Scaled chrysophytes (Chrysophyceae and Synurophyceae) from national park lakes in southern and central Finland

A total of 34 scaled chrysophyte taxa (18 Mallomonas spp., 6 Synura spp., 2 Chrysosphaerella spp., 6 Spiniferomonas spp. and 2 Paraphysomonas spp.) were recorded by SEM techniques in 61 samples from 59 lakes locating in 8 national parks of southern and central Finland in July 1987. Most of the lakes were small forest and peat bog lakes with acid (pH 4.6–7.2) and soft-water and with variable water colour (10–350 mg Pt/l). The number of taxa per lake varied from 0 to 15 and it correlated very significantly with the water pH. The species structure was rather typical for the oligotrophic and acid lakes. Besides the eurytypic and common species like Mallomonus caudata (fr. 72.1% of lakes), M. crassisquama (65.6%), M. allorgei (62.3%) and M. akrokomos (52.5%) also M. canina (41.0%) and M. hamata (21.3%) were frequently observed. M. calceolus, M. costata, M. papillosa, M. pugio and M. paludosa were more rare but typical for acid lakes. Synuru splendida which occurred in two lakes was the most rare and a new species for Finland.     

Diatom assemblies in some moorland pools in the Drenthian district (the Netherlands)

The results are presented of a survey of diatom assemblies in a number of moorland pools and lakes in the Dwingeloo area of Drenthe. Four assemblies, with some intermediate ones, are described. (1) An assembly characterized by an abundance ofFrustulia rhomboides var.saxonica, Eunotia lunaris, E. veneris var.rhomboidea andTabellaria flocculosa and found in oligotrophic water with a pH in the range 3.1–4.2 (2) An assembly solely consisting ofEunotia exigua which occurs in oligo-minerotrophic pools with brownish deposits of iron compounds and a pH of about 3.5. (3) An assembly consisting of 100%Eunotia paludosa found in the ombrotrophic habitat of emerged stands ofSphagnum with a pH averaging 3.1. This species was found in nearly all localities sampled. (4) An assembly characterized by the sympatric occurrence ofMelosira italica, Nitzschia gandersheimiensis, Gomphonema parvulum andTabellaria flocculosa and found in mesotrophic, disturbed habitats with an average pH of about 4.5. For the delimitation of these assemblies a cluster analysis was carried out by means of the TABORD computerprogram.     

Acidification of three moorland pools in The Netherlands by acid precipitation and extreme drought periods over seven decades

SUMMARY. 1. Relations between acidification by atmospheric deposition, water depth and the occurrence of dry summers in this century, as well as their effects on chemistry, macrophytes and diatoms in three moorland pools, are described.
2. Direct observations and biological data indicate a decrease of pH by c. 0.5 unit over a period of seven decades in a pool where 20% of the bottom desiccates in extremely dry years, and 2 pH units over the same period in a pool where 70% of the bottom is exposed to the atmosphere in such years.
3. Acidification promotes the growth of Juncus bulbosus L., Sphagnum and the acidobiontic diatom Eunotia exigua (Bréb.) Rabenh. and suppresses the growth of isoetids (e.g. Lobelia dortmanna L.) and of acidophilus and circumneutral diatoms. Also the acidobiontic Frustulia rhomboides var. saxonica (Rabenh.) Toni and Navicula subtilissima Cleve, characteristic of humic waters, decline by acidification.
4. In two pools where more than half of the bottom desiccated in 1976, observed concentrations of sulphate were highest in 1977–78 and decreased later on. Juncus bulbosus had a maximum in 1977–80. Eunotia exigua became the dominant diatom after 1976 and decreased after 1981 in the pool with the shortest residence time (3 years).
5. In desiccating pools the long-term decrease of pH is apparently much larger than in softwater lakes in Scandinavia and North America. During the last 50 years, pH dropped rapidly after dry summers, probably due to oxidation of sulphur and nitrogen compounds which were originally derived from the atmosphere, reduced and stored in the sediments. Rapid falls in pH were followed by an increase, presumably due to alkalinity production during sulphate reduction and denitrification.     

