Late fall phytoplankton dynamics in three lakes, Rocky Mountain National Park

We studied phytoplankton population dynamics during the month preceding formation of ice cover in three small subalpine lakes in Rocky Mountain National Park, Colorado, U.S.A. The outflow from Emerald Lake, which is surrounded by talus, flows into Dream Lake, which is surrounded by sub-alpine forest. Nymph Lake is a lower seepage lake with abundant macrophytes in summer. The major ion concentrations in the three lakes were similar during the study, although Emerald and Dream Lakes had higher concentrations of nitrate and silica than Nymph Lake. A principal component analysis (PCA) showed that the phytoplankton in Emerald and Dream Lakes were distinct from the phytoplankton in Nymph Lake. The species composition changed in each lake during the late fall. The patterns of change in Emerald and Dream Lakes were similar on the PCA diagram despite the greater abundance of diatoms in Dream Lake and the decreasing flow from Emerald Lake into Dream Lake during the fall. In Nymph Lake, a progressive shift in species distribution occurred with a decrease in the most abundant chlorophyte, Chlamydomonas sp., and increases in several species, including two chrysophytes and the diatom Eunotia sp. The marked change in species composition in all three lakes suggests that phytoplankton populations are influenced by changes in water temperatures and incident solar radiation that occur during the late fall. We also compared these data with phytoplankton data for two fall periods from two other hydrologically connected Rocky Mountain lakes. PCA analysis showed that the difference between years was greater than the change during the fall and that the fall species composition in these two lakes was distinct from that in Emerald and Dream Lakes or in Nymph Lake. Studying phytoplankton dynamics in alpine and sub-alpine lakes may offer clues as to how these ecosystems may respond to projected climate changes in the Rocky Mountain region, such as warmer temperatures and later formation of ice-cover.     

Cryopreservation of economically valuable marine micro-algae in the classes Bacillariophyceae, Chlorophyceae, Cyanophyceae, Dinophyceae, Haptophyceae, Prasinophyceae, and Rhodophyceae

The ability to routinely cryopreserve micro-algal species reduces costs associated with maintaining large culture collections and reduces the risks of losing particular strains or species through contamination and genetic drift. Cryopreservation is also a useful adjunct in aquaculture hatcheries for strains of micro-algae where the nutritional status may change as a result of continuous sub-culture. In this study, cryopreservation of isolates from seven micro-algal classes was investigated. Successful candidates included the marine dinoflagellates Amphidinium carterae, Amphidinium trulla, and Gymnodinium simplex, and the haptophytes Chrysochromulina simplex, Prymnesium parvum, Prymnesium parvum f. patelliferum, Isochrysis galbana, and Pavlova lutheri. Also successfully cryopreserved were the planktonic diatoms Chaetoceros calcitrans, Chaetoceros muelleri, Chaetoceros sp., and the benthic Nitzschia ovalis, the chlorophyte Chlamydomonas coccoides, the rhodophyte Porphyridium purpureum, the prasinophytes Tetraselmis chuii, and Tetraselmis suecica, and the cyanophytes Raphidiopsis sp., and Aphanizomenon flos-aquae. All species were successfully cryopreserved using 15% Me2SO.     

Phytoplankton and physical-chemical features of Tavropos Reservoir,Greece

Phytoplankton biomass values in Tavropos Reservoir, ranging from 92 to 1071 mg m^–3, are within a range characteristic of oligotrophic waters. The seasonal sequence of biomass shows three annual peaks, differing from the monoacmic pattern seen in oligotrophic lakes. This sequence was profoundly affected by changes in water withdrawal and inflow rates. Diatoms, cryptophytes, chrysophytes and dinoflagellates, in that order, were the major constituents of the reservoir phytoplankton. The succession, from diatoms and chrysophytes in late winter-spring, to centric diatoms in late spring-summer and again to diatom-chrysophytes in late autumn was similar to that in oligotrophic lakes.     

Spiniferomonas abrupta, sp. nov. and some rare species of Synurophyceae and Chrysophyceae, not formerly recorded from Denmark

Eight ponds and lakes were examined for scale-bearing chrysophytes (Synurophyceae and Chrysophyceae) and abiotic parameters. Samples were taken monthly, throughout one year. All species of scale-bearing chrysophytes were identified by transmission electron microscopy (TEM). Altogether 74 taxa were found including a new species of Spiniferomonas (S. abrupta sp. nov.). Some rare species, not formerly recorded from Denmark, were also observed: Mallomonas asmundiae, M. corcontica, M. pumitio var. silvicola, Paraphysomonas capreolata, P. elegantissima, P. limbata , and Spiniferomonas silverensis .     

