Seas and oceans cover 71 percent of the world’s surface and provide diverse habitats for millions of unique species. From minuscule plankton and shrimps to the enormous shapes of blue whales and giant squid, marine life take thousands of brilliant forms. Although shallow, coastal waters, which profit from extra sunlight, tend to be more fertile zones for life than the deep deserts of the open ocean, life can be found in even the bleakest crevices of the sea. Indeed, the oceans are the font of all life on earth, from which our distant ancestors wriggled onto the shore some 500 million years ago. Yet however vast the oceans may be they cannot sustain the amount of pollution human beings pour into them. Sea-life is under immense pressure from plastic, rising temperatures, acidification, fishing, and more—and sterile seas have enormous implications for the existence of human life on the planet.
What Is Marine Life?
Marine life encompasses all animal life that exists in saltwater, in the planet’s seas and oceans. Freshwater life, that inhabits rivers and lakes, is categorized differently; “marine” specifically denotes sea-dwelling creatures.
What Is The Study Of Marine Life?
The study of marine life is called marine biology. Marine biologists are at the frontlines of both the scientific and conservationist communities. Their duties include collecting organism specimens at sea, crunching data, and experimenting in the lab. Areas of research are also multifarious but might include the study of animal migration patterns, underwater photosynthesis, or investigating the impact of human pollution, for example on coral reefs.
What Are The Types Of Marine Life?
The saltwater environs which make up the majority of the Earth are home to diverse species, and members of almost all classes of creatures, from mammals and mollusks to birds and reptiles, make the sea their home.
Cephalopods, Crustaceans, And Shellfish
These are a varied group of organisms that inhabit different roles within marine ecosystems. Cephalopods are a family of mollusks which include octopus, squid, cuttlefish, and nautili. These creatures fulfill an important role in consumption within an ecosystem, acting as both voracious predators and prey for various creatures. Although their role in ecosystems could be better understood, they are highly valuable creatures to study in the field of comparable intelligence. The intelligence of creatures like octopi is remarkable, capable of complex problem solving, daring escape acts and forming emotional bonds with people.
Crustaceans are a family of creatures that include crabs, lobsters, shrimp, and prawns. Crustaceans also inhabit a wide range of ecological niches, being an essential food source for many other creatures as well as largely being carnivores, acting as predators or detritus feeders themselves.
Shellfish is a colloquial term that incorporates crustaceans, which have thick exoskeletons, alongside various mollusks with shells such as bivalves like mussels, clams, oysters, cockles, and scallops. This last group also sustains its own important role in ecology, sifting nutrients and debris out from water which can make areas more habitable for other species of animal.
Corals And Invertebrates
Corals are invertebrate marine creatures that tend to live in large colonies which form reefs.. Reefs enrich the lives of many creatures, including humans. They protect coastlines from erosion and storms, attract tourism and build livelihoods, and act as sources of food and new medicines. Although less than 0.1 percent of the ocean is covered by coral reefs, 25 percent of marine species dwell in them; they are incubators for life. Other marine invertebrates include sponges, starfishes, and anemones.
There are numerous mammals in the oceans, some of which hang closer to shore like seals and sea lions whilst others can travel vast distances, like dolphins, whales, and orcas. These creatures are some of the most intelligent of all marine life and even form interspecies bonds unprovoked, as documented by the friendly interactions between bottlenose dolphins and false killer whales, memorably captured in David Attenborough’s Blue Planet 2.
There are 20,000 different species of fish in our planet’s oceans. From tuna and marlin to clownfish, barracudas, and guppies they are the quintessential water creature. It is also the vertebrate animals that are killed by humans more than any other, with around one trillion fish being killed for human consumption each year.