Preliminary results of a classification of fifty-one selected northeastern Wisconsin Lakes (USA) using indicator diatom species

Diatom species lists were generated for 51 lakes in northeastern Wisconsin, and then classified by two-way indicator species analysis (TWINSPAN). The lakes were initially divided into two main groupings: Group I lakes which were alkaline lakes of moderate to high productivity, and Group II lakes which were acid lakes of low productivity. Group I lakes were further divided into two subgroupings, and four levels. In total, twelve indicator diatom species were recognized during the TWINSPAN lake classification, these were: Achnanthes exigua Grun., A. lanceolata var. dubia Grun., Amphora ovalis var. Affinis (Kütz.) V.H. ex Det., A. perpusilla (Grun.) Grun., Cymbella cistula (Ehrenb.) Kirch., Diploneis elliptica (Kütz.) Cl., Eunotia pectinalis (O.F. Mull.) Rabh., Fragilaria vaucheriae (Kütz.) Peters., Frustulia rhomboides var. crassinervia (Bréb. ex W. Sm.) Ross, Navicula capitata Ehrenb., N. decussis Østr., and N. scutelloides W.Sm. ex Gregory.     

Studies in African Cyperaceae 27. Miscellaneous new taxa and combinations

One new form of Fuirena Rottb., one new subspecies of Schoenoplectus Palla and one new variety of Carex L. are described from East Africa, viz. Fuirena leptostachya Oliv. f. nudiflora Lye, Schoenoplectus lateriflorus (Gmel.) Lye ssp. laevinux Lye and Carex bequaertii De Wild. var. maxima Lye. In addition, the following new combinations are made: Fuirena ciliaris (L.) Roxb. f. apetala (Wingfield) Lye, F. stricta Steudel ssp. chlorocarpa (Ridley) Lye, Schoenoplectus rhodesicus (Podlech) Lye, 5. corymbosus (Roem. & Schult.) J. Rayn. var. brachyceras (A. Rich.) Lye, S. confusus (N.E. Br.) Lye var. rogersii (N.E. Br.) Lye, S. erectus (Poiret) J. Rayn, ssp. raynalii (Schuyler) Lye, S. erectus (Poiret) J. Rayn. ssp. sinuatus (Schuyler) Lye, Eleocharis retroflexa (Poiret) Urban ssp. subtilissima (Nelmes) Lye, Machaerina Vahl subgen. Baumea (Gaud.) Lye, Machaerina flexuosa (Bock.) Kern ssp. laevinux (J. Rayn.) Lye, M. montana (J. Rayn.) Lye, M. flexuosa (Böck.) Kern ssp. polyanthemum (Kük.) Lye, Scleria lagoënsis Böck. ssp. canaliculato–triquetra (Böck.) Lye, 5. distans Poiret var. glomerulata (Oliv.) Lye, S. distans Poiret var. chondrocarpa (Nelmes) Lye, S. melanotricha A. Rich. var. grata (Nelmes) Lye, Carex echinochloë Kunze ssp. nyasensis (C. B. Clarke) Lye, C. conferta A. Rich. var. lycurus (K. Schum.) Lye, C. cognata Kunth var. abyssinica (Chiov.) Lye and C. cognata Kunth var. congolensis (Turrill) Lye.     

