78 A comparison of four native Porphyra species from coastal new england in response to ammonium and temperature in small tank system

Cosmopolitanism vs. endemism of microbial diversity in water has been debated for a long time. Finlay (2002) argued that reported similarities in microbial biodiversity in different lakes and oceans support cosmopolitanism of microorganisms. Lee and Patterson (1998) suggested that many endemism studies are flawed due to underrepresentation of taxa. On the other hand, Theriot and Stoermer (1984) showed that Stephanodiscus niagrarae , the centric diatom once thought to be a cosmopolitan species, actually consists of four slightly different species. Mating tests of Paramecium aurelia revealed 14 sibling species, which are morphologically almost identical (Sonneborn, 1957). Here, I present evidence for the cryptic speciation of Peridinium limbatum from two water bodies (Crystal Lake and Crystal Bog) that are near each other but chemically distinct. We observed that the two Peridinium limbatum had different responses to the same growth medium. Previous works at the Microbial Observatory program showed that their seasonal population dynamics were also different; while a summer bloom of Crystal Bog Peridinium limbatum was correlated with a dramatic decrease in phytoplankton diversity, and an extreme drop in bacterial diversity, a bloom of Crystal Lake Peridinium limbatum was not. To see the genetic variations in this study, I sequenced internal transcribed spacer region 1 and 2 from the two Peridinium limbatum . The sequence variations were 8.53% in ITS1 and 8.06% in ITS2, which were much larger than within variations. In another ongoing study that I expect to complete before the meeting, I've been testing their possible allelopathic differences on Cryptomonas.     

Genetically Distinct Populations of the Dinoflagellate <Emphasis Type="Italic">Peridinium limbatum</Emphasis> in Neighboring Northern Wisconsin Lakes

The extent to which free-living microorganisms exist in geographically isolated, genetically distinct populations is a subject of continuing debate. Some authorities contend that many microorganisms have cosmopolitan distributions, while others provide evidence that more limited geographical distribution of genetically distinct populations can occur. We report the occurrence of two morphologically similar, but genetically distinct, populations of the microbial eukaryote Peridinium limbatum (Stokes) Lemmermann from neighboring Northern Wisconsin freshwater bodies. Five strains of P. limbatum were cultured by single-cell isolation from both Crystal Lake and Crystal Bog (Oneida Co., WI). Genetic variation between the two populations encompassed 8.9% (mean of 35.4 of 397 nucleotides) of the nuclear ribosomal DNA internal transcribed spacer (ITS1 and ITS2) region. In contrast, 0.5% (mean of 2.25 of 397 nucleotides) variation was observed within the Crystal Lake population and 0.3% (mean of 1.21 of 397 nucleotides), within the Crystal Bog population. This difference between the two populations was highly statistically significant (p-value << 0.001). The extent of genetic variation between the two P. limbatum populations was greater than that reported in the literature for some morphologically distinguishable microalgal species, suggesting the occurrence of cryptic sister species. On the other hand, hybrid sequences obtained from one of the Crystal Lake strains suggest that the two populations may still be members of a single sexually compatible biological species. Our data suggest that the two neighboring P. limbatum populations may be diverging genetically under conditions of limited gene flow, suggesting a mechanism for the origin of geographically isolated, genetically distinct populations of microbial eukaryotes.     

Seasonal Dynamics of Phytoplankton and Planktonic Protozoan Communities in a Northern Temperate Humic Lake: Diversity in a Dinoflagellate Dominated System

