Linda Nedbalová

Effect of nitrogen and phosphorus starvation on the polyunsaturated triacylglycerol composition, including positional isomer distribution, in the alga Trachydiscus minutus

The yellow-green alga Trachydiscus minutus (Eustigmatophyceae, Heterocontophyta) was cultivated in a standard medium and under nitrogen- and phosphorus-starvation and its triacylglycerols were analyzed by RP-HPLC/MS-APCI. The molecular species of triacylglycerols included a total of 74 triacylglycerols having at least one polyunsaturated fatty acid. Polyunsaturated triacylglycerols were identified for the first time in a yellow-green alga. N-starvation brought about a nearly 50% drop in TAGs containing EPA, and also decreased TAGs containing ARA, while P-starvation had a sizable effect on those TAGs that contain two or three arachidonic acids. In four TAGs containing PUFA, i.e. EEE, EEA, EAA and AAA, N-starvation caused a rapid fivefold increase in ARA content and the ratio of TAGs containing ARA, i.e. AEE to AAA increased tenfold relative to control. Regioisomeric characterization of triacylglycerols containing palmitic, arachidonic (ARA) and eicosapentaenoic acids (EPA) showed that the proportion of positional isomers is affected by N- and P-starvation. N- and P-starvation also changed the ratio of symmetrical to asymmetrical TAGs. Positional isomers exhibited identical ratios of symmetrical and asymmetrical TAGs irrespective of the type of FAs. In control cultivation the major TAGs with a single PUFA were symmetrical ones (PEP or PAP) whose ratio to asymmetrical counterparts (PPE or PPA) was about 3:1, whereas N- and P-starvation yielded opposite ratios, 1:3-1:5. The control cultivation yielded ~90% asymmetrical TAGs with two PUFAs (i.e. PEE and PAA), whereas with N- and P-starvation the ratio of symmetrical to asymmetrical TAGs increased to 2:1 and 3:2, respectively.

Odd-numbered very-long-chain polyunsaturated fatty acids from the dinoflagellate Amphidinium carterae identified by atmospheric pressure chemical ionization liquid chromatography-mass spectrometry

A method is described for the enrichment of odd very-long-chain polyunsaturated fatty acids (VLCPUFAs) by means of RP-HPLC and argentation TLC from total fatty acids of the dinoflagellate A. carterae and their identification as picolinyl esters by means of microbore liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization (LC-MS/APCI). The combination of argentation TLC and LC-MS/APCI was used to identify rare and unusual odd VLCPUFAs up to nonacosahexaenoic acid. Two acids, (allZ)-nonacosa-11,14,17,20,23-pentaenoic acid (29:5n-6) and (allZ)-nonacosa-11,14,17,20,23,26-hexaenoic acid (29:6n-3), were synthesized for the first time to unambiguously confirm their structure. Possible biosynthetic pathways for odd VLCPUFAs are also proposed.

Biological recovery of the Bohemian Forest lakes from acidification

A limnological survey of eight small, atmospherically acidified, forested glacial lakes in the Bohemian Forest (Šumava, Böhmerwald) was performed in September 2003. Water chemistry of the tributaries and surface layer of each lake was determined, as well as species composition and biomass of the plankton along the water column, and littoral macrozoobenthos to assess the present status of the lakes. The progress in chemical reversal and biological recovery from acid stress was evaluated by comparing the current status of the lakes with results of a survey four years ago (1999) and former acidification data since the early 1990s. Both the current chemical lake status and the pelagic food web structure reflected the acidity of the tributaries and their aluminium (Al) and phosphorus (P) concentrations. One mesotrophic (Plešné jezero) and three oligotrophic lakes (Černé jezero, Čertovo jezero, and Rachelsee) are still chronically acidified, while four other oligotrophic lakes (Kleiner Arbersee, Prášilské jezero, Grosser Arbersee, and Laka) have recovered their carbonate buffering system. Total plankton biomass was very low and largely dominated by filamentous bacteria in the acidified oligotrophic lakes, while the mesotrophic lake had a higher biomass and was dominated by phytoplankton, which apparently profited from the higher P input. In contrast, both phytoplankton and crustacean zooplankton accounted for the majority of plankton biomass in the recovering lakes. This study has shown further progress in the reversal of lake water chemistry as well as further evidence of biological recovery compared to the 1999 survey. While no changes occurred in species composition of phytoplankton, a new ciliate species was found in one lake. In several lakes, this survey documented a return of zooplankton (e.g., Cladocera: Ceriodaphnia quadrangula and Rotifera: three Keratella species) and macrozoobenthos species (e.g., Ephemeroptera and Plecoptera). The beginning of biological recovery has been delayed for ∼20 years after chemical reversal of the lakes.

