Critics' Voices

Experiments in the open ocean are often controversial.  As oceans provide so much of our carbon sink, and are full of complex and fascinating ecosystems, "messing" with them at all will be an issue for some.  However, Dave Karl and Ricardo Letelier know better than anyone how much we still have to learn about the ocean. This experiment was carefully controlled and monitored, and provided the first stage in a risk analysis for future experiments. Unlike previous ocean fertilization experiments, this team is not dumping chemicals into the water. They are helping to safely enhance and better understand natural occuring upwelling. In some parts of the world, this is being affected by global warming.

Some people fear the consequences of creating plankton blooms.  Previous studies of artificial and natural blooms have shown changes in the species that make up the two lowest links of the marine food chain — the phytoplankton and the bacteria that feed on them.  Changes at this level may determine what happens to populations of larger predators, such as copepods, krill, salps, jellyfish and fishes. 

In other words, while creating a plankton bloom could increase fish stocks, it could also increase "bad" marine life  — jellyfish or algae, especially harmful algal blooms that could have impacts on fish, birds and even marine mammals up the food chain.

Twelve experiments using iron fertilization techniques to create plankton blooms have been conducted since 1993 and have generated no such toxic blooms, but they have produced blooms of certain plankton species similar to organisms associated with harmful algal blooms.

There could also be changes at higher levels, which would affect populations of larger predators.  This possible outcome, however, has not yet been studied. The goal of this experiment is to develop a better understanding of the phytoplankton ecosystem in the surface ocean, to carefully monitor the effects of enhancing a natural phenomen.

Another worry is oxygen depletion.  When a plankton bloom dies and the organic material sinks to deeper waters, the resulting bonanza of decomposition uses up oxygen in the water.  These conditions can cause significant die-offs of other marine life, including fish, shellfish and invertebrates, like the one that occurred in 2006 in the usually productive coastal region off Oregon. Years of large-scale artificial plankton creation could result in more of these so-called "low-oxygen events."

Phytoplankton take in a variety of nutrients, fixing them in their tissues.  Thus, phytoplankton deplete surface waters not only of carbon (which is the desired effect), but also of nutrients that support all the oceans' primary food webs.  Therefore, the location of what grows where might be changed. And, changing the "chemistry" of the ocean might have effects across a larger scale. So, the question becomes: "Would manipulating the oceans now cause us more problems in the long-term future?"

These deeper waters would be depleted in oxygen and enriched in nutrients produced by decomposed particles from the artificial blooms. That would set the stage for producing more nitrous oxide and methane, two potent greenhouse gases that tend to form when organic matter decomposes at depth.  According to a 1999 iron-addition study in the Southern Ocean, 6 and 12 percent of the cooling effect was annulled by increased emissions of nitrous oxide.

There are also concerns regarding the overall impact on climate change.  By absorbing sunlight, plankton blooms could actually heat up surface waters.  That would lead to higher atmospheric temperatures and further global warming. Warmer surface waters would also curtail the effectiveness of the plan, because water holds less dissolved carbon dioxide as it warms. Warmer water is also less dense, so the ocean's top layer would mix less readily with colder, deeper waters.

Other critics fear that the pipes will damage marine life.  But proponents argue that the pipes are only a few meters across and are intended to be spaced 2 kilometers apart.  For this experiment, only an infinitesimally small fraction of the ocean's volume will be in direct contact with the pipes. 

Ultimately, Dr. von Herzen argues that, as a species, humans have performed a giant geo-engineering experiment for the past 100 years, adding hundreds of giga-tons of carbon to the atmosphere.  This restoration experiment is tiny in comparison and highly important.