Ocean on the verge of mass extinctions

Two consequences of fossil-fuel combustion and the release of vast amounts of greenhouse gases since the onset of the Industrial Revolution are a warming ocean and the acidification of seawater with too much atmospheric carbon dioxide being absorbed by it. Both of these factors are now causing increased hypoxia or oxygen depletion, which initially began with nutrient overloading from agricultural run-off.

Paleoclimatic studies have shown that these three factors—warming, acidification and hypoxia—which are symptomatic of a disturbance of Earth’s carbon cycle, led to five previous mass extinctions on the planet. Today’s ocean is headed in the same direction if drastic measures are not taken to reduce greenhouse gas emissions immediately. This is the message coming from a consortium of 27 scientists, who met in Oxford in April under the sponsorship of the International Program on the State of the Ocean (IPSO).
The warming of the ocean has led to numerous coral bleaching events around the globe. When the polyps that secrete the coral reefs become heat-stressed, the algae that give them their bright colors and provide their food through photosynthesis abandon their hosts. As a result, the corals die off. Some recover, but more and more are failing to do so. Over the last half-century, 40 percent (some say 90 percent) of the world’s coral reefs have disappeared along with many of the associated fish species. This is particularly alarming since they are the most diverse ecosystem on the planet and provide habitat for millions of marine organisms.
Global warming has led to huge shifts as marine life attempts to escape hot zones for cooler ones so they can live in the most favorable temperatures. This creates problems in food supply and predation, upsetting the dynamic equilibrium of marine ecosystems. Phytoplankton in the Arctic now peak 50 days earlier as a result of decreased sea ice, which reached a record low in 2007 and has not recovered. The sequential harvest of phytoplankton by zooplankton, who are in turn fed upon by larger creatures, is programmed into the reproductive cycles of marine species, meaning food may not be available when required. This could unravel the complex tapestry of the food web.
Thus far, the ocean has acted as a buffer by taking up our excess carbon dioxide, but it is paying the price for capitalism’s pollution with dire consequences. As more anthropogenic CO2 (now at 392 ppm atmospheric concentration) is absorbed by the ocean, seawater’s natural alkaline pH has dropped by .1, or an algorithmic decline of 30 percent. This acidification of seawater makes it increasingly difficult for calcium-carbonate secreting organisms such as corals and shellfish to produce their exoskeletons, which will literally dissolve under more acidic conditions. It is particularly threatening to tiny microorganisms that build plates of calcite to armor themselves. Their inability to do so affects the foundation of the marine food web.
Also, the undersaturation of aragonite in seawater—the form of calcium carbonate required by sea life—affects marine creatures’ ability to navigate and sense their environment by hearing. (Because cold water absorbs more CO2, coldwater species are the most at risk.
We are all too familiar with the Dead Zone at the mouth of the Mississippi River in the Gulf of Mexico, which is caused by vast amounts of chemical fertilizers and manure from factory farming running off into streams and rivers. The excessive nutrients give rise to bacteria that break down organic matter. The resulting feeding frenzy depletes the oxygen in the water, creating anoxic conditions that kill off by suffocation all life unable to flee the area. There is a growing oxygen crisis, with 762 dead zones mapped by NASA. Human-caused eutrophication is also leading to ever more toxic algal blooms that are deadly to fish and people.
Global warming too is playing its role in depleting the ocean of oxygen. Just as warmer water holds less carbon dioxide, it also holds less oxygen. The ocean gets its oxygen at the interface of the atmosphere and the water. It comes either directly from the air or through the photosynthesis of algae floating at the top, then it mixes through the water column into the depths. Global warming reduces this mixing by making the surface water lighter as freshwater ice masses melt and make it less dense and saline in content.
The extra heat makes the surface waters expand, further lightening them. This lighter water does not sink and mix, depriving the depths of needed oxygen. More oxygen will remain at the surface to be used by pelagic (open water) organisms, who will have the advantage over benthic (ocean bottom) ones. A lack of oxygen constrains sea-life growth, with many organisms left gasping for breath. Fish populations are sure to decline as a result.
There are many other harmful impacts affecting the health of the ocean. Overfishing is a major one. Industrial fishing that uses bottom trawlers, which destroy huge areas of seabed, as well as enormous purseine nets and long hooks, results in a tremendous by-catch of “unwanted” fish and other animals, including dolphins and sea turtles, that are cruelly ground up and thrown back into the sea. Shark finning for soup is another wasteful and heinous practice.
Overharvesting of many fish populations has led to the collapse of fisheries, such as the cod off Newfoundland’s Grand Banks, and the depletion of big fish that take years to mature and reach reproductive age. The demise of the bluefin tuna appears imminent, yet authorities have refused to take action to protect the species from further human predation.
