Tiny Life Benefits the Whole World
Some very small organisms can produce global effects, such as the tiny crustaceans that stir the oceans every night.
What would the oceans be like without life? If minerals, gases and nutrients had to mix by diffusion, the process would be very slow. Wind and currents could help somewhat. Now, Houghton et al., publishing in Nature, have added a lively solution that is potentially big and reliable: tiny planktonic crustaceans provide a world-wide benefit by mixing the waters for the creatures of the sea. They swim down at night tens of meters, then come back up in the daytime. This diurnal activity could have a profound influence on the ocean environment, causing ocean mixing three times more powerful than diffusion alone.
Biologically generated turbulence has been proposed as an important contributor to nutrient transport and ocean mixing. However, to produce non-negligible transport and mixing, such turbulence must produce eddies at scales comparable to the length scales of stratification in the ocean. It has previously been argued that biologically generated turbulence is limited to the scale of the individual animals involved, which would make turbulence created by highly abundant centimetre-scale zooplankton such as krill irrelevant to ocean mixing. Their small size notwithstanding, zooplankton form dense aggregations tens of metres in vertical extent as they undergo diurnal vertical migration over hundreds of metres. This behaviour potentially introduces additional length scales—such as the scale of the aggregation—that are of relevance to animal interactions with the surrounding water column.
The researcher team ran lab experiments with brine shrimp – those “sea monkeys” children buy in pet stores. Since crustaceans respond to light, they were able to control their motions and measure the strength of the eddies they produced as they swam. They confirmed that the eddies are strong enough to mix the water over substantial heights of the water column. Although this remains to be observed in situ, it most likely stirs the waters each day for the benefit of all other sea creatures, even during the doldrums.
“It could represent an entirely new role played by some of the most abundant animals on the planet.”
Retired Nature editor Henry Gee was impressed with the research, even though he used the occasion to glorify Darwin. “Shrimp cause a stir,” he wrote; “Migration of brine shrimp causes substantial mixing of the water column.” His article includes a short podcast and a video clip that shows how the researchers tested the ability of shrimp to mix water. Sure enough, they found substantial water currents pushing downward as the shrimp swam upward.
A decade ago, the narrator says, scientists did not believe this kind of aggregation effect was possible. Houghton et al. believe, though, that it is probably substantial enough to influence the global climate. And if creatures as small as brine shrimp have such a large effect, bigger migrators like krill, which live in climatically-sensitive areas near the poles and swarm in numbers large enough to be seen from space, probably have an even greater influence, “changing the balance of ocean chemistry, nutrient flows, and even the climate.” The effect remains to be measured at sea, but if confirmed, the narrator says, “it could represent an entirely new role played by some of the most abundant animals on the planet.”
So what does Darwin have to do with it? Gee says,
The ability of individuals or groups to alter their physical environment has long fascinated biologists. Indeed, Charles Darwin’s final book, The Formation of Vegetable Mould through the Action of Worms (Murray, 1881), reported his analysis of the changes that could occur through the repeated actions of small creatures. This work was a fitting finale for a career spent showing how small changes could, given the time and opportunity, have large effects. As with worms, so, too, with shrimp.
Nobody could argue with the value of field work studying creatures. Darwin’s field work was sometimes honorable, but this last book could not have supported his theory of evolution. The worms were already there, doing work for the benefit of the ecosystem. That doesn’t explain the origin of worms. It also doesn’t explain the appearance of ecosystem that benefits from worms’ plowing of the soil. The new study also does not explain the origin of plankton who mix the waters, or the origin of the larger creatures that benefit from their collective work. But if ecosystems were established from the beginning, they show design to maintain a viable planet, with each organism playing its essential role. One could even ask if land and sea would be habitable without the work of these tiny animals.
Microbes and Global Climate
Most climate modelers consider silicate rocks a “carbon sink” that reduces free carbon dioxide (CO2), the greenhouse gas that Big Science worries about. A new paper in Science Magazine by Hemingway et al., though, says that microbes “eat rocks” and release a lot of that CO2 back into the atmosphere.
The reaction of atmospheric carbon dioxide (CO2) with silicate rocks provides a carbon sink that helps counterbalance the release of CO2 by volcanic degassing. However, some types of rocks contain petrogenic organic carbon, the oxidation of which adds CO2 to the atmosphere, counteracting the drawdown by silicates. Hemingway et al. present evidence from the rapidly eroding Central Range of Taiwan showing that microbes oxidize roughly two-thirds of the petrogenic organic carbon there and that the rate of oxidation increases with the rate of erosion.
Did climate modelers know this? Did they take it into account? It can’t explain current climate fluctuations, because this balance of nature has apparently been true ever since microbes lived on the land.
Scientists need to stop the bad habit of saying, ‘If it exists, it evolved,’ and start thinking, ‘If it exists, there’s a reason for it.’ Microbial release of CO2 may be just such an example of a feedback mechanism to regulate the amount of CO2 in the atmosphere.
Darwin was impressed with the effects of small, cumulative changes over time, but his bottom-up worldview portrayed individuals as selfish opportunists whose only ethic was survival. The top-down view of design theorists makes much more sense. Perturbations to complex webs can cause a catastrophic collapse; how could these beneficial networks originate by blind chance? Why would Darwin’s dog-eat-dog, survival-of-the-fittest world originate tiny organisms that play roles within systems much bigger than themselves for the good of the whole? In a designed world, every organism, like the shrimp and the worms in this article, has a purpose as part of a complex web that makes the world habitable.
Biblical creationists go a step further to follow what the Bible says about a broken world, suffering and groaning because of the curse on sin (Romans 8:18-25), but retaining, nevertheless, abundantly adequate witness of God’s common grace (Acts 14:16-17) so that everyone has no excuse for unbelief (Romans 1:20). Christians are not surprised, therefore, to see little animals helping us in ways we did not previously know about.