The Ocean Ecosystem

Naomi Lichtenstein and Nicole Ward

Although there are five named oceans, they are all connected as a singular body of water. The Arctic, Atlantic, Indian, Pacific, and Southern oceans cover about seventy percent of the Earth’s surface with an average depth of 2.4 miles. The ocean ecosystem is vast and includes saltwater bays, seas, inlets, shorelines, and salt marshes. Additionally, there are three layers of the ocean in general. The top layer, known as the euphotic zone, receives the most sunlight, starting at the ocean’s surface and going as deep as 230 feet on average. The disphotic zone, the second layer, receives some sunlight but not enough for plants to survive. The final layer, known as the aphotic zone, receives no sunlight. It is completely dark and cold, and few marine animals can survive in this layer.

There are many plants within the ocean including seaweeds, marine algae, and sea grasses. In addition, mangrove trees, living on muddy tropical shores, are an integral part of the ocean ecosystem, absorbing carbon dioxide and converting it into oxygen through photosynthesis. Additionally mangroves serve as important habitat for animals such as snails and crabs. Kelp also provides food and shelter to many ocean animals.  And phytoplankton serves as food for many ocean creatures, from the largest of whales to the smallest of fish. Producing half of the oxygen in the world, phytoplankton can be found virtually anywhere in the ocean. Marine ecosystems include various parts such as the abyssal plain which comprises deep sea coral, whale falls, and brine pools. Marine ecosystems include coral reefs, hydrothermal vents, kelp forests, mangroves, the open ocean, rocky shores, salt marshes and mudflats, sandy shores, and polar regions found in the Antarctic and Arctic. 

The abyssal plain and other parts of the deep sea are in constant darkness where photosynthesis cannot occur; other marine ecosystems go through extreme changes in temperature, light availability, oxygen levels, and other factors on a daily basis. Within these ecosystems, the organisms living there must be highly adaptable to the physical conditions. For example, organisms in the deep sea have adapted to the darkness through creating their own light source with photophores acting as cells that light up to attract prey or potential mates. 

In tropical sea environments, the euphotic zone coral reef ecosystems are built from the exoskeleton secreted by coral polyps. These exoskeletons form complex structures that help provide a habitat for many different organisms. Coral reefs are extremely diverse ecosystems that host sponges, crustaceans, mollusks, fish, turtles, sharks, dolphins, and many other ocean animals essentially accounting for a quarter of ocean species. 

The ocean is home to about 230,000 known species. However, only five percent of the oceans have been explored, therefore, the total number of species existing here could very well be over two million, with over  90% of the species having yet to be discovered. The animals that live in the oceans can be classified as shellfish, mammals, fish, sea turtles, seabirds, sharks, and invertebrates. 

In the open ocean ecosystems, many photosynthetic organisms live in the fairly warm euphotic zone. Ocean creatures such as whales, dolphins, octopi, and sharks live in varying depths of the ocean from shallow waters to fathomless depths. Earth’s oceans are home to some of the smallest organisms such as plankton and bacteria as well as the Great Barrier Reef, the world’s largest living structure, which can be seen from the moon. Fish, mollusks, dolphins, seals, sea lions, walruses, whales, crustaceans, and sea anemones, along with many other creatures cohabitate within the massive ecosystem that is Earth’s oceans. Additionally, the ocean is home to the largest animal species on earth, the blue whale, which can grow to over 100 feet long. Most marine animals, however, live in the top two ocean zones with the most access to plants and other ocean animals as a source of nutrition. The anglerfish can be found in the dark depths of the ocean where it creates its own light to attract other animals for prey. 

One of the biggest issues within our oceans is the enormous amount of plastic pollution.  According to the National Oceanic and Atmospheric Administration, an estimated 8 million metric tons of plastic make their way into Earth’s oceans each year.  Some of the most commonly found plastics in the ocean include plastic straws and bags, food wrappers, bottle caps, and plastic bottles.  Fishing equipment such as fishing lines, nets, and traps are also major contributors to the plastic pollution crisis.  Research by Greenpeace has determined that over 640,000 metric tons of commercial fishing nets, lines, pots, and traps are disposed of into the ocean each year. 

