A Beautiful Deep Green Sea?

Brandy Glett

Martin's iron hypothesis stated that iron was limiting growth of phytoplankton in nutrient rich seas. He also mentioned that there was a possibility that fertilization of the Southern Ocean with iron could increase CO 2 flux to the deep ocean. Martin did not imply that this was a good idea or that it would sequester large amounts of carbon. However this set off a round of experiments to better understand the processes in “high nutrient low chlorophyll” (HNLC) regions and there is continuing support of widespread industrial fertilization of the oceans in an attempt to sequester CO 2 .

After a number of experiments, researchers have come up with one reliable conclusion—adding iron to HNLC regions increases phytoplankton growth and production [7,2,1]. There is some data which suggests a small increase in C export [2] but there were no direct measurements of the amounts of C being exported, only estimates using the Redfield ratio. After several experiments with similar results, the first part of Martin's hypothesis has been proven, but there has been no real proof that this increase in productivity will increase CO 2 storage in the deep sea.

Later experiments could prove that there is a substantial increase in C export due to fertilization of the ocean (with any combination of trace elements). For the sake of science and a better understanding of processes which take place in the ocean, scientific experimentation should continue. Still, if proven, does that mean fertilization is a good idea? Say ½ of 1% of all the C that is exported to the deep ocean settles to the floor of the ocean and is put back into the slow carbon cycle not to be seen again for millions of years [5]. The rest of it remains in the deep ocean for about 1000 years before it returns to the atmosphere through global ocean circulation. Even if it is possible to sequester C, it is not a lasting solution, and in the mean time the side effects of such a large scale change in the ecology of the oceans may be devastating and irreversible. Models have predicted that long-term fertilization of the oceans could result in hypoxia and anoxia in the deep ocean which would increase microbial production of greenhouse gases such as methane and nitrous oxide [4]. This would set off a rapid warming of the earth, leading to increased stratification of the oceans which would slow the biological pump, and negate any probable short-lived human benefits [5].

Humans have brought C into the atmosphere a million times more rapidly than it can be removed by terrestrial plants and the invisible forest in the oceans [5]). More than half the coastal waters of the US have already been degraded by nutrient runoff from importation of large quantities of nitrogen from the atmosphere to the land for fertilizer production. One example is the notorious “dead zone” in the northern Gulf of Mexico [3,5]. Now we propose to add more fertilizer in an attempt to fix things? Contrary to popular belief amongst ocean fertilization advocates, fertilization of the ocean is not easily controlled, does not mimic nature and to say it would be environmentally safe denies nearly everything we know about aquatic ecosystems [4]. Developers of profit driven fertilization strategies are not going to look for or attempt to avoid potential environmental side effects and the only way to avoid potential disasters driven by greed is to remove the income enticement [6]. To do this Chisholm, Falkowski and Cullen [4] suggest that ocean fertilization should never be eligible for carbon credits, and I am in full agreement.

I will leave you with a picture put into my head by a good friend of mine. Imagine if we did not manage to prove that mass fertilization of the oceans could never work to significantly reduce atmospheric CO 2 and commercial companies worldwide began pumping super-fertilizers into the ocean. Imagine if the models were correct, global climate warmed rapidly melting the poles and oceanic waters became anoxic. It is possible that we would be stranded in a broken ecosystem surrounded by a foul flood of water filled with the floating corpses of a dead ocean.

References

1. Boyd, P.W. and many others. A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization. Nature 407 , 695-702 (2000).

2. Coale, K.H. and many others. A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean . Nature 383 , 495-501 (1996).

3. Chisholm, S.W. Oceanography: Stirring times in the Southern Ocean. Nature 407 , 685-687 (2000).

4. Chisholm, S.W., Falkowski, P.G., and Cullen, J.J. Dis-Crediting Ocean Fertilization. Science 294 (5541), 309-310 (2003).

6. Falkowski, P.G. The Ocean's Invisible Forest . Scientific American 287 (2), 54-61, Aug (2002).

7. Lawrence , M.G. Side Effects of Oceanic Iron Fertilization. Science 297 , 20 September 2002 .

8. Morel, F.M.M., J.G. Rueter, and Price N.M. Iron nutrition of phytoplankton and its possible importance in the ecology of ocean regions with high nutrient and low biomass. Oceanography 4 , 56-61 (1991).

9. Planktos. Add Blue Green Tags to Your Shopping List. 2002. [On-Line]. Available: http://www.planktos.com/greentagshop.htm [2003, April 4].

10. NASA's Visible Earth. Swirls of Color in the Bering Sea . [On-Line]. Available:

http://www.visibleearth.nasa.gov/cgi-bin/viewrecord?7880 [2003, April 4].
Bloom in the Bering Sea May 13, 2001. [10] Phytoplankton blooms are a natural part of the processes of production and regeneration in the ocean. Ocean fertilization would disrupt these processes and significantly alter oceanic food webs. [4]

“Scientists deploy iron micronutrients to a 50 kilometer swath of ocean approximately 300 miles east of the Hawaiian Islands .” This experiment is sponsored by Planktos, a company that refers to CO 2 endearingly as “the blanket that keeps the planet warm against the cold of outer space” and sells “blue green tags” to “neutralize your CO2 burden on the earth.” [9]