Oh, the Salty, Salty Sea

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By Julie Etra

Salt content of the seas and oceans varies, as do the types of salts they contain. The simple definition of a salt is any chemical compound formed from the reaction of an acid with a base, or cations (positively charged ions) and anions (negatively charged ions), to produce a neutral charge. We tend to think of salt as sodium chloride (NaCl), or table salt. But there is also calcium chloride (CaCl2), a de-icer and food stabilizer, or magnesium chloride (MgCl2), another de-icer and stabilizer in tofu production, etc., etc.

How the Sea Got Salty

Two of the most prevalent ions in seawater are sodium and chloride, the same as table salt. Together, they make up over 90% of all dissolved ions in the ocean, and they originate from “parent material,” or rock, and are carried by streams and rivers to be ultimately deposited into the ocean. In general, oceans have a salinity of about 3.5%, which is low compared to some of the world’s inland saline bodies of water.   

One of the saltiest bodies of water on earth is the Dead Sea, which lies between Israel and Jordan and is about 1,400 feet (430.5 meters) below sea level; its salinity level is 33.7%. However, it is neither a sea nor an ocean, but in fact a lake; evaporation has intensified its salinity.  Although there are no current saltworks in Puerto Peñasco (Rocky Point), located at the top of the Gulf of California (Sea of Cortez) in the Mexican state of Sonora, it is also a salty sea. During a college field trip to the Sonoran Desert in the 1970s, I had the opportunity to visit this area, undeveloped at the time. The water is saltier there, as it concentrates in the end of the Gulf, and is particularly high in calcium salts.  Indeed, pre-colonial indigenous group recognized the value of this salt, and it was broadly traded as far north as Phoenix, Arizona.  Puerto Peñasco has been working on desalinization, with the possibility of exporting desalinized water to Arizona.  

Even if we eliminate the high-salinity lakes and inland bodies of water, there is still a huge amount of variation in salinity of the oceans. You can get an overview of global ocean salinity levels with the NASA-developed Aquarius software:  https://www.livescience.com/30802-earth-ocean-saltiness-new-map.html. The Red Sea has the highest salinity, at 3.6-4.1%, while the Baltic Sea has the least (1.0%).

In general, higher salinity is found in the subtropics; the Atlantic has higher salinity than the Pacific or Indian oceans. As you might expect, the salinity is lower in rainy areas near the Equator, where salts are diluted by fresh water. Lower salinity also occurs in the northernmost Pacific Ocean. A combination of factors leads to these trends: large-scale patterns of rainfall and evaporation over the oceans, contributions from river runoff, and ocean currents and circulation patterns. 

Mexico’s Sea Salt

Salina means salt bed or saltworks.  Mexico is the 6th largest producer of salt in the word, with 14 major saltworks that produced 8.67 million tons of salt in 2017. Guerrero Negro in Baja California is the world’s largest saltworks; it produces 82% of Mexico’s salt. Most of Guerrero Negro’s salt goes for export.  

Even though Salinas, California, implies you’ll find salt beds, it’s actually the largest center of lettuce production in the United States. No salt at all.  Here in Mexico, however, Salina Cruz (cross) makes sense.  Located on the Isthmus of Tehuantepec, Salina Cruz has huge salt works. 

Salina Cruz is a relatively young community with no natural harbor, and was developed in conjunction with the Tehuantepec National Railway built during the Porfiriato (the period of rule by Porfirio Díaz, 1876 – 1911), in anticipation of increased commerce; Salina Cruz is the Pacific terminus of the railroad. The harbor was formed by the construction of two breakwaters.

The city, which currently serves as a major seaport and oil refinery, has long been recognized as a major source of salt and salt gathering, tied to the culture for decades. “Nacemos y morimos quemados por la sal.” (“We are born and we die burned by the salt.”)  Salt has been locally known as oro blanco, or white gold. The laguna, or lagoon, behind the beach contains brackish water, which produces salt as the water evaporates in the sun and the cross-isthmus winds.  Harvest usually occurs in February.   Zapotec chiefs controlled production until 1781, when the Spanish Crown took control. 

The largest salt beds in the isthmus those of Salinas del Marqués near Salina Cruz. There are approximately 250 workers in the Sociedad Cooperativa de Producción Salineros (Cooperative Society for Salt Production), which has had the federal concession in Salinas del Marqués for 50 years. Two major enterprises, Las Salinas and El Colchón, excavate and package salt on a commercial level, mostly distributed within Mexico.  As seen from aerial photography, salt beds are symmetrical and appear beige or pink – the pink is especially strong at Las Coloradas in the Yucatán.  

About 45 tons of salt per day are produced in Salinas del Marqués. Seawater is pumped into a series of controlled ponds and contains trace elements such as calcium, magnesium chloride, potassium, zinc, iodine and manganese, minerals not typically present in land salt mines. The salt crystallizes, impurities are removed, and it is sorted, stacked, packed, and distributed to a variety of markets. Industrial uses include processing of tuna and shrimp, water treatment, metal processing, ice production livestock feed, and tanneries.

Personal use?  Just check out Amazon, and you’ll find any number of brands from Colima – Aztec Salt is “made by hand” from salt in the Laguna de Cuyutlán, “hand-harvested” Flor Blanca Mexican sea salt comes from Manzanillo, Sal Real de Colima offers up unrefined sea salt for salt mills, QiVeda salt offers premium fine-grade Colima salt.  If you want to branch out, Baja Gold Sea Salt comes from the “mineral and trace element rich Sea of Cortez.”  And if you want some really special salt from this region, check out Huatulco’s own Jane Bauer; among her line of sea salts is Wild Porcini, flavored with mushrooms from San Antonio Cuajimoloyas, up near Oaxaca City.

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