As overfishing increases, global food security for hundreds of millions of people is threatened and ocean ecosystems are being destroyed worldwide as important biological processes cannot function properly. While reports on overfishing vary according to species, location, and reporting organization, we know that we are catching and killing aquatic life at an unsustainable pace. According to the United Nations Food and Agriculture Organization (FAO), 34.2% of fisheries are overfished. Additionally, the World Wildlife Fund (WWF) reports that 61% of the world’s fish stocks are fully fished. Extensive overfishing is encouraged by increased demand as humans eat, on average, twice as much fish per person as we did 50 years ago. If current rates persist, it is projected that the Earth’s oceans will be empty of fish by 2048. As fish populations are depleted, it has become more difficult for fishermen to turn a profit and people are working to exhaustion. In addition, commercial whaling has grown exponentially and whales are washing up on shores worldwide. 

Rising Sea Temperatures and Ocean Acidification
With rising sea levels and temperatures, ocean acidification is increasing. The increased amount of carbon dioxide in the atmosphere, as a result of climate change, is causing massive changes in the oceans pH levels. According to NOAA, the average surface temperature of the ocean globally has increased by an estimated 0.13°C every decade, for the past 100 years.  These changes may seem insignificant, but they compound quickly and have extensive effects.  These changes in temperature and pH can cause loss of habitat, damage to breeding patterns, and even extinction of some species.

Commercial Whaling
Commercial whaling is the act of hunting and killing whales, and subsequently trading and selling the whale meat and other body parts.  Scientists have approximated that nearly 3 million whales were hunted and killed commercially in the 1900’s, which has drastically harmed the functioning of the ocean ecosystem. In 1982, the International Whaling Commission (IWC) put a temporary ban in place on commercial whaling as a response to the dramatic decrease in whale populations.  However, even with this ban in place, commercial whaling has continued and its effects have been greatly damaging.  Commercial whaling has continued even after this ban due to several loopholes in the legislation.  Some countries, such as Japan, have claimed that they are hunting and killing the whales for scientific purposes, but these claims have been discredited by the IWC.  As a result of this continued commercial whaling, whale populations are at record lows. The blue whales of the Antarctic, for example, now exist at the size of less than one percent of its original population size.  Fortunately however, the public demand for whale meat has been on the decline in recent years, which will hopefully reduce the incentive to hunt and kill whales.

International Union for Conservation of Nature (IUCN)
The IUCN monitors and manages climate change impacts on the ocean, the conservation of endangered species, and supports marine protected areas. The organization’s ocean governance policies focus on sustainable use and management of coastal areas and international waters. IUCN’s goal is to provide protection to Areas Beyond National Jurisdiction (ABNJ) as these spaces in the ocean are not governed by individual countries and thus require a global initiative. 

Marine Protected Areas
Marine Protected Areas, or MPA’s, are areas of the ocean that are designated as spaces that must be conserved, managed, and protected.  Each MPA can have varying levels of protections placed on them.  Some allow recreational activities and some are closed completely off from human use. In the United States waters alone, there are nearly 400 MPA’s with varying degrees of protection.

Marine Debris Research, Prevention, and Reduction Act (MDRPRA)
Enacted in 2006, the United States’ MDRPRA outlined the Marine Debris Program (MDP), designed to limit ocean litter and protect the ocean ecosystem from debris. The goal of the MDP is to research and resolve issues that arise as a result of marine debris.  Under the MDP there are three main elements. The first part is identifying, mapping, removing, preventing, and assessing the impacts of marine debris.  The second component is to reduce and prevent the loss of gear, and the third part is outreach.

Shore Protection Act (SPA)
Created within the U.S. in 1988, the Shore Protection Act forbids vessels from transporting municipal or commercial waste in coastal areas before obtaining a valid permit.  The Environmental Protection Agency has the responsibility of creating the rules and regulations that govern the management of waste from waste sources, port reception facilities, and vessels in order to reduce the amount of waste entering coastal waters and confirm that any waste that is deposited into the water is disclosed and taken care of.  

