Unexpected consequences of increasing CO2 and ocean acidity on marine production of DMS and CH2ClI: Potential climate impacts

Increasing atmospheric mixing ratios of CO2 have already lowered surface ocean pH by 0.1 units compared to preindustrial values and pH is expected to decrease an additional 0.3 units by the end of this century. Pronounced physiological changes in some phytoplankton have been observed during previous CO2 perturbation experiments. Marine microorganisms are known to consume and produce climate-relevant organic gases. Concentrations of (CH3)2S (DMS) and CH2ClI were quantified during the Third Pelagic Ecosystem CO2 Enrichment Study. Positive feedbacks were observed between control mesocosms and those simulating future CO2. Dimethyl sulfide was 26% (±10%) greater than the controls in the 2x ambient CO2 treatments, and 18% (±10%) higher in the 3xCO2 mesocosms. For CH2ClI the 2xCO2 treatments were 46% (±4%) greater than the controls and the 3xCO2 mesocosms were 131% (±11%) higher. These processes may help contribute to the homeostasis of the planet

Microbial communities and processes in ice-covered Arctic waters of the northwestern Fram Strait (75 to 80° N) during the vernal pre-bloom phase

Marine microbial communities have been little studied in Arctic waters, especially during the winter–spring transition before the development of extensive phytoplankton blooms. This study investigated microbial plankton in the ice-covered polar surface waters of the northwestern Fram Strait (75 to 80°N) at the onset of the 24 h light period in spring (April to May). The system we encountered was characterised by low concentrations of chlorophyll a (<0.2 μg l−1) and a low abundance of both bacteria (1.4 to 2.5 × 108 cells l−1) and protists (1 to 1.7 × 105 cells l−1). Bacterial production was very low (≤0.63 μg C l−1 d−1), despite the dominance of nucleic-acid-rich bacteria (58 ± 6% of total bacterial abundance). Small (2 to 5 μm) phototrophs dominated the eukaryotic assemblage in the surface and most probably had profound effects on the composition and metabolic balance of the microbial community as a whole. Most stations appeared to have been net-autotrophic, and calculations of phagotrophy indicated a balanced carbon budget for the microbial community. Mixotrophy was seen in a large part of the ciliate assemblage and may have contributed to the productivity and stability of the pre-bloom system that we encountered.publishedVersio

Microbial communities and processes in ice-covered Arctic waters of the northwestern Fram Strait (75 to 80° N) during the vernal pre-bloom phase

Marine microbial communities have been little studied in Arctic waters, especially during the winter–spring transition before the development of extensive phytoplankton blooms. This study investigated microbial plankton in the ice-covered polar surface waters of the northwestern Fram Strait (75 to 80°N) at the onset of the 24 h light period in spring (April to May). The system we encountered was characterised by low concentrations of chlorophyll a (<0.2 μg l−1) and a low abundance of both bacteria (1.4 to 2.5 × 108 cells l−1) and protists (1 to 1.7 × 105 cells l−1). Bacterial production was very low (≤0.63 μg C l−1 d−1), despite the dominance of nucleic-acid-rich bacteria (58 ± 6% of total bacterial abundance). Small (2 to 5 μm) phototrophs dominated the eukaryotic assemblage in the surface and most probably had profound effects on the composition and metabolic balance of the microbial community as a whole. Most stations appeared to have been net-autotrophic, and calculations of phagotrophy indicated a balanced carbon budget for the microbial community. Mixotrophy was seen in a large part of the ciliate assemblage and may have contributed to the productivity and stability of the pre-bloom system that we encountered

Water quality and microbial community structure in juvenile Atlantic cod (Gadus morhua L.) cultures

The effect of water treatment and flow rate on young Atlantic cod juveniles was investigated in a 36-days experiment. Four different flow rates (10, 20, 40, and 70 times the effective tank volume per day) were set up in triplicate tanks within each of three rigs with recirculated, UV-radiated, and untreated water, respectively. Each of the 36 tanks was stocked with 200 weaned cod juveniles at a mean weight of 0.048 g. Fish mortality was recorded daily in all tanks, and growth (wet weight) was determined at the end of the experiment. The microflora in the rearing water was investigated by means of PCR-DGGE and flow cytometry. Observed mortality was significantly higher at low flow rates while otherwise unexplained mortality (presumed to be due to cannibalism) was lowest in the recirculation system. No correlation was found between survival and growth. Growth was significantly affected by both water exchange rate and treatment, as the juveniles from high flow rates and the UV-treatment showed elevated growth rates. Both growth and survival scaled in accordance with metabolic factors like oxygen saturation and unionized ammonia. Bacterial concentrations increased in all tanks and treatment from the beginning of the experiment to the end. The UV-treated and untreated water started at typical seawater concentrations (0.5−1 × 10'raised to the sixth power' mLˉ¹) and increased five to tenfold during the experiment. The recycled water tanks started with bacterial concentrations 2–5 times higher than the UV- and untreated experiments at the time of fish transfer, and ended up with 10 times higher concentrations in the end. Cluster analysis of the DGGE profiles separated the recirculation tanks, including the respective inlet water, from the flow-through systems, with one exception (the highest flow rate). Eighty-five% of the sequences clustered within the Gammaproteobacteria, further divided into four distinct clusters. One of the clusters was only detected in the recirculation system, and showed highest affiliation to bacteria belonging to the Alteromonas/Pseudoalteromonas genera. In contrast, bacteria belonging to the family Vibrionaceae were detected in the flow-through systems

