In an attempt to find a solution to global climate change, scientists are researching the effects of releasing large quantities of iron into the upper ocean. This process is known as iron seeding and it can enhance the reproduction of phytoplankton, which may lower global carbon dioxide levels, reversing climate change. This process is also known as iron fertilisation or ocean nourishment and is the topic of an on-going debate by climate scientists. One criticism of the approach is that iron seeding may lead to a harmful algal bloom, which leads to the phenomenon known as the red tide, releasing numerous toxic chemicals into the ocean.