Species diversity and richness, and seasonal population dynamics of phytoplankton, planktonic protozoa, and bacterioplankton sampled from the epilimnion of Crystal Bog in 2000, were examined in order to test the hypothesis that these groups diversity and abundance patterns might be linked. Crystal Bog, a humic lake in Vilas County, Wisconsin, is part of the North Temperate Lakes Long-Term Ecological Research Site. Phytoplankton and planktonic protozoa were identified and enumerated in a settling chamber with an inverted microscope. Bacterial cells were enumerated with the use of fluorescence 4, 6-diamidino-2-phenylindole (DAPI)-staining procedures, and automated ribosomal intergenic spacer analysis (ARISA) was used to assess bacterioplankton diversity. Bacterial cell counts showed little seasonal variation and averaged 2.6 × 10⁶ cells/mL over the ice-free season. Phytoplankton and planktonic protozoan numbers varied by up to two orders of magnitude and were most numerous in late spring and summer. Dinoflagellates largely dominated Crystal Bog throughout the ice-free period, specifically Peridiniopsis quadridens in the spring, Peridinium limbatum in summer, and Gymnodinium fuscum and P. quadridens in fall. Brief blooms of Cryptomonas, Dinobryon, and Synura occurred between periods of dinoflagellate domination. The dominant dinoflagellate, Peridinium limbatum, was calculated to have a growth rate of 0.065 day^–1 and a doubling time of 10.7 days. Heterotrophic nanoflagellates (HNFs) were a consistent component of the planktonic protozoa; seasonal patterns were determined for three genera of HNFs (Monosiga, Bicosoeca, and Desmarella moniliformis). Three genera of ciliates (Coleps, Strobilidium, and Strombidium) comprised the greater part of the planktonic protozoa in Crystal Bog. The number of species of planktonic protozoa was too low to calculate a diversity index. Shannon–Weaver diversity indices for phytoplankton and bacterioplankton in the epilimnion followed very similar seasonal patterns in this lake, supporting the hypothesis that in freshwaters, diversity patterns of these groups are linked.     

COMPARATIVE ULTRASTRUCTURE OF VEGETATIVE AND SEXUAL THECAE OF PERIDINIUM LIMBATUM AND PERIDINIUM CINCTUM (DINOPHYCEAE)

Peridinium limbatum (Stokes) Lemmerman reproduces sexually in nitrogen deficient medium. Sexual reproduction is homothallic and similar to that reported for other Peridinium species. Thecate planozygotes of P. limbatum and P. cinctum enlarge greatly. Suture bands connecting thecal plates enlarge unequally in P. cinctum producing a “warty” zygote and equally in P. limbatum maintaining the regular but enlarged appearance of the cell. Zygotes can be recognized by greatly enlarged striated suture bands.     

A SURVEY OF AUXOTROPHY IN FIVE FRESHWATER DINOFLAGELLATES (PYRRHOPHYTA)1

Peridiniopsis polonicum (Wolosz.) Bourrelly requires vitamin B₁₂, and Peridinium limbatum (Stokes) Lemm. requires thiamin for growth. Unlike marine Peridinium species, Peridinium willei Huit.-Kaas, P. volzii Lemm., and P. inconspicuum Lemm. do not display auxotrophy. Peridinium volzii is strongly inhibited by concentrations of biotin above 1 μg L^?1.     

The effects of oils and oil components on algae: A review

Plate structure analysis of the bloom-forming Peridinium of Lake Kinneret (previously identified as P. cinctum fa. westii) established its identity as P. gatunense. Peridinium cinctum was not observed. Material from different years and periods of the bloom, as well as specimens from cultures and P. gatunense from Lago Cristalino (Brazil), were studied using light and scanning electron microscopy. Peridinium gatunense from Lake Kinneret showed slight differences of the plate pattern as compared with specimens from other localities.     

Stable patterns in size structure of a phytoplankton species of Lake Kinneret

The aim of the study was a search for typical structure patterns of phytoplankton assemblages, based on the long-term dynamics analysis. As a test case we used the interannual phytoplankton variability of Lake Kinneret (Israel). The dominant phytoplankton species (Peridinium gatunense) structure was presented as the frequency-weighted taxonomic size spectrum (TSS) which describes the size distribution of the operational taxonomic unit (OTUj) occurrence frequencies. Using 24 years monitoring data, the TSS annual patterns of P. gatunense were compared. Typical persistent TSS patterns were evident even during years of pronounced deviations from the typical patterns of phytoplankton biomass dynamics and species composition. By correlation analysis, hierarchical cluster analysis and ANOVA the TSS variability was quantified and compared. While the TSS general shape was almost constant, its amplitude variations allowed us to distinguish between three levels of annual bloom intensity. Electronic Supplementary Material Supplementary material is available for this article at and accessible for authorised users     

