Stephanodiscus Hantzschii Research Articles

A LIGHT AND ELECTRON MICROSCOPE STUDY OF PREVIOUSLY DESCRIBED AND NEWSTEPHANODISCUSSPECIES (BACILLARIOPHYCEAE) FROM CENTRAL AND NORTHERN CANADIAN LAKES, WITH ECOLOGICAL NOTES ON THE SPECIES

Stephanodiscus species from central and northern Canadian lakes have been investigated and their morphology illustrated with the help of light and electron microscopy. Stephanodiscus vestibulis Hakansson, Theriot & Stoermer and Stephanodiscus hantzschii fo. tenuis (Hustedt) Hakansson & Stoermer are identified with certainty. Morphological variation in the S. niagarae-complex and the S. alpinus-complex is discussed and a new species, S. agassizensis sp. nov., is described. S. subtranssylvanicus Gasse and S. oregonica (Ehrenb.) Hakansson, previously considered extinct, are reported from living material.

Late Quaternary Palaeoenvironment of Spring Lake, Alberta, Canada

Palaeoenvironmental investigations based upon sediment cores taken from Spring Lake in the Peace River District of Alberta, Canada (latitude 55° 31′ N; longitude 119° 35′ W) show that the sedimentary record spans the Holocene period. Chemical and diatom changes coincide with regional climatic change since deglaciation (about 11 000 yr. B.P.). Calcite laminations in the basal 3 metres of the cores are evident, and were probably formed through elevated water temperature although photosynthetic removal of CO2 undoubtedly contributed. The disappearance of the laminations, and concurrent decrease in calcite X-ray diffraction peaks ca. 5000 yr. B.P. may have been caused by a change from a partially meromictic to a dimictic lake as the climate changed. Benthic and alkaline diatoms dominate before 5000 yr. B.P., while the planktonic Stephanodiscus hantzschii dominated between 5100 and 4200 yr. B.P. probably owing to increased nutrient levels. From ca. 4200 yr. B.P. until the present, benthic Fragilaria spp. and more circumneutral diatoms were dominant. Palaeoproduction, as measured by chlorophyll derivates, was highest in the early developmental stages of the lake, decreased coinciding with a major disturbance of the sediments and lowered water levels, and then gradually increased again until present. Only during the earlier period of peak production does biogenic calcite formation appear more important than calcite deposition caused by high water temperatures.

Optimization of the Electron Transport System (ETS) method for natural phytoplankton assemblages tested with some species of freshwater phytoplankton

The applicability of the ETS method for natural phytoplankton assemblages was tested with a number of freshwater phytoplankton species: Scenedesmus quadricauda, Chlamydomonas reinhardtii, Oscillatoria agardhii and Stephanodiscus hantzschii. The reproducibility and recovery of the method is very good when membrane filters are used and the concentrated sample is removed from the filter by brush. Three to five minutes appear to be sufficient to release the ETS activity. The following aspects conditions should be taken into account: (1) The processed sample stored for not longer than 30 min on ice; (2) the extinction must not be higher than 0.6, (3) reaction time not longer than 30 min, and (4) no “hard” species must dominate the water sample. The recovery of the size-fractionated water sample, based on the activity of the whole sample, was not significantly different from 100% at the level of P = 0.01.

Phytoplankton communities in navigation pool no. 7 of the Upper Mississippi River

A study of the phytoplankton community dynamics in Navigation Pool No. 7 of the Upper Mississippi River was conducted from May through October, 1982. The objectives of this study were to estimate total standing crops, determine the taxonomic composition and examine the seasonal succession of the phytoplankton community. Four sampling sites were established: two in Lake Onalaska, a large backwater lake on the Wisconsin side of the main channel; one in the main channel near Dakota, Minnesota; and one in the main channel just upstream from Lock and Dam No. 7. The phytoplankton communities at all sampling sites were dominated by diatoms except during July and August when a bloom of blue-green algae was observed. The dominant diatoms from May through mid-July were Melosira italica, Stephanodiscus niagarae, Stephanodiscus hantzschii, Stephanodiscus astrea, and Synedra ulna. Aphanizomenon flos-aquae and Microcystis aeruginosa were the most prevalent blue-green algae during the mid-summer bloom. The diatoms Melosira italica and Melosira granulata were dominant in September and October. Lesser amounts of green algae, cryptomonads and euglenoids were also observed at various times of the sampling period. Total standing crops based on cell volume were usually greatest at the Lock and Dam No. 7 site. The maximum standing crop (10.4 mm3 1−1) was observed at the Lock and Dam No. 7 site on 4 September; the minimum standing crop (0.4 mm3 1−1) was observed at the eastern Lake Onalaska site on the same date. Concentrations of nitrogen, phosphorus, and silica remained at high levels throughout the study period and did not appear to limit phytoplankton standing crops.

