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A Polar Dinoflagellate that Can Really Take the Heat

Reference
Zheng, S., Wang, G. and Lin, S. 2012. Heat shock effects and population survival in the polar dinoflagellate Polarella glacialis. Journal of Experimental Marine Biology and Ecology 438: 100-108.
Authors Zheng et al. (2012) write that dinoflagellates "are generally believed to prefer warm temperatures and presumably may do better in the face of temperature increases," noting that Prorocentrum donghaiense was able to grow at temperatures ranging from 10 to 27°C and that it achieved its maximum specific growth rate at the latter temperature (Xu et al., 2010). Likewise, they state that for P. minimum "growth rates increased from 0.25/day at 4°C to 0.98/day at 20°C," citing Lomas and Gilbert (1999a,b). And they report that the composition of phytoplankton exposed to a temperature rise in the vicinity of a nuclear power plant's thermal effluent "tipped toward dinoflagellates both in terms of species number and cell abundance (Li et al., 2011)," likely due to the fact that "some dinoflagellates were found to produce heat-shock proteins to stabilize protein secondary structure in response to thermal stress (Alexandrov, 1994)," while further noting in this regard that "heat shock protein 70 was induced in Alexandrium tamarense when subjected to a 10°C jump from its acclimated temperature of 20°C (Kobiyama et al., 2010)."

In an effort to gain further enlightenment about the subject, Zheng et al. studied the effects of temperature shock on the growth of the dinoflagellate Polarella glacialis. This they did "by monitoring its physiological and biochemical responses to temperature rises from 4°C to 10 and 15°C," while examining the growth rate and expression of two important genes for this alga.

The three researchers say "it is noteworthy that in the present study the cultures were directly transferred from 4°C to 10 and 15°C without progressive intermediate steps," and they state that in response to these sudden temperature shifts, "the cultures first experienced a period of declination, then cell density tended to become stable, a sign that a part of the cell population survived."

In light of what they observed, Zheng et al. conclude that "if the species can survive such heat shock in the long term, there is good opportunity that it can be transported from polar regions to temperate or even warmer waters," which perhaps explains, in their words, why "taxa closely related to this species occur in temperate aquatic environments (Lin et al., 2009, 2010)." And if P. glacialis and other related species can do that, coping with projected global warming should be a non-problem.

Additional References
Alexandrov, V.Y. 1994. Functional Aspects of Cell Response to Heat Shock. Academic Press, San Diego, California, USA.

Kobiyama, A., Tanaka, S., Kaneko, Y., Lim, P.-T. and Ogata, T. 2010. Temperature tolerance and expression of heat shock protein 70 in the toxic dinoflagellate Alexandrium tamarense (Dinophyceae). Harmful Algae 9: 180-185.

Li, T., Liu, S., Huang, L, Huang, H., Lian, J., Yan, Y. and Lin, S. 2011. Diatom to dinoflagellate shift in the summer phytoplankton community in a bay impacted by nuclear power plant thermal effluent. Marine Ecology Progress Series 424: 75-85.

Lin, S., Zhang, H., Hou, Y., Zhuang, Y. and Miranda, L. 2009. High-level diversity of dinoflagellates in the natural environment, revealed by assessment of mitochondrial cox 1 and cob genes for dinoflagellate DNA barcoding. Applied and Environmental Microbiology 75: 1279-1290.

Lin, S., Zhang, H., Zhuang, Y., Tran, B. and Gill, J. 2010. Spliced leader-based metatranscriptomic analyses lead to recognition of hidden genomic features in dinoflagellates. Proceedings of the National Academy of Sciences USA 107: 20,033-20,038.

Lomas, M.W. and Gilbert, P.M. 1999a. Temperature regulation of nitrate uptake: a novel hypothesis about nitrate uptake and reduction in cool-water diatoms. Limnology and Oceanography 44: 556-572.

Lomas, M.W. and Gilbert, P.M. 1999b. Interactions between NO3- and NH4+ uptake and assimilation: comparison of diatoms and dinoflagellates at several growth temperatures. Marine Biology 133: 541-551.

Xu, N., Duan, S., Li, A., Zhang, C., Cai, Z. and Hu, Z. 2010. Effects of temperature, salinity and irradiance on the growth of the harmful dinoflagellate Prorocentrum donghaiense Lu. Harmful Algae 9: 13-17.

Archived 14 May 2013