst flora of Racze Lake, Wolin Island (Poland) in relation to paleoenvironmental conditions

The study presents stratigraphic distribution of fossil chrysophycean cysts in the bottom sediments of Racze Lake (Poland). Thirty morphotypes are described, most of them for the first time. The description of the cyst includes SEM microphotographs. The long-term relationship between the lake's conditions and the occurrence of characteristic morphotypes of chrysophycean cysts is discussed.

Sedimentation of biogenic siliceous particles in Antarctic waters from the Atlantic sector

Sediment traps were deployed in the Drake Passage, Bransfield Strait and west of South Orkney Islands (Powell Basin) during December 1980/ January 1981, December 1983, and between March and December 1983, respectively. Most of the trapped material is biogenic opal except in the lower half of the water column in Bransfield Strait where large amounts of resuspended aluminosilicates and quartz grains were present. Frustules and skeletons of siliceous microorganisms (diatoms, silicoflagellates, radiolarians, chrysophycean cysts), fragments and moults of crustaceans and tests of foraminifera were found. Quantitatively diatoms are the dominant constituent of the trapped biogenic material. Alteration of diatom assemblages in the water column is due to mechanical breakdown by grazing zooplankton. It mainly affects large frustules (e.g. Corethron criophilum Castracane) in the uppermost part of the water column. Dissolution of frustules occurs mostly at the sediment/water interface and leads to the enrichment of strongly silicified valves [e.g. Nitzschia kerguelensis (O'Meara) Hasle, Thalassiosira antarctica Comber (resting spores)]. At the Bransfield Strait site a large part of biogenic opal was incorporated into fecal pellets of krill and copepods. The bulk of pellet content consists of fragmented diatom frustules (1–10 μm in size). Most intact valves found in the sediments have settled through the water column by means other than fecal pellet transport: e.g. settling as solitary particles or incorporated into or attached to “Marine Snow” or “Large Amorphous Aggregates”.

The chrysophycean paleocyst flora of the bottom sediments of Kortowskie Lake (Poland) and its ecological significance

The postglacial sediments of Kortowskie Lake contain well preserved chrysophycean cysts. Forty-six morphotypes were identified by scanning electron microscopy (SEM) and light microscopy (LM). Ten new morphotypes of fossil chrysophycean cysts are described. Some of the most abundant taxa show clear trends associated with the increase in lake trophic status. The cyst flora is divided into four groups: eutrophic forms (Cysta globata, C. cortoviensis, C. vermicularis); oligotrophic forms (Cysta curvicollis); cool-water forms (Cysta carinifera, C. crassicollis, C. microspinosa, C. modica and Cysta stellata), and indifferent forms (all other morphotypes which did not show a clear tendency). The percentage abundance of chrysophycean cysts wa related to climate changes, showing a considerable increase during the Subboreal period. Two factors, lake fertility and water level changes affected the abundance of the fossil cyst flora in the sediments of Kortowskie Lake.

Composition and formation of laminated sediments in Diss Mere, Norfolk, England

The chemical and biological composition of laminated lake‐sediments deposited between about 2,500 and 5,500 years B.P. in Diss Mere, Norfolk, England is described. The distribution of Ca, Fe, S, and Si in pale and dark laminae is established by energy‐dispersive X‐ray microanalysis. The pale laminae consist primarily of calcium carbonate and the dark layers contain mainly Fe, S, Si, and dark organic material. The diatom composition of 16 individual light and dark laminae shows no consistent differences between light and dark layers. There are, however, higher frequencies of chrysophycean cysts in seven of the eight dark layers, suggesting these layers were deposited in late summer or fall. Pollen analyses of the pale and dark layers show that pollen percentages of early‐flowering trees and shrubs are highest in the dark laminae and that pollen values of late‐flowering plants are highest in the pale layers. The biological data indicate that the pale layers were formed in the late spring and early summer, whereas the dark laminae were deposited in late summer, fall, winter, and the early spring. Seasonal supply of CaCO3 was the major variable responsible for couplet formation.

Chrysophycean cysts: indicators of eutrophication in the recent sediments of Frains Lake, Michigan, U.S.A.

The recent sediments of Frains Lake, Michigan contain a rich and well preserved association of chrysophycean cysts. Forty one forms are revealed by scanning electron microscopy (SEM) and light microscopy (LM). Taxonomic descriptions. and SEM micrographs are provided for the dominant forms. The three dominant taxa throughout the sediments, Cysta minima, C. modica and C. subbavaricum, do not show significant shifts in proportional abundance associated with European settlement and the onset of cultural eutrophication. However, certain subdominant taxa do show clear trends. Density counts indicate a dramatic decline in cyst concentration (by volume and by dry mass) and a sharp increase in absolute accumulation (net annual influx) following settlement. The Frains Lake profile of chrysophycean cysts is compared to sequences of other North American and European temperate lakes. The utility of chrysophycean cysts as paleoenvironmental indicators is considered on the basis of these results.