Scale–bearing Chrysophyceae (Mallomonadaceae) from Central and Northern Canada

In this study, scale–bearing Chrysophyceae (Mallomonadaceae) have been examined by means of transmission and scanning electron microscopy. Lakes in four areas in central and northern Canada, viz. Experimental Lakes Area (ELA), in northwestern Ontario, Whiteshell Provincial Park and Southern Indian Lake in eastern and northern Manitoba, respectively, and Saqvaqjuac on the west coast of Hudson Bay in the Northwest Territories have been investigated. Forty–three species of the genera Mallomonas, Paraphysomonas, Spiniferomonas and Synura have been identified in addition to three species of the genus Chrysochromulina (Prymnesiophyceae). Ten species are new to Canada; five of these have not previously been recorded from North America. Paraphysomonas elegantissima sp. nov. is described. The composition of the Canadian chrysophycean flora is compared with the chrysophycean flora of North America as a whole.     

Brevilinea pocosinensis Siver, Hamilton & Morales gen. et sp. nov., a new diatom (Bacillariophyceae) genus from North Carolina, USA

A new diatom genus, Brevilinea gen. nov., is described from an acidic freshwater lake situated on the Atlantic Coastal Plain of North Carolina, USA. The type for the genus, Brevilinea pocosinensis sp. nov., differs from other diatoms by the presence of a unique and reduced raphe that is restricted to the central portion of the valve. The new taxon has large and distinctive areolae that also serve to separate it from existing genera. The taxonomic placement of the new organism relative to other diatoms possessing a reduced raphe is discussed. Although Brevilinea may eventually be placed into a new family, given the current dynamic state of diatom systematics, it is premature to do so at this time.     

Responses of phytoplankton and epilithon during acidification and early recovery of a lake

1. Lake 302S in the Experimental Lakes Area of Canada was acidified from pH 6.7 (1981) to 5.1 (1986). The pH was further reduced to 4.5 in 1987 and held at that level until 1991. From 1992 to 1995, the pH was allowed to increase to a target value of 5.8.
2. The response of the phytoplankton community to decreasing pH from 6.0 to 5.1 was similar to that observed in another experimentally acidified lake (223) and in other atmospherically acidified lakes. Acidification affected species diversity of both the phytoplankton and epilithon. Phytoplankton diversity was positively correlated with pH. Epilithic algal diversity was more variable and did not correlate with pH.
3. Phytoplankton biomass was enhanced by acidification as the assemblage shifted from a dominance of chrysophytes to large dinoflagellates ( Gymnodinium sp. and Peridinium inconspicuum ). Epilithon biomass was unaffected, but dominance shifted from filamentous cyanophytes ( Lyngbya ) to acidophilic diatoms ( Tabellaria quadriseptata and Anomoeonis brachysira ).
4. The only taxon to be similarly affected in both the phytoplankton and epilithon was the cyanobacteria, being significantly reduced below pH 5.1. During early recovery (pH 5.5–5.8), cyanobacteria increased and species present prior to acidification recolonized both habitats.
5. In the early stages of recovery, planktonic and benthic assemblages remained more similar to acidified than natural assemblages, but more profound change began at pH > 5.5.     

Winter phytoplankton community structure in three shallow temperate lakes during ice cover

The general model of seasonal phytoplankton succession in temperate lakes suggests that winter phytoplankton growth is minimal under ice-cover. However, some studies have found diverse phytoplankton communities during winter. The primary objectives of this study were to determine the species composition and the changes in the winter phytoplankton community structure under the ice. For 2 consecutive winters, phytoplankton samples were collected under ice-cover at 4 sites on 3 lakes in Arrowwood National Wildlife Refuge (ANWR), near Pingree, North Dakota. Ninety taxa were identified and enumerated. Densities of several of these taxa frequently exceeded 10⁶ cells l^–1. The winter phytoplankton communities in these lakes were dominated by flagellates, principally cryptomonads, a synurophyte (Synura uvella), small chrysophytes (Chrysococcus spp., Kephyrion spp.) and a dinoflagellate (Peridinium aciculiferum), as well as non-flagellate microchlorophytes (Monoraphidium spp., Ankistrodesmus spp., and Pseudodictyosphaerium sp.), a cyanobacterium (Gloeocapsa aeruginosa) and centric diatoms (Stephanodiscus minutulus, S. parvus and Cyclotella meneghiniana).     

