Middling Worlds
Can we imagine a climate future
inside a giant plastic bag?
In virtually any field of scientific inquiry, producing knowledge requires the fabrication of interiors. One such interior is a mesocosm—an experimental device used to observe natural interactions in a bounded and partially enclosed environment. The term was coined by Eugene Odum, the pioneer of ecosystems ecology, who used it to describe the “middle-sized worlds” where researchers try to bridge the distance between the reductionism of the laboratory and the entangled understanding that emerges from observations in the field.1
In a recent oceanographic study on the island of Gran Canaria, researchers from the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, deployed a series of mesocosms in Taliarte harbor, on the island’s east coast, to determine how plankton communities respond to the addition of alkaline minerals to seawater.
Each system consists of a translucent, four-meter-long thermoplastic polyurethane bag, mounted on a hexagonal floating frame. It is filled with water collected outside the harbor, and contains the range of microscopic life one would typically find in this section of the North Atlantic. To each bag, researchers add a solution of sodium carbonate and sodium bicarbonate to produce a series of gradual increments in the level of total alkalinity, from the natural baseline (no intervention) to twice as much alkalinity as in the surrounding waters.
The setup is that of a classic perturbation experiment, in which certain environmental parameters are selectively altered to observe changes in an ecological community. Every two days, researchers extract samples from each of these “giant test tubes,” as they sometimes describe them, to assess particulate and dissolved organic matter, phytoplankton and zooplankton communities, chlorophyll concentration and photosynthesis levels, and to measure changes in alkalinity and in the concentration of dissolved inorganic carbon.
On the surface, the research design could not be simpler: adding more salt to saltwater. Yet this ocean alkalinization study represents a landmark experiment in “climate repair.”
Ocean alkalinization describes a set of strategies to rapidly increase the alkalinity of the upper ocean in order to accelerate the uptake of atmospheric CO2. The ocean holds fifty times more carbon than the atmosphere, and it is estimated to have absorbed about a third of all the CO2 emitted by the burning of fossil fuels since the beginning of the Industrial Revolution. One of the mechanisms of this absorption is the presence of alkaline substances. Runoff from the natural weathering of carbonate- and silicate-based rocks carries alkaline molecules into the ocean, and these molecules react with the CO2 dissolved in seawater to form stable bicarbonate and carbonate ions. This creates an imbalance between the pressure exerted by CO2 in the air and by CO2 dissolved in surface waters, and the result of this imbalance is that more atmospheric CO2 enters the ocean.
This process unfolds constantly, slowly drawing carbon from the atmosphere over geological timescales; ocean alkalinization seeks to speed it up to human-relevant timescales by directly dumping alkaline minerals into the sea.
That is at least the idea—and, at this point, it is not much more than an idea. The appeal of ocean alkalinization as a climate solution rests on a series of theoretical calculations, a modest effort to model the Earth system under different intervention scenarios, and the advocacy of a few scientific groups and start-ups. They may appear unassuming, but the mesocosms calmly floating along the pier in Taliarte harbor were the first ever attempt to investigate, in natural or at least semi-natural conditions, how the rapid addition of alkalinity to seawater might affect marine biological communities and food webs. Despite the modesty of this experiment, it could augur a radical intervention in geoengineering.
Carbon Runaways
“A member of the research team marvels at how quickly all this effort will be forgotten once the scientific study begins, a phenomenon he describes as ‘mesocosmic amnesia.’”
One thing that becomes apparent when one spends time around mesocosms and the research community that looks after them is that these experimental devices are not self-evidently interiors—or, to put it another way, that their interiority demands constant work.
The fabrication of interiority begins with the assembly of the system, which requires several days of intense work by students and postdoctoral researchers, a small and joyous international community of budding marine biologists. They construct the floating frames, lower the polyurethane bags into the water, and attach plastic roofs to prevent the introduction of bird droppings and airborne dirt. A member of the research team marvels at how quickly all this effort will be forgotten once the scientific study begins, a phenomenon he describes as “mesocosmic amnesia.”2
Yet this memory is never quite lost, if only because preserving the interiority of each mesocosm is an ongoing endeavor. Cleaning is the activity that brings this effort into focus. As soon as the experiment starts, algae, particulate matter and marine detritus begin to accumulate on the exterior and interior walls, creating a biofilm that threatens the comparability of observations. If organic material is allowed to grow on the interior walls, then the mesocosm will fail to mimic interactions in the open ocean; growth on the exterior walls creates irregular shading effects that influence the ecological dynamics inside each enclosure in unpredictable ways.