Marine Mammal Protection Act of 1972 (MMPA)
The United States’ Marine Mammal Protection Act was created in response to the decrease in population sizes of marine mammals such as blue whales, polar bears, orca whales, and sea lions.  Under this act, it is illegal to harm any marine mammal through actions such as hunting, harassing, capturing, or killing.  The MMPA is a critical piece of legislation in the protection of marine mammals that helps to ensure the health of the ocean ecosystem.

The various issues that have arisen in our world’s oceans have caused tremendous harm to the animals who inhabit them.  One of the most direct effects on marine animals is happening as a result of plastic pollution in the waters.  Marine animals can be harmed or killed by entangling themselves in plastic debris, or ingesting it.  It has been estimated that fish in the North Pacific alone ingest between 12,000 and 24,000 tons of plastic annually.  Not only is this an issue for the fish that ingest the plastic, but it also becomes an issue for larger marine animals who then consume those fish, and humans who eat seafood.  The sea turtle is one of many sea creatures frequently impacted by plastic pollution.  To a sea turtle, plastic debris can appear to be a food source.  Plastic bags can look like jellyfish and fishing nets can look like seaweed. When they mistake the plastic for food and consume it, their digestive system is severely damaged.  Ingesting the plastic can create blockages within their intestines and can also result in internal bleeding.  Furthermore, when the turtles consume the plastic, it makes them feel as though they are full, which can cause them to starve as they are not obtaining any beneficial nutrients. According to studies done by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the University of the Sunshine Coast (USC), there is a 22% chance that a sea turtle will die if it consumes just one small piece of plastic. Other animals who are greatly harmed by plastic debris include sea lions, seals, seabirds, whales, and dolphins.  Aside from the issues that arise as a result of plastic in the oceans, marine animals are also greatly harmed by disasters such as oil spills.  When oil enters the ocean, it harms animals such as sea otters and seabirds by limiting their ability to stay insulated which can cause hypothermia.  Furthermore, marine animals including dolphins and whales can inhale the oil in the water, damaging their lungs, immune system, and their reproductive systems.  

A simple volunteer activity you can participate in is a beach clean up near you!  By cleaning up littered shorelines, you are directly decreasing the amount of trash that is entering the ocean and endangering marine life.  There are tons of resources to help you find beach clean ups local to you.  Even if you can’t attend an organized beach clean up, do your part to pick up any litter you see whenever you’re visiting the beach or near any waterway which may eventually feed into a larger body of water!

Reduce Your Plastic Consumption
Making simple changes to your everyday life is probably the easiest thing you can do to help protect our oceans.  Many products are made of plastic such as single-use shopping bags, plastic cutlery, bottles, straws, food wrappers. By making small changes in your daily life like swapping out plastic grocery bags for reusable ones and purchasing a reusable water bottle instead of using multiple single use plastic water bottles, you are reducing the amount of plastic that could eventually end up in our oceans.

Participate in Citizen Science
Citizen science is when individuals of the general public take part in the collection or analysis of data in collaboration with real scientists and researchers.  For example, the National Oceanic and Atmospheric Administration has a plethora of citizen science opportunities for anyone to join in on.  Some of these opportunities include, observing whales, collecting debris for research, and collecting water samples. By assisting in this research, you help progress our understanding of oceans and marine life.

Learn more about Ocean Conservation Bills and Efforts 
Government websites and local delegate sites provide information on new bills. You can easily look up certain keywords regarding marine pollution and climate change effects on the ocean and it will direct you to bills aiming to prevent more destruction.  After finding certain bills you’d like to see passed, give your local delegates and legislators a call, or rally some friends to start petitions in support of the cause. Check out Fanimal’s Direct Action Corner for more ways to directly get involved!

Sources: Center for Biological Diversity, Environmental Protection Agency, Greenpeace, International Union for Conservation of Nature, Marine Science Today, National Geographic, National Oceanic and Atmospheric Administration, National Ocean Service, National Resources Defense Council, Ocean Conservancy, One Green Planet, Sciencing, Sloactive, Sustainable Fisheries, WorldAtlas, World Resources Institute, World Wildlife Fund