The Effects Of Climate Change On Oceans & Marine Ecosystems

Climatic changes due to phenomenon such as El Niño and La Niña are well known to affect terrestrial land as well as sea surface waters.  What is less known is that these climatic fluctuations have great impacts on the environment as well as ecosystems of the deep sea.  These deep-sea ecosystems are altered with impressive speed, reacting almost immediately to changes in weather patterns thousands of feet above.  These effects change the fabric of deep-sea life, limiting the reproduction of some organisms and giving rise to others.  The greenhouse effect plays a crucial role in the altering of the climate today, making it the primary component of change in the climate. This change affects oceanic currents, ecosystems, evolution, as well as chemical makeup, ultimately changing life, as we know it in the deep seas of our Earth.

“Oceans need more attention because climate change IS an ocean issue. Our oceans will be the first victim, and sea life will suffer dramatically. Detailed proof is hard in ocean science, but I think we’re already seeing big ocean changes caused by climate change, such as starvation of whales, seabirds, and other animals off the US west coast.” — Mark Powell

For centuries humans, as well as animals, have relied on a symbiotic relationship with their environment.  This relationship is built upon chemical processes and actions, which in turn help one another to live and flourish.  Without this relationship between organisms and their environment, there would be no life on the planet to contemplate these issues.  Environmental changes can occur for many different reasons, but the primary factor in altering an organism’s ecosystem is the climate: its symbiotic counterpart.

In addition, these relationships are present deep in the ocean. Although they may not be in direct contact with the climate that affects them, these deep seas are significantly affected by the climate changes that take place thousands of feet of above.  The greenhouse effect is the primary cause of change in our climate today; thus, this is also the primary matter of importance and influence on the change in deep-sea life and its processes.  These effects vary from a change in chemical composition in the deep sea to a change in dominant organisms in the ecosystem.  Thankfully, similar events have taken place in the past, giving clues as to what can be expected as well as what humans can do to try to reverse or slow down this change in climate.

A Brief History of Climate Change

Humans have followed weather patterns for centuries, noting days of unusual warmth or cold as well as times of adverse wind patterns.  This tradition is carried out to this day, although using much more sophisticated machinery and methods, done for the same primary purposes, to predict the weather.  Along with predicting the weather comes many other challenges, including predicting what the effects of this climate will have on processes and ecosystems around the world.  Approximately 55 million years ago a rapid rise in global temperatures created what is now known as the Paleocene-Eocene Thermal Maximum (PETM).  This change in climate triggered many events that changed the make-up of the world at the time.

This figure shows climate change over the last 65 million years. The data is based on a compilation of oxygen isotope measurements (δ18O) on benthic foraminifera by Zachos et al. (2001) which reflect a combination of local temperature changes in their environment and changes in the isotopic composition of sea water associated with the growth and retreat of continental ice sheets. For more information, see the original file. “65 Myr Climate Change” by Robert A. Rohde via Wikimedia Commons is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Average Temperatures in the Eocene and Paleocene eras.

Those effects include the reversal of the ocean currents and creating a change in the overturning process that takes place in the southern hemisphere.  This process exchanges warm water with cold nutrient-rich water of the deep seas.  However, this process slowed down and eventually stopped.  Ultimately this process moved from the southern hemisphere to the northern hemisphere, creating a drive of unusually warm water into the deep seas.  This furthered the global warming by causing the release of methane into the atmosphere.

“Preservation of our environment is not a liberal or conservative challenge, it’s common sense.” — Ronald Regan

In due course, this led to an endemic of death to sea life. Although it is not apparent why the temperatures shot up during the PETM period, it is hypothesized that the levels of carbon dioxide in the atmosphere are linked to the rise in temperature.  The rise in temperature caused by the greenhouse effect happens rapidly and it takes thousands of years for these effects to be reversed.  The PETM is a primary example of what can happen if the greenhouse effect takes a turn for the worse.  Although it happened thousands of years ago, it can give us a great deal of information as to the causes and effects of global warming, thus affecting the deep sea and its vital processes.

