Geoengineering in the ocean: a solution or not ?

The recent publication of a geoengineering trial using phytoplankton to remove carbon dixoide from the atmosphere again raises the question as to whether this course of action is either sensible or safe notwithstanding the difficulties in controlling CO2. The trial called Eifex was carried out in the Southern Ocean in 2004 and involved adding iron to the ocean in order to stimulate plankton to grow. In many ocean regions, iron is not plentiful so the theory operates on the basis that if iron was added, phytoplankton would grow and in turn remove carbon dioxide. The plankton then die and sink to the bottom of the ocean taking the CO2 with them. A similar trial called Lohaflex was run in 2009 but failed after causing an algae bloom instead so the idea was considered a failure. But how sensible is this solution of iron fertilisation ? And what impacts on other species and various oceans will this artifical intervention cause ? And why was there a delay in publishing the results of a 2004 trial in 2012 ?

Geoengineering is seldom as straighforward as it appears and risks are rarely fully understood.