Phytoplankton indicator taxa for reference conditions in Northern and Central European lowland lakes

Phytoplankton data from 606 lakes were used to characterize indicator taxa of near-pristine reference conditions in clearwater and humic lowland lakes of Northern and Central Europe. Reference lakes were selected based on low pressure from catchment land-use, low population density and the absence of point sources. Reference lakes had low phytoplankton biomass and taxa richness compared to non-reference lakes. In low alkalinity lakes of Northern Europe, the reference communities had high biomass proportions of chrysophytes and low proportions of cyanobacteria; in the Central European high alkalinity lakes, the biomass was distributed more evenly among algal groups. Indicator species analysis and similarity analysis listed 5–29 taxa indicating reference conditions. Indicator taxa differed especially between the low alkalinity and the high alkalinity lakes, but there were also country-specific differences. Most common indicator taxa for the northern reference lakes were chrysophytes (e.g. Bitrichia, Dinobryon). In the Central European reference lakes, diatoms (e.g. Cyclotella) were more characteristic. Despite the differences, there was a general finding that taxa present in reference lakes were often also present in non-reference lakes, but typically in lower biomass proportions; another characteristic of the reference communities is the absence of many taxa typically found in non-reference lakes.     

Development of phytoplankton in Lake Pääjärvi (Finland) during under-ice convective mixing period

The development of winter phytoplankton communities was studied in both shallow and deep areas of Lake Pääjärvi, southern Finland, during the final 2 weeks of winter ice cover. Phytoplankton was mainly composed of diatoms, cryptophytes and chrysophytes. The diatoms Aulacoseira and Rhizosolenia were always uniformly distributed with depth, initially probably due to mixing induced by heat flux from the sediment and later due to thermal convection. Motile Rhodomonas cryptophytes and Chrysococcus chrysophytes were most abundant near the ice showing that, despite their small size, they were partly able to resist mixing by convection. Their ability to stay in more illuminated water layers was reflected in net rates of increase about an order of magnitude higher than those of diatoms in the middle of the lake. Given the low temperatures and convection, the observed net rates of increase of motile taxa were very high compared to growth rates reported in the literature. The gradual increase in light availability following melting of ice led to a consistent increase in the abundances of major phytoplankton taxa irrespective of deep convective circulation. It is suggested that those algae most abundant at the time of ice break have a competitive advantage in the following open water conditions when nutrients are abundant but deep water circulation limits light availability. The results emphasize that in lakes which cool below the maximum density of water before freezing, apparently small differences in temperature and light conditions can cause important changes in the circulation patterns that impact on phytoplankton development.     

SOME PRYMNESIACEAE (HAPTOPHYTA,PRYMNESIOPHYCEAE) FROM THE MEDITERRANEAN SEA,WITH THE DESCRIPTION OF TWO NEW SPECIES: CHRYSOCHROMULINA LANCEOLATA SP. NOV. AND C. PSEUDOLANCEOLATA SP. NOV.1

Five species belonging to the family Prymnesiaceae (one Prymnesium and four Chrysochromulina) have been identified in cultures obtained from water collected in the Bay of Banyuls‐sur‐Mer (Mediterranean Sea, France) using LM, SEM, and TEM. Two are described as new species, Chrysochromulina lanceolata sp. nov. and C. pseudolanceolata sp. nov. Both species are large and lanceolate with an acute posterior and two anterior arms. They are easily detectable with LM but difficult to distinguish to species level with live cells, without experience. EM reveals two completely different scale patterns in the two species. Cells of C. lanceolata are 21–38 μm long, 7–12 μm wide, and 3–7 μm thick. They possess two subequal flagella (30–51 and 29–44 μm), and the haptonema is shorter than the flagella (23–37 μm). The cell body is covered by plate and spine scales. Cells of C. pseudolanceolata sp. nov. are slightly smaller (15–18 × 6–8 μm) with more rounded extremities, two subequal flagella (19–26 and 17–24 μm), and the haptonema is longer than the flagella (about 35 μm). Three types of plate scales are observed in this species. Other findings are C. alifera Parke et Manton and C. throndsenii Eikrem (a new record for the Mediterranean Sea). Prymnesium faveolatum Fresnel, a new toxic species recently described, is illustrated with both LM and SEM.     