Myxosporea parasites in roach, Rutilus rutilus (Linnaeus), from four lakes in central Finland

Ten myxosporean species belonging to three families were found in roach, Rutilus rutilus (Linnaeus), obtained in 1985 and 1986 from four lakes in central Finland which are connected to each other, but differ in water quality. One of the lakes is polluted by paper and pulp mill effluent, two are eutrophic and one is oligotrophic and still in its natural state. Eight species were found in all the lakes. The most common species were Myxidium rhodei Léger, 1905, Myxobolus muelleri Bütschli, 1882 and Myxobolus pseudodispar Gorbunova, 1936 with prevalences varying between 66–80, 16–31 and 32–59%, respectively, in the four lakes. The largest difference in myxosporean prevalence between lakes was found in the case of M. pseudodispar infection, which was highly significantly lower in the polluted lake. The locations of the myxosporean species in the tissues of the fish were found to be species-specific. M. rhodei and M. muelleri being prevalent in the kidney and M. pseudodispar in the muscles.
No clear seasonal variation was found but a tendency for a decrease in infection with increasing age was recorded in the case of M. rhodei and M. pseudodispar .     

Bewegungs- und Teilungsverhalten der Chromatophoren vonEunotia pectinalis var.polyplastidica und andererEunotia-Arten bei der Zellteilung

Summary The correlation between the start of chromatophore division and cell division is very different in various species ofEunotia. In some species the chromatophore division occurs before, in others after cell division. Eunotia pectinalis var.polyplastidica, with eight chromatophores per cell, represents an extreme type of behaviour in so far as two of the four plastids in each daughter cell prior to their division are shifted to the new hypovalve while the other two rest in situ. There occur two patterns of distribution of the four plastids, and that in the ratio 11, whereas the theoretically possible third pattern is never realized. The cause of that phenomenon is discussed. The division of the four plastids, in the meantime grown to full size, is performed not before they have reached their definitive equilibrium position at the epivalve or, respectively, at the hypovalve in twos. InEunotia pectinalis var.polyplastidica, by its mode of chromatophore division, the constant dissymmetric (right-left-handed) arrangement of the growing chromatophores, established inEunotia arcus, is not to be expected and is in fact not realized. InEunotia lunaris, however, the shift of the daughter chromatophores, in relation to the dorsiventrality of the cell, shows not only the same kind of dissymmetry as inEunotia arcus but also the same direction of shifting.The four and four chromatophores inEunotia pectinalis var.polyplastidica correspond to the two chromatophore plates in other species but the are not comparable with the numerous little chromatophore discs of Diatomaceae and other species the number of which decreases with the reduction of cell size.Cells ofEunotia pectinalis var.polyplastidica are capable to move by raphe action.

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Herrn Dr.Franz Berger zum 70. Geburtstag gewidmet.     

Delayed spawning of perch, Perca fluviatilis L., in acidified lakes

The timing of spawning of perch was examined in four acidified lakes (pH 4.4–4.8) and in one circum-neutral lake (pH 6.3) in southern Finland in spring 1987. In three of the lakes, perch started to spawn soon after the ice melt (4–14 degree days > 5° C) and had spawned by the end of May at about 100 degree days > 5° C. In the two most acidified lakes, fish started to spawn later, at 35 and 60 degree days > 5° C, and had spawned in early June, at about 200 degree days > 5° C. The maturing of gonad products was delayed in both males and females.     

湖南的新记录植物(五)

报道了湖南植物分布新记录,其中新记录种10个,即短茎淫羊藿(Epimedium brachyrrhizum Steam)、婺源凤仙花(Impatiens wuyuanensis Y.L．Chen)、滑叶猕猴桃(Actinidia laevissima C．F．Liang)、江浙狗舌草(Tephroseris pierotii(Miq．)Holub)、卵叶韭菜(Allium ovalifolium Hand．-Mzt．)、细花虾脊兰(Calanthe mannii Hook．f．)、银带虾脊兰(Calanthe argenteo-striata C．Z．Tang et S．J．Cheng)、乐昌虾脊兰(Calanthe lechangensis Z．H．Tsi et T．Tang)、大花羊耳蒜(Liparis distans C．B．Clarke)和牛虱草(Eragrostis unioloides(Retz．)Nees ex Steud．);新记录变种1个,即多裂荷青花(Hylomecon japonica vat．dissecta(Franch．et Savat．)Fedde)。     

中国短缝藻属植物二新记录

本文报道了采自安徽的我国短缝藻属植物二新记录种, 即缺刻短缝藻(Eunotia incisa W.Sm.exGreg.)和弧形短缝藻悬钩变种(E.arcus var.uncinata(Ehr.Grun.)。     

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.     

