Dead Zones

I saw Stephen King’s “The Dead Zone” for the very first time a few months ago. Interesting to see Christopher Walken, Tom Skerritt, and Canadian Nicholas Campbell as young actors. But the movie was not very scary. Probably partly because there have been much scarier films since then, with much more graphic violence. Moreover, the film is not as scary as the real “dead zones”.
In 1974, The Gulf of Mexico near the mouth of the Mississippi was noted to be a largely dead zone. Except for some slimy creatures (jelly fish) and algae and bacteria, there were little to no fish or shellfish or worms – organisms that require oxygen dissolved in the water. The Mississippi –Missouri river system is 5970 km long and has a drainage area (watershed) of 3 million km2. It covers all or part of 31 states (and parts of southern Saskatchewan and Manitoba. It is heavily polluted with sewage from 50 cities (about 18 million people), with many also using the Mississippi as their source of drinking water.
The Mississippi also receives considerable amounts of pesticides, insecticides, and fertilizers (containing in particular, nitrogen and phosphorus) from agricultural run -offs through some of the most productive farmland in the U.S. There are also considerable amounts of toxic substances from household sewage and storm sewers (oil and other automobile fluids) as well as industrial wastes (heavy metals, solvents, etc.) from what is the industrial heart of the U.S. Most of pollutants are NOT good for obvious reasons. It’s less obvious why nitrogen and phosphorus from fertilizers are not good. After all, in their biologically accessible forms as nitrates and phosphates, these two elements are normally in limiting amounts in the environment, but they are absolutely essential for all life forms, primarily (but not exclusively) for their roles in synthesis of proteins and DNA. That is why they are added to soil as fertilizer, to supplement nutrients that are deficient or limited in heavily farmed land, to maintain its productivity and promote faster growth and higher yields. Human sewage is no different from animal waste spread as manure; It’s rich in nitrogen and phosphorus, and human sewage is still used in many parts of the world, euphemistically called “night soil”, for fertilizing farmland.
In the case of fertilizer run-offs into streams, lakes, rivers, and (ultimately) the oceans, these limiting nutrients are a case of “too much of a good thing”. The enrichment in nitrates and phosphates can theoretically boost the growth of all aquatic and marine organisms. However, the “benefits” of faster growth are specifically enjoyed by those organisms at the bottom of the food chain , those that can reproduce the fastest. These include, in particular, photosynthetic organisms such as algae that convert sunlight into sugars for their use in growth. The algae in turn are a source of food for many other organisms such as filter-feeding shrimp and copepods. Even the largest fish, sharks, sea birds and whales ultimately depend on these microscopic algae for their survival, since smaller animals and other plants are their food. So far, it still looks like a good thing: more algae, means more food for the rest of the organisms higher up in the food chain. Unfortunately, the rapid, localized growth of algae, called an “algal bloom” also consumes most of the oxygen dissolved in the water. This is called “hypoxia” (literally “less oxygen”). Therefore fish and other large organisms might have more food available, but no oxygen. The fish that don’t or can’t migrate out of these oxygen depleted waters die, as in this massive fish kill in a Louisiana bayou..

Ironically, the algal bloom population will also “crash” after it exhausts the oxygen, and the dead remnants may coagulate, forming sticky mats that either wash up onto the shore as a slimy floating scum . . . or sink to the sea (or lake) floor, coating it in a sticky mess with trapped dead organisms, heavy metals, etc.
This same process can occur from untreated human sewage since it is rich in nitrates, phosphates and carbon sources (sugars). In the case of sewage, the ability of to cause accelerated growth of algal blooms is called Biological Oxygen Demand (BOD) and the successively stringent steps of Primary, Secondary, and Tertiary (“third”) sewage treatment are reducing greater amounts of BOD at each step.
Phosphates were once used in laundry and dish washing detergents as cleaning agents. However, because of their role in promoting toxic blooms, they were banned or at least greatly curtailed, and most detergents today will boast that they are phosphate-free.
The scariest part about a dead zone? It’s not just one anymore. There are now over 400 dead zones along continental coasts! And this number is expected to continue to increase rapidly in the coming decades. As you can see in this map there are many more dead (and threatened) zones along the ocean shores, to the point where nearly the entire Pacific and Atlantic coasts of the U.S., the southern mainland of B.C. and some waters off the Maritimes, as well as much of Europe, and the east Asian coastline are under severe threat. (There is a very large number of sources about dead zones on the web. An excellent starting point for someone wanting simple but more in-depth coverage is found at No Fish Left.)
For us locally here in London, Ontario, the oceans may seem far away, but our untreated sewage and agricultural run-offs also contribute. The Great Lakes do ultimately drain into the Gulf of St. Lawrence. However, we don’t have to pretend anymore that it’s that far away. The dead zones are coming to us. Lake Erie, the shallowest and warmest of the Great Lakes has seen massive algal blooms over the past few years. The massive algal bloom of summer 2013 was reported as being the same size as Prince Edward Island (about 5600 km2) or about 20% of Lake Erie’s total surface area., This satellite image from March 2012 is not colour enhanced – the green algal bloom can be seen from space.

The National Geographic Society published a highly readable and comprehensive report from the 2011 algal bloom.

Peter Ferguson
Ward 12 Candidate for London City Council
New Chemistry for London
“On Oct 27 vote for progressive positive change – vote Ferguson”


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