Evidence for Local Ciliate Endemism in an Alpine Anoxic Lake

Despite its long history, biogeography has received relatively little attention within the field of microbial ecology. Consequently, a fierce debate rages whether protists inhabit restricted geographic areas (endemism hypothesis) or are globally dispersed (ubiquitous dispersal hypothesis). The data presented in this article support the endemism hypothesis. We succeeded in isolating an oligohymenophorean ciliate from a microbial mat in a meromictic anoxic alpine lake (Alatsee) in Germany. The ciliary pattern and the morphometry of this isolate are remarkably similar to Urocentrum turbo (Mueller, 1786) Nitzsch, 1827. However, the organism does not possess trichocysts, a conspicuous and characteristic feature of U. turbo. Instead, the U. turbo-like isolate from lake Alatsee displays merely trichocyst anlagen (“ghosts”) in the cytoplasm that are only visible after protargol impregnation and which become never attached to the cell’s cortex. Despite the distinctness of this difference, such a morphospecies has not been described from any other environment. Thus, we suggest that the U. turbo-like isolate from lake Alatsee is a local endemic ecotype, although the sequences of the 18S rRNA, ITS1, 5.8S rRNA, and ITS2 genes are nearly identical to those of U. turbo (Mueller, 1786) Nitzsch, 1827. This indicates that neither 18S rDNA nor ITS1, ITS2, and 5.8S rDNA sequences are reliable means to conclusively resolve different morphospecies or ecotypes of ciliates. As a consequence, we argue that protist species richness can only be reliably accounted for by considering both molecular and morphological data.     

Diversity of Freshwater <Emphasis Type="Italic">Thioploca</Emphasis> Species and Their Specific Association with Filamentous Bacteria of the Phylum <Emphasis Type="Italic">Chloroflexi</Emphasis>

Phylogenetic diversity among filamentous sulfur-oxidizing bacteria of the genus Thioploca inhabiting freshwater/brackish environments was analyzed in detail. The 16S rRNA gene sequence of Thioploca found in a freshwater lake in Japan, Lake Okotanpe, was identical to that of Thioploca from Lake Ogawara, a brackish lake. The samples of the two lakes could be differentiated by the sequences of their 23S rRNA genes and 16S–23S rRNA internal transcribed spacer (ITS) regions. The 23S rRNA-based phylogenetic relationships between Thioploca samples from four lakes (Lake Okotanpe, Lake Ogawara, Lake Biwa, and Lake Constance) were similar to those based on the 16S rRNA gene sequences. In addition, multiple types of the ITS sequences were obtained from Thioploca inhabiting Lake Okotanpe and Lake Constance. Variations within respective Thioploca populations were also observed in the analysis of the soxB gene, involved in sulfur oxidation. As major members of the sheath-associated microbial community, bacteria of the phylum Chloroflexi were consistently detected in the samples from different lakes. Fluorescence in situ hybridization revealed that they were filamentous and abundantly distributed within the sheaths of Thioploca.     

Dinoflagellate bloom development and collapse in Lake Kinneret: a sediment trap study

