KNOW YOUR POSITION
The painting depicts a food web of the ocean, and every creature in this painting has a role to play in this complex food web based on their trophic level, which is their position in the food web.
Producers
Plankton are aquatic organisms that are unable to swim effectively against currents. There are two types: zooplankton and phytoplankton. Phytoplankton or plant plankton serve as the chief producer in the oceans. They are mostly green due to having chloroplasts, which enables them to carry out photosynthesis. They drift in the ocean's surface to take in sunlight.
Low-level consumers
Zooplankton or animal plankton comprise of various types of small animals such as fish fry, small invertebrates and their larvae. They usually feed on phytoplankton, which are generally smaller.
Corals get their food from algae living in their tissues or by capturing and digesting prey, especially plankton. Most reef-building corals have a unique partnership with tiny algae called zooxanthellae. The algae live within the coral polyps, using sunlight to make sugar for energy, as well as providing color to the corals.
Barnacles are small crustaceans that feed on plankton they sweep from the water with their fan-like feet in a process called suspension feeding. Barnacles usually attach themselves temporarily to a hard surface such as a rock or a large animal such as a whale or a turtle's shell.
Benthic organisms include a wide range of animals, plants, and bacteria from all levels of the food web. such as starfish, sea urchins, clams, worms, oysters, mussels and nudibranchs. They feed on other organisms on the ocean floor.
Mid-level consumers
In the ocean, many different types of fish fill in various ecological roles in the food web. Larger fish such as groupers usually prey on other smaller fish. Tropical fish feed on a wide range of organisms. Some tropical fish such as parrotfish and surgeonfish feed on coral all day, eating not only the hard calcium carbonate skeleton, but also the soft polyps that cover the skeleton and the zooxanthellae that live inside them.
Jellyfish play an essential role in the ocean’s food chain. Jellyfish eat many different types of things, such as phytoplankton, zooplankton, fish eggs, fish fry, and the planktonic eggs and larvae of many different kinds of marine invertebrates. They do not actively chase down prey but instead prefer to catch whatever is within reach. In turn, jellyfish are a significant part of larger sea creatures’ diets.
Octopuses feed on crabs, clams, snails, small fishes, and even other octopuses. Octopuses are carnivores, and they actively forage or hunt their prey. What octopuses eat depends on what species they are and where they live.
Crustaceans are known to have broad diets that include a variety of food sources. Crustaceans are omnivores, although some species eat algae and others like crabs and lobsters are predators and scavengers of other animals including fish, clams, mussels, and sea urchins.
Higher-level consumers
Sea turtles are placed in a higher trophic level in the food web than most fish. What a sea turtle eats depends upon the species. Some are omnivores, eating a variety of plants and animals, while the hawksbill and the leatherback are specialists, subsisting primarily of sponges (hawksbills) and jellyfish (leatherbacks). The turtle in the painting is a green sea turtle, which diet changes with age: Juveniles are omnivorous, but adults are strictly herbivorous.
Sea lions are marine predators that eat fish, squid, crabs, octopus and clams. They feed mainly offshore in coastal areas. Many species will switch prey depending upon the season or what type of food is most abundant.
The ocean sunfish is one of the heaviest bony fish in the ocean. Their food of choice is jellyfish, though genetic analysis reveals that sunfish are actually generalist predators that consume largely small fish, zooplankton, squid, and crustaceans, with jellyfish and salps making up only around 15% of its diet. This range of food items indicates that the sunfish feeds at many levels, from the surface to deep water, and occasionally down to the seafloor.
Apex consumers
Apex predators occupy the highest trophic level in the food web. They are usually tertiary or quaternary consumers.
The shark is among the ocean's apex predators. The shark in the painting is a great white shark, the largest and most powerful predatory shark. It feeds on large seagoing animals such as seals, sea lions, large fish, turtles, dolphins, small whales and other sharks. Without sharks, prey species could grow unchecked and create an imbalance in the ocean's food web.
The sperm whale is one of the ocean's largest predators. It mainly feeds on cephalopods such as octopi and large squid. Only the lower jaw of the sperm whale has teeth, while the upper jaw only contains sockets where the teeth fit in when the jaws are closed. This enables the whale to take in slippery prey such as squids.
Recycling the nutrients
Sperm whales, as well as other large whales, help fertilize the surface of the ocean by consuming nutrients in the depths and transporting those nutrients to the oceans' surface when they defecate, an effect known as the whale pump. This fertilizes the phytoplankton and other plant-based organisms on the surface of the ocean and contributes to ocean productivity and the drawdown of atmospheric carbon. This fertilizing role is also carried out by most aquatic animals, regardless of trophic level. The nutrient cycle starts over in the process.
Conclusion
Food webs provide a framework within which a complex network of predator–prey interactions can be organised, and also shows the transfer of energy and nutrients across the trophic levels. Complex food webs support diverse ecosystems.
The effect of removing or reducing a species in a food web varies considerably depending on the particular species and the particular food web. In general, food webs with low biodiversity are more vulnerable to changes than food webs with a higher biodiversity. In some food webs, the removal of a producer species can negatively affect the entire food web, but the loss of one producer species that makes up only part of the diet of a herbivorous consumer may have little or no effect.
Some species in a food web are described as a ‘keystone’ species, which have a greater impact on a food web than one would expect in relation to their abundance. The removal of a keystone species characteristically results in a major change, in the same way that removing a keystone from an arch or bridge could cause the structure to collapse.
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