Marine ecosystem

The ocean is very big.

Many places live in the sea.

Trees called mangroves grow near the coast. Their roots help stop the land from washing away. They also give food to many animals.

Some water is a mix of fresh and salt. This happens where rivers meet the sea. These places are called estuaries.

We must keep the water clean.

The ocean is huge. It covers more than 70% of Earth. Most of our water is in the sea.

Marine ecosystems are salty. They have much more salt than fresh water. These systems have many different parts.

Some areas are very deep. We call the open ocean the oceanic zone. Sharks and whales live there. Other animals live on the bottom. This is the benthic zone.

Near the coast, life is busy. Mangroves are trees that grow in salty water. Their thick roots protect the land.

Seagrass meadows are like underwater fields. They provide food for turtles and fish. They also help stop climate change.

Kelp forests are made of large brown algae. They create a home for many sea creatures.

Estuaries happen where rivers meet the sea. The water there is brackish. This means it is a mix of fresh and salt water.

Humans use the ocean for food and jobs. But pollution and overfishing can hurt these places. We must work to protect life below water.

Marine ecosystems are the largest aquatic systems on our planet. They exist in waters with a high salt content. This is different from freshwater systems which have less salt. These salty waters cover more than 70% of Earth's surface. They also hold more than 97% of all the water on Earth. Most of our habitable space is found in these oceans.

These ecosystems work in many different ways depending on depth. The oceanic zone is the vast and open part of the sea. Animals like whales, sharks, and tuna live in this area. Below them is the benthic zone, which is the sea floor. Many invertebrates live on these bottom surfaces. There are also intertidal zones between the high and low tides.

Scientists study many different types of coastal habitats. Coral reefs are famous and include the Great Barrier Reef. Mangroves are trees that grow in low-oxygen soil near coasts. They have thick roots that help protect the land from storms. Seagrass meadows are like underwater fields that provide food for turtles. Kelp forests are made of large brown algae called macroalgae.

Nature has many specific numbers and facts to note. Seawater has an average salinity of 35 parts per thousand. Mangroves store about 34 million metric tons of carbon every year. Seagrass meadows are being destroyed at two football fields every hour. Estuaries are very important for people and cities. In fact, 22 of the 32 largest cities are on estuaries.

Marine life is closely linked to how humans live. Many people rely on the ocean for food and jobs. However, human actions can create hard jobs for these ecosystems. Overfishing and pollution are major threats to ocean stability. Climate change also causes ocean acidification, which changes water chemistry. Because of this, the United Nations set a goal called "Life below water."

Marine ecosystems are the largest aquatic systems on our planet. They exist in waters with a high salt content. This distinguishes them from freshwater ecosystems, which have lower salinity levels. These salty waters cover more than 70% of the Earth's surface. They account for more than 97% of the total water supply on Earth. Furthermore, they provide 90% of the habitable space on our planet.

The physical environment of the ocean is divided into several distinct zones. The oceanic zone is the vast, open part of the sea. This area is home to large animals like whales, sharks, and tuna. Below this lies the benthic zone, which consists of the substrates or surfaces on the sea floor. Many invertebrates live in this bottom layer. There is also the intertidal zone, which is the area between high and low tides.

Coastal environments create specialized habitats with unique biological communities. Coral reefs are famous examples, such as the Great Barrier Reef. These reefs are made of large coral colonies living in symbiotic relationships. Mangroves are trees or shrubs that grow in low-oxygen soil near tropical coastlines. They use adaptations like salt excretion and root aeration to survive. Their dense roots help protect coasts from erosion caused by waves and tides.

Other specialized habitats include seagrass meadows and kelp forests. Seagrasses are plants that evolved from marine algae that returned to the ocean 100 million years ago. These meadows provide food and refuge for species like seahorses and turtles. Kelp forests are formed by brown macroalgae found in temperate and polar waters. These forests can influence coastal oceanographic patterns. However, they are threatened by overfishing, which can lead to overgrazing by herbivores.

Estuaries and lagoons represent different ways water interacts with the land. Estuaries occur where rivers meet the ocean, creating brackish water. This water is a mix of fresh and salt water. Estuaries are highly productive and support many human activities. In fact, 22 of the 32 largest cities in the world are located on estuaries. Lagoons are areas separated from the ocean by sandbars or coral reefs. They can be coastal or atoll lagoons, which are circular reefs surrounding deep water.

Salt marshes serve as a vital transition between the ocean and the land. The soil in these marshes often contains peat, which is decomposing plant matter. This peat can create hypoxic conditions, or low oxygen levels, in the water. These conditions allow specific bacteria to grow, often creating a sulfurous smell. Salt marshes are divided into the low marsh, high marsh, and the upland border. They are incredibly productive, supporting more than 75% of fishery species.

Human activity presents significant challenges to the stability of these systems. Unsustainable exploitation, such as overfishing, unbalances the food web. Pollution and climate change are also major threats. The ocean absorbs much of the carbon dioxide that causes global warming. This leads to ocean acidification, which changes the chemistry of the water. Because of these risks, the United Nations established Sustainable Development Goal 14. This goal, titled "Life below water," aims to conserve and sustainably use marine resources.