Marine ecosystems growth limitation

Kirchman, D. L., Meon, B., Cottrell, M., Hutchins, D. A., Weeks, D., and Bruland, K. W. (2000). Carbon versus iron limitation of bacterial growth in a coastal marine ecosystem. Limnol. Oceanogr. 45, 1681-1688. 

In vitro incubations differ from acmal ocean conditions in important ways that limit the applicability of their results to marine ecosystems. The fixed light intensity used in these experiments is a poor mimic of the variable conditions in the ocean mixed layer, while the walls of the incubation bottles themselves may provide unnatural growth surfaces. Bottle experiments cannot hope to accurately represent that nature or scale of the community response [151]. The artificial restriction on the abundance of grazers in bottle incubations, for instance, has been offered as an alternative (and confounding) explanation for the phytoplankton blooms observed in these experiments [221-223]. In an effort to overcome the limitations of bottle experiments, researchers have conducted a series of mesoscale in situ Fe enrichment experiments, in which large areas of the surface ocean were seeded with iron and the ecosystem response measured over many days. 

On the contrary, lysis and particularly viral lysis could be a major process in these bioassays. In cultures of natural marine bacteria inoculated into 0.2 pm filtered sea water, Wilcox and Furhman (1994) reported that virus abundance increased after few days of bacterial growth. The high abundance and production of bacteria in the HFe bioassay could enhance viral activity and consequently increase specific mortality rates. In agreement with this, during the mesoscale Fe fertilization EISENEX, a higher viral infection of bacterioplankton was estimated in the Fe-enriched patch (Weinbauer et al. 2003). Lysis could be of significance in Fe-limited ecosystems, as Fe released via lysis can be highly bioavailable (Poorvin et al. 2004). 

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