Why the Dead Sea Is Dead (Or Is It?)

When you hear the name "Dead Sea," you might not picture your ideal vacation spot, yet this body of water has been attracting tourists for thousands of years. The minerals in the water are believed to offer therapeutic benefits, plus the high salinity of the water means it's super easy to float. Have you ever wondered why the Dead Sea is dead (or if it really is), how salty it is, and why so many people drown in it when you can't even sink?

Chemical Composition of the Dead Sea

The Dead Sea, nestled between Jordan, Israel, and Palestine, is one of the saltiest bodies of water in the world. In 2011, its salinity was 34.2%, which made it 9.6 times more salty than the ocean. The sea is shrinking each year and increasing in salinity, but it has been salty enough to prohibit plant and animal life for thousands of years.

The chemical composition of the water isn't uniform. There are two layers, which have different salinity levels, temperatures, and densities. The very bottom of the body has a layer of salt that precipitates out of the liquid. The overall salt concentration varies according to depth in the sea and the season, with an average salt concentration of about 31.5%. During flooding, the salinity can drop below 30%. However, in recent years the amount of water supplied to the sea has been less than the amount lost to evaporation, so the overall salinity is increasing.

The chemical composition of the salt is very different from that of sea water. One set of measurements of the surface water found the total salinity to be 276 g/kg and ion concentration to be:

Cl^-: 181.4 g/kg

Mg²⁺: 35.2 g/kg

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Na⁺: 32.5 g/kg

Ca²⁺: 14.1 g/kg

K⁺: 6.2 g/kg

Br^-: 4.2 g/kg

SO₄^2-: 0.4 g/kg

HCO₃^-: 0.2 g/kg

In contrast, the salt in most oceans is about 85% sodium chloride.

In addition to the high salt and mineral content, the Dead Sea discharges asphalt from seeps and deposits it as black pebbles. The beach is also lined with halite or salt pebbles.

Why the Dead Sea Is Dead

To understand why the Dead Sea doesn't support (much) life, consider how salt is used to preserve food. The ions affect the osmotic pressure of cells, causing all of the water inside the cells to rush out. This basically kills plant and animal cells and prevents fungal and bacterial cells from thriving. The Dead Sea is not truly dead because it does support some bacteria, fungi, and a type of algae called Dunaliella. The algae supplies nutrients for a halobacteria (salt-loving bacteria). The carotenoid pigment produced by the algae and bacteria have been known to turn the blue waters of the sea red!

Although plants and animals don't live in the water of the Dead Sea, numerous species call the habitat around it their home. There are hundreds of bird species. Mammals include hares, jackals, ibex, foxes, hyraxes, and leopards. Jordan and Israel have nature preserves around the sea.

Why So Many People Drown in the Dead Sea

You might think it would be difficult to drown in water if you can't sink in it, yet a surprising number of people run into trouble in the Dead Sea. The density of the sea is 1.24 kg/L, which means people are unusually buoyant in the sea. This actually causes problems because it's hard to sink enough to touch the bottom of the sea. People who fall into the water have a hard time turning themselves over and may inhale or swallow some of the saltwater. The extremely high salinity leads to a dangerous electrolyte imbalance, which can harm the kidneys and heart. The Dead Sea is reported to be the second most dangerous place to swim in Israel, even though there are lifeguards to help prevent deaths.

Sources:

• "Dead Sea Canal". American.edu. 1996-12-09.
• Bein, A.; O. Amit (2007). "The Evolution of the Dead Sea Floating Asphalt Blocks:Ssimulations by Pyrolisis". Journal of Petroleum Geology. Journal of Petroleum Geology. 2 (4): 439–447.
• I. Steinhorn, In Situ Salt Precipitation at the Dead Sea, Limnol. Oceanogr. 28(3),1983, 580-583.