L. V. Ilyash

Probing of photosynthetic reactions in four phytoplanktonic algae with a PEA fluorometer

High-resolution light-induced kinetics of chlorophyll fluorescence (OJIP transients) were recorded and analyzed in cultures of diatoms (Thalassiosira weissflogii, Chaetoceros mulleri) and dinoflagellates (Amphidinium carterae, Prorocentrum minimum). Fluorescence transients showed the rapid exponential initial rise from the point O indicating low connectivity between PS II units and high absorption cross-section of PS II antenna. Dark-adapted dinoflagellates revealed capability to maintain the PS I-mediated re-oxidation of the PQ pool at the exposure to strong actinic light that may lead to the underestimation of FM value. In OJIP transients recorded in phytoplanktonic algae the fluorescence yield at the point O exceeded FO level because QA has been already partly reduced at 50xa0μs after the illumination onset. PEA was also employed to study the recovery of photosynthetic reactions in T. weissflogii during incubation of nitrogen starved cells in N-replete medium. N limitation caused the impairment of electron transport between QA and PQs, accumulation of closed PS II centers, and the reduced ability to generate transmembrane ΔpH upon illumination, almost fully restored during the recovery period. The recovered cells showed much higher values of NPQ than control ones suggesting maximization of photoprotection mechanisms in the population with a ‘stress history.’

Multidisciplinary studies of the separating lakes at different stage of isolation from the White Sea performed in March 2012

639 The multidisciplinary expedition was performed from March 20 to April 2, 2012, on the Kindo Penin sula in Kandalaksha Bay of the White Sea. The expe dition was aimed to study the salty waterbodies that appeared due to the separating of the sea inlets from the sea by the isostatic lifting of the seashore. The sci entists from the Biological and Geographical Faculties and the Belozersky Institute of Physico Chemical Biology of Lomonosov Moscow State University, the Shirshov Institute of Oceanology, the Winogradsky Institute of Microbiology, Zubov State Oceanograph ical Institute, the Institute for Information Transmis sion Problems (the Kharkevich Institute), and the Institute of Ecological Problems of the North (Urals Branch of the Russian Academy of Sciences) partici pated in the expedition. The work was performed at the N.A. Pertsov White Sea Biological Station of Lomonosov Moscow State University.

Present-Day State of Coral Reefs of Nha Trang Bay (Southern Vietnam) and Possible Reasons for the Disturbance of Habitats of Scleractinian Corals

Our investigations were conducted from 1990 to 2002. Sampling of bottom sediments and biological objects, as well as photo and video shooting, were performed during scuba diving. The state of the environment and coral reef communities was assessed using the chemical–analytical, fluorometric, and luminometric methods, as well as the Ames test and the transect technique. The research results suggest that the spectrum and distribution pattern of persistent congeners of PCDD/Fs (dioxins) in bottom sediments are similar to those of the defoliant “Agent Orange” and that the bottom sediments are toxic and display photo inhibition and a mutagenic effect. The bottom of the bay is heavily silted throughout its depth. Many large dead colonies of corals without mechanical damage were observed everywhere. The total coverage by live corals in all sites investigated does not exceed 30%. Although, without a doubt, many factors contributed much to the disturbance of the bay ecosystems, the actual trigger for the degradation of the coral reefs seems to be the input of dioxin-containing chemicals used as defoliants during the American–Vietnamese war (Vietnam War).

Effects of local hydrophysical conditions on the spatial variability of phytoplankton in the White Sea

The species composition and biomass of phytoplankton, chlorophyll a concentration (Chl), and hydrophysical characteristics of water masses have been studied in Onega and Kandalaksha bays (Chupa Inlet and Knyazhaya Inlet) of the White Sea at 16 stations June 17–26, 2012. Structural analysis of the phytoplankton community according to the Bray-Curtis similarity index has revealed two groups of stations. The first group united stations in stratified waters in Kandalaksha Bay; all stations located in Onega Bay formed another group. In turn, the stations in Onega Bay were separated into two subgroups corresponding to mixed (MWs) and stratified (SWs) waters. The total phytoplankton biomass and the biomass of diatoms and small unidentified flagellates were higher in Onega Bay. The biomass of dinoflagellates and cryptophytes, as well as Chl, did not differ significantly in Kandalaksha and Onega bays. In Onega Bay, the total phytoplankton biomass, Chl, and contribution of dinoflagellates to the total biomass were higher in SWs than in MWs. The contribution of diatoms was higher in SWs. The study addresses the role of the frontal zones in shaping the structure and distribution of the phytoplankton community.

Spatial variability of the species composition, abundance, and productivity of the phytoplankton in the white sea in the late summer period

The species composition, cell concentration (N), and biomass (B) of the phytoplankton, as well as the chlorophyll a (Chl a) concentration, primary production (PP), and the concentrations of the dissolved inorganic micronutrients (phosphorus, silica, nitrogen as nitrite), were estimated for Kandalaksha Bay (KB), Dvina Bay (DB), and the basin (Bas) of the White Sea in August of 2004. The micronutrient concentrations were lower compared to the average long-term values for the summer period. The Chl a concentration varies from 0.9 to 2.0 mg/m3 for most of the studied areas, reaching up to 7.5 mg/m3 in the Northern Dvina River estuary. The surface water layer of the DB was the most productive area, where the PP reached up to 270–375 mg C/(m3 day). The phytoplankton biomass varied from 11 to 205 mg C/m3 with the highest values observed in the Bas and DB. Three groups of stations were defined during the analysis of the phytoplankton’s species composition similarity. The dinoflagellates Dinophysis norvegica and Ceratium fusus were particular to the phytoplankton assemblages in the KB; the diatom Ditylum brightwellii was particular to the upper and central parts of the DB. These three phytoplankton species were less abundant in the Bas.

