aquatic systems

Have you ever spit off of a tall building or bridge? Cried during a sad movie? Drunk a cool glass of water on a hot day? Of course you have. Humans (and every animal and plant on Earth) constantly consume and excrete water. H20 makes up 60 percent of the human body. The primordial waters of ancient Earth are where the first single celled–organism evolved. All living things depend on the cycling of water through our earth’s ecosystems. Even in places where there seems to be no water, animals and plants wait for rare rainfall, find underground wells, or consume plants to get their fill. Marine biologist Sylvia Earle said, “Even if you never have the chance to see or touch the ocean, the ocean touches you with every breath you take, every drop of water you drink, every bite you consume. Everyone, everywhere is inextricably connected to and utterly dependent upon the existence of the sea.”

No wonder aquatic ecosystems are some of the most valuable and productive resources in the entire world. The bounty of life found in the ocean feeds the world. All of those fish, plants, and marine animals are the basis of many of our global food webs. But it is not just a source of food—plants in our aquatic ecosystems produce over half of the oxygen in Earth’s atmosphere. Water that evaporated from our oceans becomes the fresh water that falls as rain, even in some of the world’s driest places. Without our oceans, we absolutely could not survive.

Although oceans, lakes, and other aquatic ecosystems may seem like endless resources, our world is much smaller than you may think. As human populations grow, pollution and overfishing are destroying many of our important aquatic ecosystems. The water that flows throughout the world sustains life on this planet, and protecting it should be one of our highest priorities.

Ecosystem of the Open Ocean

The open waters of the ocean have been called “the great blue desert.” Where crowded coastal waters end, the open ocean begins, covering more than 70 percent of our planet’s surface. Although open water forms the largest surface area on our planet, only 10 percent of marine species live there. Not many nutrients are found in the open ocean, because dead matter sinks to the ocean floor to decompose. What the surface does have, though, is hard-working microscopic algae called phytoplankton, which create oxygen through photosynthesis. They are the basis of almost the entire ocean’s food chain. Occasionally, an upwelling or a storm will bring nutrients from the bottom of the ocean up to the surface, creating an algae bloom followed by a feeding frenzy for marine animals.

The animals that call the open seas home need to be powerful and fast. They travel from one end of the ocean to the other in search of food and mating grounds. Strong swimmers like whales, dolphins, and marine turtles navigate the oceans’ currents, which act like underwater rivers. Underneath the ocean’s surface is the dimly lit “twilight zone” where the animals have evolved to be stealthy. Diurnal (daytime) animals that live in this zone usually come to the surface to eat plants or scavenge. At night, twilight-zone predators will swim toward the surface to hunt their prey, usually luring them with fluorescent and bioluminescent markings.

The seas may seem endless, but they are not an inexhaustible resource. We need to take from our oceans responsibly if we hope to preserve them for the future.

BIGGEST BENEFITS

The open ocean is the beating heart of the entire world. The deep blue waters absorb over half of the sun’s heat that hits the earth, and the evaporation of sea water is vital to creating rain that distributes fresh water worldwide. The different hot and cold ocean currents also control weather patterns and climate for the entire planet. Most importantly, the water’s surface supports phytoplankton, which produce over half of the atmosphere’s oxygen.

The bluefin tuna can accelerate as fast as a sports car and can reach speeds of 47 miles per hour.

Crustaceans and squid in the open ocean have clear bodies that camouflage them to blend in with their environment.

The Great Pacific Garbage Patch is an area of littered ocean about the size of Texas. Ocean currents between the United States and Japan consolidate the trash in one place, allowing it to pile up. This is one of many “garbage vortexes” throughout the ocean.

Most of the animals that live in the deep ocean never see land in their lives.

GREATEST THREAT

Pollution of our oceans from pesticides and oil spills destroy ecosystems and cause dead zones like the ones in the Gulf of Mexico and the Baltic Sea. Tons of garbage is thrown into the ocean each year, which kills marine life. Overfishing is also a major problem: right now, we are fishing the ocean at twice the level it can support. About 32 percent of the world’s fisheries are over-exploited and being depleted of fish. However, we can change this through creating protected parts of the ocean, improving waste management, and enforcing sustainable fishing practices.