Chrysochromulina laurentiana: an electron microscopic study of a new species of Prymnesiophyceae from Canadian Shield lakes

Three species of Chrysochromulina have been observed from the plankton of Canadian Shield lakes of the Experimental Lakes Area, northwestern Ontario. Chrysochromulina parva Lackey is ubiquitous and well known. C. breviturrita Nicholls and C. laurentiana described here appear similar to one another under the light microscope, but with the aid of the transmission electron microscope it is possible to distinguish them as two different species.     

Identification of Freshwater Phycodnaviridae and Their Potential Phytoplankton Hosts, Using DNA pol Sequence Fragments and a Genetic-Distance Analysis

Viruses that infect phytoplankton are an important component of aquatic ecosystems, yet in lakes they remain largely unstudied. In order to investigate viruses (Phycodnaviridae) infecting eukaryotic phytoplankton in lakes and to estimate the number of potential host species, samples were collected from four lakes at the Experimental Lakes Area in Ontario, Canada, during the ice-free period (mid-May to mid-October) of 2004. From each lake, Phycodnaviridae DNA polymerase (pol) gene fragments were amplified using algal-virus-specific primers and separated by denaturing gradient gel electrophoresis; 20 bands were extracted from the gels and sequenced. Phylogenetic analysis indicated that freshwater environmental phycodnavirus sequences belong to distinct phylogenetic groups. An analysis of the genetic distances “within” and “between” monophyletic groups of phycodnavirus isolates indicated that DNA pol sequences that differed by more than 7% at the inferred amino acid level were from viruses that infect different host species. Application of this threshold to phylogenies of environmental sequences indicated that the DNA pol sequences from these lakes came from viruses that infect at least nine different phytoplankton species. A multivariate statistical analysis suggested that potential freshwater hosts included Mallomonas sp., Monoraphidium sp., and Cyclotella sp. This approach should help to unravel the relationships between viruses in the environment and the phytoplankton hosts they infect.     

Rapid quantification of the toxic alga Prymnesium parvum in natural samples by use of a specific monoclonal antibody and solid-phase cytometry

The increasing incidence of harmful algal blooms around the world and their associated health and economic effects require the development of methods to rapidly and accurately detect and enumerate the target species. Here we describe use of a solid-phase cytometer to detect and enumerate the toxic alga Prymnesium parvum in natural samples, using a specific monoclonal antibody and indirect immunofluorescence. The immunoglobulin G antibody 16E4 exhibited narrow specificity in that it recognized several P. parvum strains and a Prymnesium nemamethecum strain but it did not cross-react with P. parvum strains from Scandinavia or any other algal strains, including species of the closely related genus Chrysochromulina. Prymnesium sp. cells labeled with 16E4 were readily detected by the solid-phase cytometer because of the large fluorescence signal and the signal/noise ratio. Immunofluorescence detection and enumeration of cultured P. parvum cells preserved with different fixatives showed that the highest cell counts were obtained when cells were fixed with either glutaraldehyde or formaldehyde plus the cell protectant Pluronic F-68, whereas the use of formaldehyde alone resulted in significantly lower counts. Immunofluorescence labeling and analysis with the solid-phase cytometer of fixed natural samples from a bloom of P. parvum occurring in Lake Colorado in Texas gave cell counts that were close to those obtained by the traditional method of counting using light microscopy. These results show that a solid-phase cytometer can be used to rapidly enumerate natural P. parvum cells and that it could be used to detect other toxic algae, with an appropriate antibody or DNA probe.     

Long-term trends and regional differences of phytoplankton in large Finnish lakes

