Plankton, nekton, benthos - three groups into which all aquatic living creatures can be divided. Plankton is formed by algae and small animals that swim near the surface of the water. Nekton consists of animals that can actively swim and dive in the water, these are fish, turtles, whales, sharks and others. Benthos are organisms found in the lowest layers of aquatic habitats. It includes bottom-dwelling animals, including many echinoderms, demersal fish, crustaceans, mollusks, annelids, and so on.
Types of marine life
Marine animals are divided into three groups: plankton, nekton, benthos. Zooplankton is represented by drifting animals, which are usually small in size, but can grow to quite large sizes (for example, jellyfish). Zooplankton may also include temporary larval forms of organisms that maygrow up and leave planktonic communities and join groups like nekton, benthos.
The Nekton class makes up the largest part of the animals living in the ocean. A variety of fish, octopuses, whales, moray eels, dolphins and squid are all examples of nekton. This large-scale category includes a number of very diverse creatures that are very different from each other in many ways.
What is benthos? The third type of marine animal that spends their entire life at the bottom of the ocean. This group includes lobsters, starfish, all kinds of worms, snails, oysters and many others. Some of these creatures, such as lobsters and snails, can move on their own along the bottom, but their lifestyle is so closely connected to the ocean floor that they could not survive away from this environment. Benthos are organisms that live at the bottom of the ocean and include plants, animals and bacteria.
Plankton is the most common form of life in the aquatic environment
When you imagine life in the ocean, usually all associations are somehow connected with fish, although in fact fish are not the most common form of life in the ocean. The largest group is plankton. The other two groups are nekton (actively swimming animals) and benthos (these are living organisms that inhabit the bottom).
Most plankton species are too small to see with the naked eye.
There are two main types of plankton
- Phytoplankton, whichproduces food through photosynthesis. Most of them are various algae.
- Zooplankton that feeds on phytoplankton. It includes tiny animals and fish larvae.
Plankton: general information
Plankton are the microscopic inhabitants of the pelagic environment. They are essential components of food chains in aquatic habitats as they provide food for nekton (crustaceans, fish and squid) and benthos (sea sponges). They also have a global impact on the biosphere, since the balance of the components of the Earth's atmosphere is largely dependent on their photosynthetic activity.
The term "plankton" comes from the Greek planktos, which means "wandering" or "drifting". Most of the plankton spend their existence swimming with the ocean currents. However, not all species go with the flow, many forms can control their movements, and their survival is almost entirely dependent on their independence.
Sizes and representatives of plankton
Plankton range in size from tiny microbes that are 1 micrometer long to jellyfish, whose gelatinous bell can be up to 2 meters wide and whose tentacles can extend over 15 meters. However, most planktonic organisms are animals less than 1 millimeter in length. They survive on the nutrients in seawater and through photosynthesis.
Representatives of plankton are the most diverseorganisms such as algae, bacteria, protozoa, larvae of certain animals and crustaceans. Most planktonic protists are eukaryotes, predominantly unicellular organisms. Plankton can be divided into phytoplankton, zooplankton and microbes (bacteria). Phytoplankton carry out photosynthesis, and zooplankton are represented by heterotrophic consumers.
Nekton
Nekton are active swimmers and often the best-known organisms in marine waters. They are top predators in most marine food chains. The distinction between nekton and plankton is not always sharp. Many large animals (such as tuna) spend their larval stage as plankton, while in the adult stage they are quite large and active nekton.
The vast majority of nekton are vertebrates, these are fish, reptiles, mammals, mollusks and crustaceans. The most numerous group is made up of fish, in total there are approximately 16,000 species. Nekton is found at all depths and latitudes of the sea. Whales, penguins, seals are typical representatives of nekton in polar waters. The greatest variety of nekton can be found in tropical waters.
The most diverse form of life and its economic value
This also includes the largest mammal on planet Earth, the blue whale, which grows up to 25-30 meters in length. These giants, as well as other baleen whales, feed on plankton and micronekton. the largestrepresentatives of nekton are whale sharks, which reach a length of 17 meters, as well as toothed whales (killer whales), great white sharks, tiger sharks, bluefin tuna and others.
Nekton is the backbone of fisheries around the world. Anchovies, herring, sardines usually make up one quarter to one third of the annual marine harvest. Economically valuable nekton are also squids. Halibut and cod are demersal fish that are commercially important as food for humans. As a rule, they are mined in the waters of the continental shelf.
Benthos
What is the meaning of the word "benthos"? The term "benthos" comes from the Greek noun bentos and means "depths of the sea". This concept is used in biology to refer to the community of organisms at the bottom of the sea, as well as fresh water bodies such as lakes, rivers and streams.
Benthic organisms can be classified according to size. Macrobenthos refers to organisms larger than 1 mm. These are various gastropods, bivalves, sea lilies, predatory starfish and gastropods. Organisms with sizes from 0.1 to 1 mm are large microbes that dominate the bottom food chains, acting as a biogenic utilizer, primary producer, and predator. The category of microbenthos includes organisms less than 1 mm in size, these are diatoms, bacteria and ciliates. Not all benthic organisms live in sedimentary rocks, some communities live on rocky substrates.
There are three different types of benthos
- Infauna - organisms that live at the bottom of the ocean, buried in the sand or hiding in shells. They have very limited mobility, live in sediment, are exposed to the environment, and have fairly long life spans. These include sea shells and various shellfish.
- Epifauna can live and move on the surface of the seabed to which they are attached. They live by attaching themselves to rocks or moving along the surface of sediments. These are sponges, oysters, snails, starfish and crabs.
- Organisms that live at the bottom of the ocean but can also swim in the water above it. This includes soft bottom fish - pufferfish, flounders, using crustaceans and worms as a food source.
Relationship between pelagic environment and benthos
Benthos are organisms that play a critical role in the marine biological community. Benthic species are a heterogeneous group that is the main link in the food chain. They filter water in search of food, remove sediment and organic matter, thus purifying the water. Unused organic matter settles at the bottom of the seas and oceans, which are then processed by benthic organisms and returned to the water column. This process of mineralization of organic matter is an important source of nutrients and is critical for high primary production.
The concepts of pelagic and benthic environments are interconnected in many ways. For example, pelagic plankton are an important food source for animals that live on soft or rocky ground. Anemones and barnacles serve as a natural filter for the surrounding water. The formation of the pelagic environment at the bottom is also carried out due to the molting of crustaceans, metabolic products and dead plankton. Over time, plankton forms marine sediments in the form of fossils, which are used to determine the age and origin of rocks.
Aquatic organisms are classified according to their habitat. Scientists believe that the habitat of these animals has a huge impact on their evolution. Moreover, most of them have adapted well to life in the specific environment they inhabit. What is the main difference between the groups called plankton, benthos and nekton?
Plankton are microscopic or small animals compared to the other two types. Nekton are free-swimming animals. What is benthos? It includes both freely moving and those organisms that cannot imagine their existence without the ocean floor. What about organisms that live mostly on the bottom, but can also swim - octopus, sawfish, flounder? Such life forms can be quite called nektobenthos.