Isolation and characterization of a virus that infects \u3ci\u3eEmiliania huxleyi \u3c/i\u3e(Haptophyta)

The isolation and characterization of a virus (designated EhV) that infects the marine coccolithophorid Emiliania huxleyi (Lohmann) Hay & Mohler are described. Three independent clones of EhV were isolated from Norwegian coastal waters in years 1999 and 2000. EhV is a double-stranded DNA-containing virus with a genome size of ~415 kilo-base pairs. The viral particle is an icosahedron with a diameter of 160–180 nm. The virus particle contains at least nine proteins ranging from 10 to 140 kDa; the major capsid protein weighs ~54 kDa. EhV has a latent period of 12–14 h and a burst size of 400–1000 (mean, 620) viral particles per cell. A phylogenetic tree based on DNA polymerase amino acid sequences indicates EhV should be as¬signed to the Phycodnaviridae virus family and that the virus is most closely related to viruses that infect Micromonas pusilla and certain Chlorella species

Viral, bacterial and ciliate abundance and viral-bacterial diversity in mesocosm experiments, 2007-2008, Kongsfjorden

Two mesocosm experiments, PAME-I and PAME-II were conducted in 2007 and 2008 to investigate fate of organic carbon in the arctic microbial food web. Mesocosms were nutrient fertilized initially to induce phytoplankton bloom development. In PAME-I eight units (each 700 L) formed two four point gradients of additional DOC in form of glucose (0, 0.5, 1 and 3 times Redfield ratio in terms of carbon relative to the nitrogen and phosphorus additions) (Fig. 1). All the eight units also got a daily dose of NH4+ and PO4**3- in Redfield ratio. Two gradients were set up, one with silicate addition, performed in the Arctic location Ny Ålesund, Svalbard, have previously been reported to give different food-web level responses to similar nutrient perturbations. In PAME-II all ten units (each 900 L) formed two four point gradients of additional DOC in form of glucose (0, 0.5, 1, 2 and 3 times Redfield ratio in terms of carbon relative to nitrogen and phosphorus additions). The two gradients in glucose were kept silicate replete. NH4+ was used as the DIN source in one gradient (units 1 to 5) and NO3- in the other (units 6-9). All units got a daily dose of PO4**3- in Redfield ratio. Prokaryotes and viruses were measured by flow cytometry, while ciliate abundances were counted using a Flow Cam. Viral and bacterial diversity was measured by PFGE and DGGE, respectively. In PAME-II the abundance of ciliates was lower than in PAME-I, presumably caused by higher copepod grazing. The abundances of prokaryotes and viruses were also lower in PAME-II compared to PAME-I. Further, less diversity was detected in the viral community (FCM and PFGE) in PAME-II, and no response was observed in the bacterial community structure due to addition of organic carbon

The plankton community in Norwegian coastal waters-abundance, composition, spatial distribution and diel variation

International audienceThe purpose of the present study was to explore the composition and variation of the pico-, nano- and micro-plankton communities in Norwegian coastal waters and Skagerrak, and the co-occurrence of bacteria and viruses. Samples were collected along three cruise transects from Jaeren, Lista and Oksoy on the south coast of Norway and into the North Sea and Skagerrak. We also followed a drifting buoy for 55 h in Skagerrak in order to observe diel variations. Satellite ocean color images (SeaWiFS) of the chlorophyll a (chl a) distribution compared favorably to in situ measurements in open waters, while closer to the shore remote sensing chl a data was overestimated compared to the in situ data. Using light microscopy, we identified 49 micro- and 15 nanoplankton sized phototrophic forms as well as 40 micro- and 12 nanoplankton sized heterotrophic forms. The only picoeukaryote (0.2-2.0 mu m) we identified was Resultor micron (Pedinophyceae). Along the transects a significant variation in the distribution and abundance of different plankton forms were observed, with Synechococcus spp and autotrophic picoeukaryotes as the most notable examples. There was no correlation between viruses and chl a, but between viruses and bacteria, and between viruses and some of the phytoplankton groups, especially the picoeukaryotes. Moreover, there was a negative correlation between nutrients and small viruses (Low Fluorescent Viruses) but a positive correlation between nutrients and large viruses (High Fluorescent Viruses). The abundance of autotrophic picoplankton, bacteria and viruses showed a diel variation in surface waters with higher values around noon and late at night and lower values in the evening. Synechococcus spp were found at 20 m depth 25-45 nautical miles from shore apparently forming a bloom that stretched out for more than 100 nautical miles from Skagerrak and up the south west coast of Norway. The different methods used for assessing abundance, distribution and diversity of microorganisms yielded complementary information about the plankton community. Flow cytometry enabled us to map the distribution of the smaller phytoplankton forms, bacteria and viruses in more detail than has been possible before but detection and quantification of specific forms (genus or species) still requires taxonomic skills, molecular analysis or both