Some look like miniature spaceships. Some look like tiny jewel boxes. Others look like miniature versions of shrimp. They constitute most of the biomass on the planet, regulate earth’s carbon and oxygen, and provide food for fish, birds, and blue whales — the largest animals to ever grace the earth. What are they? Collectively, we call them “plankton,” a word meaning drifters. Such a catch-all term hardly does justice to their incredible diversity and importance to us all. A few recent papers are opening wider the black box of these wonderful plants (phytoplankton) and animals (zooplankton).
The Jewel Boxes: Diatoms
We discussed the diatoms and their delicate silica shells a couple of months ago, so we won’t go into detail here. Suffice it to say that one of the papers we will look at confirms that these single-celled algae are useful as well as ornamental. “Among autotrophs, diatoms are commonly attributed to being important in carbon flux because of their large size and fast sinking rates.”
The Spaceships: Rhizaria
Diatoms are not the only Baroque artists. Other microbes in the plankton community build even more elaborate 3-D shapes, notably the radiolarians and foraminifera. Not your ordinary amoebas, the Rhizaria share characteristics with the familiar blob-like protists, including pseudopodia, but they also construct “intricate mineral skeletal structures of opal (SiO2), celestite (SrSO4) or calcite (CaCO3),” David A. Caron says in Nature. Classification of these organisms continues to the present day.
Do you know the name and evolutionary affiliation of any of the most conspicuous groups of single-celled organisms in the world’s oceans? Did you guess the Rhizaria, or one of the more familiar groups of plankton that make up this supergroup, such as the Radiolaria, Acantharia or Foraminifera? If you didn’t, you’re not alone — until recently, neither did the vast majority of biological oceanographers. Biard et al. report on page 504 of this issue that the abundance and biomass of these enigmatic species in the ocean are much greater than previously recognized. In addition, Guidi et al. (page 465) reveal the extent of the Rhizaria’s involvement in the export of carbon from the atmosphere to the ocean depths. [Emphasis added.]
Ernst Haeckel had many faults, but he provided one worthy achievement that continues to grace textbooks today. No, it’s not his infamous embryos; it’s a series of detailed drawings of Rhizarians he made from samples collected by the oceanic Challenger expedition of 1872-1876. The fantastic skeletons of these creatures have to be seen to be believed (searching on rhizaria+Haeckel quickly brings up the drawings). Caron shows a few of the colonial forms in his article. By “holding hands” with their pseudopodia, these animals can form large colonies. “Some species can even form cylindrical colonies approximately 1 cm in diameter and greater than 1 m in length,” Caron notes.
While over-designed for Baroque symmetry and detail, Rhizarians are also useful. That’s what Caron and the two papers he references focus on: “the vital export of carbon from upper ocean layers to the deep ocean.” Without the help of these organisms reducing atmospheric carbon dioxide, where would the earth be today? And do they have to be so doggone beautiful to carry on that task? None of the papers explain how these amazing spaceships, cathedrals and geodesic domes evolved. To fill that gap, design scientists could take leadership over this vast research opportunity.
One of the reasons for their anonymity to oceanographers is the delicate morphologies of living specimens. These structures deteriorate badly as a result of the methods and preservatives that have routinely been used for collection and species identification. Some species contain no skeletal material, and in plankton samples their remains are often not recognizable. Substantial abundances of Rhizaria were detected by divers in the open ocean more than two decades ago, and are visible in earlier underwater images. However, truly global surveys have never been conducted.
The Mighty Migrating Micro-Shrimp
Illustra Media’s documentary Flight: The Genius of Birds briefly mentions the annual bloom of plankton in the Weddell Sea that coincides with the arrival of the Arctic terns. In the bloom, the phytoplankton feed the zooplankton which set the table for birds, fish and mammals. Blue whales migrate to this Antarctic sea to scoop up the krill in their gigantic mouths.
Illustra’s Design of Life films showcased the amazing animal migrations of butterflies, birds, salmon and sea turtles, but there are microscopic migrators you probably didn’t know about. That’s because scientists didn’t know much about them, either. Among them are tiny shrimp-like crustaceans like copepods, amphipods and krill. Scientists at the Alfred Wegener Institute discovered something amazing about these little guys. They migrate hundreds of meters almost every day. The scientists spent three years studying this phenomenon.
The daily vertical migration of zooplankton — often crustaceans with body lengths ranging from millimetres to centimetres — is mainly triggered by the day-night cycle. In order to escape potential predators, they dive into the dark depths at sunrise and stay there during the day. After sunset, they once again rise to the upper layers to feed where the sunlight has allowed planktonic algae to grow. Until now, only short time snippets of the migration pattern of the zooplankton in the Southern Ocean existed. Because of its seasonal sea ice cover, many areas are not accessible by ship during the southern winter. At this time of year, biological network samples can only be taken intermittently.
The current study is based on data that was collected during three Polarstern expeditions and with deep-sea moorings deployed in the Southern Ocean between 2005 and 2008 within the framework of the LAKRIS project (Lazarev Sea Krill Study). As part of this study ADCPs were moored at three different geographical locations along the Greenwich meridian; the ADCPs send out sound waves at fixed intervals and cover an up to 500 metres deep water layer under the surface. While the strength of the echo provides information about the concentration of the zooplankton, the migration velocity can be calculated based on the Doppler shift of the sound frequency.
It was a pretty clever method of data collection. The only times crustaceans don’t make the daily trip is during the spring bloom when their algae prey are so abundant, they need not worry about predators; or else, possibly, the predators can’t see them as well at that season. Regardless, they don’t seem to be passively riding currents, because the migration is timed to the threat and can be switched off.
As the Illustra films demonstrated, any migration requires navigation, energy planning and timing. To migrate 500 meters every day is a big task for a 5-millimeter animal. That’s roughly 100,000 body lengths, like swimming 10 marathons a day. How do they do it? Is there an ID researcher that would like to explore these uncharted waters?
We’ve taken a brief look at microscopic organisms with a big job: regulating the carbon and oxygen cycles of the whole planet. They’re implicated in nitrogen and phosphorus regulation as well. How did the earth get along before these amazing creatures “evolved”? Don’t ask the evolutionists, because they didn’t say.
Here’s what makes earth stand out from all the exoplanets that the Kepler spacecraft is finding. It’s not just water. It’s not just air. Only the earth, as far as we know, is filled with functioning creatures that do what they do because of complex specified information — the hallmark of intelligent design.
Image: Radiolaria (Stephoidea), by Ernst Haeckel [Public domain], via Wikimedia Commons.