Current Featured Articles
The Featured Article for the September 2008 issue of L&O is:
Preferential grazing of Oxyrrhis marina on virus infected Emiliania huxleyi by Claire Evans and William H. Wilson. Limnol. Oceanogr. 53(5): 2035-2040.
This article can be read by clicking here.
Introductory comments by Michael R. Landry (L&O Associate Editor):
This month's L&O feature article by Evans and Wilson should capture the imaginations of laboratory experimentalists, plankton field ecologists and biogeochemical modelers alike. It relates to our evolving understanding of the primary fates of phytoplankton in aquatic systems, i.e., the ways in which they die. In the oceans at least, phytoplankton mortality was initially thought to result almost entirely from the feeding of large metazooplankton (Steele 1974). We now recognize, of course, the importance of alternate fates-microzooplankton grazing (Calbet and Landry 2004), direct sinking (Billett et al. 1983), and cell lysis (Bratbak et al. 1993)-and to each we assign substantially different implications for elemental cycling, trophic transfer, and export processes. Field research has tended to view these mortality mechanisms as competing "either-or" propositions, the sum of the independently measured components of which should add up to the whole. They may however be inter-related and difficult to separate as to cause and effect.
In a simple yet effective laboratory study, Evans and Wilson have shown for the first time that virus-infected phytoplankton cells can be grazed preferentially by phagotrophic protists. Via this cropping, production that would have been released to the dissolved organic pool of the upper ocean via the viral shunt (Wilhelm and Suttle 1999) is channeled elsewhere to higher trophic levels and/or other uses. The mechanisms by which this twist of fate occurs-whether by increased size of infected cells, by modified cell surface chemistry or by release of small molecular signaling chemicals-remain speculative at present, but are sure to be the focus of interesting future research, as is also the more difficult task of documenting the relative importance of this phenomenon in natural systems. Still, it is intriguing to speculate on the possibility that the last actions (or strategy?) of a stricken cell may be to invite its consumers to clear it and a concentrated patch of its pathogens from the water. Now, that's payback!
References
BILLETT, D.S.M., R. S. LAMPITT, R.S., A. L. RICE, AND R. F. C. MANTOURA. 1983. Seasonal sedimentation of phytoplankton to the deep-sea benthos. Nature 302: 520-522.
CALBET, A., AND M. R. LANDRY. 2004. Phytoplankton growth, microzooplankton grazing and carbon cycling in marine systems. Limnol. Oceanogr., 49: 51-57.
BRATBAK, G., J. K. EGGE, AND M. HELDAL. 1993. Viral mortality of the marine alga Emiliania huxleyi (Haptophyceae) and termination of algal blooms. Mar. Ecol. Prog. Ser. 93: 39-48.
WILHELM, S.W., AND C. A. SUTTLE. 1999. Viruses and nutrient cycles in the sea. Bioscience 49: 781-788.
STEELE, J. H. 1974. The structure of marine ecosystems. Harvard Univ. Press, Cambridge, Mass. 128 pp.