Turtles And Reptiles
Sea turtles are the most iconic marine reptile species, although other marine reptiles include sea snakes, marine iguanas, and saltwater crocodiles. Sea turtles provide irreplaceable ecological functions. Hawksbill turtles, for example, eat common sponge species which proliferate on coral reefs, which saves the corals from being strangled by the sponges and allows less common sponges to grow, adding to the reef’s biodiversity. Marine iguanas, which Charles Darwin heartlessly described as “most disgusting, clumsy lizards”, are poster boys for the Galapagos archipelago, and help draw in ecotourism funds which lead to the islands’ continued conservation.
Seabirds fish the coasts of various continents and include a wide array of creatures, from gulls, to albatrosses, penguins, cormorants, and puffins. Seabirds have provided some of the most emotive and haunting images of oil spills, and such disasters prove irreversibly damaging and lethal to such birds.
Sharks And Rays
Finally, sharks and rays, which are cartilaginous fish, whose skeletons are primarily composed of cartilage, remain. Sharks like Great Whites may have a bad rap due to movies like Jaws, but humans kill 100 million sharks each year, whilst sharks only kill 12 humans. Rays kick up sand when excavating for food, which created microhabitats for tiny invertebrates in an example of healthy ecosystem engineering.
How Much Marine Life Is In The Ocean?
Curiously, although the oceans make up 71 percent of the earth’s surface they only contain 15 percent of the Earth’s species; 80 percent of species dwell on land, and the remaining 5 percent in freshwater. The reasons for this are varied, including a lack of diversity in the architecture of ocean environments as opposed to the various geographies of land like deserts, mountains, forests, grasslands, and so on. However, this is no black mark against the oceans, which still contain an immense plethora of life. There are still a predicted 2 million species in the oceans, and only 228,450 are known to humanity. The oceans also contain the vast majority of animal life in terms of quantity, even if the types of life are less varied. Indeed 78 percent of animal biomass can be found in the oceans, which makes the oceans the home to the largest numbers of sentient beings out of any setting.
Why Are Marine Environments Important?
Marine environments are crucial to the entire planet for several reasons. Firstly, although estimates vary it is widely agreed that marine photosynthesizers, most notably tiny phytoplankton, create over 50 percent of the globe’s oxygen. This means that the health of these ocean organisms is integral to the continued breathability and temperature of the Earth; they also sequester carbon dioxide, the greenhouse gas, during photosynthesis. When these ecosystems are destroyed billions of tons of carbon dioxide are released into the atmosphere, accelerating global heating.
If that was not crucial enough, there are further reasons marine environments are important. They help regulate the planet’s climate and weather systems, and the warming of the oceans may lead to a higher incidence of extreme weather events like hurricanes and tsunamis, which are often deadly, and the El Niño and La Niña weather events which cause starvation in Asian and Pacific countries like Timor Leste.
Degrading marine environments actually endangers the 40 percent of global communities who live on the coast. Ecosystems on coasts, like mangroves, often provide services of flood and storm protection for adjacent human settlements. The destruction of marine environments can wreck people’s livelihoods. This is true for fisherman and tourist industries, like those anchored to marine wonders like the Great Barrier Reef, over half of which has died due to rising ocean temperatures. Even more alarming are those island nations which may be swallowed up as global warming melts the ice caps and ocean levels rise, and many have already had to evacuate their homes to escape the rising ocean, a bleak omen of what could occur if climate change proceeds unchecked.
How Does Pollution Affect Marine Life?
Pollution can be devastating for marine life, which is often sensitive to changes in their environment. Chemical pollution is a big problem for the oceans and before 1972 copious toxic chemicals, industrial waste, untreated sewerage, and even millions of tons of heavy metals and radioactive material were dumped into the sea. Although regulations have increased, chemical pollution continues to be a problem with animal agriculture being a lead cause, whose fertilizers, herbicides, and pesticides leach into rivers which lead in turn to the ocean. Other chemical pollutants include crude oil, which has ended up in the ocean through spills like the Deepwater Horizon disaster. The effect of these chemicals can be devastating. In recent years, dead zones caused by toxic algae which feed on the nutrients which run off farms into the sea have become a more common occurrence, and these zones can be hundreds of miles long and kill all the marine life beneath them. Harmful chemicals are consumed by sea creatures and end up in their digestive systems.
