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Bioremediation of Polluted Waters by Macroalgae
Reference
Suarez-Alvarez, S., Gomez-Pinchetti, J.L. and Garcia-Reina, G. 2012. Effects of increased CO2 levels on growth, photosynthesis, ammonium uptake and cell composition in the macroalga Hypnea spinella (Gigartinales, Rhodophyta). Journal of Applied Phycology 24: 815-823.

Background
The authors write that "the increase of coastal activities which produce important amounts of wastes, including inorganic nutrients (Troell et al., 2003), makes micro- and macroalgae interesting organisms to predict possible impacts, responses, and remediation processes by considering biomass production through cultivation techniques," citing Gao et al. (1991, 1993), Gao and McKinley (1994), Keffer and Kleinheinz (2002), Doucha et al. (2005) and Israel et al. (2005). And they say that "macroalgae, in particular, have been the object of additional interest for CO2 remediation (Gao and McKinley, 1994) because of their solar energy conversion capacity, high productivity values (higher than most productive terrestrial crops) and the possibility of being, in many cases, intensively cultivated."

What was done
In a further assessment these possibilities and how they might be impacted by atmospheric CO2 enrichment (750 and 1600 ppm compared to an ambient value of 360 ppm), Suarez-Alvarez et al. cultivated 8-gram fragments of the macroalga Hypnea spinella in 1-L flasks containing filtered seawater enriched with 140 ÁM NH4Cl and 14 ÁM KH2PO4 for 7 days of acclimation, after which they were culled to their initial density and grown for 9 more days, during which period the three researchers measured various plant physiological properties and processes.

What was learned
In the case of light-saturated net photosynthesis, rates in the 750-ppm and 1600-ppm CO2 treatments were 41.5% and 50.5% greater, respectively, than what was measured in the 360-ppm treatment, while relative growth enhancements were 85.6% and 63.2% greater, respectively, and maximum ammonium uptake rates were enhanced by 24.2% and 19.9%, respectively, in the 750- and 1600-ppm CO2 treatments.

What it means
"From a practical point of view," in the words of Suarez-Alvarez et al., "these results suggest that intensive culture of H. spinella operated in biofilters might be enhanced by CO2 supply to generate higher biomass productivities and better nitrogen biofiltration efficiencies," and they say that "the use of flue gases for this purpose would also improve the ability of bioremediation of these biofilters, as has already been tested for Gracilaria cornea," citing Israel et al. (2005). And thus it is that what climate alarmists call an air pollutant (CO2) may ironically soon play the role of a cleanser of water pollutants.

References
Doucha, J., Straka, F. and Livansky, K. 2005. Utilization of flue gas for cultivation of microalgae (Chlorella sp.) in an outdoor open thin-layer photobioreactor. Journal of Applied Phycology 17: 403-412.

Gao, K., Aruga, Y., Asada, K., Ishihara, T., Akano, T. and Kiyohara, M. 1991. Enhanced growth of the red alga Porphyra yezoensis Ueda in high CO2 concentrations. Journal of Applied Phycology 3: 355-362.

Gao, K., Aruga, Y., Asada, K. and Kiyohara, M. 1993. Influence of enhanced CO2 on growth and photosynthesis of the red algae Gracilaria sp. and Gracilaria chilensis. Journal of Applied Phycology 5: 563-571.

Gao, K. and McKinleuy, K.R. 1994. Use of macroalgae for marine biomass production and CO2 remediation: a review. Journal of Applied Phycology 6: 45-60.

Israel, A.,Gavrieli, J., Glazer, A. and Friedlander, M. 2005. Utilization of flue gas from a power plant for tank cultivation of the red seaweed Gracilaria cornea. Aqaculture 249: 311-316.

Keffer, J.E. and Kleinheinz, G.T. 2002. Use of Chlorella vulgaris for CO2 mitigation in a photobioreactor. Journal of Industrial Microbiology and Biotechnology 29: 275-280.

Troell, M., Halling,C., Neori, A.,Chopin,T., Buschmann,A.H., Kautsky, N,. and Yarish,C. 2003. Integrated mariculture: asking the right questions. Aquaculture 26: 69-90.

Reviewed 16 January 2013