The exhaustive list of marine animals begins with microscopic zooplanktons and ends with extremely large whales. In between them, lie millions of species … each boasting of being quite peculiar in itself.
Rainforests of the Sea
Home to 25 percent of all marine species, coral reefs are nicknamed the rainforests of the sea.
More than a million species of plants and animals are endemic to the marine biome, which makes it the richest biome in the world in terms of biodiversity. While the World Registry of Marine Species (WoRMS) has over 200,000 species enlisted in it, the actual number is believed to be at least ten times greater than that. When we talk about marine species, we restrict ourselves to fish, reptiles, mammals, and invertebrates that dwell in oceans and estuaries. However, if we are to study the marine biome in its true sense, it is important to take into consideration seabirds and terrestrial mammals that are dependent on it for food.
The marine biome is a key component of the Earth’s ecosystem, comprising five oceans―namely the Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean, and the Southern Ocean―and several estuaries as well as millions of living organisms that inhabit them. It is the largest and most diverse biome in the world. The study of this biome and its components is known as marine biology, while the scientists who study marine life are known as marine biologists.
Marine Biome Animals
When we talk about marine life, the first thing that is likely to come to your mind is various species of fish. Some of you may also come up with the names of sea turtles, sea snakes, and marine mammals like dolphins and whales. All these names put together give a mere glimpse of the diversity in the marine biome, as the list of animals found in this biome is quite lengthy and has a wide range of species to its credit.
Species of Fish
Great White Shark
Of the 32,700 odd species of fish identified by FishBase―the global database of fish species―around 60 percent are found in oceans. These include species ranging from tiny stout infantfish to whale sharks―the world’s largest fish. Some of the most popular species include sardines, halibuts, sharks, etc., which form an important part of our diet. Additionally, there are species, like salmons and sea trouts, which frequent between seas and rivers, and deep-sea species, like lanternfish and anglerfish, which are found at depth where even sunlight doesn’t penetrate.
Some species of fish are solitary, while others live in groups known as shoals or schools. Their dietary habits are determined by their size and natural habitat. While the great white shark is the apex predator of the marine biome, there are other species, which despite being small, are pretty notorious for their aggressive traits and don’t hesitate to take on species larger than themselves.
Note: The absence of whales and dolphins in this list may come across as a surprise for many people, but one needs to understand that technically, they are mammals.
Invertebrates are typically characterized by the absence of a vertebral column. In oceans, they are usually found in the vicinity of coral reefs and hence, are often classified as coral reef animals. Examples of invertebrates in the marine biome include jellyfish, sponges, sea worms, shellfish, sea stars or starfish, squids, octopi, crabs, etc. With an average length of 39 – 46 ft., the colossal squid is the largest known invertebrate on the planet. In course of evolution, some of these species, like crabs and mollusks, have developed a hard shell (exoskeleton) as a protective covering. As in the case of various terrestrial biomes, invertebrates form a major chunk of living organisms in aquatic biomes.
The list of marine reptiles includes various species of sea snakes and sea turtles, as well as species that frequent between sea and land, such as the marine iguana and saltwater crocodile. A closer look reveals that most of the reptilian species found in oceans are oviparous, i.e., they lay eggs; sea snakes being the only exception. Sea turtles come to the land to lay eggs and thus, are often seen in shallow water close to the land. Saltwater crocodiles, on the other hand, are mostly seen in estuarine water. As for sea snakes, despite the fact that they don’t leave water, they seem to prefer shallow parts of the sea wherein they can take shelter from their predators.
Galapagos Sea Lion
Coming to marine mammals, the list includes whales, like the blue whale, gray whale, and humpback whale, as well as dolphins, seals, sea otters, walruses, sea cows, and polar bears. Unlike whales and dolphins, which live and feed in water, seals, otters, and walruses only rely on oceans for food. Statistically, there are a total of 129 species of mammals which either inhabit oceans or depend on it for sustenance.
While one may find it difficult to make sense of polar bears featuring in this list of marine species, it’s important to understand that they fit the criterion, as the definition of marine species clearly includes species that ‘depend upon the sea for sustenance’. More importantly, there is no questioning the fact that polar bears have a key role to play in the marine ecosystem in polar areas.
Northern Giant Petrel
Whether marine birds, more often referred to as seabirds, should be taken into consideration when compiling a list of marine animals is again an issue of debate. Marine biologists are of the opinion that they cannot be ignored, as they have adapted to the marine environment and play a crucial role in the ocean food chain. Some of the most popular species of seabirds are penguins, albatrosses, gulls, petrels, terns, skuas, auks, gannets, frigatebirds, etc.
Seabirds have specific adaptations, such as the presence of salt glands and waterproof plumage, which help them survive at sea. Additionally, these birds are also known for their migratory habits; the Arctic tern, for instance, plies between the north pole and south pole every year.
Other than all the animals we have discussed until now, the marine biome also has zooplankton―predominantly comprising small crustaceans and fish larvae―to its credit. Zooplankton are important because the energy transfer in the marine food web begins with them feeding on phytoplankton. The Sargasso Sea in the North Atlantic Ocean alone has more than 500 species of zooplankton. As for their world population, it is estimated to be in millions.
Like their counterparts on land, even sea animals have had to bear the brunt of our follies. Both, marine biome plants and animals are threatened by human activities like overfishing, oil drilling, marine transportation, etc. The cumulative effect of these problems has been extinction of marine lifeforms, like the Caribbean monk seal and Japanese sea lion, while several others have been left battling for their survival in the list of endangered species. The need of this hour is to come up with proper conservation measures and implement them, as any further delay and we are set to lose a huge chunk of planet’s biodiversity―something that we cannot afford to.