Global Warming and the Greenhouse Effect

The greenhouse effect is no new phenomenon; in fact, it has been playing a major role on Earth since the beginning of its formation.  To explain the greenhouse effect, some background knowledge of the sun’s radiation as well as the earth’s is needed.  The sun, when shining down on the earth, is transmitting energy through light called ultraviolet radiation.  Ultraviolet radiation operates on the short wavelength spectrum, giving it the ability to pass through Earth’s atmosphere mostly unabsorbed and reach the surface of the Earth. To prevent the Earth from becoming continuously hotter and hotter, it needs to release the same amount of heat as the sun is inundating on the Earth.

As the sun heats up the Earth with visible light radiation, the Earth then emits heat in the form of infrared radiation.  This type of radiation has a higher wavelength than that of visible or ultraviolet radiation; therefore gases, which exist in the atmosphere, trap it.  Water vapor, carbon dioxide, methane, ozone, nitrous oxide all absorb infrared radiation that is emitted from the Earth.   These gases trap heat in the atmosphere, thus warming up the Earth.  This is the principle of the greenhouse gas effect.  The truth is that the greenhouse effect is an important process that normally takes place in the atmosphere, giving the world a warm climate.


“Earth’s greenhouse effect (US EPA, 2012)” by the EPA is licensed under CC0

The problem exists when there are too many greenhouse gases in the atmosphere.  If this happens, the excess greenhouse gases absorb additional heat naturally emitted from the Earth’s surface.  Global warming can cause many problems, but the most feared is melting of the polar ice caps.  If the polar ice caps melt, they could possibly cause the sea level to rise 20 feet.  This would not only submerge many cities along coasts, but also a large portion of Florida.  Another effect, often feared by oceanographers, is the slowing or stopping of the great ocean circulation, which would cause a disruption in all aspects of life in the oceans.  Global warming can thus affect life in all forms.

How Climate Change Can Affect Ocean Currents

For centuries people thought that the deep seas of the oceans were unaffected by surface climate and wind patterns, now it has been proven otherwise.  It was believed that the deep seas were an abyssal plain, scarce of life and devoid of any characteristic features.  When this hypothesis was proved wrong, so was the idea that the deep seas were not affected by the climate thousands of feet above.  The oceans circulate much like the atmosphere, due to the fundamental laws of physics.

Seawater, as well as air, aligns itself in a pressure gradient, having the densest water on the bottom and the least dense on the top.  This causes a circulation motion across the oceans of the world.  The cold dense deep-sea water then sinks and the warm tropical water rises to the surface.  As the warm water rises it migrates towards the poles, cooling it off and thus sinking it to the depths of the Arctic oceans.  This, in turn, pushes the already cold dense water from the poles toward the equator, heating it up and causing it to rise to the surface.


“Thermohaline Circulation” by NASA is licensed under CC0

This oversimplified explanation shows the ocean’s main circulation patterns. If the average temperature of the earth’s climate were to increase by only a few degrees Celsius due to the greenhouse effect, this could cause dramatic changes in the oceans.  A warming of the atmosphere would cause an increase in glacial melting, providing a tremendous increase in fresh water into the North Atlantic waters.  This fresh water, being much less dense than salty water, would create a blanket of fresh water at the surface of the North Atlantic Sea.

This would cause a disruption in circulation, which starts in the North Atlantic Ocean.  If the fresh water is less dense, it will no longer sink down to the depths of the ocean and thus fuel the circulation.  The cold dense water is nutrient-rich due to chemical reactions that take place in the deep seas, while the less dense warm water is nutrient deficient, having had most of its nutrients used up by various organisms.  This example, which took place during the PETM period, and which is hypothesized to be taking place right now, causes a disruption and possibly a halt to one of the primary processes that take place in the oceans.  The deep sea would be affected dramatically, causing its environment as well as its ecosystem to change.

