The US Food and Drug Administration is concerned that Americans consume too much salt. Yet, when my wife was pregnant with our sons, her obstetrician was concerned that she was not consuming enough salt. In other words, too much—or too little—salt in our diets can be harmful. And what is true for humans is true for every life-form. Now a new scientific discovery reveals that cyanobacteria play a vital role in maintaining a perfect salt balance in our oceans.1

Our Oceans’ Salinity History
While some life-forms can tolerate higher or lower salt concentrations, for every life-form the salt concentration must be fine-tuned. Land-based animals can regulate their salt intake by carefully choosing what they eat. Land-based plants can sprout and thrive in soils with the appropriate salt concentration. Marine life, on the other hand, is at the mercy of the ocean’s salt concentration.

Today, our oceans’ salt concentration is equivalent to that of human blood. This salt concentration is ideal for large, active animals and permits the greatest diversity of marine life Earth has ever possessed. However, the concentration has not always been at this optimal level.

Vital Poison
Salt is a “vital poison.” Too little salt in your diet will kill you (less than 1,250 milligrams per day). Too much salt in your diet also will kill you (more than 5,750 milligrams per day). Our bodies are designed to operate within a narrow range of salt concentration. For optimal health, the salt concentration in our bodies must be just-right (227±5 grams for a 150-pound man).

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What is true for humans is true for every life-form that exists now and has previously existed. While some life-forms can tolerate higher or lower salt concentrations, for every life-form the salt concentration must be fine-tuned.

Land-based animals can regulate their salt intake by carefully choosing what they eat. Land-based plants can sprout and thrive in soils with the appropriate salt concentration. Marine life, on the other hand, is at the mercy of the ocean’s salt concentration.

At the current time in Earth’s history the ocean’s salt concentration is equivalent to that of human blood. This salt concentration is ideal for large, active animals and permits the greatest diversity of marine life Earth has ever possessed. However, the concentration has not always been at this optimal level.

Salinity History of the Oceans
Until the beginning of the supercontinent cycle 2.4 billion years ago, the oceans’ salinity was about twice the modern value.2 Previous to 2.4 billion years ago, the absence of continents meant no sequestering of giant brine (saline) beds from evaporating seawater was occurring. With no mechanism for removing salt from the oceans, ocean salinity remained high. High ocean salinity limited marine life to salt-tolerant microbes. Since oxygen solubility in the oceans decreases strongly with increasing salinity, previous to 2.4 billion years ago oceans were anoxic (oxygenless) and therefore dominated by anaerobic (nonphotosynthetic) microbes.

The launch of the supercontinent cycle reduced ocean salinity to about 50 percent greater than the modern value. This ocean salinity level kept the oceans sufficiently starved of soluble oxygen to limit marine life to microbes. More of these microbes were aerobic than previous to 2.4 billion years ago. Nevertheless, anaerobic microbes likely still dominated marine life.

The occurrence of three major glaciation events just previous to the Avalon explosion of Earth’s first animals (575 million years ago) dramatically cooled Earth. Since oxygen solubility in the oceans increases with decreasing ocean water temperature, ocean oxygen solubility rose sufficiently to permit the existence of the first animals. These first animals, however, lacked eyes, a brain, and a digestive tract. The ocean oxygen content at that time was too low to support such body organs.

Just previous to the Cambrian explosion of Earth’s first complex animals (543 million years ago), major tectonic events sequestered enormous amounts of salt and brine in giant evaporite basins. These events brought ocean salinity down to only a few percent above the modern value, resulting in sufficient ocean oxygen solubility to permit the existence of complex animals for the first time.

As I explain and document in my book Improbable Planet, the sudden rise in soluble oxygen content in the oceans was accompanied by an equally sudden and simultaneous rise in tens of phyla of complex animals.3 This Cambrian explosion event ranks as one of the greatest challenges to naturalistic evolution.4

Since the Cambrian explosion, major asteroid collision events and their accompanying massive volcanic eruptions, plus the formation and breakup of the Pangea supercontinent, have caused ocean salinity to suddenly jump up and down by as much as 40 percent.5 These jumps played major roles in both mass extinction and mass speciation events that occurred during the past half billion years.

Role of Cyanobacteria
Until recently scientists assumed that the only factors operating to lower open ocean salinity were precipitation, melting of glaciers, and the creation of evaporite basins through the supercontinent cycle. It was also assumed that on timescales briefer than a century the only significant factor was precipitation.

A team of nine marine biologists and chemists published a paper in Geophysical Research Letters in which they show that large blooms of cyanobacteria (a phylum of bacteria that get their energy through photosynthesis) floating on the ocean surface play a vital role in reducing the salinity of ocean surface water.6 The team performed high-resolution observations on several large cyanobacteria blooms. In each case, their observations showed that in the vicinity of the large cyanobacteria blooms the blooms slightly warmed the ocean surface water and substantially lowered its salinity. As such, major cyanobacteria blooms create habitats for life-forms that can thrive under the reduced salinity conditions. Thus, it is not only at the estuaries of major rivers where marine life that requires reduced ocean salinity can thrive but also in the vicinity of major cyanobacteria blooms.