This loss of keystone species in the form of top predators means there is nothing to keep other marine populations in check and is leading to gross imbalances. As a result, there is an oversimplification of ecosystems occurring, with the proliferation of less nutritious jellies and squirts that are coming to dominate some regions. Sixty-three percent of fish stocks are overexploited or depleted, with many near extinction. Consequently, an important source of protein upon which millions of people depend is being undermined by industrialized greed and corruption while local fisherfolk are finding it harder to make a living.
Oil spills and chemical pollution are another major problem. As we know from the Exxon Valdez and BP oil spills, marine and coastal ecosystems have been severely poisoned by hydrocarbons and chemical dispersants and will take generations to recover. In addition, the microbial breakdown of the petroleum contributes to hypoxic conditions that asphyxiate sea life.
All of the chemicals that we now find part of the human body burden—PCBs, DDT, dioxins, flame retardants, plasticizers, and heavy metals—are making their way into the ocean. They are even migrating to the polar regions, where they are bio-accumulating up the food chain with heavy concentrations in the human breast milk of indigenous women. Many of these compounds are endocrine disruptors that are altering early development and undermining the immune and nervous systems of sea creatures, who are thus losing their resilience. The toxic cocktail to which marine life is being exposed reduces it ability to withstand disease and other stresses by 40 percent.
Our garbage—the stuff that capitalist industry refuses to recycle—has made its way into huge oceanic gyres. Plastics are a major part of this colossal mess. They are eaten by birds, which starve for lack of real sustenance. Plastic bags are confused for jellyfish and are fatally swallowed by sea turtles. Other creatures get caught up and are strangled by the junk. As plastics break down into microscopic particles, they enter the tissues and cells of marine organisms. With the increased surface area of the smaller particles, they become efficient delivery systems for the numerous chemical contaminants contained in seawater.
Melting ice masses are now the largest contributor to sea-level rising at a rate of 2.1 millimeters per year. When the thermal expansion of the water is added in, it is even more. Rising sea levels threaten to inundate not only coral reefs but also shallow-water ecosystems such as salt marshes, estuaries, and mangrove swamps, which provide habitat and nurseries for other species.
There is a huge pool of freshwater that now lies within the Arctic Circle as a result of flow from Arctic rivers and melting ice masses. So far, wind patterns and ocean currents have kept this water within the region, but changes could cause its release into the Atlantic, where it could freshen and slow the Gulf Stream that gives Europe its temperate climate. Other seas, such as the Baltic, one of the largest brackish ecosystems, could have its salinity levels dramatically lowered, negatively impacting its species.
According to the report issued by the international earth system workshop on the ocean, the impact of these multiple stressors is “often negatively synergistic meaning that the combination of the two magnifies the negative impacts of each one occurring alone.” In other words, “the whole of marine degradation is greater than the sum of its parts.” This degradation is now occurring at an accelerating rate.*  
The ocean comprises 70 percent of the planet and makes up its heart and lifeblood. Since everything is interconnected from the water we drink and food we eat to the air we breathe, human beings cannot survive on a world with a dead ocean. As the Science Director for IPSO, Dr. Alex Rogers, points out, “If the ocean goes down, it’s game over.” Therefore, we must take drastic measures to end the capitalist exploitation of marine ecosystems by ending overfishing and establishing a system of protected marine reserves, taking only sustainable catches to allow fish populations to recover. The complete elimination of agricultural chemicals and moving toward a more plant-based diet with organically grown foods will also help along with benign substitutes for non-agricultural chemicals.
Climate change has already caused an enormous drop in the primary productivity of the ocean, with phytoplankton populations having declined by 40 percent since 1950 because of warmer sea surface temperatures. To enable marine ecosystems to survive, we must reduce greenhouse gas emissions from all sources to zero in order to bring down carbon dioxide concentrations to a safe 300-325 ppm (300 ppm CO2 is the limit to prevent further ocean acidification, according to climatologist James Hansen).
This requires that we ban offshore drilling and leave all fossil fuels in the ground while converting to clean, renewable energy and retooling all industry for green production that is based solely on ecological and human needs rather than private profits. Since plastics are petroleum-based, that will put an end to them. These are the only sensible ways to cool down the planet and prevent catastrophic climate change and the collapse of not only our marine ecosystems but terrestrial ones as well.
Time is running out for the ocean and humanity. The capitalist class cannot be allowed to engage in the willful destruction of 70 percent of the planet or any of Mother Earth’s other matrices. The ruthless exploitation of the world’s natural resources can be stopped by the action of the majority of humankind, acting in unity to create an eco-socialist society that exists in harmony with nature. We need to get to work on that before it’s too late.

*Rogers, A.D. & Laffoley, D.d’A.: International Earth System Expert Workshop on Ocean Stresses and Impacts.  Summary Report. IPSO Oxford, 2011, 18 pp.
> The article above was written by Christine Frank.  It first appeared in the July 2011 print edition of Socialist Action newspaper.