Baltic Sea biodiversity – it is time to bring back the balance

Biodiversity in the Baltic Sea – why we need to bring back the balance
Key learning

Biodiversity underpins all life, from genes to ecosystems, and can encompass the evolutionary, ecological, and cultural processes that sustain life. But, what is biodiversity, and why should we care about it?

This article will give you a basic overview of biodiversity and its importance. In the context of the Baltic Sea, we will also highlight concepts like habitats and food webs.

When you dive into the Baltic Sea, you realize that your eyes do not hurt as much as when you, let us say, throw yourself into the waves of the Mediterranean Sea.

The difference is the level of salt in the water. And in the Baltic Sea, the water is brackish, which means that the water is saltier than freshwater but not as saline as in other oceans.

However, the unique salinity in the Baltic Sea not only affects the sensation in your eyes. But it also links to the variety and number of animals and plants in the sea. What scientists refer to as biodiversity.

And due to the low salt levels, species diversity is lower in the Baltic Sea than in many other seas. Still, it has a remarkable mix of life habitats, resulting in a unique biodiversity.

The water in the Baltic Sea is known as brackish. Rivers and streams in the north supply fresh water and mix with the saltier water from the North Sea. This creates a salinity gradient in the Baltic Sea, influencing biodiversity, habitats and food webs.
The water in the Baltic Sea is known as brackish. Rivers and streams in the north supply fresh water and mix with the saltier water from the North Sea. This creates a salinity gradient in the Baltic Sea, influencing biodiversity, habitats and food webs.

This article will give you a basic overview of biodiversity and its importance. In the context of the Baltic Sea, we will also highlight concepts like habitats and food webs.

What is biodiversity?

The term biodiversity stems from biological diversity. And it is the variety of all living species in a given area – including plants, animals, bacteria, and fungi.

Biodiversity underpins all life, from genes to ecosystems, and can encompass the evolutionary, ecological, and cultural processes that sustain life.

The Baltic Sea is home to many species. Birds, mammals, big and small fishes, crustaceans and molluscs, algae and seagrass. Even micro species like zooplankton, phytoplankton and bacteria. All of them are part of the biological variety and variability of life in the Baltic Sea.
The Baltic Sea is home to many species. Birds, mammals, big and small fishes, crustaceans and molluscs, algae and seagrass. Even micro species like zooplankton, phytoplankton and bacteria. All of them are part of the biological variety and variability of life in the Baltic Sea.

Why do we need to care for biodiversity?

As you can imagine, biodiversity is the very foundation for life, including human life. And a healthy and dynamic nature cleans our water, purifies our air, and maintains our soil. It provides us with materials we need in our lives, and it helps to regulate the climate.

In a way, the vibrant environment in the ocean constantly improves the health of our planet.

With this in mind, let us now bring the discussion of biodiversity and jump into the Baltic Sea.

A unique sea – connecting people

The Baltic Sea is an extension of the Atlantic Ocean and the North Sea, enclosed by Sweden, Denmark, Germany, Poland, Latvia, Lithuania, Estonia, Finland, and Russia. The sea connects almost 149 million people in the bordering countries, and it is a source of human livelihood.

As long as people have lived in the area of the Baltic Sea, it has provided a strong connection between the nine neighbouring countries. Today we share the challenge of managing pressures from our activities and reducing the impacts.
As long as people have lived in the area of the Baltic Sea, it has provided a strong connection between the nine neighbouring countries. Today we share the challenge of managing pressures from our activities and reducing the impacts.

Rivers and streams supply fresh water and oxygen to the Baltic Sea. Mixed with the saltwater from the North Sea – via a narrow strait between Sweden and Denmark – it makes the Baltic Sea one of the largest brackish water areas in the world.

Habitats – the backbone of biodiversity

As already mentioned, even if the environment in the Baltic Sea is less salty than in other oceans, it still houses a vast mix of habitats.

So what is a habitat?

Temperature, sea depth, salinity, and distance from the shore are examples of factors that determine the types of plants and animals living in an area – from shallow bays to sandy or rocky seafloors to open water.

These areas, or underwater landscapes, are what we refer to as habitats.

And they are the pillar of an ecological system – nurturing and evolving the life that creates and sustains biodiversity in the Baltic Sea.

At first, when you look beneath the surface, it seems deserted. But if you look more carefully, it is buzzing with life.

So let us explore those habitats, which usually are divided into two types,

Seabed, or benthic, habitats.
Open water, or pelagic, habitats.
An underwater landscape is comparable to a block in your city. And in a block (or habitat) live many organisms with unique features and functions. Together they make up the underwater community where they live. Habitats are split into two main categories - benthic and pelagic - and form the backbone of biodiversity.
An underwater landscape is comparable to a block in your city. And in a block (or habitat) live many organisms with unique features and functions. Together they make up the underwater community where they live. Habitats are split into two main categories – benthic and pelagic – and form the backbone of biodiversity.

Seabed habitats

We can easily relate to the so-called benthic habitats since they make up the seafloor.

The first thing that comes to mind is beaches full of fine-grained sand washed by the waves. And the shallow bays, where fish enter to spawn protected by the seagrass, and insects lay their eggs in the bottom sediments.

