Marine ecosystems are aquatic environments with high levels of dissolved salt. These include the open ocean, the deep-sea ocean, and coastal marine ecosystems, each of which has different physical and biological characteristics. Marine ecosystems are defined by their unique biotic (living) and abiotic (nonliving) factors. Biotic factors include plants, animals, and microbes; important abiotic factors include the amount of sunlight in the ecosystem, the amount of oxygen and nutrients dissolved in the water, proximity to land, depth, and temperature.
Sunlight is one of the most important abiotic factors for marine ecosystems. It’s so important that scientists classify parts of marine ecosystems—up to three—by the amount of light they receive. The topmost part of a marine ecosystem is the euphotic zone, extending down as far as 200 meters (656 feet) below the surface. At this depth, there is sufficient light for regular photosynthetic activity. Most marine life inhabits this zone. Below the euphotic zone is the dysphotic zone, which can reach from 200 to as deep as 1,000 meters (656 to 3,280 feet) below the surface. At these depths, sunlight is still available, but only enough to facilitate some photosynthesis. Below the dysphotic zone lies the aphotic zone, which does not receive any sunlight.

Types of Marine Ecosystem

Marine ecosystems types include open deep sea, salt water wet-land, coral reefs, estuary, mangroves, sandy beach, kelp forest, polar marine and rocky marine ecosystem

Open Marine Ecosystem:
Whenever you think of the marine ecosystem, the first picture that comes to your mind is the open water surface. This open water surface is known as the marine ecosystem; This is the upper layer of the ocean where sun rays reach quite easily.
The open marine ecosystem extends up to 150 meters from the ocean surface. The open marine ecosystem provides habitat to various sea creatures such as plankton, algae, whales, jellyfish, etc.

Deep-Sea Marine Ecosystem:
The ecosystem deep inside the oceans at its floor is known as the deep sea marine ecosystem. Deep-sea marine ecosystem inhabiting various animal species in the seabed up to 1000 meters depth underwater.
Sunlight is one of the big challenges to penetrate at the seafloor; however, the species have adapted the marine environment of this region. A huge range of animal species is found in deep-sea marine ecosystems such as squids, fishes, elephant seals, sperm whales, crabs, worms, some sharks, etc.

Coral Reef Marine Ecosystem:
Coral reefs are special type of marine ecosystem found in the seafloor. This ecosystem is mostly found in tropical waters and is quite a productive ecosystem found on the Earth. The coral reefs are the skeleton made up of limestone i.e., calcium carbonate. The coral reef ecosystem provides food and shelter to almost ¼ of marine water species. Coral reefs attract exotic color fishes like sponges, snails, seahorses, sometimes large animals like sharks & dolphins, etc.

Saltwater Wetland Marine Ecosystem:
The coastal areas of oceans and seas are known as the saltwater wetland ecosystem. The saltwater wetland marine ecosystem is again classified into two types – saltwater swamps and salt marshes.
Saltwater swamps are regions dominated with trees, whereas salt marshes are covered with grasses. Commonly found water species of saltwater wetland ecosystem are amphibians, reptiles, some migratory birds, shellfishes, few fishes, etc.

Estuary Marine Ecosystem:
The area around the river mouth where it merges with marine water is usually termed as an estuary marine ecosystem. The salinity in this ecosystem varies with the tides. The estuary ecosystem does not support a variety of species.
Mostly the species of the neighbouring ecosystem are found in the Estuary marine ecosystem. This ecosystem also plays an essential role in nurseries for various kinds of fishes, shrimps, etc.

Mangrove Marine Ecosystem:
In some tropical and sub-tropical coastal regions, a special type of saltwater swamp is found, which is known as mangroves. Mangrove swamps are home for special types of trees that can survive in the saline ecosystem.
These mangroves are characterized by a special kind of roots to absorb oxygen to survive. The roots are extended above the water surface. Mangrove ecosystem provides shelter to various species such as shrimps, jellyfish, birds, sponges, crabs, fish, crocodiles, etc.

Sandy Beach Ecosystem:
Sandy’s ecosystem is quite poor in terms of biodiversity as compared to different marine ecosystems. The environment in the sandy beach ecosystem varies a lot. However, the species that are found in the sandy beach ecosystem are very much adapted to a constantly variable environment.

Kelp Forest Marine Ecosystem:
The kelp forest ecosystem is found in comparative cooler water. The average temperature of this ecosystem ranges from 42-72 degrees Fahrenheit with depth up to 60-90 feet.
Kelp forest ecosystem supports various animal species such as seabirds, shorebirds, invertebrates (like crabs, sea stars, snails, etc.), fishes, mammals (like sea lions, seals, whales, sea otter, etc.

Polar Marine Ecosystem:
As the climate of Polar Regions is extremely cold; thus, the temperature of this type of marine ecosystem is also too cold. The species found in the polar marine ecosystem have adapted to the adverse climatic conditions of this region.
The most common species found in the polar marine ecosystem includes planktons, algae, birds like penguins, polar bears, seals, walruses, etc.

Rocky Marine Ecosystem:
The rock shores, rock cliffs, boulders, tide pools, etc. combine to make rocky marine ecosystems. The biodiversity of rocky marine ecosystem generally have species like lichens, birds, invertebrate (lobsters, urchins, barnacles, sea stars, sea squirts, seal, etc.

The marine ecosystem is a unique ecosystem that supports various plant and animal lives. All these species set an excellent example of a great food chain as compared to other ecosystems.
The sad part is that we are spoiling such an amazing ecosystem by polluting it through disposing of unwanted wastes. We are disposing of our wastes into the oceans and seas that are affecting the marine ecology big time.