Warm monomictic Lake Kinneret, Israel, is characterized by awinter–spring water bloom of the large (~50 µm diameter)dinoflagellate Peridinium gatunense Nygaard. Usually the P.gatunense bloom declines in May–June and a less prominentbloom of smaller dinoflagellates (mostly Peridiniopsis spp.of ~20–30 µm diameter) develops. Water column abundancesand sedimentation losses to those dinoflagellates were followedthroughout 1994 and 1995. The objective was to quantify thevariables that describe population dynamics, that in turn willshed more light on the seasonal patterns of bloom dynamics.Sedimentation losses were measured by means of sediment trapswith and without a preservative (formaldehyde) that were exposedfor 24 h once every 2–3 weeks. Annual sedimentation lossesof Peridinium (hypolimnetic trap catches) were 209 g wet wtm^-2 year^-1 in 1994 and 187 g wet wt m^-2 year^-1 in 1995, whichconstituted 16 and 23% of Peridinium production in those years,respectively. This study revealed that increased death ratespreceded a mass sedimentation flux of Peridinium and causedthe decline of the bloom in Lake Kinneret. Annual sedimentationlosses of Peridiniopsis were 55 g wet wt m^-2 year^-1 in 1994and 34 g wet wt m^-2 year^-1 in 1995. In contrast to live Peridiniumcells, Peridiniopsis cells continued to swim to the lower trapafter the onset of thermal stratification, possibly taking advantageof the higher nutrient concentrations below the thermocline,at a time when the lake is already stratified and the epilimnionis nutrient depleted. This could be an important factor allowingPeridiniopsis spp. to peak after the decline of Peridinium.     

Controls on Microbial Production of Methane and Carbon Dioxide in Three Sphagnum-Dominated Peatland Ecosystems as Revealed by a Reciprocal Field Peat Transplant Experiment

We examined controls on mineralization of carbon to methane (CH₄) and carbon dioxide (CO₂) in Sphagnum (moss)-dominated peatland ecosystems by transplanting surface (5 cm deep) and subsurface (40 cm deep) peat samples reciprocally among three sites for periods ranging from 4 to 25 months. The sites were Big Run Bog in West Virginia, USA, Bog Lake Bog in Minnesota, USA, and Bog 307 in Ontario, Canada. Immediately upon retrieval, we incubated the peat samples in the laboratory at 12 and 22°C under both anoxic and oxic conditions to estimate rates of carbon mineralization. Transplanting affected surface peat more than subsurface peat. Peat incubated within Bog Lake Bog in Minnesota had the highest rates of CH₄ production, regardless of origin, whereas transplanting did not affect rates of CO₂ production measured concomitantly. Peat that originated in Big Run Bog in West Virginia generally maintained higher rates of CH₄ production and CO₂ production than peat from the other two sites after incubation in the field. The temperature dependence (Q ₁₀) of CH₄ production and CO₂ production varied among transplant sites, but not among peat origins, suggesting physiological adaptations of microbial communities to local environmental conditions. Differences in organic matter quality of the peat, particularly lignin chemistry, helped explain the results: (a) CH₄ production correlated with fresher lignin derived from Carex sedges, and (b) CO₂ production correlated with woody lignin. We concluded that, although both site conditions (climate, nutrient status, and microbial communities) and organic matter quality influence carbon mineralization in peat, interactive effects occur and may differ depending on peat temperature. Moreover, CH₄ production and CO₂ production respond differently to environmental regulators.     

WINTER PHYTOPLANKTON BLOOMS UNDER ICE ASSOCIATED WITH ELEVATED OXYGEN LEVELS1

Many shallow lakes in north temperate zones experience reduced dissolved oxygen concentration under ice. However, some shallow lakes display supersaturated dissolved oxygen concentrations (>20 mg·L ^{? 1}) in late winter under conditions of maximum ice thickness. During the winters of 1996, 1997, and 1999, we collected phytoplankton samples from Arrowwood Lake near Pingree, North Dakota to determine whether a specific alga was involved in dissolved oxygen supersaturation in this lake. Although dissolved oxygen supersaturation was not observed during this period, we did observe an increase in dissolved oxygen concentration that was associated with a phytoplankton bloom during late February and early March in both 1996 and 1997. In 1996, the bloom was composed of the dinoflagellate, Peridinium aciculiferum (Lemm.) Lemm. and several species of cryptomonads. A similar bloom of P. aciculiferum was followed by a bloom of several species of euglenoids in 1997. In contrast, P. aciculiferum was only a minor component of the winter phytoplankton, dissolved oxygen concentrations remained low, and no bloom event was observed in 1999. Statistical analyses indicated a significant relationship (r_s = 0.57, P = 0.019) between dissolved oxygen levels and the density of the dinoflagellate, P. aciculiferum, but no significant relationship between dissolved oxygen levels and densities of other phytoplankton. These results suggest that the elevated levels of dissolved oxygen are associated with the dinoflagellate, P. aciculiferum. This bloom was most likely the result of an excystment event rather than a general growth response.     