Ecosystem of the Deep Ocean

Imagine a place where the atmosphere is over 400 times heavier than it is at sea level. There is no sunlight, and strange creatures with sharp teeth, huge eyes, and glowing bodies float in the darkness. While this may sound like a place out of science fiction, it is right here on Earth, thousands of feet deep in the ocean. The “deep ocean” is the region 13,000 feet below the sea’s surface, a depth where there is no sunlight. As the water gets deeper, additional water weight creates more pressure. Only special equipment and submarines can withstand this intense pressure without imploding, making the deep ocean one of the most unexplored places in the world.

Plants depend on sunlight for photosynthesis and are the base for most food chains. Therefore, in the past, scientists assumed that since there was no sunlight in the deep ocean, there could be no life. But in exploring the deep ocean, scientists have found that it is actually full of life. Hydrothermal vents on the sea floor spew minerals and energy from the earth’s core. And microbes found in the deep ocean can turn minerals in the water into energy through a process called chemosynthesis. Marine animals at this depth have evolved to withstand the darkness, cold waters, and the intense pressure of the deep ocean. Giant tube worms and feather duster worms feed on vent microbes and are eaten by vent crabs. Other strange animals found in the world’s deep ocean include the frilled shark (which is a “living fossil”!), the luminescent viperfish, and an animal with the biggest eye-to-body proportion, the vampire squid. Scavengers like the rattail fish and crustaceans called amphipods eat and decompose dead animals that sink to these depths. There is still so much to discover in the deepest parts of our earth.

BIGGEST BENEFITS

There are more volcanic eruptions on the ocean floor than anywhere else on Earth. Volcanoes thousands of feet underwater disperse thermal energy from the earth’s core all around the world, and contribute to the formation of islands and the ever-changing surface of the earth.

Every ten meters underwater adds another atmosphere of pressure to the ocean. That means most of the ocean floor has the equivalent of over 1,300 Earth atmospheres!

The giant spider crab is thought to be the largest arthropod on Earth.

Deep underwater vents spray out white wooly flocculent material, which means there is bacteria living under the earth’s crust.

The Mariana Trench is the deepest known ocean depth, at 36,070 feet under water.

Constant volcanic activity means the ocean floor is always changing shape.

GREATEST THREAT

Overfishing and destructive practices are harming our oceans, and the effects are in even the most remote depths. Bottom trawling is a fishing method that indiscriminately crushes everything in its path. This irresponsible practice destroys deep-sea corals and kills fish that we don’t even eat, which in turn impacts whole ecosystems. There is no regulation in the deep seas, and overfishing is rampant. Commercial deep-sea fishing catches fish in spawning areas before they have a chance to reproduce. This means fewer fishing resources for humans in the long run.

Ecosystem of Rivers

If the oceans are the heartbeat of our planet, then rivers are its veins and arteries. Fresh water is vital to most life on Earth, and massive networks of rivers and streams transport this important resource throughout the world. Rivers begin in various places where rainwater builds up, such as glaciers, snowy mountaintops, or ancient underground springs. Rivers can also start from easily accessible fresh water sources like lakes and wetlands, where water runoff builds up and comes together to become a moving river. Rivers intertwine and mingle with each other, creating tributaries.

Humans have depended on the natural resources provided by rivers and have transformed them to use their water and movement as a tool. We have built dams, canals, and irrigation systems for farming. Rivers have provided a means of transportation, trade, and exploration throughout human history. Almost all large cities are built near rivers. From the ancient Egyptian pharaohs building their civilization near the mighty Nile, to the Ming dynasty thriving in the delta of the Yangtze, to present-day London, which still depends on the Thames, rivers have allowed people to populate the world!

