Almost every form of life we see today on land or in water had first emerged from marine habitat around billions of years ago. Marine ecosystems are one among the largest; the most prevalent aquatic ecosystems on Earth. Two-thirds of the total surface area of the planet is covered by marine water.
The marine ecosystems can broadly be classified into two main categories constituting 5 major marine ecosystems. Water/Pelagic environment consists of two major marine ecosystems, Neritic and Oceanic zones. Bottom/Benthic environment consists of the other three major ecosystems, Supralittoral, Intertidal/Littoral, and Sublittoral zones.
The major five marine ecosystems nurture almost half of the identified species on Earth. However, scientific estimation suggests that there may be a million more species yet to be discovered. Among the known species in marine ecosystems, Pelagic and Benthic environment sustains most of the life inside the oceans.
WHAT ARE THE 5 MARINE ECOSYSTEMS?
- Neritic Zone
- Oceanic Zone
- Supralittoral Zone
- Intertidal/Littoral Zone
- Sublittoral Zone
WHAT IS WATER/PELAGIC ENVIRONMENT?
Water/Pelagic environment covers 1300 million km^3, consisting of open ocean. It can be further divided into ecosystems based on their depth. The depth of pelagic environment varies from 3.50 km (2.17 miles) to 11 km (6.83 miles). Water environment is divided into two major ecosystems:
- Neritic Zone – The passively drifting Algae (Phytoplankton) is dominant in the Neritic Zone. It extends from a high tide mark to the continental shelf. The depth in this region is extended to 200 meters. The Algae found in this region is pigmented in the form of red, green and brown algae.
The amount of sunlight enters the Neritic waters which allow photosynthesis with the help of deep-sea organisms. Some examples of animals found in the neritic zone such as Dolphin, Polar Bear, Lobster, Marine Otter etc.
- Oceanic Zone – This region lies beyond the continental shelf. It is composed of approximately 65% of open water. Extending up to 200 meters, both Phytoplankton and Zooplankton helps marine life to survive in Oceanic Zone.
Beyond 200 meters, deficiency of sunlight makes the region inhabitable to support plant and marine life. However, there are creatures surviving around the hydrothermal vents that expel superheated water that is rich in minerals.
WHAT IS BOTTOM/BENTHIC ENVIRONMENT?
Starting from the shoreline, benthic environment being an ecological region reaches the bottom of the ocean, lake or river. Contrary to its lifeless appearance, this region plays a vital role in aquatic life.
Abundance of microscopic organisms in this region helps the bottom feeding animals to survive. The organisms found in the benthic environment are often referred to as Benthos. Benthos acts as a source of food to not just aquatic animals but humans too.
In benthic environment, the temperature changes due to the industrial operations and use of dams can severely affect Benthos. Based on the types of marine ecosystems, a benthic environment can be classified into three categories:
- Supralittoral Zone – Also known as Splash Zone, this area lies above the high tide line on the coastlines and estuaries. This region lies from low water line to the edge of the continental shelf.
In Supralittoral zone, cyanobacteria, crabs, green algae, lichens, snails and some of the marine vegetation are some of the dominant species found here. The organisms living in this region must constantly resist the lack of water. This region predominantly has high salt content gathered by the spray of tides.
- Intertidal/Littoral Zone – This is a region between high and low tides that constantly resist harsh and unfavorable habitat. This zone is exposed to water during high tides and air during low tides, which is the defining characteristic of the Intertidal zone.
The organisms that have adapted to life in the Intertidal zone have an advantage of the abundant supply of food. The longshore high tides in this region can go up to a depth of 5-10 meters. The algae and other intertidal plants grow in abundant sunlight and act as a food source for animals.
- Sublittoral Zone – Lying between the low tides and the continental shelf, this region has a range in depth of between 150-300 meters. Unlike the Intertidal zone, this region of the marine ecosystem is always submerged in water. The primary characteristics of this region are red and brown algae.
Due to its functional ability to have abundant sunlight, sublittoral zone hosts almost all marine life. Low water pressure makes the plant and fish life to survive in this region.
ARE THERE OTHER MARINE ECOSYSTEMS OTHER THAN THE DISCUSSED ONES?
Majority of the marine ecosystems dwells within five major ecosystems. But, there are several other sub-categories of marine ecosystems that exist slightly away from the oceans. Some of the examples of such marine ecosystems are:
WHAT ARE THEY & WHERE ARE THEY FOUND?
Mangroves are mainly found in tropical deltas, estuaries, and lagoons. Trees are the most vital characteristics of mangroves. Lagoons are the shallow water body separated by reefs or barrier island from the large water bodies such as oceans.
The only distinction between lagoons and estuaries is that lagoons often restrict themselves from any freshwater inflow. Whereas, lagoons that have a regular inflow of freshwater is often referred to as an Estuary.
HOW MARINE ECOSYSTEMS ARE AFFECTED?
- Water pollution is one of the biggest threat to marine ecosystems. It can be caused by a careless rendering of industrial waste, a dramatic rise in CO2 levels gave rise to ocean acidification.
- Coral bleaching occurs when conditions such as temperature, light, nutrition start to change and resulted in the whitening of coral.
- Rapid sea level rise due to global warming.
- Oil Spills results in pollution and the death of millions of marine species every year.
WHAT ARE THE POSSIBLE SOLUTIONS TO PROTECT MARINE LIFE?
- Reduce plastic usage that would prevent thousands of species to die every year.
- Influence change in the community for an overall advancement of lifeforms on Earth.
- Avoid trawling during fishing.
WHAT IS THE IMPORTANCE OF MARINE ECOSYSTEMS?
Most vital exchange of gases for human survival is done by Marine Ecosystems. They secrete as much carbon dioxide as possible and help us breathe fresh oxygen. Phytoplankton alone provides 55% to 75% oxygen on Earth.
HOW DIVERSE IS THE MARINE ECOSYSTEM?
More than half of the species on Earth are found in marine ecosystems. Approximately 700,000 to 1 million species are found in the marine ecosystems.