The Effects of Ocean Pollution on Marine Mammals
By Bob Bohle
The impact of humans has now reached every square mile of Earth’s oceans, and implications are ominous for ocean creatures and humans alike. In a study released in the February 2008 journal Science, researchers found that human activity - from over-fishing to greenhouse gases and global warming to the introduction of toxins into the environment – has affected every square mile of ocean on the planet and strongly impacted roughly 40 percent of marine ecosystems.
What the study didn’t cover directly may be even more disturbing: marine mammals are suffering dramatic rises in devastating illnesses, such as nervous and digestive system problems, liver disease, contaminant-induced immunosuppression, endocrine system damage, reproductive malformations, and growth and development issues. Worse yet is the alarming growth in cancer cases. Many scientists around the world believe these illnesses are being caused by contamination of the ocean with man-made toxic chemicals.
Because marine mammals are at the top of their food chain, the toxins in their food sources accumulates in their bodies, especially in their fatty tissues and breast milk. Toxins in plankton are consumed by small fish, which are in turn eaten by larger fish, which are eaten by even larger fish. Eventually marine mammals and humans, each higher up the food chain, eat the now-toxic fish, further concentrating the toxins. This bio-concentration is what causes high levels of toxins in dolphins, whales, and other marine mammals. Nine of the 10 species with the highest polychlorinated biphenyl (PCB) levels are marine mammals.
The Toxic Top Ten: bottlenose dolphin, orca. Risso’s dolphin, harbor seal, beluga, Mediterranean monk seal, common dolphin, gray seal, polar bear. The 10th is the Steller’s sea eagle.
The declining health of ocean-going mammals, especially the increase in various cancers, sends an undeniable message to humans. Thus dolphins and other marine mammals are showing us our future – unless we change our ways.
Marine mammals are sending an unambiguous message to humankind: clean up the toxic soup we live next to, swim in, and draw fish from, or pay a very high price in human lives.
Toxic Chemicals in The Ocean Environment
Scientists have been finding higher and higher levels of man-made chemicals in marine mammal bodies, which have corresponded with increases in mass die-offs, otherwise inexplicable population declines and strandings. They have found that many of these events are associated with immune system dysfunction, suggestive of broad environmental distress in the oceans.
How have the entire planet’s oceans become so contaminated? Environmental toxins are spread by wind, rain and currents. Thus, the toxic waste of one area, such as the United States and now Asia, where industrialized development and contamination are growing rapidly, become the toxic problems of the world. Persistent Organic Pollutants, or POPs remain in the environment for decades, even centuries. POPs resist environmental breakdown via biological, chemical and photolytic processes, some taking as long as a century to degrade to a safe level.
Even if we totally banned the use of POPs tomorrow, the health problems they cause would remain for many generations.
Today new contaminants are a growing problem in marine eco-systems. Polybrominated diphenyl ethers (PBDEs) are flame retardants used in 85 percent of commercial plastics, foam and textiles. We are surrounded by them. They are found in computers, television sets, cars, furniture fabrics, foam mattresses, and indoor dust.
PBDE concentrations are doubling every four years in marine mammals, according to one study. They are similar in chemical structure to PCBs and are particularly found in very high levels world-wide in harbor seal pups. PBDEs cause endocrine disruption and developmental defects and, like many other POPs, can cause cancer in animals and humans, according to the Environmental Working Group, which studies San Francisco Bay.
PBDE levels between 1997 and 2003 more than tripled in striped bass and more than doubled in halibut in San Francisco Bay. The fish are large and mobile, and are good indicators of the increasing levels of toxins in the Bay. PBDEs were banned in Europe in 2004/2005. They have not been banned in the U.S. California banned two forms of the fire retardants chemicals known to accumulate in the blood of mothers and nursing babies. Two other states, Washington and Maine, have also banned PBDEs. Bans were proposed last year in California, Connecticut, New York, Hawaii, Illinois, and Montana.
PBDEs have been escaping into the environment for years, and are rapidly becoming a major marine health issue. Despite this fact, they are not among the 12 chemicals being considered for reduction of use or elimination by a United Nations treaty.
Ocean Pollution and Beluga Whales
The beluga whales (Delphinapterus leucas) of the St. Lawrence Seaway and Estuary have had the dubious honor of being the "most toxic mammal" in the western hemisphere. Beluga carcasses are so saturated with agricultural runoff-delivered chemicals, such as pesticides, herbicides and phosphorus, that their carcasses must be handled like toxic waste.
The SLE belugas also suffer from polycyclic aromatic hydrocarbons (PAHs), which are involved with the etiology of cancer. Among several kinds of cancer observed in these belugas is cancer of the proximal intestine, a rare form in all species, including humans. But it is frequently seen in species exposed to 2,4-dichlorophenoxyacetic, commonly known as 2,4-D, an herbicide used to control broadleaf weeds.
According to researcher Daniel Martineau, the rate of cancer among these belugas is higher than in any population of wild terrestrial or aquatic animals. As a comparison, a study of 50 belugas examined in the Canadian Arctic found no cancers.
Orcas (Killer Whales) and PCBs
A 22-year-old female orca (Orcinus orca), or killer whale, was found dead on Washington's Olympic peninsula, and her PCB level was so high, technically the carcass was toxic waste. The PCBs probably came from an earlier dredging in the late 1990s of the harbor in Seattle, which sent out a plume of PCB-laced sediment. Two years prior to this disturbing discovery, PCB levels averaged 58 parts of PCB per million of fat in dead orcas found by scientists. This particular orca had roughly 1,000 ppm.
High toxin levels throughout its habitat have dropped the average life expectancy for a male orca more than in half, according to Ken Balcomb of the Center for Whale Research in Friday Harbor, WA. Some orca calfs don’t even make it at all: typically, the first calf born to a female dies, because the mother passes on much of her accumulated contaminants to that first calf through her breast milk. Subsequent calfs, however, fare better because the mother’s toxin levels have been lowered.
A 2007 study found that the effects of PCB contamination in Pacific Northwest orcas will last to at least 2030 for the northern population of 230 animals. The southern population of 85 may face risks until 2063. PCBs make whales more vulnerable to infectious diseases, and impede normal growth and development. Also, POPs impair reproduction because they are estrogen imitators and cause low sperm counts. Because of the “persistent” nature of the contaminants known collectively as POPs, we need to take action immediately. The toxins that have quickly and quietly impacted the health of marine mammals, our sentinels, are in all of us.