Every other day, standing on the floating frames and bending carefully over the open mesocosms, a researcher gently wipes the inside of each polyurethane bag with a pool brush attached to a long pole, reaching all the way to the sediment trap at the bottom. The brushes themselves must be carefully cleaned before moving from one mesocosm to the next, to prevent them from cross-contaminating the different containers.
Cleaning the exterior walls is an even more dramatic affair. Once a week, scuba divers perform a careful scrubbing routine around the underwater sections of the mesocosms. The operation requires a careful calibration of force—brushing a surface that offers little resistance to the hand while staying stationary underwater is an arduous exercise—and can only be carried out by members of the research team who are certified to work as scientific divers.
These maintenance operations provided the first indication that something unexpected was unfolding inside one of the mesocosms. Toward the end of the six-week study, divers began to observe the formation of an unusual white calcareous film inside the system that contained the highest addition of alkalinity. An analysis of water samples suggested that the carbonate chemistry in this bag had shifted due to runaway calcium carbonate precipitation. It was (and remains) unclear what exactly triggered this process, but the researchers surmised that plankton or inorganic matter had served as condensation nuclei for the emergence of solid calcium carbonate. The regular cleaning of the interior walls, by scraping off carbonates, may have created additional nuclei, thereby hastening the reaction.
This was just one of several examples of minerals “just not doing what we expected them to do,” as one member of the research team put it, but it was by far the most momentous. It meant that, in at least one of the mesocosms, the addition of alkaline substances had led to a net loss in total alkalinity, as precipitation of calcium carbonate would consume bicarbonate and carbonate ions. If this had been an actual intervention in the ocean—as opposed to a contained experiment in a giant floating plastic bag—it would likely have led to an increase in the leakage of CO2 from the ocean into the atmosphere. A much-vaunted climate solution would have only compounded our climate problem.
Interior (Dis)comforts
Arguably, runaway precipitation is the sort of surprising finding that a good field study should be expected to generate, a recalibration of our way of thinking about the world born of an experimental encounter with the matter at hand. Yet it is difficult to draw a sharp line between the kind of surprise that enriches our understanding, and the equally unexpected but much less welcome anomaly that forces us to jettison hitherto useful certainties.
Among the certainties to be questioned here, one may be the solace provided by a conceptual form of interiority, that of the global carbon cycle. This idea presupposes a world divided into discrete “reservoirs” or “pools” of carbon, and a linear transportation of the element from one to the other to the next. Thinking through and within the global carbon cycle is a precondition for modeling the Earth system, and for anticipating how different human interventions might impact climate change. It is a core assumption of the models making the case for ocean alkalinization. The concept of the global carbon cycle suggests an elegant (in metaphysical terms, perfect) form of movement, which sequences time into the interlocking segments of a full circle. It is only by inhabiting this spatio-temporal geometry that we can imagine accelerating geological time into human-relevant scales.
A phenomenon like runaway carbonate precipitation, by contrast, foregrounds reaction and change, thresholds and tipping points, unpredictable dissolution kinetics, and shifts in material states that acquire their own momentum and irreversibly disrupt a previous equilibrium. The cyclical movement of a chemical element becomes less relevant than its ongoing, escalating transformation. When a human intervention expected to remove carbon out of the atmosphere leads to even greater emissions into the atmosphere, we are reminded that carbon is not a discrete actor tracing a geometrical figure across planetary domains, but an element constantly entering into diverse configurations of living or lifeless matter.
The mesocosm provides its own interior comforts, of course. Even in a short-lived experiment like this one, it is easy to get used to the idea that each enclosure provides a perfect encapsulation of the relevant world—in this case, a miniaturized version of the nutrient-poor marine food webs and biogeochemistry of the eastern North Atlantic Ocean biome. Yet there is something about the physical characteristics of this particular interior, and about the research life that gathers around it, that counters the tendency to see these worlds as self-contained.
The routine handling of the experimental apparatus—the laboriousness of its assembly and maintenance, the challenge of preserving a sense of enclosure while maneuvering equipment into and around it—seems to keep researchers grounded in a fairly modest understanding of the affordances of their midsized universes. There is just enough contingency and openness to the surrounding world to short-circuit the temptation to extrapolate just a bit too far, to jump too quickly to a definitive conclusion. “Mesocosmic amnesia” never quite sets in, and researchers find themselves constantly referring their findings back to particulars of their equipment, or to specific moments and circumstances in their investigations.
In sum, mesocosms are remarkable climate interiors. Unlike mathematical models or metaphysical representations of the Earth as a closed or autopoietic system, they produce a form of epistemic interiority that is never entirely self-contained or fully self-assured. In that respect, they are a great vantage point—an aperture, as Emma Pask and Emily Lee describe in this issue—into problems that are neither outside nor inside human experience, and that might require middling interventions rather than definitive solutions. ⦿