Book Readings: Week 8

For my Marine Resources class (GEOG 646) at SF State this semester I am reading The Sea Around Us, by Rachel Carson (1951), and The Tide: The Science and Stories Behind the Greatest Force on Earth, by Hugh Aldersey-Williams (2016). Please check out my first Book Reading blog post to read about why I chose these two books and why I chose to blog about them concurrently.

This week in The Tide, Aldersey-Williams begins by discussing the works of George Crabbe, an English poet who was active in the 1770s to 1830s. Aldersey-Williams discusses Crabbe, who was based in the coastal town of Aldeburgh in Suffolk, England, because the tide and the coast were recurring themes in Crabbe's work. In fact, in one of the stanzas of Crabbe's work The Borough, the poet described in detail the type of vegetation he saw in the intertidal zone, providing a very vivid image of ecological zonation from the water line to above the high tide line. It was a nice example of how the sea influences the minds of people not just on a scientific level but an artistic, emotional one.

Aldersey-Williams goes on to make the case, quite convincingly, that in Crabbe's time the tides were imbued with symbolism related to sin, punishment, and mortality, and that symbolically, the tides in literature often served as a moral warning. It makes sense that because of their awesome power and capacity to cause injury and even death, the tides would be connected to themes of retribution for sin and take on other religious connotations. Indeed, the story of the biblical flood, the Christian god's punishment for humanity's evil, is perhaps the ultimate representation of how the tides are connected to the themes of sin and death.

After leaving Crabbe and Aldeburgh, the author takes us to Normandy, where he discusses the role of tides in D-Day, the pivotal day in World War II when Allied forces invaded northern France. I was very impressed to read that the D-Day landings were actually carefully planned using tidal calculations that took into account eleven different types of harmonic oscillations that create the local tides. For perspective though, Aldersey-Williams points out that modern tide tables involve anywhere between 60 to 100 different harmonic cycles!

German forces had positioned tank traps and other obstacles on the beaches of Normandy to thwart the Allied forces and induce them into landing at low tide, which would have forced the soldiers to advance a long way up a large stretch of exposed beach, making themselves easy targets for snipers. However, the Allied forces realized that they could use particularly high, rising tides to carry their boats over most of these obstacles, and that after they unloaded their soldiers high up on the beaches, the ships could retreat back over the traps while the waters were still high. I was impressed by the planning that must have gone into taking this (ultimately successful approach), because, as the author points out, the invasion had to be planned for a spring tide and timed exactly right so that there would not be loss of the element of surprise if the ships ended up having to wait for the right moment.

In contrast to this successful endeavor, Aldersey-Williams recounts how American forces failed to capture the island of Tarawa (now called Kiribati) from the Japanese because they disregarded the tides. Despite the fact that some in the Allied forces advocated waiting out a neap tide to invade Tarawa because higher tides would allow the ships to pass more ably over the coral reefs and onto the beaches, this advice was disregarded by those higher up in the chain of command. The attempt to take Tarawa ended in disaster, with ships being stranded on the reef for a few days. These two contrasting tales are a good reminder of the need to understand, study, and ultimately respect nature.

Switching gears, Aldersey-Williams talks about the California grunion, a fish whose breeding cycle is synchronized exclusively to spring tides. Female grunion utilize the crashing waves to fling themselves onto beaches in order to lay their eggs (or spread their milt, in the case of males) in the upper high-tide zone. Impressively, the grunion do this in the days just after the highest high tide (after the full moon or new moon), so that as the days progress the high tides get lower and lower, preventing the fertilized eggs from being washed away. It's not until just before the next highest high tide approaches, just under two weeks later, that the eggs, now developed enough, are stimulated by the motion of the waves to hatch into larvae, which are then able to be carried away into the ocean by the waves of the next peak spring tide.

It's difficult to deduce exactly how organisms like the grunion carry this "tidal memory" in their bodies, and how they know, without any conscious knowledge about the monthly tidal rhythms, when to perform which behaviors. Aldersey-Williams argues that it's probably not related to the light that comes from the moon, or the height of the tides, but to gravity itself. He refers to John Steinbeck, who wrote in The Log from the Sea of Cortez that in Precambrian times, when single-celled life in the seas were beginning to form multicellular organisms, the tides were much stronger because the moon was orbiting much closer to the Earth at the time, exerting a much stronger gravitational pull. Steinbeck asserts that it's the "memory" of this gravitational pull that is imprinted on the genetic makeup of many organisms.

One of the reasons the story of the grunion stood out to me this week was because in a previous blog post I recounted how Rachel Carson talks about the grunion in The Sea Around Us. Indeed, Aldersey-Williams does namecheck Carson after discussing the grunion and talks about the Rachel Carson Reserve, which are protected barrier islands off the coast of North Carolina where Carson once made observations of various birds that timed their hunting for various fish species to coincide with the rising tides that brought their prey into the shallows. The reserve is now part of the North Carolina National Estuarine Research Reserve.

I don't have much left to read in Carson's The Sea Around Us, so this week I only read a short chapter on the various dissolved minerals of significance that are present in the ocean, such as Na (sodium), Ca (calcium), and Si (silicon).

Carson asserts that the saltiness of the seas have been increasing over time, as water flowing seaward from rivers and streams collects minerals on its journey. As someone who took a class on chemical oceanography last year, I was particularly interested by Carson's description of how the mineral content of freshwater in rivers and creeks were wildly, fundamentally different to that of ocean waters. In particular, ocean water are far more depleted in calcium and silicon because various animals use those minerals to build their body parts: foraminifera, mollusks, and corals use calcium, while diatoms use silica for their shells.

I was amused to read Carson imagine, in a lighthearted tone, how humans might extract gold and silver from seawater. According to Carson, there is about $93 million in gold in a cubic mile of seawater and $8.5 million in silver. Considering that The Sea Around Us was first published in the 1950s, these are staggering dollar values. While this is an entertaining thought, Carson quickly points out that the cost and effort required to treat all that seawater just to extract these two metals would make the whole endeavor economically unfeasible.

Finally, what I found particularly interesting this week was Carson's discussion of iodine, and how ubiquitous it seems to be in the ocean: not just in the water, but in all manner of organisms and seaweeds. Carson states that iodine in the ocean is in a constant state of flux, being oxidized, reduced, and being bound to or unbound from organic molecules. It would seem that iodine atoms are part of the various process of energy transfer in the oceans. Carson also points out that living organisms, including terrestrial ones, have become increasingly dependent on iodine and that it plays an important role in their basic metabolic processes. This seems to hearken back to an era when all life on Earth was marine in nature, and was suspended in an environment where iodine was readily available.

I'll be blogging again about both books at the same time next week. Stay tuned!

References:

• Aldersey-Williams, H. (2016). The tide: The science and stories behind the greatest force on Earth. New York, NY: W. W. Norton & Company, Inc.
• Carson, R. L. (1951). The sea around us (1989 ed.). New York, NY: Oxford University Press, Inc.