汉江中下游浮游植物群落结构及水质评价

南水北调中线工程调水后,汉江中下游水华频发引起社会关注。为掌握调水后汉江中下游浮游植物的群落结构特征,于2017年11月、2018年2月、4月和8月在汉江中下游的8个断面对浮游植物进行了定量调查。调查结果显示:共鉴定浮游植物163种,群落组成以硅藻门(Bacillariophyta)、绿藻门(Chlorophyta)为主,其次是蓝藻门(Cyanophyta)。浮游植物优势种主要为硅藻门的梅尼小环藻(Cyclotella meneghiniana)、颗粒直链藻最窄变种(Melosira granulata var.)、变异直链藻(Melosira varians)、颗粒直链藻(Melosira granulata),隐藻门的卵形隐藻(Cryptomonas ovata),蓝藻门的弯曲颤藻(Oscillatoria sp.)和伪鱼腥藻(Pseudoanabaena sp.),且都有较高的优势度。浮游植物密度和生物量的季节变化范围分别为0. 33×106cells/L～1. 82×106cells/L和0. 49 mg/L～7. 38 mg/L。基于Shannon-Weaver多样性指数和Pielou均匀度指数以及优势种评价法对汉江中下游的水质进行评价,判断汉江中下游水质整体处于中污状态。     

Limnochemical and phytoplankton studies on Nyumba ya Mungu reservoir, Tanzania

This publication reports on the chemical and phytoplankton aspects of a three month biological survey of Nyumba ya Mungu reservoir, Tanzania.
The lake had a total salt concentration of about 8 meq dm^-3 and specific conductivity of 900 μS cm^-1. The main salt in solution was sodium bicarbonate, and when the lake level fell it sometimes formed a crust on the exposed shore. The concentrations of major nutrient ions were probably not limiting to algal growth and good nutrient replenishment was provided by the two inflow rivers.
Nyumba ya Mungu supports a rich phytoplanton dominated by Melosira and blue-green algae. Acetone extractions gave chlorophyll 'a' concentrations ranging from 20–40 mgm^-3 in the vertical profiles, and light and dark bottle experiments indicated a maximum gross photosynthesis of about 800 mg O₂ m^-3h^-1. There was evidence of chemical stratification in the open water and diurnal stratification in the sheltered bays, but discontinuities were short-lived and the Trade Winds ensured regular mixing of the water. The lake appeared to have a higher primary production than the larger Rift Valley lakes and it was considered that this level of production would continue.     

How many fish populations in Finland are affected by acid precipitation?

Synopsis The number of fish populations affected or lost from small lakes in southern and central Finland due to acid precipitation is estimated. Tolerance limits (pH and labile aluminum) of common fish species were obtained from a fish status survey of 80 lakes. These tolerance values were used to estimate the proportion of affected lakes from the water chemistry data of 783 statistically selected lakes. The proportion of anthropogenically acidified lakes was estimated by calculating pre-acidification pH and aluminum concentrations of the lakes, using a steady-state model based on water chemistry. The number of fish populations for which acidification has affected growth or population structure was estimated at between 2200 and 4400. Out of these, the number of fish populations that have disappeared due to acid precipitation would be about 1000–2000. Almost 60% of the affected or lost populations are roach, Rutilus rutilus, the most sensitive of the common fish species in small lakes in southern and central Finland. Less than 15% of the damaged population is European perch, Perca fluviatilis, the most common species. This is due to the substantially higher tolerance of perch to acidified water in comparison with roach.     