As Earth’s dominant form of life presently, phytoplankton are responsible for about half of the global net primary production.7 Cyanobacteria are one of the more prevalent phytoplankton life-forms, making up about 15 percent of all phytoplankton.8 Thus, cyanobacteria play a key role in regulating the salinity of the oceans’ surface layers. For a great diversity of both simple and advanced life to thrive in the oceans, the salinity levels at different parts of the world’s oceans must be fine-tuned. This fine-tuning requirement implies both the quantity and location of cyanobacteria must be fine-tuned. It’s a tiny creature with massive implications. Thank God for his fine-tuned design of the quantity, type, and location of cyanobacteria.

Endnotes
  1. O. Wurl et al., “Warming and Inhibition of Salinization at the Ocean’s Surface by Cyanobacteria,” Geophysical Research Letters 45 (May 16, 2018): 4230–37, published online May 2, 2018, https://doi:10.1029/2018GL077946.
  2. L. Paul Knauth, “Temperature and Salinity History of the Precambrian Ocean: Implications for the Course of Microbial Evolution,” Palaeogeography, Palaeoclimatology, Palaeoecology 219 (April 11, 2005): 53–69, https://doi:10.1016/j.palaeo.2004.10.014.
  3. Hugh Ross, Improbable Planet: How Earth Became Humanity’s Home (Grand Rapids, MI: Baker, 2016): 175–78.
  4. Ross, Improbable Planet, 177–78.
  5. William W. Hay, “Evaporites and the Salinity of the Ocean During the Phanerozoic: Implications for Climate, Ocean Circulation, and Life,” Palaeogeography, Palaeoclimatology, Palaeoecology 240 (October 2006): 3–46, https://doi:10.1016/j.palaeo.2006.03.044.
  6. Wurl et al., “Warming and Inhibition of Salinization.”
  7. Christopher B. Field et al., “Primary Production of the Biosphere: Integrating Terrestrial and Oceanic Components,” Science 281 (July 10, 1998): 237–40, https://doi:10.1126/science281.5374.237.
  8. W. K. W. Li et al., “Biomass of Bacteria, Cyanobacteria, Prochlorophytes, and Photosynthetic Eukaryotes in the Sargasso Sea,” Deep Sea Research Part A: Oceanographic Research Papers 39 (March–April 1992): 501–19, https://doi:10.1016/0198-0149(92)90085-8.

Check out more from Dr. Hugh Ross @Reasons.org

 

About The Author

Dr. Hugh Ross

Reasons to Believe emerged from my passion to research, develop, and proclaim the most powerful new reasons to believe in Christ as Creator, Lord, and Savior and to use those new reasons to reach people for Christ. I also am eager to equip Christians to engage, rather than withdraw from or attack, educated non-Christians. One of the approaches I’ve developed, with the help of my RTB colleagues, is a biblical creation model that is testable, falsifiable, and predictive. I enjoy constructively integrating all 66 books of the Bible with all the science disciplines as a way to discover and apply deeper truths. 1 Peter 3:15–16 sets my ministry goal, "Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect, keeping a clear conscience." Hugh Ross launched his career at age seven when he went to the library to find out why stars are hot. Physics and astronomy captured his curiosity and never let go. At age seventeen he became the youngest person ever to serve as director of observations for Vancouver's Royal Astronomical Society. With the help of a provincial scholarship and a National Research Council (NRC) of Canada fellowship, he completed his undergraduate degree in physics (University of British Columbia) and graduate degrees in astronomy (University of Toronto). The NRC also sent him to the United States for postdoctoral studies. At Caltech he researched quasi-stellar objects, or "quasars," some of the most distant and ancient objects in the universe. Not all of Hugh's discoveries involved astrophysics. Prompted by curiosity, he studied the world’s religions and "holy books" and found only one book that proved scientifically and historically accurate: the Bible. Hugh started at religious "ground zero" and through scientific and historical reality-testing became convinced that the Bible is truly the Word of God! When he went on to describe for others his journey to faith in Jesus Christ, he was surprised to discover how many people believed or disbelieved without checking the evidence. Hugh's unshakable confidence that God's revelations in Scripture and nature do not, will not, and cannot contradict became his unique message. Wholeheartedly encouraged by family and friends, communicating that message as broadly and clearly as possible became his mission. Thus, in 1986, he founded science-faith think tank Reasons to Believe (RTB). He and his colleagues at RTB keep tabs on the frontiers of research to share with scientists and nonscientists alike the thrilling news of what's being discovered and how it connects with biblical theology. In this realm, he has written many books, including: The Fingerprint of God, The Creator and the Cosmos, Beyond the Cosmos, A Matter of Days, Creation as Science, Why the Universe Is the Way It Is, and More Than a Theory. Between writing books and articles, recording podcasts, and taking interviews, Hugh travels the world challenging students and faculty, churches and professional groups, to consider what they believe and why. He presents a persuasive case for Christianity without applying pressure. Because he treats people's questions and comments with respect, he is in great demand as a speaker and as a talk-radio and television guest. Having grown up amid the splendor of Canada's mountains, wildlife, and waterways, Hugh loves the outdoors. Hiking, trail running, and photography are among his favorite recreational pursuits - in addition to stargazing. Hugh lives in Southern California with his wife, Kathy, and two sons.



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