Plastic pollution is another hugely pressing problem, and the amount of plastic in the oceans is incredibly vast. The Great Pacific Garbage Patch, for example, is a floating body of garbage of immense size – at 620,000 square miles, it is twice the size of Texas. A huge contributor to ocean pollution is single-use plastics like plastic bags, which slowly dissolve into microplastics, small, insoluble particles that species of coral choose to eat over actual food, and kills them. Indeed, plastic bags are mistaken by sea turtles, who see them as jellyfish, who eat them and die as a result. Decaying plastic releases a smell similar to the foods of some seabirds, who proceed to choke on the plastics they try and consume. Marine mammals like whales also end up consuming the plastic, which kills them; some 88 pounds or 40 kilograms of plastic was discovered inside the body of a juvenile Cuvier’s beaked whale, who had been reported vomiting blood before he died. Yet domestic consumers are not the only ones responsible; unmoored nets used in commercial fishing nets drift freely for miles, ensnaring animals in their path and 46 percent of the Pacific garbage patch is made from fishing lines.
Although plastic and chemical pollution are perhaps the most egregious forms of marine pollution, humans also pollute the sea in other ways. Shallow waters near urban environments inevitably suffer from light pollution, which interferes with the circadian rhythms of coastal organisms which regulate their feeding, migratory and reproductive habits. Light pollution also makes it easier for predators to hunt small fish and damages the breeding capabilities of reef fish.
Noise pollution, from sonar devices, oil rigs, and large ships also pose problems. Mass beachings of various species of whales have been attributed to loud artificial noises caused by seismic human activity like oil or gas exploration, which panics and disorients whales, which exhaust themselves fleeing.
Finally, one of the most worrying ways pollution affects the ocean is through a gradual process of acidification. This is caused by humanity’s CO2 emissions, 30 percent of which are absorbed by the sea. This process of acidification is having damaging effects on wildlife across the seas; creatures like oysters and corals, which build shells and exoskeletons from calcium particles in seawater, are struggling as such particles are more rapidly dissolved. Miniature sea snails called pteropods, which feed organisms like krill and whales, are at risk. When researchers placed pteropod shells in water with the predicted pH and carbonate levels of the oceans by the year 2100, they found the shells dissolved over 45 days.
Other Marine Life Issues and Threats
Pollution is one way we damage marine environments, by poisoning them through neglect, but humanity also destroys them for its own benefit, financial and culinary.
Whaling has long been a highly controversial practice, particularly after some species of whale were nearly hunted to extinction in the late nineteenth and early twentieth centuries. Most whaling countries agreed to an effective moratorium on whaling in 1986, enforced by the IWC (International Whaling Commission). However, some allowances were made for whaling to persist for scientific research, a process that was allegedly abused by Japan. However, commercial whaling has remained persistent; Norway and Iceland continue to partake in commercial whaling and Japan followed suit as recently as 2019. Although whaling levels are minute compared to rates in the late 1960s the brutal and drawn-out method of killing whales, whereby they are stuck with numerous explosive harpoons and shot with rifles, is inhumane. Bearing in mind whales’ complex intelligence and sociality, such violence is inherently cruel.
Confinement of Marine Life
Marine life, particularly mammals, does not fare well in captivity. Killer whales provide the best example of this. Killer whales born in captivity lead unnaturally short lives, and captive orcas exhibit unique, stress-induced behaviors such as grinding their teeth against stone and bouts of aggression, which can be deadly for trainers. These creatures normally travel thousands of miles through the oceans, yet are confined into confined spaces; Lolita, an orca at the Miami Seaquarium, lives in a tank less than twice the length of her body.