Differences between two species of Daphnia in the use of 10 species of algae in Lake Washington1

The ability of Daphnia pulicaria and Daphnia thorata to grow and reproduce when given the same concentrations of single species of algae was compared. The 10 algae selected included some of those most frequently found in the guts of Daphnia in Lake Washington. Clearing rates were determined and consumption of food expressed as number of cells ingested per day, cell volume, and carbon content. Cryptomonas erosa and Stephanodiscus hantzschii supported the highest egg production and increase in biomass. Colonial forms (Asterionella formosa, Fragilaria crotonensis, Tabellaria fenestrata, and Melosira italica) were less favorable as food. Growth and reproduction were lowest with Chlorella sp. and Melosira italica tenuissima. Daphnia pulicaria grew and reproduced faster than D. thorata with 7 of the 10 food species. The greater success of D. pulicaria than of D. thorata in the lake may be explained partly by its ability to use more effectively the energy available in a variety of foods.

Seasonal Growth and Community Composition of Phytoplankton in a Eutrophic Wisconsin Impoundment

ABSTRACT During 1981 the seasonal growth and community composition of phytoplankton were investigated at six sampling stations in Eau Galle reservoir, a shallow eutrophic basin located in central Wisconsin, U.S.A. Eau Galle was strongly dominated by diatoms (spring and fall), and co-dominated by cyanophytes and dinoflagellates (summer). Three species (Stephanodiscus hantzschii Grun., Aphanizomenon flos- aquae (L.) Ralfs, and Ceratium hirundinella (O.F.M.) Schrank) collectively contributed about 50% of total annual phytoplankton biomass. Phytoplankton response was quite similar at open water sampling stations, but differed at a station in the littoral zone and at another located near the mouth of the primary inflowing river. Depressed epilimnetic silica concentrations occurred during spring and fall periods of diatom growth. The development of nitrogen-fixing cyanophyte populations during the summer reflected reduced dissolved inorganic nitrogen availability. Midsummer mixing events reduced water column stability. Shifts in the phytoplankton species composition of Eau Galle appeared to occur in response to major changes in water column stability.

Growth Rates of Five Freshwater Algae in Well-Buffered Acidic Media

Growth rates for five freshwater algae, Asterionella formosa, Stephanodiscus hantzschii, Scenedesmus sp., Cryptomonas ozolini, and Anabaena flos-aquae, in media ranging in pH from 5.0 to 7.5 using three zwitterionic buffers, MES, PIPES, and TES, were determined. These buffers supported similar growth rates when compared with each other in treatment groups of similar pH. For pH values below 6.0 no growth occurred or growth rates were significantly reduced in some treatment groups for all species except Cryptomonas. In some cases, these lowered growth rates were partially or completely restored by reducing trace metals in the media by one or two orders of magnitude. We suggest that these buffers could provide a useful technique for investigating the physiological responses of phytoplankton in lakes undergoing acidification.

The effect of fungal parasitism on the succession of diatoms in Lake Maarsseveen I (The Netherlands)

SUMMARY. During late winter and early spring, diatoms are predominant in Lake Maarsseveen I and show a succession in blooming. To elucidate the role of parasitism in this succession, samples were taken once a week in 1978, 1979and 1980 and examined for fungal parasites, further, factors which presumably influenced the phytoplankton growth. including temperature and chemical compounds, were studied. Parasites were found on Asterionella formosa Hass., Stephanodiscus astraea (Ehr) Grun. and Cyclotella comta (Ehr) Kütz. The chytrid fungus Zygorhizidium planktonicumCanter was parasitic tin Asterionella formosa. This was the only case where high infection percentages were registered. The developmental phases of Zygorhizidium plunktonicum on Asterionella formosa were studied. The fungus was capable of affecting the spring increase and bringing about a premature end to the bloom. Only when the fungus was temporarily inhibited in its parasitic activity (this phenomenon coincided with periods of frost) was A. formosa able to reach a high abundance. Severe parasitism on A. formosa favoured the development of other diatoms (mainly of Fragilaria crotoriensis Kitt., Stephanodiscus hantzschii Grun. and Stephanodiscus astraea).Host‐parasite interrelationship studies performed in the laboratory showed that temperature can be an important environmental factor associated with epidemics of Zygorhizidium plankiomcum on Asterionella formosa. At very low temepratures (1.5. 1) the fungal activity was inhibited while Asterionella fortnosa still grew well. However, at 5, 10 and 18 the fungus manifested a high infection rate and was able to overtake Asterionella.

