Picoplankton

Picoplankton 0.2 to 2.0jjum Proteobacteria Cyanobacteria Pelagibacter, Roseobacter Prochlorococcus, Synechocco-cus, Trichodesmium... 

Oxygenic photosynthetic bacteria include the nitrogen fixer Trtchodesmtum and the cyanobacteria Synechococcus and Prochlorococcus. The latter represent a major fraction of the microbial biomass in the ocean and are probably the most abimdant primary producers in the ocean. They were not discovered until the late 1980s, probably because of their small size as they are members of the picoplankton. These cyanobacteria are photosynthetic. They use bacteriochlorophyll a and plastocyanin, a blue Cu-based pigment, for light harvesting. 

Algal sources are ice algae, diatoms, cyanobacteria, dinoflagellates, and picoplankton petroleum sources include eroded bitumens, oil seeps, etc. 

Fig.1 Generalized pelagic food web [ 13]. The old view of a simple food chain vertical line in this figure) with phytoplankton (mainly diatoms) at the base, herbivorous mesozoo-plankton (mainly copepods) at the second trophic level, and planktivorous fish has been extended to a pelagic food web including nanoplankton (<20 pm), picoplankton (<2 pm), and their protozoan feeders lower left). Herbivorous tunicates and jellyfish as primary carnivores also play a role, as do mixotrophic flagellates. The main pathway of energy flow depends on the nutrient scenarios [13]. DOC=dissolved organic carbon, HNF=heterotrophic nanoflageUates. From [13] with permission of Kluwer Academic Press...

Other cultivation strategies which were followed were the enrichment of picoplankton bacteria under a wide range of nutrient and incubation conditions [33], and isolation of biofilm bacteria that had grown in situ on artificial surfaces. 

Fig. 5. Genetic diversity of marine picoplankton bacteria from the a-subclass of the Proteobacteria. Determination by random amplified polymorphic DNA (RAPD) fingerprinting of colonies from marine Cytophaga medium (lanes 2-32) and from Hg medium (lanes 33-35). Identical strains are present in lanes 33 and 34 and in lanes 11 and 12, while all other lanes represent different isolates...

Moon-van da Staay, S.Y. De Wachta, R. Vaulot, D. (2001) Oceanic 18S rDNA sequences from picoplankton reveal unsuspeaed eukaryotic diversity. Nature, 409, 607-10. 

Schmidt, T. M., E. F. DeLong, and N. R. Pace. 1991. Analysis of a marine picoplankton community by 16S rRNA gene cloning and sequencing. Journal of Bacteriology 173 4371-4378. 

Kemer, M., and Spitzy, A. (2001) Nitrate regeneration coupled to degradation of different size fractions of DON by the picoplankton in the Elbe estuary. Microb. Ecol. 41, 69-81. 

Paerl, H.W. (1991) Ecophysiological and trophic implications of light-stimulated amino acid utilization in marine picoplankton. Appl. Environ. Microbiol. 57, 473-479. 

Vesk, M., and Jeffrey, S.W. (1987) Ultrastructure and pigments of two strains of the picoplanktonic alga Pelagococcus subviridis (Chrysophyceae). J. Phycol. 23, 322-336. 

Corn M, Belviso S, Partensky F, Simon N, Christaki U (1996) Origin and importance of picoplanktonic DMSP. In Kiene RP, Visscher PT, Keller MD, Kirst GO (eds) Biological and environmental chemistry of DMSP and related sulfo-nium compounds. Plenum Press, New York, pp 191-201 Crocker KM, Ondrusek ME, Petty RL, Smith RC (1995) Dimethylsulfide, algal pigments and light in an Antarctic Phaeocystis sp. bloom. Marine Biol 124 335-340... 

Garcia, N., Raimbault, P., and Sandroni, V. (2007). Seasonal nitrogen fixation and primary production in Southwest Pacific (New Caledonia) Some evidence for nanoplanktonic diazotrophy and rapid transfer of newly fixed nitrogen to picoplankton organisms. Mar. Ecol. Prog. Ser. 343, 25-33. 

Bird, C., and Wyman, M. (2003). Nitrate/nitrite assimilation system of the marine picoplanktonic cyanobacterium Synechococcus sp strain WH 8103 Effect of nitrogen source and avaflabflity on gene expression. Appl. Environ. Microbiol. 69, 7009-7018. 

Pernthaler, J., Pernthaler, A., and Amann, R. (2003). Automated enumeration of groups of marine picoplankton after fluorescent in situ hybridization. Appl. Environ. Microbiol. 69, 2631-2637. 

Waite, A. M., Safi, K., Hall, J., and Nodder, S. D. (2000). Mass sedimentation of picoplankton embedded in organic aggregates. Limnol. Oceanogr. 45, 87—97. 

Two other N2 fixers that have been studied are Aphanizomenon and Nodularia. In a study in the Baltic, 7.7 2.1% and 6.7 2.1% of the N2 gas recently fixed by Aphanizomenon and Nodularia respectively appeared in the picoplankton fraction, which indicates N2 fixation and subsequent N release and reincorporation. 

Gasol, J. M., and Moran, X. A. G. (1999). Effects of filtration on bacterial activity and picoplankton community structure as assessed by flow cytometry. Aquat. Microb. Ecol. 16, 251—264. 

Metzler, P., Gilbert, P., Gaeta, S., and Ludlam, J. (2000). Contrasting effects of substrate and grazer manipulations on picoplankton in oceanic and coastal waters off Brazil. Plankton Res. 22(1), 77-90. 

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