This article from National Geographic News addresses the possibility of adding iron to ocean systems in order to improve phytoplankton growth, which would remove carbon dioxide from the atmosphere and decrease global warming via increased photosynthesis.
Subject: Geoscience:Atmospheric Science:Climatology , Geoscience:Oceanography:Chemical, Biological, Geoscience:Atmospheric Science, Biology:Biogeochemistry Resource Type: Scientific Resources:Overview/Reference Work Theme: Teach the Earth:Course Topics:Oceanography, Teach the Earth:Incorporating Societal Issues:Climate Change, Teach the Earth:Course Topics:Atmospheric Science, BiogeoscienceKeyword: carbon sink