Ocean Phytoplankton Apocalypse—Perhaps Not

Last summer, Nature published a worrisome study by a team of researchers at Dalhousie University in Halifax, Nova Scotia that found that oceanic plankton had declined by as much as 40 percent over the last century. The researchers suggested much of the decline might be related to man-made global warming. The AP reported:

Despite their tiny size, plant plankton found in the world's oceans are crucial to much of life on Earth. They are the foundation of the bountiful marine food web, produce half the world's oxygen and suck up harmful carbon dioxide.

And they are declining sharply.

Worldwide phytoplankton levels are down 40% since the 1950s, according to a study published Wednesday in the journal Nature. The likely cause is global warming, which makes it hard for the plant plankton to get vital nutrients, researchers say.

The numbers are both staggering and disturbing, say the Canadian scientists who did the study and a top U.S. government scientist.

"It's concerning because phytoplankton is the basic currency for everything going on in the ocean," said Boris Worm, Dalhousie University biology professor and study co-author. "It's almost like a recession … that has been going on for decades."

Provocative findings provoke. Consequently, other researchers took a closer look at the Dalhousie findings, and their new results are far less alarming. In a recent issue of Nature, researchers find the original study defective and report:

Identifying major changes in global ecosystem properties is essential to improve our understanding of biological responses to climate forcing and exploitation. Recently, Boyce et al. reported an alarming, century-long decline in marine phytoplankton biomass of 1% per year, which would imply major changes in ocean circulation, ecosystem processes and biogeochemical cycling over the period and have significant implications for management of marine fisheries. Closer examination reveals that time-dependent changes in sampling methodology combined with a consistent bias in the relationship between in situ and transparency-derived chlorophyll (Chl) measurements generate a spurious trend in the synthesis of phytoplankton estimates used by Boyce et al.. Our results indicate that much, if not all, of the century-long decline reported by Boyce et al. is attributable to this temporal sampling bias and not to a global decrease in phytoplankton biomass.

So good news: No massive decline in ocean phytoplankton after all. Over at his excellent New York Times blog, Dot Earth, Andrew Revkin takes readers through the whole saga (really folks, please go read it). Revkin points out that this is how science is supposed work—claims are made, challenged, defended, rechallenged, with the process leading us ever closer to actually describing reality.

However, how the study was reported in the mainstream press illustrates a big problem with journalism. Alarming studies get reported prominently and at length, but when they are later called into question, the mainstream press reports the refutations with a buried paragraph, if that much. Googling around, this seems to be happening in this case. Of course, the problem is that, for reasons of evolutionary psychology, only bad news is actually news to most editors and consumers.

Revkin brings up an intriguing issue:

I [Revkin] asked Rykaczewski [one of the authors of the paper that challenged the earlier results] whether the issues with the original paper reflect problems with the process of peer review and he added this note:

I prefer not to speculate on why the original paper was published by Nature, but I think it does hint at issues with the editing and peer-review process. On the other hand, Nature was willing to publish these additional comments and deserves credit for recognizing the level of skepticism within the oceanographic community concerning the original, highly publicized conclusions. Our present conversation gives me some hope that the peer-review process is not completely defective.

Not completely defective? Setting aside the thorough-going politicization of climate science (assuming that's possible), I believe that a more general problem with peer-review is that studies that tend to confirm the dominant narrative in a science have a much easier time getting through the peer-review seive than those that challenge it. And this is especially so, if the claimed results are strikingly novel, e.g., phytoplankton declining massively.

More happily, I do note that Nature published several early blogposts responding to original article that were quite skeptical of the results. In my column, News Ages Quickly, I argued that expanding the ability of researchers to make immediate formal comments on new studies is a good idea.

Also, keep in mind the point made by Martin Blume, editor-in-chief of the American Physical Society and its nine physics journals, who said,

"Peer review doesn't necessarily say that a paper is right. It says it's worth publishing." 

I hope that my fellow journalists will make this point to their readers, viewers, and listeners, whenever they report startling new results, especially results relevant to highly politicized areas of science.

In the spirit of ongoing peer-review, the Dalhousie researchers are apparently standing by their earlier results.