Marine Microbes See a Sea of Gradients

Ocean Monarchs It is hard to grasp that the unseen microorganisms of the oceans are the most productive on the planet, at orders of magnitude greater than sharks and whales or even terrestrial forests. The plankton is thus a major contributor to the geochemical cycles that are currently under pressure from climate change. Stocker (p. 628 ) reviews the state of knowledge of the web of myriad ephemeral microenvironments within the ocean's bulk and how microorganisms respond to the ever-shifting chemical spectrum. To this end, Taylor and Stocker (p. 675 ) report experiments on the effects of turbulence on nutrient uptake by chemotactic marine bacteria. They propose that turbulence favors motile bacteria that adopt an optimal foraging strategy, which trades off the relative high cost of motility to gain the benefits of plumes of nutrients by zipping between them at optimized speeds. Scaled up, such apparently “micro” behavior will influence the rate of remineralization of dissolved organic matter and in turn will feed into global patterns of geochemical cycling.