Major nutrients (N and P) and phytoplankton from 19 large lakes from southern (61°) to northern (69°) Finland were analyzed to detect long-term trends and regional differences. The data sets from June, July and August cover the period from the early 1980s to the present. Altogether >700 phytoplankton and >4000 N, P and Chl a results were used for the study. In 40% of the lakes, the total phosphorus (TP) concentration decreased significantly and in >25% of the lakes a significant reduction was found in the total nitrogen (TN) concentration. At the same time, the phytoplankton biomass declined only in 15% of the lakes and the long-term trends in chlorophyll a more often increased than decreased. A clear gradient from southern to northern Finland and western to eastern Finland was found in the phytoplankton biomass. During the study period, the biomasses of cyanobacteria and centrales (diatoms) decreased whilst there was an increase in the biomass of pennales (diatoms) in one-third of the lakes. The proportion of chlorophytes in the total biomass also increased in >20% of the study lakes. In southern and western Finland, the total biomass and the contribution of cyanobacteria were higher. Centrales made a higher contribution to the total biomass in the north. Pennales and chlorophytes were less abundant and chrysophytes more abundant in the east. Differences in the community composition reflected the gradients in the total nutrients, and particularly in TP. The observations support the assumed role of phosphorus as the key limiting nutrient in large Finnish lakes irrespective of lake′s location. The N:P ratio proved to be a poor predictor of cyanobacteria occurrence in the study lakes.     

Nutrient ratios and phytoplankton community structure in the large, shallow, eutrophic, subtropical Lakes Okeechobee (Florida, USA) and Taihu (China)

Analysis of ten- and four-year datasets for the large, shallow, subtropical, and eutrophic Lakes Okeechobee (USA) and Taihu (China), respectively, suggest that resource-ratio explanations for cyanobacteria dominance may not apply to these two lakes. Datasets were examined to identify relationships between nutrient ratios [total nitrogen (TN):total phosphorus (TP) and ammonium (NH₄ ⁺):oxidized N (NO _x )] and phytoplankton community structure (as proportions of cyanobacteria and diatoms to total phytoplankton biomass). Datasets were pooled by sampling month, averaged lake-wide, and analyzed with linear regression. In Okeechobee, the cyanobacteria proportion increased and the diatom proportion decreased with increasing TN:TP. In Taihu, cyanobacteria decreased with increasing TN:TP, but the opposite trend observed for diatoms was marginally significant. Okeechobee cyanobacteria increased and diatoms decreased with increasing NH₄ ⁺:NO _x , but no significant relationships between phytoplankton and NH₄ ⁺:NO _x were observed in Taihu. Both lakes had significant relationships between phytoplankton community structure and total nutrients, but these relationships were the opposite of those expected. Relationships between phytoplankton community structure and water quality parameters from the previous month resulted in improved relationships, suggesting a predictive capability. Statistical analysis of the entire datasets (not pooled) supported these and additional relationships with other parameters, including temperature and water clarity.     

A new species of Penicillium from the Chilean Tierra del Fuego

A new species of Penicillium is described and illustrated. It is represented by two isolates recovered from sandy soils on the shores of Lake Sarmiento, in the Chilean Tierra del Fuego. The new species clearly differs from all species of the genus described so far among the monoverticillate ones, especially by the unique wall ornamentation pattern as viewed with the SEM. It is therefore, described and proposed as a new taxon: Penicillium lacussarmientei sp. nov.     

中国台湾秃蝗亚科一新属四新种(直翅目，斑腿蝗科)(英文)

记述了采自中国台湾斑腿蝗科秃蝗亚科1新属台秃蝗属Taipoodisma gen. nov. 和4新种：红股台秃蝗Taipodisma rufifemora sp. nov., 谢氏台秃蝗Taipodisma hsiehi sp. nov., 周氏台秃蝗Taipodisma chowi sp. nov., 黑胫台秃蝗Taipodisma nigritibia sp. nov.。新属台秃蝗属Taipoodisma gen. nov.同蹦蝗属Sinopodisma Chang, 1940近似,不同之处为前胸背板后缘中央缺凹口,中隆线在沟前区不显,在沟后区留有痕迹。新属同辽秃蝗属Liaopodisma Zheng, 1990也近似,不同之处为雄性后胸腹板两侧叶分开,不毗连。新种红股台秃蝗T. rufifemora sp. nov. 后足股节内侧和下方红色可与同属其他种相区别。新种谢氏台秃蝗T. hsiehi sp. nov. 缺黑色眼后带可与同属其他种相区别。新种周氏台秃蝗T. chowi sp. nov. 同红股台秃蝗T. rufifemora sp. nov.近似,不同之处为后足股节内侧和下方非红色。新种黑胫台秃蝗T. nigritibia sp. nov. 同周氏台秃蝗T. chowi sp. nov.近似,不同之处为前胸背板沿中隆线缺黑色纵带和前翅黄褐色,缺黑色带纹。列出了该属的种检索表。     

Comparing microscopic counts and pigment analyses in 46 phytoplankton communities from lakes of different trophic state

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