Silicon Consumption and Population Density Changes of Dominant Planktonic Diatoms in Lake Constance

(1) Interactions between silicon concentration and diatom growth have been studied in Lake Constance with data on number and volume of cells per unit volume of water and concentration of dissolved reactive silicon. (2) Concentration of dissolved reactive silicon was found to decrease markedly during the spring and summer growth period of diatoms in 1979 and 1980. (3) Amounts of silicon taken up per cell and per unit cell volume have been calculated from the changes in silicon concentration and the increases in population density for several diatom species. The silicon to cell quotient (mg per million cells) varied over a wide range from 0.005 for Stephanodiscus hantzschii to 0.72 for Synedra acus, while that of silicon per unit cell volume (mg mm-3) varied over a narrower range from 0. 10 for Stephanodiscus hantzschii and Fragilaria crotonesis to 0.36 for Synedra acus. (4) A four-compartment model, that allows estimates of the rates of growth and of loss of diatom populations to be calculated, is outlined. (5) Summer succession from Asterionellaformosa to either Fragilaria crotonensis (in 1979) or Stephanodiscus binderanus (in 1980) is explained by interspecific differences in the effects of silicon concentration on growth and death. For Asterionellaformosa, silicon depletion did not stop cell-division but led to the death of most of the population. For Fragilaria crotonensis and Stephanodiscus binderanus cell division stopped but cells did not die and population growth continued after the concentration of dissolved silicon had increased again

The relationship between fossil diatom assemblages and limnological conditions

Fossil diatom assemblages from the sediment/water interface in 105 Minnesota lakes were compared with measurements of alkalinity, sulphate, total phosphorus, transparency, and water depth at the sample site. Similar assemblages were placed together using cluster analysis and comparisons of environmental variables between diatom clusters were made using an analysis of variance. Total alkalinity and transparency showed the greatest difference among clusters. Samples from shallow eutrophic prairie lakes were dominated by Melosira granulata, Stephanodiscus niagarae and, occasionally, by Stephanodiscus hantzschii. Deep oligotrophic lakes had modest percentages of Cyclotella comta. Dilute acid lakes were dominated either by Melosira distans and M. italica or by Tabellaria fenestrata, Cyclotella stelligera, and in some cases C. glomerata. Assemblages with Cyclotella glomerata and Synedra nana were found in naturally meromictic lakes. Stephanodiscus hantzschii showed a preference for extremely eutrophic lakes. The relationships between recently deposited diatom assemblages and the lake environmental conditions studied here can be used to evaluate the extent of past environmental change in lakes.

The Phytoplankton Biomass and Species Composition at Two Stations in Western Lake Erie, 1975/76

AbstractIntegrated phytoplankton samples from two stations in the northern waters of western Lake Erie were analyzed by the Utermöhl technique for the period from June, 1975 to September, 1976, with weekly sampling in the summer of 1975. No consistent differences were observed between the two stations. Two annual peaks were found: the first was a vernal pulse (1.4 to 4.8 g/m3) comprised primarily of diatoms (86.0–95.7% of total biomass; principal species were Tabellaria fenestrata (Lyngb.) Kg., Stephanodiscus hantzschii Grun., and Fragilaria capucina Desm.); the second peak (3.1 to 9.9 g/m3) was in late summer – early fall. This latter peak consisted of initially diatoms (Coscinodiscus rothii Ehr. Grun. and Melosira granulata (Ehr.) Ralfs being the chief components), later dominated by bluegreens (Aphanizomenon flos‐aquae (L.) Ralfs and Chroococcus minutus (Keutz.) Naegeli), and finally diatoms (Coscinodiscus rothii, Stephanodiscus spp., Fragilaria crotonensis (Edw.) Kitton, and Melosira granulata). The importance of phytoflagellates (25.5 to 93.4% of total biomass), especially Gymnodinium sp., Cryptomonas erosa Ehrb., and Cryptomonas erosa v. reflexa Marsson., in June – early July samples and the overwhelming dominance of diatoms during the remainder of the year are stressed. No patterns in biomass and composition could be observed in vertical phytoplankton profiles. The present study provides an important connecting link between past and future studies performed with the standard Utermöhl technique.

