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The hardest part of creating any documentary series is selecting just what materials can and cannot be included. The number of phenomenal stories, researchers, groups and agencies doing amazing work far outweighs the amount of screen time available for coverage. Here's your chance to plunge into some of the research we weren't able to showcase in depth (or at all) as well as discover some of the major groups involved in this vital issue.

Dead Zones

According to recent United Nations Environmental Program Reports, the number of dead zones across the world is nearing 150 and includes such vital areas as the Black and Baltic Seas. Dead zones are large coastal areas so depleted of oxygen that any organisms that cannot migrate clear of the area are likely doomed to perish. The lethal consequences of these zones are predicted to prove a greater menace to humans than depleted fisheries.

The primary cause of these zones is human agricultural practices. Here's how it works in one of the most notorious of dead zones — the Gulf of Mexico — which has been known to swell to the size of Massachusetts. When nitrogen, an agricultural fertilizer product, gets washed into the watershed, it causes rapid blooms of marine algae. This occurs mainly in the summer when the water is relatively warm and calm. When the algal blooms die, they sink and rot. This decomposition process depletes the water of oxygen to the point that marine animals must either leave the area or die. (When oxygen content falls below two mg/liter, this is when fish and shrimp are forced to move out of the area.)

References and More Information on Dead Zones
» United Nations Environment Programme Off-site Link
 
» Action Plan for Reducing and Controlling Hypoxia in the Northern Gulf of Mexico Off-site Link
 
» Rabalais, N.N., Turner, R.E., and Scavia, D. (2002). Beyond science into policy: Gulf of Mexico hypoxia and the Mississippi River. BioScience, 52, 129-142.
 
» National Centers for Coastal Ocean Science - Gulf of Mexico Hypoxia Assessment Off-site Link
 

The Toilet That Doesn't Flush

Off the west coast of North America swirls a colossal, clockwise-rotating current called the North Pacific gyre. In 1999, researchers sampled this area and compared the ratio of plankton to plastics. What they revealed was shocking. The mass of plastic in this area was six times that of the plankton. Plastics were finding their way into this massive eddy and being retained there — literally unflushable. Plastic fragments, thin films and polypropylene/monofilament line comprised 98% of the pieces.

Tracking the impact of plastics on marine wildlife is a hot area of research. According to N. Wallace in 1985, nearly 100,000 marine mammals die annually due to ingestion and entanglement. In another study conducted by P.G. Ryan in 1990, 82 of 144 examined bird species were carrying plastic debris in their stomachs. The clear message from these studies is that plastics simply don't vanish when we throw them away. On the contrary, they find their ways into the most remote corners of the globe and carry with them the potential to wreak havoc on unsuspecting marine wildlife.

For more information
» For a review of this story in Natural History Magazine November 2003 see Trashed: Across the Pacific Ocean, plastics, plastics, everywhere. Off-site Link
 
» Moore, C. J., Moore, S. L., Leecaster, M. and Weisberg, S. B. (2001). A comparison of plastic and plankton in the North Pacific central gyre. Marine Pollution Bulletin, 42, 12:120-124.
 
» Ryan, P.G. (1987). The effects of ingested plastic on seabirds: Correlations between plastic load and body condition. Environmental Pollution, 46, 119-125.
 
» Wallace, N. (1985). Debris entanglement in the marine environment: A review. In R.S. Shomura and H.O. Yoshida (Eds.), Proceedings of the Workshop on the Fate and Impact of Marine Debris. US Department of Commerce, NOAA Technical Memorandum. NMFS, NOAA-TM-NMFS-SWFC-54, pp. 259-277.
 

Feminized Male Fish

In 2001, James Nagler, an ichthyologist from the University of Idaho, and his coauthors discovered a shockingly high proportion of sex-reversed wild Chinook salmon in the Columbia River of central Washington State. A whopping 84% of what looked to be wild females came up positive for carrying a male genetic marker while not a single hatchery-raised females tested positive.

One likely reason for this is that the river was contaminated by endocrine disrupting compounds. According to Nagler, during hatching time, male Chinook salmon are extremely susceptible to sex reversal. In fact, lab studies show that sex change can be induced by exposing males to high estrogen levels for even as short a time as one hour.

Endocrine disruptors have been found in the Columbia River and trace their origins back to detergents, plasticizers and pesticides that enter the water through human activities like agriculture and domestic sewage processing.

For more information
» Nagler, J.J., Bouma, J., Thorgaard, G. H., and Dauble, D.D. (2001). High Incidence of a Male-Specific Genetic Marker in Phenotypic Female Chinook Salmon from the Columbia River. Environmental Health Perspectives, 109, 67-69. http://ehp.niehs.nih.gov/docs/2001/109p67-69nagler/abstract.html%20 Off-site Link
 
» Nagler lab at University of Idaho: http://www.sci.uidaho.edu/ biosci/labs/nagler/people/ Off-site Link
 

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