BIGGEST BENEFITS

Rivers provide fresh water to entire ecosystems. People and animals all over the world depend on rivers for water and food. Throughout human history, the fresh water of rivers has been used to irrigate crops. Rivers are also a source of energy, and the kinetic energy from the flowing current can be stored for later use. As rivers move through the land, they pick up minerals that eventually end up in the ocean, providing nutrients to those ecosystems as well.

Most of a river’s current flows beneath the surface where it isn’t visible and is sometimes much stronger and faster than it appears.

The Mississippi River is still a major shipping route for many American industries today.

The longest river in China, the Yangtze, supports the famous giant panda and the Siberian crane.

Most river animals live exclusively in fresh water, with the exception of a few special animals like salmon, which live as adults in the salty ocean and swim upstream to spawn in freshwater rivers.

GREATEST THREAT

Flooding and erosion are a natural and healthy parts of a river’s ecosystem. But when that natural flooding is disrupted by poorly managed building, floods can become catastrophic. Pollution and overfishing of rivers can also destroy river ecosystems and devastate nearby communities. Pollution in groundwater makes its way to the ocean, polluting the “heart” of our planet. Only through proper management and a knowledge of ecology can we keep our rivers healthy and productive.

Ecosystem of Lakes

Water covers over half of our planet’s surface, but most of that water is too salty to drink. Most of the fresh water is locked away in frozen glaciers or in the ground. Luckily, there are lakes! Lakes can be found on every continent and in many climates, from the coldest snowy mountaintops to barren-seeming deserts. Lakes can even be found at the brutally cold South Pole, like the frozen Lake Vostok. Lakes are created when fresh water fills up a basin on the earth’s surface. Like the Great Lakes of North America, many lakes were formed 18,000 years ago during the end of the Ice Age, when large ice sheets and glaciers began to melt. With melting came movement, and these large sheets of ice slowly slid away from the Earth’s polar regions, filling up basins and craters all over the world with melting water. Other lakes are formed by rainwater filling craters and bowl-shaped depressions that are often created by earthquakes.

Lakes are contained ecosystems and can be very different from one another. The main factors that determine the ecological makeup of a lake are its exposure to sunlight and wind, its temperature, and the chemical and pH balance of the water. The wildlife found in each individual lake has evolved to survive in the specific attributes of their home. For example, tilapia fish can live only in acidic waters. It is also important that all lakes have the correct balance of nitrogen and phosphorus to promote plant growth. Too little of these nutrients means no plants and no life. Too much phosphorus or nitrogen will cause algae to grow out of control. This pond scum (a type of algae) can take over a lake, making it impossible for other wildlife to survive. By understanding the balance and qualities of individual lakes, we can protect and preserve them.

BIGGEST BENEFITS

Like rivers, lakes also provide us with water for drinking, farming, and transportation. Like the ocean, they are a source of diverse marine life that supports commercial fishing. Cooling winds that come off large lakes help to regulate temperatures. The fresh water and marine life in lakes support entire communities of people and animals; millions of people depend on lakes to live.

Lake water mixes when the seasons change. As the water cools, it sinks to the bottom and the dense lower layers rise to the top.

Many lakes are formed in inactive volcanoes that fill up with rainwater.

The difference between a pond and a lake is size; many classify small bodies of water as ponds when they have rooted plants growing in them.

Lakes can be closed off or the source of a mighty river. Many closed-off lakes become saltier than the ocean through thousands of years of evaporation.

Dry lakebeds are great for fossil hunting.

GREATEST THREAT

Lakes have natural life cycles. Over time, dead animals and plants decompose and sink to the bottom to form sediment. Eventually, this sediment can fill up a lake until it becomes a marsh or a swamp. Over thousands of years, lakes do naturally dry up, but human activity and poorly planned construction can speed up this process, causing lakes to dry up in a matter of decades, which is too fast for wildlife to adapt. Another threat is when pollution changes the chemical makeup of a lake, causing pond scum to grow. Too much pond scum can block the sunlight and use up all the oxygen in the water. This turns a lake into a dead zone where nothing can survive.