Development of a high-resolution molecular marker for tracking Pseudo-nitzschia pungens genetic diversity through comparative analysis of mitochondrial genomes

The harmful algal bloom (HAB) species Pseudo-nitzschia pungens is widely distributed in almost all continents. Accumulating evidence suggests that P. pungens has high genetic diversity and many strains can produce the toxin domoic acid (DA) that harms animals and humans. Nevertheless, different P. pungens strains cannot be distinguished using morphological features or using common molecular markers including 18S rDNA, 28S rDNA, ITS, cox1, and rbcL. As such, high-resolution molecular markers need to be developed to resolve P. pungens genetic diversity, facilitating accurate tracking of toxic P. pungens strains. We hypothesized that molecular markers with high resolution and high specificity can be designed through identifying regions with high genomic variations in the mitochondrial genome. Here, we describe the development of a new molecular marker Pseudo-nitzschia pungens mitochondrial 1 (ppmt1) with high resolution and high specificity through comparative analysis of mitochondrial genomes of nine P. pungens strains isolated from coastal regions of China. In conclusion, we have developed ppmt1 as a high-resolution and high-specificity molecular marker for tracking strains and genetic diversity of the HAB species P. pungens.

     

羊卓雍措水体可培养酵母菌多样性及其与理化因子相关性

【目的】开展羊卓雍措水体可培养酵母菌多样性研究,探究影响其多样性的主要理化因子。【方法】采用膜过滤平置培养法分离纯化酵母菌,并结合rRNA ITS区域序列分析与经典分类法对酵母菌菌株进行鉴定。运用SPSS 20.0和CANOCO 5分析可培养酵母菌多样性及其与理化因子之间的关系。【结果】羊卓雍措水体可培养酵母菌为16个属25个种,优势属为Vishniacozyma,优势物种为Vishniacozyma victoriae。Pearson相关系数显示,pH、电导率、总溶解固体量、盐度与各样点可培养酵母菌种数和属数呈显著正相关;总磷与各样点及各区域可培养酵母菌属数呈显著负相关,与各样点种数呈显著负相关。冗余分析显示,pH和总磷是影响羊卓雍措水体可培养酵母菌分布的主要环境因子。【结论】羊卓雍措水体酵母菌资源比较丰富且存在明显的空间异质性,人类活动对酵母菌分布有较大影响。酵母菌分布与人类活动的关系值得进一步研究。     

Methods used to reveal genetic diversity in the colony-forming prymnesiophytes Phaeocystis antarctica, P. globosa and P. pouchetii—preliminary results

Previous work on the genetic diversity of Phaeocystis used ribosomal DNA and internal transcribed spacer (ITS) sequence analyses to show that there is substantial inter- and intraspecific variation within the genus. First attempts to trace the biogeographical history of strains in Antarctic coastal waters were based on a comparison of ITS sequences. To gain deeper insights into the population structure and bloom dynamics of this microalga it is necessary to quantify the genetic diversity within populations of P. antarctica from different locations (i.e., each of the three major gyres in the Antarctic continental waters) and to calculate the gene flow between them. Here we describe methods to quantify genetic diversity and our preliminary results for P. antarctica in comparison to two other colonial species: P. globosa and P. pouchetii. For this study of genetic diversity, two fingerprinting techniques were used. First, amplified fragment-length polymorphisms (AFLPs) were established as a pre-screening tool to assess clone diversity and to select divergent clones prior to physiological investigations. Second, the more-powerful microsatellite markers were established to assess population structure and biogeography more accurately. Results show differences in the AFLP patterns between isolates of P. antarctica from different regions, and that a wide variety of microsatellite motifs could be obtained from the three Phaeocystis species.     