Life‐history and distribution of Simulium austeni (Diptera: Simuliidae) in relation to phytoplankton in some southern English rivers

SUMMARY. Regular sampling of larval and pupal simuliids in the River Stour (Dorset) showed that Simulium austeni produces a single generation of larvae per year, pupating in late April‐early May. The species is abundant in the middle and lower reaches of the Stour and its larger tributaries, but in nearby rivers of comparable size it is rare or absent, Unlike these other rivers, the Stour supports a true phytoplankton dominated by small centric diatoms (Stephanodiscus hantzschii). Peak concentrations of particulate chlorophyll‐α sometimes correspond with the growth period of S. austeni larvae. The distribution of S. austeni relative to that of phytoplankton is discussed and the importances of suspended bacteria and water chemistry are briefly considered.

Das Sediment des Kummerower Sees. Untersuchungen des Chemismus und der Diatomeenflora

The Sediment of Lake Kummerow. Investigations on the Chemism and the Diatom FloraThe paper deals with the distribution of chemical parameters and of diatoms in the deposits of the eutrophic Lake Kummerow (GDR), produced during about the last 3500 years. The sediment consists of a calcareous gyttja with a very low content of sand and clay. The results indicate a relatively constant trophic state of the lake in former times and an increased production within the last five centuries. Stephanodiscus astraea and its variety minutula is by far the most constant diatom species; in the uppermost parts of the sediment small sized planctonic taxa are increasing, in the main Stephanodiscus hantzschii var. pusillus, Melosira granulata var. angustissima, Asterionella formosa and Synedra acus var. angustissima and var. radians.

The postglacial diatom history of Sunfish Lake, southwestern Ontario

An investigation was made of the diatom stratigraphy in a sediment core from Sunfish Lake, a small (8.3 ha), deep (20 m), meromictic lake in southwestern Ontario. About 340 diatom species and varieties distributed among 37 genera were identified from the sediments; however, only 16 taxa had more than 2% representation in any sample. On the whole, the number of individuals and diversity of the samples increase over the postglacial period. Diatoms first appear in pollen zone A and consist mainly of the littoral forms Cymbella diluviana, Fragilaria lapponica, and F. construens var. venter. It is suggested that these taxa are typical of early postglacial lacustrine sediments in northeastern North America. Cyclotella bodanica first appears in zone B and is dominant in most samples throughout the core. It is euplanktonic and typical of subalpine, circumneutral, oligotrophic lakes. In C2, when the climate was possibly warmer and drier than present, there is evidence for a lower lake level: C. bodanica is temporarily replaced in importance in the sediments by C. kuetzingiana and the proportion of littoral and epiphytic diatoms increases. Cyclotella bodanica regains its former importance in C3 sediments with the possible return to a cooler, wetter climate. About 850 years before present (B.P.) the lake evidently became eutrophic. Cyclotella bodanica declines and there is an increase in the proportion of several species typical of a higher trophic level, e.g., Stephanodiscus hantzschii, Cyclotella glomerata, and several Synedra spp. The cause is unknown. The lake probably became meromictic about 140 B.P. at a time when the forest was cleared and agriculture began in the watershed.

Quantitative studies on the phytoplankton of the Rivers Thames and Kennet at Reading

SummaryThe phytoplankton of the River Thames and its tributary the River Kennet was studied weekly from May 1966 to May 1968. Samples were concentrated by sedimen‐tation and counted in a haemocytometer.Data on discharge, temperature and silica concentration are followed by descriptions of the variations in the number and composition of the phytoplankton. In both rivers there were spring and autumn peaks of the centric diatom. Stephanodiscus hantzschii. Chlorophyceae were most abundant during summer. Two cryptophyceans, Cryptomonas and Rhodomonas were sometimes numerous.In the Thames, the size of the population was closely correlated with the discharge, highest numbers always occurring during periods of low discharge. In the Kennet, increases in discharge often brought about increases in cell number due to the infiux of benthic forms.It appeared that nutrients were always present in sufficient quantity and did not limit algal growth.Comparisons were made with earlier studies on the Thames and differences were noted in the composition of the phytoplankton which were almost certainly due to the process of eutrophication.