Massive occurrence of heterotrophic filaments in acidified lakes: seasonal dynamics and composition

We documented permanent presence of heterotrophic filaments in three acidified lakes (pH<5) in the Bohemian Forest. Due to acidification, crustacean zooplankton were absent in all but one lake. In terms of carbon flow, microorganisms were thus almost exclusive players in the pelagic food webs. Variety of extremely long (>100 microm) heterotrophic filaments occurred in the lakes. The filaments usually accounted for >50% of total heterotrophic microbial biomass in the pelagic zone (medians of the total biomass: 82-108 microg C l(-1)), except for anoxic bottom layers and for episodic appearance of Daphnia longispina in one lake. Seasonal filament formation was mainly induced and maintained by grazing of mixotrophic flagellates (Dinobryon spp.) on small unicellular bacteria in the absence of cladoceran filtration. The filaments were less active than unicellular suspended bacteria. Fluorescence in situ hybridisation revealed that usually <50% of total bacteria were targeted with oligonucleotide probes for Eubacteria.

Freshwater lakes of Ulu Peninsula, James Ross Island, north-east Antarctic Peninsula: origin, geomorphology and physical and chemical limnology

Abstract This study describes the origin, bedrock geology, geomorphology, hydrological stability and physical and chemical characteristics of a representative set of 29 lakes in the ice-free parts of the Ulu Peninsula, James Ross Island, located close to the northern tip of the Antarctic Peninsula. Based on these features, six different types of lakes were defined: stable shallow lakes on higher-altitude levelled surfaces, shallow coastal lakes, stable lakes in old moraines, small unstable lakes in young moraines, deep cirque lakes and kettle lakes. We observed a significant relationship between lake type and water chemistry. Bedrock, lake age and morphometry together with altitude were the most important factors underlying the observed limnological variability. Our results further suggested possible nitrogen limitation in the lake ecosystems. However, physical factors such as low temperature and light were also likely to be limiting.

Diversity, ecology and biogeography of the freshwater diatom communities from Ulu Peninsula (James Ross Island, NE Antarctic Peninsula)

The diversity, ecology and biogeography of diatoms in lakes, seepage areas and streams on the Ulu Peninsula, a large ice-free area in the northern part of James Ross Island (Weddell Sea), were studied. A diverse diatom flora of 123 taxa was observed, dominated by several Nitzschia taxa, Psammothidium papilio, Eolimna jamesrossensis, Fragilaria capucina and Fistulifera saprophila. The results from the similarity and diversity analysis suggest James Ross Island to be biogeographically positioned within the Maritime Antarctic region, yet with some affinities with the flora of Continental Antarctica, as shown by the presence of Luticola gaussii and Achnanthes taylorensis. Based on our data, James Ross Island can thus be located close to the boundary of the two main Antarctic biogeographical regions. Diatom communities present in streams and seepage areas could be clearly distinguished from those in lakes, the latter being much more species rich. Based on the multivariate analysis, conductivity and nutrients were selected as the two main environmental factors determining the diatom composition in the Ulu Peninsula lakes. The revised taxonomy of the Antarctic diatom flora induced the construction of a transfer function for water conductivity in the studied lakes that can be applied in further palaeoecological studies.