How Ocean Currents Affect Deep-Sea Ecosystems

As ocean circulation begins to slow down or possibly stop due to climate change, this causes adverse results in the deep-sea ecosystems around the world.  The circulation of the belt delivers nutrient-rich deep-sea waters to strategic locations in the oceans.  As this water is upwelled, organisms rely on these nutrients to survive.  If the ocean currents are misdirected or stopped, the nutrient-rich deep waters will no longer be upwelled as much.  This would cause diminishing amounts of phytoplankton in the oceans.  Phytoplankton are key to the majority of life in the oceans, providing the beginning of the food chain all the way from zooplankton to sharks and whales.

This, in turn, would affect the whole ocean, down to the deepest depths, causing starvation and an altering in the food chain for many organisms.  If there is a depletion of the food source in the upper limits of the ocean, it will continue down to the bottom as well.  Deep-sea organisms rely on fecal pellets formed by marine organisms to fall down to the depths of the sea.  This provides many of the nutrients needed to sustain life.  A decrease in food causes a decrease in fecal pellets raining down from the upper portions of the earth.  These fecal pellets provide the majority of the phosphorus present in the depths of the ocean, a key component in many biological processes.  Fecal pellets also are an important source of food for marine animals as well as bacteria and fungi.

Oxygen As A Component of Life

“Most of the ocean has never been seen by anybody, let alone explored… Even in the same place, every day is different, every minute of every day. It’s a constantly dynamic system.” — Sylvia Earle

In addition to fecal pellet depletion, depletion of oxygen causes a drastic effect on deep-sea ecosystems.  The primary source of oxygen to the oceans is from the atmosphere, which is accomplished by churning water near the surface thus saturating it with oxygen from the atmosphere.  Ocean waters are saturated with oxygen only when they are near the surface.  If the circulation motion stops, deep-sea waters would no longer be upwelled nearly as fast to the ocean surface thus causing a depletion of the oxygen present in the depths of oceans.  This lack of oxygen would have major effects on deep-sea animals.

Since the primary source of energy in the deep seas requires respiration and oxygen, their life source would be dramatically low.  This would cause a depletion in the number of organisms as well as a change in the dominant organisms.  As some organisms die out due to starvation or lack of nutrients, other organisms will take their place which may be more adapted to the environment, but they substantially alter the makeup of the ecosystem.  A change in one primary organism to another could result in a disruption in the whole food web, from plankton to whales.

A Reason To Care

It may not seem obvious why one would care about the deep-sea ecosystems and their functions.  Although it is miles away and out of sight, it is very important to human’s daily lives.  All living creatures are part of a certain trophic level, of the food chain.  Humans are located at the top of the food chain and therefore rely on smaller organisms to feed on.  A huge source of these smaller organisms is located in oceans.

If the ecosystems of the oceans are changed this will lead to a change in dominant populations of marine organisms, perhaps limiting or wiping out a valuable food source for humans. Another way that deep-sea ecosystems affect people’s lives is through respiration.  If the circulation is stopped, not only will deep-sea ecosystems shut down but also phytoplankton would be reduced.  A reduction in the population of phytoplankton near the surface of the ocean would cause a dramatic decrease in the overall photosynthesis taking place in the world.  This would throw off the balance between respiration and photosynthesis, causing an increase in carbon dioxide in the atmosphere and a decrease in oxygen.

“If we wipe out the fish, the oceans are going to die. If the oceans die, we die.” — Paul Watson

An analysis of the causes and effects of climate on deep-sea ecosystems provides clues as to what will come and what can be done to lessen the extent of global warming.  Despite all that may be done, it is inevitable that the Earth’s climate has changed, thus altering the ocean’s make-up.  The greenhouse effect, caused by an increase in greenhouse gases such as carbon dioxide in the atmosphere, is the primary cause of global warming.  This warming, in turn, slows down or stops ocean circulation, limiting nutrients from fecal pellets as well as oxygen to reach the deep-sea ecosystems.  This had an adverse effect, causing a mass change in dominant organisms along with becoming extinct or endangered. Humans know more about the surface of the moon than they do about the depths of the Earth’s oceans. Humans cannot deny nor avoid their crucial role in this process, and thus it is necessary to study and know the things that cause and effect deep-sea ecosystems.