Genetic diversity of Cladophora oligocladoidea forming a bloom in the coastal area of Korea

Green algal blooms by Cladophora species are primarily reported in freshwater and coastal regions and cause severe ecological problems. A taxonomic report of the geographic distribution of Cladophora blooms is essential to explore the cause and impact of macroalgal blooms and for eco-physiological studies. The identification of blooming species is necessary for monitoring and controlling algal blooms. Genetic information of DNA sequences is useful for identifying species in the genus Cladophora. In the coastal area of Sangrok, Korea, a large-scale Cladophora bloom was reported for the first time in September 2015. In the present study, we identified the taxonomic entity of Cladophora oligocladoidea (Ulvophyceae, Cladophorales) in Korea. We report for the first time a green algal bloom by this species globally. This is the second report about genetic diversity of C. oligocladoidea since the species was established in Japan. Four ribotypes in the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA represent the genetic diversity of Korean C. oligocladoidea. The results from this taxonomic report and our analysis of the green algal bloom of Korean C. oligocladoidea can provide valuable data to understand the geographic distribution and the genetic diversity of the species.     

Phenotypically Different Microalgal Morphospecies with Identical Ribosomal DNA: A Case of Rapid Adaptive Evolution?

The agents driving the divergence and speciation of free-living microbial populations are still largely unknown. We investigated the dinoflagellate morphospecies Scrippsiella hangoei and Peridinium aciculiferum, which abound in the Baltic Sea and in northern temperate lakes, respectively. Electron microscopy analyses showed significant interspecific differences in the external cellular morphology, but a similar plate pattern in the characteristic dinoflagellate armor. Experimentally, S. hangoei grew in a wide range of salinities (0–30), whereas P. aciculiferum only grew in low salinities (0–3). Despite these phenotypic differences and the habitat segregation, molecular analyses showed identical ribosomal DNA sequences (ITS1, ITS2, 5.8S, SSU, and partial LSU) for both morphospecies. Yet, a strong interspecific genetic isolation was indicated by amplified fragment length polymorphism (F _ST = 0.76) and cytochrome b (cob) sequence divergence (∼1.90%). Phylogenetic reconstructions based on ribosomal (SSU, LSU) and mitochondrial (cob) DNA indicated a recent marine ancestor for P. aciculiferum. In conclusion, we suggest that the lacustrine P. aciculiferum and the marine-brackish S. hangoei diverged very recently, after a marine–freshwater transition that exposed the ancestral populations to different selective pressures. This hypothetical scenario agrees with mounting data indicating a significant role of natural selection in the divergence of free-living microbes, despite their virtually unrestricted dispersal capabilities. Finally, our results indicate that identical ITS rDNA sequences do not necessarily imply the same microbial species, as commonly assumed.     

Annual Patterns in Bacterioplankton Community Variability in a Humic Lake

Bacterioplankton community composition (BCC) was monitored in a shallow humic lake in northern Wisconsin, USA, over 3 years using automated ribosomal intergenic spacer analysis (ARISA). Comparison of ARISA profiles of bacterial communities over time indicated that BCC was highly variable on a seasonal and annual scale. Nonmetric multidimensional scaling (MDS) analysis indicated little similarity in BCC from year to year. Nevertheless, annual patterns in bacterioplankton community diversity were observed. Trends in bacterioplankton community diversity were correlated to annual patterns in community succession observed for phytoplankton and zooplankton populations, consistent with the notion that food web interactions affect bacterioplankton community structure in this humic lake. Bacterioplankton communities experience a dramatic drop in richness and abundance each year in early summer, concurrent with an increase in the abundance of both mixotrophic and heterotrophic flagellates. A second drop in richness, but not abundance, is observed each year in late summer, coinciding with an intense bloom of the nonphagotrophic dinoflagellate Peridinium limbatum. A relationship between bacterial community composition, size, and abundance and the population dynamics of Daphnia was also observed. The noted synchrony between these major population and species shifts suggests that linkages across trophic levels play a role in determining the annual time course of events for the microbial and metazoan components of the plankton.