Although orcas are the most famous examples of marine life suffering confinement there is evidence that other marine mammals experience similar effects. Obie, a rescued walrus who lived at SeaWorld San Diego, died at age 28, 12 years shy of life expectancy in the wild, and apparently exhibited stereotype behavior like biting the glass of his enclosure and regurgitating and re-eating his food, acts indicative of mental illness.
Commercial fishing is a significant contributor to the global decline of sustainable fisheries, and as the market continues to expand from $240.99 billion to a projected $438.59 billion by 2026 there is no sign that pressure is letting up. There is no acknowledgment from the fishing industry that fish may feel pain or emotion, despite studies to the contrary, leading to inhumane practices like killing by asphyxiation and the live gutting of fish, some of which can take an hour to die. Commercial fishing is also deeply inefficient and indiscriminate in its targets; about 40 percent of the global catch is bycatch, which is unwanted sea life thrown overboard, dead or dying. It isn’t only fish who are affected as an estimated 300,000 cetaceans (whales and dolphins) are accidentally killed by fishing vessels each year.
Although international agreements are trying to halt its spread, shark finning remains a major problem. Over 90 percent of certain shark populations have been lost over the previous half-century due to this practice. The practice itself is also inhumane; sharks have their fins cut off whilst alive before they are thrown back into the ocean, where they inevitably die of blood loss or are eaten by other predators. Highly endangered shark species are among those who fall prey to this practice, and many vendors of shark fin soup don’t know what shark species the fins they purchase come from. This huge pressure on shark numbers, 100 million killed each year, can lead to ecosystem damage that spreads far and wide—without sharks rays proliferate, which eat more bivalves, which can harm dependent human communities and water quality.
How Can We Protect Marine Life?
One of the United Nations’ sustainable development goals, goal number 14, is to ensure that the seas and their marine resources are sustainably used and developed. The United Nations has indeed seen progress towards the implementation of these goals, most notably their achievement of procuring the signatures of 97 countries on to the Agreement for Port State Measures, the first internationally binding agreement which seeks to disincentivize illegal, unreported, and unregulated fishing. The amount of national waters which have gained protected status has doubled since 2010, with most progress made in the Caribbean, Oceania, and Latin America. This represents progress, although such strides remain insufficient. The UN’s statistics report that although sustainable fisheries are declining at a slower rate, they are nonetheless declining—from 90 percent of stocks being biologically sustainable in 1970 to 65.8 percent in 2017. The UN freely admits that current efforts to protect marine environments are falling short of sustainability targets. It is also noteworthy that in the UN’s SDG Good Practices manual, a compilation of SDG-related success stories from around the globe, only three examples cited helped the oceans, and even these only tangentially. The UN only has limited power as an international broker—governments and consumers must act unilaterally.
Therefore, group organizing and lobbying local politicians, Members of Parliament, and Members of Congress to acknowledge and act on the importance of marine habitats for both animal and human communities is one way to apply pressure and enact change.
As an individual, there are impactful changes one can make. Limit your use of plastics, when you purchase items like plastic bags re-use them as much as you can and try and recycle when you do dispose of them. Discarding seafood from your diet is an effective change and a way to undermine the commercial foundations of an industry like fishing, which is so devastating to a wide range of animals and ecosystems. Adopting a fully plant-based diet is also the single biggest way an individual can contribute towards reversing climate change, so eating vegan will help stop ocean acidification, rising water temperatures, and sea levels, and limits the extent of the noxious agricultural chemicals which pour into the sea.
The Road Ahead
The oceans are where life on Earth began and contain the bulk of our planet’s animal life. Once thought a boundless reservoir of resources, time has revealed just how sensitive marine ecology is, and how deeply humanity and the planet rely on its continued health. Immense strides need to be made in protecting the oceans from the ravages of pollution, overfishing, and climate change. Otherwise, the vast and diverse oceans may become barren, ruining human and animal lives in the process.