Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Pollution Bulletin 56 (2008): 1049-1056, doi:10.1016/j.marpolbul.2008.03.010.
The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with
thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple
reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates,
many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky,
and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the
atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many
grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates
form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms
even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to
hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage,
further limiting the potential for net carbon sequestration. The environmental and economic impacts are
potentially great and need to be rigorously assessed.
This paper was developed under the Global Ecology and Oceanography of Harmful Algal Blooms
(GEOHAB) core research project on HABs and Eutrophication and the GEOHAB regional focus on HABs
in Asia. GEOHAB is supported by the International Oceanographic Commission (IOC) of UNESCO and
by the Scientific Committee on Oceanic Research (SCOR), which are, in turn, supported by multiple
agencies, including NSF and NOAA of the USA.
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