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20 Characteristics of the Sunlit Zone in the Ocean

by Fitriani

The sunlit zone is also known as the photic or the euphotic zone in the ocean. This sunlit zone is the region of the ocean water that receives the most light from the sun. It’s important to the oceans because it helps carry out photosynthesis and feed most of the marine animals. Read these 20 Characteristics of the Sunlit Zone in the Ocean to know more about how important the zone is.

1. Receives the Most Sunlight

The sunlit zone is the upmost layer of the ocean water. It is the first surface where the sunlight hits the water. The photic zone serves as a gateway for all sorts of useful light and nutrients to reach into the deeper parts of the oceans where many marine creatures also live.

2. Photosynthesis Happens Here

Since the sunlit zone is the only area with the most sunlight, it is where photosynthesis occurs for most of the time. Photosynthesis can happen successfully in the zone. Thus, many marine creatures can still flourish as they solely rely on the process.

3. Reaches Certain Depths

There is a limitation on the depths of the water where it can be categorised as the sunlit zone. Apparently, the sunlit zone is around 200 metres deep into the water. Beyond that amount of depth lies the disphotic zone. However, that depth can vary depending on how clear the water is from the surface.

4. Source of Nutrients for Aphotic Zone

Most of the ocean’s nutrients are made up in the sunlit zone. These nutrients will feed the creatures that live beyond the zone. So, those that live in disphotic and aphotic zones can continue living by eating from any materials that flow down to their regions. Those zones heavily depend on the sunlit zone to survive.

5. Marine Plants Live in the Sunlit Zone

A wide array of types of ocean vegetation and all sorts of plants can grow in the sunlit zone. These plants include kelp, plankton, seaweed and even mangroves. The body structure of these plants are already modified to enable them to float in the zone. Moreover, they have that special ability to carry out photosynthesis. Thus, they also serve as diet to the marine animals.

6. Various Marine Animals are Found in the Zone

Plenty of marine animals live in the sunlit zone. These aquatic animals include all kinds of jellyfish, whales, fish and even sharks. Most of these creatures also find a way to adapt with the zone. The upper part of their bodies is darker then the lower one. This is to avoid hovering predators to come after them.

7. Perfect Condition for Marine Lives

The sunlit zone provides the perfect condition for marine lives. The temperature along with the water pressure of the ocean water is suitable for many creatures. A lot of marine plants and animals find it easy to adapt in the zone. It has the largest source of food among other layers of the oceans.

8. Temperature Variety

The temperature in the sunlit zone can actually varies. It all depends on the season and the month. In the month of July and during the long winter season, the temperature reaches around 22 degrees Celcius. On the other hand, in January and the Summer season, the temperature rises up to 27 degrees Celcius. Read more about Characteristics of Ocean Temperature

9. Rainfall Rate

The rate of rainfall in the sunlit zone also varies. The sunlit zone will get additional water from the rain depending on which months it happens. Between the months of April to October, the rain is around 1 meter because it’s the dry season. But in the wet season, which is between November and March, the rainfall can be around 2 meters. Read more about Causes of Ocean Tides Rise and Fall

10. Threatened by Human Waste

The sunlit zone is the most exposed layer of the ocean to human civilisations. It is under threat by all sorts of waste that humans have created. These waste heavily pollute the ocean. The ocean pollution includes plastic which takes decades to degrade. Other pollution could be from chemical contaminants, styrofoam or cans.

11. Threatened by Human Activities

Besides being threatened by human waste, the sunlit zone is also threatened by human activities. They include oil drilling or using explosives to catch more fish. All those will cause damage to the sunlit zone. The water will become toxic and murky, which will make it hard for sunlight to penetrate the water. Read more about  Human Impacts on the Great Barrier Reef

12. Make the Main Producer in the Food Chain

The most important and main producer in the marine food chain is the phytoplankton. Phytoplankton grows best in the sunlit zone. They can get adequate amount of sunlight in the zone. The zone gives the perfect condition for this main producer to thrive. Read more about Functions of the Phytoplankton in Ocean Ecosystem

13. Visibility Depends on Water Clarity

The visibility of the sunlit zone depends on the water clarity. Some sea water can get murky due to pollution, sands or even seaweed. Visibility and clarity are important characteristics of the sunlit zone. They help people and marine creatures to navigate through the water.

14. Home to the Coral Reefs

Coral reefs live in the sunlit zone. Coral reefs are important to the ocean ecosystem and can affect the climate of the world. Close to the coral reefs, there are also rocks and sands. In the sunlit zone, they are important in providing a shelter or a hiding place for marine creatures from their predators. You may want to read about Effects of Coral Reefs Destruction

15. Helped by the Ocean Currents to Distribute Nutrients

Surface currents happen in the sunlit zone. These currents help to distribute nutrients to all parts of the world’s oceans. There is also a specific ocean currents called upwelling that helps to rotate nutrients. Food from the sunlit zone is brought down to deeper water through upwelling. Read more about  Effects of Ocean Currents on Economic Activities

Others (16-20)

Below are more characteristics that are useful to know.

  • Provide Recreational Activities: Swimming, snorkeling and fishing.
  • Affected by Tides: Visible during low tide and under water for high tide.
  • Vulnerable: Marine creatures are vulnerable to death in the zone as they more exposed.
  • Affected by Clouds: They affect the amount of sunshine that reaches the zone.
  • Covers Most Ocean Regions: Around 25% covers the ocean regions.

Knowing these characteristics of the sunlit zone will help you understand how crucial it is to the marine ecosystem. Without the sunlit zone, the whole marine creatures would die out.

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