Oceans form the largest habitat on earth which supports the greatest variety of life. The ocean is a major source of food, medicine and jobs for our human family. More than 3.5 billion people rely on fish and other seafood as the primary source of protein, and many other species of mammals and birds on our planet depend on it. From tiny plankton to multi-ton whales, a vast web of microbes and fisheries overlap to form a complex relationship of life that encompasses yet goes beyond a simple food chain. As on land, the web includes links between organisms that produce, consume and decompose nutrients. This ocean food web faces threats on several fronts from our industrial society, climate change and the growing human population. The health of our species depends on our understanding of how we are affecting the ocean web, so we can take action to curb the damage and protect and conserve this vital resource. Below is a primer on the most critical issues impacting our food chain, with links to more educational resources.
Our carbon emissions in the past two centuries from fossil fuel burning and deforestation have not only contributed to climate change, they are also harming life in the oceans.
The ocean absorbs at least a quarter of atmospheric CO2 through natural processes, which reduces this greenhouse gas, but at a price. As carbon dioxide levels increase, the pH balance of seawater is becoming more acidic.
Studies have shown that ocean acidification has a dramatic effect on calcifying species – reef-building corals, shellfish such as mussels and oysters, and plankton, the tiny plants and animals that form the base of the marine food web. When these organisms are in jeopardy, the entire food chain is at risk.
The old adage that there’s plenty of fish in the sea doesn’t ring true anymore when it comes to our food supply. Fishing fleets worldwide have the capacity to catch two to three times more fish and other marine species than our oceans can sustainably support.
The ocean has long been humankind’s dumping ground. In recent decades, however, the scale and breadth of industrial and household chemicals that reach the ocean has become staggering. From oil spills and inadvertent shipwreck dumps, to sewage, pesticides, detergents, pharmaceuticals and industrial tailings, many of our coastlines are increasingly contaminated and areas of the deep ocean are becoming a toxic soup. Toxic metals such as mercury are a big concern, with coal-fired plants as a major source of mercury pollution. The mercury is absorbed by algae which sinks and releases it in the ocean depths, where its works its way up the food chain right to us, most notably in the form of tuna and other large fish. This pollution harms us and ocean mammals directly by endangering our health when we eat contaminated fish, as well as stressing the larger food web.
Chemical Pollution – Ocean Health Index Toxic Mercury in Seas Tied to Algae, Air
Garbage & Plastic
Garbage in the ocean is literally strangling and starving wildlife. Our highly practical yet non-biodegradable plastic makes up the majority of marine debris on shorelines and floating in oceans worldwide. Most ocean pollution starts out on land and is carried by wind, rain and through watersheds, with increasing concern of plastic microbeads used in cosmetics, synthetic microfibers and other ingredients in our waste water. The plastic waste concentrates in gyres, systems of rotating ocean currents. The North Pacific Gyre, also known as the Great Pacific Garbage Patch, is roughly the size of Eastern Austrailia or twice the size of Texas (and growing) and consists mostly of small plastic particles suspended and swirling at, or just below, the surface, where fish and other animals and birds mistake the particles for food. Fish and sea mammals consume or get entangled in plastic debris. Seabirds ingest plastic and have less room in their stomachs for food, leading to starvation. Plastics also absorb toxins such as PCBs when drifting in the water and break apart in the ocean, releasing potentially toxic chemicals such as bisphenol A (BPA), which can then enter the food web. Other debris such as fishing net scraps can trap whales, seals and other animals on shore. Reducing plastic waste is one of the most important things we can individually do to protect our food web. What is the Problem? 5 Gyres Video: TED – The Great Pacific Garbage Patch Fast Company Article on Cosmetic Microbead Disaster Where does plastic pollution go? Interactive demo! The Great Plastic Tide. Excellent educational article.
While the Fukushima nuclear disaster in Japan in 2011 has raised serious concerns about the dangers of radioactivity in our oceans, we have been dumping radioactive waste in the oceans worldwide ever since nuclear power was developed. From 1946 for almost 50 years, low-level radioactive waste had been disposed in “sealed” containers in the ocean, some even with rifle shots inflicted to help them sink, others with questionable lifespans. Nuclear weapons tests were conducted by various countries above ground in the ocean, contributing to radioactive conditions. Scientists are monitoring the impact of Fukushima meltdown to ocean life and humans while collecting and analyzing data to determine radioactivity levels and potential health and environmental impacts long-term from the cesium, strontium and trillium isotopes in the waste released into the ocean. Radiation from Fukushima: FAQs from WHOI Nuclear Waste Sits on Ocean Floors – Wall Street Journal
The food web is also threatened by related issues, both from manmade and natural causes. The health of the ocean corals as a critical habitat for marine organisms is top of mind for many ocean researchers and organizations. Although coral reefs comprise less than 0.5 percent of the ocean floor, it is estimated that more than 90 percent of marine species are directly or indirectly dependent on them. Besides pollution, global warming is contributed to the loss of coral due to higher sea temperature. Other issues include the introduction of invasive species such as the lionfish in the Caribbean which upset the natural balance of specific ecosystems, and fish farming (or aquaculture) which can also upset that natural balance. Farmed fish have been proven to escape into the ocean and outcompete or mix with wild fish, which dilutes the fitness of wild fish, making them less able to survive in a natural environment. We’ll explore these issues more in our blog and with updated news from leading science research.