While most of us give it little consideration, researchers are modeling ocean circulation in labs to figure out potential ways to improve the health of the Earth’s largest bodies of water. Now, it turns out oceanographers may be able to harness the energy of zooplankton — some of the tiniest ocean creatures — to potentially influence nutrient flows, ocean chemistry and maybe even the climate.
While the work to date has been conducted in tall tanks inside research labs, it’s possible field studies may one day validate an important new role for some of the most abundant animals on the planet. As large groups of brine shrimp, for example, swim up all at once, they force ocean water down, effectively churning and mixing it. This action is important because ocean water, due to differences in salinity and temperature, stratifies into layers that don’t mix easily.
Researchers suggest if large-scale turbulence by creatures such as krill could be accomplished in the ocean, it could potentially affect the climate. If you are not yet a fan of krill, this may be just one more reason to appreciate these amazing coldwater crustaceans. The best reason to love krill, in my opinion, is because they provide one of the most beneficial forms of animal-based omega-3 fatty acids. Among other benefits, omega-3s promote heart, joint, skin and vision health.
Turbulence Caused by Shrimp and Krill May Have Beneficial Effect on Oceans
A study published in the journal Nature1 suggests turbulence generated by tiny marine life, when harnessed on a large scale, could be a significant factor in nutrient transport and ocean chemistry. Using tall tanks and LED and laser lights, scientists from Stanford University were able to create a simulated environment to study the migration patterns of brine shrimp (Artemia salina). Because they are attracted to light, scientists used the lights to draw the brine shrimp, also known as sea monkeys, up to the surface.
In the process of swimming up, researchers noticed the shrimp were able to generate swirling eddies that forced water down. Though the effects of individual brine shrimp on saltwater mixing would be negligible due to their tiny size, large groups of them could make a decidedly different impact.
This is believed to be so because the flows generated by the group of shrimp were powerful enough to mix the tank’s salt gradient. “They weren’t just displacing fluid that then returned to its original location,” said Stanford University graduate student Isabel Houghton, coauthor of the study. “Everything mixed irreversibly.”2
According to ScienceNews,3 brine shrimp moving vertically in two lab tanks created small eddies that aggregated into a large jet powerful enough to mix what would otherwise remain isolated layers of ocean water with different densities. With a fluid velocity of about 0.4 to 0.8 inches (1 to 2 centimeters) per second, the jet enabled shallow waters to mix with deeper, saltier waters.
Given the successful lab outcomes, in-ocean turbulence generated by multitudes of tiny sea creatures such as krill could potentially be powerful enough to extend hundreds of meters beneath the water’s surface.4 Said the study authors, “The results illustrate the potential for marine zooplankton to considerably alter the physical and biogeochemical structure of the water column, with potentially widespread effects owing to their high abundance in climatically important regions of the ocean.”5
Next Step Is to Try to Replicate Downward Jets in the Ocean
The current research builds on a 2014 study6 written, in part, by fluid dynamics expert John Dabiri, Ph.D., a professor of civil and environmental engineering and mechanical engineering at Stanford University, that introduced the tank and lighting setup used in the current work. “The original thinking is these animals would flap their appendages and create little eddies about the same size as their bodies,” said Dabiri.7
Using LED and laser lights to simulate the vertical migration brine shrimp undergo daily — rising up at night to find food on the water’s surface and diving down during daytime hours to avoid potential predators — Dabiri and his colleagues noticed the tens of thousands of lab shrimp migrated in close proximity.
“As one animal swims upward, it’s kicking backward,” Dabiri noted.8 As such, each parcel of water is kicked downward by another shrimp and another and so on. The total effect is a downward rush that gets stronger as the vertical migration continues.
The water movement eventually extends nearly as deep as the entire migrating group, which when applied in the ocean could generate effects for hundreds of meters. The researchers believe if the creatures can effectively mix simulated ocean-water layers in the lab, the chances are good they can do the same in the ocean.9
The lab method helped magnify the efforts of individual shrimp and generated a swirling effect potentially useful in delivering nutrient-rich deep waters to the ocean’s surface. Once there, these deeper waters could benefit a wide variety of marine life, such as phytoplankton, which live near the surface. Now that the downward jets have been observed, Dabiri suggests the next step would be to attempt to replicate the lab results in the ocean using shipboard measurements.10
The future work would involve locating and tracking swarms of krill in locations as diverse as the California coast and the frigid waters of the Antarctic.11 In ocean conditions, the power of tiny creatures such as krill are expected to generate similar effects as those noted when using brine shrimp.
It’s possible, suggests Dabiri, the current findings might apply to not only krill, which dwell in the upper kilometer of the ocean, but also to fish, jellyfish, mammals and squid — all of which swim even deeper and have the potential to churn the entire water column.
As for the use of brine shrimp in their lab experiments, the researchers called them “a stand-in for less lab-hardy krill.”12 Recognized as one of the most common zooplankton, krill are abundant marine organisms known to make their daily migrations in giant swarms. Similar to brine shrimp, they dive hundreds of meters deep during daytime hours and return to the ocean’s surface at night to feed.