Larger fish and wading birds gather in such habitats to feed on the plentiful fish and invertebrates.

The benthic habitats or seabeds of the Baltic Sea come in different kinds. You can find soft bottoms such as seagrass, sand and algae beds, and hard bottoms made of stone or gravel. These differences create an even richer environment that improves the biodiversity of the Baltic Sea.
The benthic habitats or seabeds of the Baltic Sea come in different kinds. You can find soft bottoms such as seagrass, sand and algae beds, and hard bottoms made of stone or gravel. These differences create an even richer environment that improves the biodiversity of the Baltic Sea.

In the reef-like hard-bottom habitats, you find bladderwrack accommodating numerous small animals. Many are crustaceans, such as the Baltic prawn.

Going further down, passing by brown and red algae, rocky surfaces are covered by mussels and polyps.

Pelagic habitats

In the open water of the Baltic Sea, the environmental conditions are pretty much the same everywhere. Therefore, the diversity of larger plants and animals is lower here than in benthic areas.

On the other hand, the open water is a habitat for many tiny organisms, the so-called plankton. Which includes both plant and animal species. These phyto- and zooplankton are found from the surface and several meters down.

Then again, even deeper, swim cod, herring and other fish species.

The Baltic Sea's pelagic habitats or open water are home to large species such as seals and cod. But also home to micro species like plankton, which are especially abundant in the Baltic Sea.
The Baltic Sea’s pelagic habitats or open water are home to large species such as seals and cod. But also home to micro species like plankton, which are especially abundant in the Baltic Sea.

Food webs – the ocean grocery store

There are about 2 700 larger species in the Baltic Sea and innumerable smaller (microscopic) species. And they all have to eat.

Most species depend on each other in an ingenious web of food chains. Where a set of animals and plants are linked to each other – and where big eat small.

And the tiny plankton plays an essential part as they make the base for the entire food web. For example, many fishes feed on zooplankton and smaller fish. Who, in turn, are eaten by larger fishes like cod and mammals like seals.

Keystone species is the name given to a specific organism whose existence profoundly alternates the ecosystem. And since the food web is simple in the Baltic Sea, it is more vulnerable. If one keystone species decreases in number (or even disappears), other species will be affected.
Keystone species is the name given to a specific organism whose existence profoundly alternates the ecosystem. And since the food web is simple in the Baltic Sea, it is more vulnerable. If one keystone species decreases in number (or even disappears), other species will be affected.

The food web is simple in the Baltic Sea compared to other seas. There are only a few species within each group, making the system more vulnerable.

If a species disappears, it is not sure that there is a substitute that can fulfil its function in the food chain. So changes in one species will impact others.

Threats to biodiversity

As you have seen, life in the Baltic Sea is fascinating yet fragile. There is a constant dance of, and for, life. A delicate order that sustains biodiversity at its core.

Unfortunately, human activities are putting biodiversity at risk.

Eutrophication happens when the water gets overly enriched with nutrients, leading to excessive growth of algae or plankton. It is one of the biggest challenges in the Baltic Sea since it affects the quality of the water and, therefore, the biodiversity.
Eutrophication happens when the water gets overly enriched with nutrients, leading to excessive growth of algae or plankton. It is one of the biggest challenges in the Baltic Sea since it affects the quality of the water and, therefore, the biodiversity.

And with increased pressure on biodiversity – including unsustainable use of resources and pollution – comes fragmented food chains, habitat loss and climate change. All in all, changing the conditions for human life negatively.

So, there are many reasons why we should care about biodiversity.

All neighbouring countries to the Baltic Sea share the challenge of managing pressures from human activities and reducing their impacts. And how we act in our everyday lives can sustain or drain biodiversity.

Time to bring back balance

Okay – we have discovered that biodiversity is the variety of plant and animal life in a particular region. And that it is essential because it helps maintain the balance of nature and ensures that there is food and other resources for all species.

Without biodiversity, ecosystems would collapse, and many species would become extinct.

At Voice of the Ocean, we understand that it is time to bring back balance in the Baltic Sea. And we believe that cross-sector collaboration is the key.

Therefore, we support and promote science and communication regarding the sea and its dynamic processes.

To contribute to the sound management of the ocean, we help scientists understand the sea as a system. This is done by providing unique data, research methods, and infrastructure.

By spreading knowledge about the ocean’s multi-faceted nature, culture, and history, we contribute to a broader understanding of the importance of and interaction with the sea.

Hand in hand with science and technology, the Voice of the Ocean foundation creates tools that seek to support the research and find ways to improve the state of the Baltic. For example, in our data gathering project SAMBA, we aim to change the landscape of ocean observation in the Baltic Sea.
Hand in hand with science and technology, the Voice of the Ocean foundation creates tools that seek to support the research and find ways to improve the state of the Baltic. For example, in our data gathering project SAMBA, we aim to change the landscape of ocean observation in the Baltic Sea.

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Further reading

Center for Biodiversity and Conservation
Livet i havet (in Swedish)
HELCOM – Baltic Marine Environment Protection Commission
United Nations
WISE Marine – Marine Information System for Europe
Baltic Sea Action Group