Tales From The Baltic: The Baltic Sea - Past, Present, and Future
Updated: Sep 5
Modern technology allows us to easily find information about the history of any region. We can visualize what it looked like thousands and even millions of years ago and how it changed over the decades to finally be what we know today. This knowledge is acquired by analyzing data from sediment samples taken from the ground. This was the method used to establish the history of the Baltic Sea. Even though this particular sea is young, being only about 8,000 years old, it still has its own history and unique characteristics, which will be discussed in this article.
The Baltic Sea was first a region covered entirely by an ice sheet. 20,000 years ago the ice glaciers originating from Scandinavia started spreading east and south, deepening the region by dragging large rocks and smaller pieces of stone and clay. The ice slowly melted, filling the created basin with water and forming what is now known as the Baltic Ice Lake.
With the ice melting, the basin continued to fill with water until it started to overflow, causing the excess freshwater to travel directly into Skagerrak (strait between Denmark, Norway, and Sweden). When the outflow finally stopped, seawater was able to reach the lake through the newly created mid-Swedish channel. That is when the salinity levels allowed the bivalve Yoldia to flourish, thus creating the name Yoldia Sea, lasting a short period of time.
The next step in its history was the Ancylus Lake period - a time when the freshwater basin covered an area larger than today’s Baltic Sea. This period was also relatively short, as about 8,000 years ago, seawater flowed into the lake, creating what we know today - the Baltic Sea.
So, what makes this particular sea unique? The basin itself is about 1600 km long, with an average depth of 55 metres, the deepest point reaching 459 metres. It is one of the largest brackish inland seas by area. This means that this sea’s water contains more salinity than that of freshwater, but less than that of seawater. This particular characteristic is one of the most important pillars of shaping its biodiversity. Unlike other seas, the Baltic Sea has an exceptionally low biodiversity. Low salinity is caused by many freshwater points of flow (rivers) and narrow connections to the salty ocean. This means that most marine species cannot survive because the water is too fresh, and most freshwater species cannot survive because it is too salty. Therefore, there are a limited number of adaptable species that can thrive in this basin. The relatively young age of this sea also means that species have not had enough time to fully adapt to these unique conditions.
The Baltic Sea is shallow and holds a relatively small volume of water, causing it to be highly sensitive to temperature changes and pollution. Any pollutants and chemicals that enter the sea remain trapped inside for decades - the narrow connection to the open ocean means that water exchange is extremely slow, taking it roughly 40 years to flush out. When it comes to tides, they are usually less than 10 centimeters, which makes it difficult to wash away debris and mix nutrients, having to rely on wind-driven currents to move water.
On top of that, the Baltic Sea contains some of the largest human-caused marine dead zones in the world. In these zones, benthic life suffocates and dies, leaving an underwater oxygen dead zone populated only by anaerobic bacteria.
The Baltic Sea is one of the most unique seas. Its low biodiversity doesn’t make it interesting for many marine biologists, however, many who decide to appreciate its beauty find that it has much more to offer than it shows. From its history to the species living in it and to many historical wonders that hide beneath it, in this series we will slowly unravel its beauty, hoping to shed light on this undermined basin.
Tales from the Baltic - a vow to the currents that carried my childhood.
Directories / Credits
Citation No. 1: “The Origin of the Baltic Sea”, Written by Robert Spielhagen, and Published at an Unknown Date. Credit to GEOMAR.
Citation No. 2: “State and Evolution of the Baltic Sea (1952-2005)”, Written by Rainer Feistel, Günther Nausch, and Norbert Wasmund, and Published in 2008. Credit to John Wiley & Sons.
Citation No. 3: “Treatise of Marine Ecology and Paleoecology - Chapter 24: Baltic Sea”, Written by Sven G. Segerstråle, and Published on December 1st, 1957. Credit to The Geological Society of America.
Citation No. 4: “Water in motion”, Written by Unknown, and Published at an Unknown Date. Published by MarineFinland.
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