Distribution and diversity of diatom assemblages in surficial sediments of shallow lakes in Wapusk National Park (Manitoba,Canada) region of the Hudson Bay Lowlands

The hydrology of shallow lakes (and ponds) located in the western Hudson Bay Lowlands (HBL) is sensitive to climate warming and associated permafrost thaw. However, their biological characteristics are poorly known, which hampers effective aquatic ecosystem monitoring. Located in northern Manitoba along the southwestern coast of Hudson Bay, Wapusk National Park (WNP) encompasses numerous shallow lakes representative of the subarctic zone. We analyzed the distribution and diversity of diatom (microscopic algae; class Bacillariophyceae) assemblages in surficial sediments of 33 lakes located in three different ecozones spanning a vegetation gradient, from NE to SW: the Coastal Fen (CF), the Interior Peat Plateau (IPP), and the Boreal Spruce Forest (BSF). We found significant differences (P < 0.05) in diatom community composition between CF and IPP lakes, and CF and BSF lakes, but not between IPP and BSF lakes. These results are consistent with water chemistry measurements, which indicated distinct limnological conditions for CF lakes. Diatom communities in CF lakes were generally dominated by alkaliphilous taxa typical of waters with medium to high conductivity, such as Nitzschia denticula. In contrast, several IPP and BSF lakes were dominated by acidophilous and circumneutral diatom taxa with preference for low conductivity (e.g., Tabellaria flocculosa, Eunotia mucophila, E. necompacta var. vixcompacta). This exploratory survey provides a first detailed inventory of the diatom assemblages in the WNP region needed for monitoring programs to detect changes in shallow lake ecosystems and ecozonal shifts in response to climate variations.     

The relative abundance of brown trout in acidic softwater lakes in relation to water quality in tributary streams

The influence of the water quality of tributary streams on the relative abundance in benthic gillnet catches (catch per unit effort, cpue) of allopatric brown Salmo trutta was assessed in associated acidic, softwater lakes. The study was carried out over 6 years (1989–1994) in 15 lakes located at altitudes between 230–715 m a.s.l. in two Norwegian catchments. The water quality of the main inlets and outlets varied little, as indicated by their of pH range (4·93–5·51) and calcium concentrations (0·19–0·44 mg 1⁻¹), but varied more with respect to concentrations of inorganic, monomeric aluminium (7·0–41·0 μg l⁻¹). Most of the lakes were also fed by secondary streams with better water quality: a maximum pH of 6·56, calcium levels of up to 0·74mg 1⁻¹, and inorganic aluminium levels as low as l·0 μg 1⁻¹. The cpue was inversely correlated with lake altitude ( r ²=0·50), and thus was adjusted to a mean altitude. The calcium concentration in the richest secondary stream to each lake, its richness judged on the basis of its acid-neutralizing capacity, had the highest predictive power of the variability in cpue ( r ² = 0·49).The calcium content in the other secondary streams or in the main inlets and outlets did not correlate with cpue. Alkalinity in the main outlets correlated to some extent with cpue ( r ² = 0·27). It is suggested that secondary streams with good water quality provide important refuges for the recruitment of brown trout in acidic softwater lakes.     

Does ionic strength affect the configuration of aquatic humic substances,as indicated by gel filtration?

SUMMARY. 1. The effect of ionic strength on the configuration of aquatic humic substances was studied by gel filtration and dialysis of water from small. Finnish forest lakes of varying colour.
2. Sephadex gel filtration of water from the most humic lake gave similar elution profiles of UV absorbance and dissolved organic carbon (DOC). Gel filtration of unconcentrated samples from all three lakes under natural conditions of ionic strength (I = 1.7 × 10⁻⁴) and pH (5.5–6.0) gave similar fractionation of humic substances, despite their widely differing colour (30–350 mg Pt l⁻¹) and DOC (5–25mg C l⁻¹).
3. Increasing the ionic strength by two orders of magnitude caused considerable retardation on the Sephadex columns of the humic substances, suggesting a decrease in their molecular size and/or shape.
4. Dialysis experiments strongly indicated that ionic strength-induced changes in the configuration of the aquatic humic substances are indeed real. Hence it is probable that the elution behaviour of aquatic humic substances on Sephadex gels has previously been wrongly attributed to ionic strength-dependent interactions between the gel and the humic substances.     