Phylogenetic position and taxonomy of three heterocytous cyanobacteria dominating the littoral of deglaciated lakes, James Ross Island, Antarctica

Several communities of autotrophic microorganisms, in which cyanobacteria are dominant or play a substantial role in their structure, were studied on the deglaciated Ulu Peninsula, northern part of James Ross Island, NW Weddell Sea, Antarctica, in 2007–2009. Our results were compared with similar data from maritime Antarctica (King George Island, South Shetland Islands, 2005). Characteristics and taxonomic description of three important heterocytous species, which participate in cyanoprokaryotic assemblages in the littoral of small lakes, seepages, and on wetted rocks during the Antarctic summer season, are included in this study. They belong to the form-genera Calothrix and Hassallia, respectively, and are unidentifiable according to the present determination literature. Therefore, after a polyphasic evaluation, they are described as three new species, Calothrix elsteri sp. nova, Hassallia andreassenii sp. nova, and Hassallia antarctica sp. nova. 16S rRNA gene sequencing of isolated strains confirmed the taxonomic position of all three species, and their ecology and seasonal development are described. All three discovered species are dominant in distinct communities with a specialized ecology and may be endemic for coastal maritime Antarctica.

THREE NEW TERRESTRIAL DIATOM SPECIES FROM SEEPAGE AREAS ON JAMES ROSS ISLAND (ANTARCTIC PENINSULA REGION)

A recent survey of the non-marine diatoms from seepage areas on James Ross Island (Antarctic Peninsula Region) resulted in the discovery of three new diatom species belonging to the genera Diadesmis, Eolimna and Luticola. Based on both light and scanning electron microscopical observations, these species were described as new to science: Diadesmis inconspicua sp. nov., Eolimna jamesrossensis sp. nov. and Luticola truncata sp. nov. The morphology of each species was compared to similar species worldwide with a special focus on those present in the Antarctic Region. Notes on the ecology of the species were added.

Effect of starvation on the distribution of positional isomers and enantiomers of triacylglycerol in the diatom Phaeodactylum tricornutum.

The diatom Phaeodactylum tricornutum was cultivated in a standard medium and under sulfur, silicon, nitrogen and phosphorus starvation and its triacylglycerols (TAGs) were analyzed by RP-HPLC/MS-APCI. Nearly 100 molecular species of polyunsaturated TAGs were identified. RP-HPLC was used to isolate positional isomers of TAGs, which were further separated by chiral HPLC. First eluted were those TAGs that have an eicosapentaenoic acid moiety in the sn-1 position. The ratios of symmetrical to asymmetrical TAGs in P. tricornutum were affected under sulfur-, nitrogen-, phosphorus- and silica-starvation, i.e. in cultivations involving cells in nutrient stress. The ratios of positional TAGs and also the proportions of enantiomers were changed. The ratios of symmetrical to asymmetrical TAGs in the control and under N- and P-starvation were very close. In the control, the ratio of 1,2-dipalmitoyl-3-eicosapentaenoyl-rac-glycerol to 1,3-dipalmitoyl-2-eicosapentaenoyl-rac-glycerol was 3:1 and the ratio of 1,2-dieicosapentaenoyl-3-palmitoyl-rac-glycerol to 1,3-dieicosapentaenoyl-2-palmitoyl-rac-glycerol was 9:1. Under N-starvation the ratios were reversed irrespective of the presence or absence of silicate in the medium. A similar pattern was found in P- and S-starvation.

Identification of very-long-chain polyunsaturated fatty acids from Amphidinium carterae by atmospheric pressure chemical ionization liquid chromatography-mass spectroscopy

A method is described for the enrichment of very-long-chain polyunsaturated fatty acids (VLCPUFAs) from total fatty acids of Amphidinium carterae and their identification as picolinyl esters by means of microbore liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization (LC-MS/APCI). The combination of argentation TLC and LC-MS/APCI was used to identify unusual VLCPUFAs up to hexatriacontaoctaenoic acid. Two acids, 36:7n-6 and 36:8n-3, were also synthesized to unambiguously confirm their structure. The possibilities of VLCPUFAs biosynthesis are proposed.