Contrasting summer phytoplankton communities in stratified and mixed waters of the white sea

The species composition and biomass of the phytoplankton, as well as the hydrophysical characteristics of the water masses have been analyzed in different regions of the White Sea at 37 stations during the period from June 20 to July 3, 2008. Three communities with different structures have been identified, each associated with water masses with specific structures and dynamics. The community dominated by Skeletonema costatum has been growing in Dvina Bay in stratified waters with the highest temperature and the lowest salinity compared with the other areas of the sea. The community dominated by Thalassiosira nordenskioeldii has been associated with mixed waters of Onega Bay and adjacent areas of the Basin with low temperatures and high salinity. The community dominated by dinoflagellates has been growing in different areas of the sea: both in stratified and mixed waters. The average phytoplankton biomass in the surface water layer and the total biomass under 1 m2 in the studied areas have been 134 ± 157 mg C/m3 (n = 37) and 1157 ± 874 mg C/m2 (n = 18), respectively.

Metagenomic analyses of white sea picoalgae: First data

Picoalgae (defined as cells smaller than 2-3 μm) include members of diverse taxonomic groups. They are an important constituent of marine plankton and ice biota and play a significant ecological role in biogeochemical cycles. Despite their importance, the true extent of their diversity has only recently been uncovered by molecular surveys. The diversity of picoeukaryotes has not yet been studied in the White Sea, which is a unique marine environment combining features of temperate and Arctic seas. Here, we investigated the taxonomic composition of eukaryotic picoalgae in ice and under-ice water at a station located in the Kandalaksha Bay of the White Sea. We applied metagenomic survey using Illumina sequencing. Eight main algae phyla, namely, Chlorophyta, Katablepharidophyta, Haptophyta, Dinophyta, Cercozoa, Bacillariophyta, Cryptophyta, and Ochrophyta were identified. The genera Paraphysomonas and Micromonas and the order Pedinellales were most numerous in plankton; the genera Paraphysomonas, Micromonas, and Metopion were most abundant in ice. The number of “rare” phylotypes was 80 in under-ice water and 112 in ice. Some taxa of nanoand microalgae are identified for the first time in the White Sea phytoplankton. Our data provide a basis for further research of tiny phototrophs in the Russian Arctic.

Vertical flux of phytoplankton and particulate matter in the White Sea according to the long-term exposure of sediment traps

The vertical fluxes of phytoplankton (VFPhyto) and particulate organic carbon (VFPOC) in the White Sea were determined using seven long-term (292 to 296 days) sediment traps moored at five stations at 67–255 m depths. The annual VFPhyto and VFPOC ranged from 0.55 to 24.64 g C/m2 and from 3.7 to 93.9 g C/m2, respectively. The highest VFPhyto was observed in the Basin region located close to the Gorlo along the Tersk coast. The algal biomass accounted for 15–43% of the VFPOC. Diatoms comprised the most important group, accounting for 83–100% in the sedimented biomass. Thalassiosira nordenskioeldii dominated in the VFPhyto at all the stations except for the station in the basin close to Onega Bay, where Ditylum brightwellii was the most abundant.

Spatial distribution of phytoplankton in the White Sea in the late summer period with regard to the water structure and dynamics

The species composition and biomass of the phytoplankton, as well as the hydrophysical and hydrochemical characteristics of the water masses, were estimated for different areas of the White Sea at 24 stations for the period of August 26 to September 3, 2007. The micronutrient concentrations were lower compared to the average long-term values for the summer period. The total biomass of phytoplankton (Bt) varied from 87 to 1914 mg C/m2. For most of the studied sites, Bt was low; dinoflagellates were the most abundant species. Diatoms dominated in the areas of elevated hydrodynamic activity, i.e., in the Gorlo (vertical mixing of the water layers), in intrusions of the Gorlo water masses into the basin of the White Sea, and in the peripheral areas of the Dvina outflow current. The Bt was also the highest in the listed areas.

Metagenomics of bolidophyceae in plankton and ice of the White Sea

The molecular diversity of poorly studied algae of Bolidophyceae class was first estimated by Illumina sequencing of V4 region of 18S rRNA gene in ice, under-ice water and summer water of the subarctic White Sea. We used two clustering thresholds–93 and 97%–and revealed 31 phylotypes of Bolidophyceae. Triparma pacifica and Т. strigata were identified to species level. The association of individual phylotypes to certain biotopes (ice or plankton) and stages of seasonal succession (under ice or summer plankton) has been established. Some phylotypes are found in different biotopes and over a wide temperature range. Due to changing their genetic composition, Bolidophyceae are a constant component of the photoautotrophic plankton and ice communities.