The effects of temperature and salinity on Tilapia rendalli Boulenger 1896

Temperature and salinity tolerances of Tilapia rendalli were determined experimentally. Results indicate that they are tolerant over a wide range of temperatures (11-37°C), but are incapable of surviving in salinities above 19 ‰ The maximum salinity tolerance is at temperatures between 20–28°C. The osmotic concentration of the blood rises from 255 mosmol/1 in freshwater to 340 mosmol/1 in a salinity of 19‰ T. rendalli is restricted to the warmer waters of the Zambezi river system in central Africa and southwards to the Pongolo river, as well as certain tropical and subtropical brackish water lagoons and lakes. Evidence from these experiments suggest that the distribution of T. rendalli isgoverned by both temperature and salinity.     

Fossil diatoms and the paleolimnology of Lake Rukwa, Tanzania

SUMMARY. 1. A 23.1 m sediment core from Lake Rukwa, southwest Tanzania, records 13,000 years of climatic change in five diatom assemblage zones. Zone E (13,000–12,7000 bp ) reflects the transition from the waning late glacial arid phase to pluvial conditions, as indicated by the co-occurrence of diatoms associated with fresh and relatively saline conditions. Zone D (12,700–4400 bp ) represents a moist period with frequent stratification, indicated by the halophobic genera Melosira and Stephanodiscus , whieh also represent alternating silica-rich and silica-dcpleled waters. Beginning with Zone C (4400–3900 bp ) the lake became much more saline with Thalassiosira predominating. This drying trend was reversed slightly in Zone B (3900–3300 bp ). During the last three millennia (Zone A), lake salinity was further reduced, while transitory moist phases were occurring in more northerly lakes such as Victoria and Kivu.
2. Lake Rukwa was relatively stable over a time scale of centuries, but on an annual basis is quite variable in salinity depending on the local rainy season.
3. These results agree well with the generalized paleoclimatie chronology of East Africa and suggest that the Holocene climatic regime of East Africa extended at least to 8°S.     

Seasonality of phytoplankton in some South Indian lakes

The landscape of South India is dotted with innumerable man-made lakes. They differ vastly in age, physiography, water flow characteristics, chemistry and trophic state, yet maintain a phytoplankton overwhelmingly dominated (43–93%) by blue-green algae; the subdominants are diatoms and/or Chlorococcales and euglenoids. The blue-greens apparently reach them from soils which are known to harbour a rich blue-green flora and several species in common with limnoplankton.South Indian lakes resemble some tropical counterparts in sustaining dense phytoplankton populations all the year round and temperate dimictic ones in showing two annual growth peaks that usually occur in summer (February–May) and the post-monsoon period (October–November), in synchrony with rise in temperature. In the chemically more oligotrophic lakes, the peaks are constituted by Raphidiopsis mediterranea Skuja, Navicula cryptocephala Kütz., Melosira granulata (Ehr.) Ralfs, and others and in hypereutrophic lakes by Microcystis aeruginosa Kütz., Synechocystis aquatilis Sauv., Oscillatoria spp., Burkillia coronata West & West and Euglena acus Ehr. The bimodal seasonality in abundance of phytoplankton reflects in chlorophyll and biomass concentrations although these are not in strict synchrony with each other. At the maxima chlorophyll a and over-dry biomass may rise to 8.5 mg l^–1 and 204 mg l^–1 respectively in highly productive waters. The highest rate of carbon assimilation recorded in such phases is 10.6 g C m^–3 d^–1.