ISSUE #1 – Don’t Get Salty!

This last month has been ‘tough’ on our ambassadors. From getting shiny new equipment, having their claws and beaks trimmed up, and enjoying some enclosure upgrades, you’d think they’d be excited about all the nice things we do for them, but they’re creatures of habit. They get a bit salty about change.

As it just so happens, TUI is focusing on oceans this month. So, in honor of those briny waves, and our slightly salty (at the moment) Ambassadors, we decided to dedicate this entire newsletter to the most abundant mineral on Earth: Salt!

What exactly is Salt?

The first thing we need to ask ourselves is: What exactly is the substance we call salt? Our immediate thought is to consider the table salt we may use in our kitchen to season food. It’s small, and looks kind of like a rock or a crystal, right? Scientifically, salt is any substance produced by combining an acid and a base together. This means, the kitchen salt we have on our counter is the product of mixing two other chemicals together. In the case of table salt, those chemicals are Sodium and Chlorine

By themselves, each of these elements are highly reactive and potentially hazardous to our health, but when they are combined, they create the wonderful and useful substance we call salt. 

On its own, sodium is an extremely light and malleable substance known as an alkaline metal. This substance is easily bent, torn or cut, and serves as a good conductor of electricity. But its most notable property is perhaps its reactivity to water. When water comes into contact with sodium, the material will violently burst into flames. The danger of combustion is so high, that even airborne humidity can cause a reaction. (

Chlorine, on the other hand, is a naturally gaseous element of a yellow-green hue. While the gas is toxic, it is not found alone in nature, and is instead combined with other elements to create a chloride or bonded chemical of some sort. In the theme of our topic, it is most often found bonded with sodium to create sodium chloride, or common salt. (



What Makes the Ocean Salty?

Bernard Spragg. NZ from Christchurch, New Zealand, Weathered limestone (20125209969)CC0 1.0

Donarreiskoffer, Carbonic acidCC BY-SA 3.0




So if salt is just Sodium and Chlorine combined, then where does salt come from, and why does it collect in the ocean?

The earth’s oceans actually get their salt from the rocks on land. Whenever it rains on land, the droplets contain some of the carbon dioxide from the air it falls through. This causes the rainwater to become slightly acidic, as some of the water molecules and the carbon dioxide combine to create trace amounts of carbonic acid. This slightly acidic rainfall erodes the rocks, and the carbonic acid breaks down the rocks into salts, which are then swept out to the sea via rivers and streams. 

Over 90% of all ions in seawater are sodium and chloride; this makes the ocean “salty.” If all of the salt in the ocean could be removed and spread out over the earth’s land surface, it would be over 500 feet thick. That’s about as tall as 25 giraffes stacked on top of each other! (

How do Marine Animals Handle this salt?

While water is a crucial component of life, the saltwater of the ocean is largely unhealthy for any human and most land animals to drink. But the abundance of sea life on this planet does beg the question: How do they stay hydrated?

Solutions and Equilibrium

To understand how animals keep hydrated, we need to first understand solubility and equilibrium. In a nutshell, a solution is a homogeneous mixture of a solvent and a solute. This means that one component is mixed into another until the solute is completely mixed or dissolved into the solvent, reaching an equilibrium.

In the case of the ocean, water would be the solvent, and salt would be the solute. Now imagine we had a bowl with a solution of salt water. If we were add more fresh water to the bowl slowly and evenly, we would be able to see that the fresh water remains largely separate from the salt water, because the salt already existing in the bowl has dissolved evenly with the water that existed before we added more, making the salt water more dense than the fresh water being added. 

Now unlike oil and water, if we let the two solutions sit, over time the fresh water will slowly mix with the salt water until we are left with a uniform solution, like we started with. This is because salts will always flow toward areas of lower salinity. Alternatively, fresh water will always flow towards areas of higher salinity. Because of these two traits, both the fresh water and the salts will “seek” equilibrium. This process is slow but consistent, and can be sped up by agitating the water and effectively mixing the two solutions.

Most bony fish are like people. They cannot survive with too much salt in their bodies. So there is not a lot of salt mixing with the water and blood inside of a fish. These fish are kind of like the fresh water we talked about in the paragraphs above. But unlike the fresh water above, their skin prevents salt from entering the body to mix with the water inside the fish. Unfortunately, their skin cannot keep water from leaving their body to mix with the more salty solutions around them. So these fish are always losing water to the ocean around them

To combat this, most fish species actually drink a LOT of seawater. Their kidneys are efficient at removing the salt from the water they drink and excreting it in their urine so their bodies can use the new water properly. (


Because they don’t breathe with gills and because their skin is thicker than most fish, marine mammals do not share the same problems that fish do. Instead, they need to find sources of fresh water. To do this, they have adapted a different method of finding drinkable water than simply drinking from the ocean: their food! Most marine mammals obtain their water from their meals, which makes sense since we learned that fish have a higher concentration of drinkable water in their bodies. Marine mammals can also produce water via metabolic breakdown of food. This means they can get fresh water simply by digesting their meals!

To get rid of any excess salt they consume, or any they may drink, marine mammals produce extra salty urine. Since the surrounding seawater is almost 3x saltier than its own blood, the sea lion will collect this excess salt in their urine and excrete it all at once. This means that when they urinate, their urine will be almost 8x saltier than the rest of the water in their bodies, and almost 3x saltier than the surrounding ocean water. (


Interestingly, unlike other fish species, sharks lose far less water from their skin and gills. This is due to a handy chemical called urea, which helps keep shark’s body in a chemical equilibrium with the ocean water around it. Instead of drinking seawater, sharks absorb some seawater through their gills. Sharks also possess a specialized gland which removes the excess salt and secretes it from the body. This salt gland is found in several species of fish, rays, and even marine reptiles and birds. (


Anonymous, Reef0097. Marked as public domain. More details on Wikimedia Commons.





VassilLion de mer Amnéville 01. Marked as public domain. More details on Wikimedia Commons.

The Amazing Salt Gland

Helixitta, Salt glandCC BY-SA 4.0

The salt gland is a magnificent natural structure which allows a number of species to survive on little to no fresh water, using the properties of salinity and equilibrium we discussed above. The final product of this process is a solution we call saline. 

To work properly, the gland pumps blood with high salt concentrations close to a membrane supplied with fresh water. The salts are attracted to the low salinity of the fresh water, while the membrane keeps the water from mixing back into the blood. This creates a highly concentrated saline solution.

This solution is then excreted from the gland and out of the body, leaving the animal’s blood and body fluids far less salty than their surroundings. 

Final Thoughts 

What an interesting topic to discuss. We never even dreamed there could be so much to explore about salt, and something tells us, we haven’t even scratched the surface! 

What are your thoughts about salt? What else are salts used for? 

If you, your classmates, or your friends have more interesting information on salt and the roles it plays in our oceans, or even our lives, please share it with us! You can email us at the link below or even just tag @tuiwildlife on social media! Who know, we might even share your thoughts on our page!

And as always, if you have any questions for our handlers or ambassadors about salts or even the ocean, please feel free to ask! We’re always happy to answer questions, and if we don’t know the answer, we’ll work to find it for you! 


Activities, Videos and More!

The Eyrie is a Patreon based Newsletter dedicated to exploring the intricate and fascinating topics found within the realms of science, nature, education, and conservation. Each month, our team explores a different subject, taking the time to examine the fascinating world around us. With the (mostly) helpful perspectives of our ambassador animals and the insight from our team, this newsletter is chock full of amazing facts, intriguing concepts, and even activities or experiments you can try at home!


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