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This article was originally published as a chapter in the book “Design and Catastrophe: 51 Scientists Explore Evidence in Nature"
From beginning to end, the Bible presents a picture of God as actively involved in human history. To the Christian, the influence and power of God’s Word to shape and transform the life of a single person, the dynamics of a community, the fate of a country, or the history of humankind is readily apparent. However, things become more complicated when trying to reconcile the current predominant scientific paradigm (naturalism) with the Scriptures.
In my own experience, the biblical account of Creation inspires and motivates me to look in nature for signs and clues about a Creator. Many can be found, whether at the macroscopic or microscopic level. For me, though, one of the most amazing things in this journey of discovery is unveiling the beauty and design of microscopic organisms. In this chapter we will explore the unseen wonder of microscopic algae known as coccolithophores and the extraordinary design and functions of their calcareous exoskeletons, which are the smallest skeletons in the marine world.
Living Coccolithophores
Coccolithophores are unicellular calcifying marine algae (haptophytes) characterized by the possession of a unique flagellum-like structure (haptonema). The function of the haptonema seems to be related to swimming, attachment, and capture of particles.[1] About 200 species of coccolithophores currently live in the oceans and are part of the plankton, which constitute 98% of the living biomass in the oceans. The remaining 2% comprises all the animals we can see macroscopically, like crabs, fish, and whales.[2]
Coccolithophores have an essential role in the global carbon cycle through photosynthesis and calcification. These algae reduce the amount of carbon dioxide (CO2) in the atmosphere by converting CO2, water (H2O), and minerals into oxygen and organic matter and into calcium carbonate (CaCO3) by calcification.[3] Coccolithophores and the rest of the phytoplankton form the basis of the marine food chain and are responsible for about half of the global primary production of oxygen, therefore being more important to our atmosphere than all of the earth’s rainforests.
Haptophyte algae possess a tiny exoskeleton made of multiple scales. This exoskeleton (coccosphere) that covers the cell is made by an inner layer of organic body scales and an outer layer of minuscule calcite plates named coccoliths. Coccoliths (and organic scales) are secreted internally in the Golgi body and then extruded to the surface of the cell where they form the coccosphere[4] (see Figure 19-1A).
The Incredible Designs of Coccoliths
Coccolithophores produce diverse calcareous coccospheres of extraordinary designs. Although many other microalgae form exoskeletons of organic or inorganic scales, coccoliths are distinct and unique to the haptophytes.[5] Since coccolithophores possess remarkably small coccoliths, usually between 5 and 10 microns (0.005 and 0.01 mm) long, they are also called calcareous nannoplankton (less than 30 µm). Individual coccoliths and sometimes, under exceptional preservation, coccospheres can be found preserved in the fossil record. These tiny fossils are about the size of a human red blood cell.
Observation of coccolith morphology using scanning electron microscopy (SEM) and light microscopy reveals complex and multicyclic rim architectures (cycles of crystals). Broadly, coccoliths of living nannoplankton are built entirely of different submicroscopic calcite crystals organized in one or more radial cycles of circular to elliptical discs or rings (see Figure 19-1B). The morphologies of coccoliths are used for classification of species. In the fossil record, nannofossils also include coccoliths with uncertain biological affinities. This heterogeneous group shows some features of modern coccoliths including a wide range of shapes (e.g., star or rose, spindle, cylindrical, conical, pentagon).[6] One example within this group, Braarudosphaera, shows exceptional geometrical attributes, being characterized by pentagonal calcareous scales, called pentaliths, arranged in a regular pentagonal dodecahedron (see Figure 19-1C).
Coccolith scales are thought to perform several functions for the organism, although no definitive use is agreed upon. Some of the suggested functions are related to protection, flotation, light regulation, and biochemical balance. Among these hypotheses, the one that captures my attention is the flotation or buoyancy function for the cell. The algae need to maintain their position within the photic zone to have access to sunlight and benefit from relative control over sinking and flotation. Imagine a person wearing a wingsuit falling from a high cliff and parachuting when approaching the land. The shape of the wingsuit and the parachute resembles the shape of coccoliths, and the fluid in our example would be air instead of water. The coccolith size and shape might give greater control over sinking rates.[7] This is just a simple aspect illustrating the importance of the design of coccoliths to coccolithophore ecology.
Conclusion
Beauty and design of microscopic organisms in association with functionality is not always appreciated in science. The design of coccoliths is important for the role of coccolithophores as a part of the marine ecosystem. Indeed, the functions of coccoliths are not limited to those mentioned above, and there is still much more to discover and understand. Yet, when I am looking at them with light or electron microscopes, I cannot help but admire their spectacular design. This combination of function and beauty reminds me of the infinite wisdom and power of God; it inspires me to join the psalmist’s praise to our Creator, and declare: “Many, Lord my God, are the wonders you have done, the things you planned for us. None can compare with you; were I to speak and tell of your deeds, they would be too many to declare” (Ps. 40:5).
NOTES
[1] PR Bown, JR Young. Calcareous nannofossil biostratigraphy. Dordrecht (The Netherlands): Kluwer Academic; 1998, pp. 1–15.
[2] C Sardet. Plankton: wonders of the drifting world. Chicago: University of Chicago Press; 2015, p. 7.
[3] PH Raven, RF Evert, SE Eichhorn. Biology of plants. 7th ed. New York: W. H. Freeman; 2005, p. 301.
[4] Bown and Young, op. cit.
[5] Ibid.
[6] HA Armstrong, MD Brasier. Microfossils. 2nd ed. Oxford (UK): Blackwell; 2005, pp. 129–140; Bown and Young, op. cit.
[7] Bown and Young, op. cit.
Emilia R. Belia is a postdoctoral research associate at the University of Nebraska-Lincoln. She holds a PhD in Earth Sciences from Loma Linda University. Her expertise is biostratigraphy, specifically through calcareous nannofossil analysis. Her scientific research has been mostly concentrated in the Pisco Basin of west central Peru. Her research findings have been presented at several scientific meetings and published in conference articles and peer-reviewed publications. She is currently working on the study of nannofossils from the Cretaceous/Paleogene mass extinction recovered from the Mentelle Basin (western margin of Australia).