Marine ecosystems

Leon loves diving in the ocean. He likes coral reefs the most - with all the colourful fish, sponges, and sea anemones that look almost like flowers! A coral reef consists of living elements, such as corals, other animals and algae, and depends on non-living elements, for example sunlight, sand, and temperature. Each one impacts the other. Together, they create an ecosystem.

A coral reef is an example of a marine ecosystem. This means that it is an ecosystem in, or linked to the sea or the ocean. A typical characteristic of a marine ecosystem is the high salt content in the seawater - more than 3%. This distinguishes marine ecosystems from freshwater ecosystems, such as lakes or rivers. The ocean provides a living environment that is about 9 times larger than the one on land.

This makes the ocean the largest ecosystem on Earth. It is one of the most diverse too! Apart from coral reefs, there are several other types of smaller marine ecosystems. Each of them has unique characteristics and hosts different organisms. Let’s take a look!

Ecosystems at the very bottom of the ocean are called ocean floor ecosystems. They differ from each other depending on how deep the ocean is. Where the ocean is deep, sunlight cannot reach to the very bottom, so plants or algae cannot live there. Animals in the deep sea depend on nutrients sinking from the surface. Some of the animals can generate their own light, which helps them find food or attract organisms they eat!

We don’t know much about deep ocean ecosystems because many areas are still unexplored. The closer to the shore, and the more shallow the ocean is, the more life there is on the ocean floor. This is because plants and algae can grow in shallow waters where there's plenty of sunlight. Here the ocean floor is home to oysters, crustaceans, worms, and certain types of fish. Around coastlines, the sea level changes because of the tide.

When the tide is high, the sea level rises, and the shore is covered by saltwater. When the tide is low, the sea level drops, and larger areas of the coastline become exposed. These areas are called intertidal zones. Because of the tide, conditions in the intertidal zones change very frequently. Organisms living here need to be able to withstand these changing conditions.

For this reason, many animals in the intertidal zone have protective layers, for example barnacles, mussels, crabs, or urchins. Another type of marine ecosystem is mangrove forests. These are special types of saltwater swamps that occur around sandy shorelines in warm tropical areas. The conditions here are quite harsh, and not many plants can grow in such a salty environment. But certain kinds of trees and shrubs, mangroves, are specially adapted to these conditions.

Their roots reach down into the water creating a dense root system, which protects the shore from being worn away. Mangrove forests are home to many animals, such as shrimp, crabs, birds, and sometimes even crocodiles. Another type of marine ecosystem is often formed in shallow, sheltered areas where rivers join the sea. Here, freshwater from the rivers mixes with the salty seawater, so the concentration of salt decreases. Such places are called estuaries.

This mix of fresh- and saltwater in estuaries is perfect for shellfish. Many types of fish or shrimp lay their eggs here too. Out of all the different ecosystems on the planet, marine ecosystems are the most common and widespread. But they are still the least explored. Maybe you can help discover more about them!