The plankton are dying

One can only imagine what Jacques Cousteau, who in some ways was the oceanic version of Carl Sagan before Sagan was a household name, would have to say about the news ricocheting around the blogosphere about the paper just published in Nature, Global phytoplankton decline over the past century. The paper’s abstract (emphasis added):

In the oceans, ubiquitous microscopic phototrophs (phytoplankton) account for approximately half the production of organic matter on Earth. Analyses of satellite-derived phytoplankton concentration (available since 1979) have suggested decadal-scale fluctuations linked to climate forcing, but the length of this record is insufficient to resolve longer-term trends. Here we combine available ocean transparency measurements and in situ chlorophyll observations to estimate the time dependence of phytoplankton biomass at local, regional and global scales since 1899. We observe declines in eight out of ten ocean regions, and estimate a global rate of decline of ~1% of the global median per year. Our analyses further reveal interannual to decadal phytoplankton fluctuations superimposed on long-term trends. These fluctuations are strongly correlated with basin-scale climate indices, whereas long-term declining trends are related to increasing sea surface temperatures. We conclude that global phytoplankton concentration has declined over the past century; this decline will need to be considered in future studies of marine ecosystems, geochemical cycling, ocean circulation and fisheries.

Joe Romm has a longish post on the news. In particular, he says:

Recognizing the importance of the article, Nature published a second piece by two leading ocean scientists, that discussed the methodology and findings, calling the work “an impressive synthesis of the relevant data”:

Taking great care, they created time series of phytoplankton biomass in the pelagic ocean, quantified as surface chlorophyll concentrations. They find a strong correspondence between this chlorophyll record and changes in both leading climate indices and ocean thermal conditions. They also show statistically significant long-term decreases in chlorophyll concentrations for eight of the ten ocean basins, and for the global aggregate.

In the discussion on Joe’s site, the issue of oxygen depletion arose, which lead me to Google and the paper Atmospheric oxygen and carbon dioxide observations from two European coastal stations 2000-2005: continental influence, trend changes and APO climatology, published in February 2010. The paper’s conclusion includes the text (emphasis added):

The analysis of this data set gives new insights into the CO2 exchange processes occurring regionally in Europe, by showing seasonal variations over 5 years, in both the atmospheric O2/N2 ratios and CO2 concentrations as measured from the costal stations of Lutjewad and Mace Head. In the period from mid-2001 until mid-2005, we see an average increase of CO2 in the atmosphere of (1.7±0.2) ppm y?1, and a corresponding decrease of the airborne O2 fraction of (?20±2) per meg y?1, mainly caused by human activities, particularly fossil fuel burning. The major feature in the records is the fast decrease of the airborne O2. This decrease must be caused by an O2 sink up to now not accounted for. Two mechanisms have recently been proposed in the literature (Ciais et al., 2007; Randerson et al., 2006). An O2 decrease acceleration seems to have started during or shortly after the anomalously hot and dry summer in Europe of 2003. A relation between both is, however, still speculative, and the statistical base and significance are still small.

A few observations…

The result in the first paper, showing a 40% decline in phytoplankton since 1950, really needs further research because of its startling conclusion and terrifying implications. In reading about energy and climate issues, we all run across many individual papers and news reports that we wish weren’t true. This includes all the “it’s worse than we thought revelations”, of course. Considering the already realized decline in phytoplankton reported in this paper, the ongoing rate of decline, and the overall importance of phytoplankton to oceanic life, this paper might be the biggest single example to date of a finding we desperately need to be wrong.

I don’t know if the oxygen decrease reported in the second paper is related to the phytoplankton issue, but it certainly has a smoking gun feel to it. I suspect this will be a topic of additional study, as well.

If the basic conclusions hold up — the decline was and continues to be that large, and it’s caused by global warming and/or ocean acidification — then the next two questions that suddenly become almost unimaginably urgent are: How low can phytoplankton go before it triggers catastrophic changes in ocean life, and what can we do about it? The first question is likely to lead us down a path that’s predictable, at least in its general outline: Experts disagree on whether we’re right on the verge of a tipping point or if we’re still a decade or two away, with a few fringe researchers claiming that either phytoplankton levels aren’t dropping or that they are and the oceanic food chain has been crashing for a decade or two and it just hasn’t crashed completely enough for us to notice. Blue ribbon research committees are appointed, research is done, massive PDF documents are produced, and seemingly only the climate geeks notice as politicians do far too little and mainstream voters remain largely ignorant (until the price of seafood skyrockets).

The second question is the one I find truly unsettling. Given the immense amount of carbon already in the atmosphere, the rate we’re still adding to it, and the rate at which the phytoplankton are disappearing (roughly 1%/year), I can’t imagine what we could do. Even if you make the very generous assumption that we would undertake an unprecedented worldwide effort to cut CO2 emissions as fast as the provision of basic human necessities allows, coupled with a massive geohacking effort to pull CO2 out of the atmosphere, I doubt we could turn the tide back (so to speak) before the oceanic food chain collapsed in various regions.

Of all the possible facets of climate change, from heat to droughts and floods to melting ice and rising sea levels to spreading diseases to ocean acidification to whatever you can name, phytoplankton succumbing to higher temperatures wasn’t even remotely on my radar screen. More than I can begin to express here, I hope this finding turns out to be wrong.