9/26/16 – Nutrient flow

9/26/16 – When you think about streams, rivers, and oceans you might think that sounds like Bald eagle habitat, which is correct. When ecologists think about these systems they might think about the nutrients that are carried from the forests down the streams and rivers to the oceans.

Juvenile Bald eagle on rock, Aleutian Isl.
Juvenile Bald eagle on rock, Aleutian Island. Photo courtesy of Hal Heatwole.

In some cases this flow of nutrients can be bad. Think about how much ’stuff’ flows into the Gulf of Mexico…everything you put on your lawn, down your drain, on the roads, if you live in the vast middle of the United States. You might be thinking about toxins, but you also need to understand what happens to nutrients. But nutrients are good, right? Well, like with many things too much of a good thing can be bad, and this holds true for nutrients.

Excessive amounts of nutrients can’t be used by the plants they encounter on the journey from your yard to the ocean. These nutrients are then carried into lakes, bays, gulfs, and other large spillways where they are available for algae to use, and this causes algae to overgrow. Ecologists call the process of nutrient overload leading to algal blooms ‘eutrophication’. So there is an overgrowth of algae, other than sounding kinda gross, what’s so wrong with that? The problem is that all that algae leads to low oxygen levels, called hypoxia.

Project to reduce risk of harmful algal blooms in ponds and lakes
Project to reduce risk of harmful algal blooms in ponds and lakes. Photo Credit: U.S. Geological Survey, Dr. Jennifer L. Graham.

But plants produce oxygen, so how can an overgrowth of algae lead to lowered oxygen levels? Well, all that algae is not just growing, some of it is dying too. When the algae dies it begins to decompose, and that process of decomposition uses up more oxygen than all that growing algae produces. Then there is not enough oxygen in the area, eventually everything dies, the fish, plants, and animals. Then we call the area a dead zone. The Gulf of Mexico contains America’s largest and most famous dead zone, but there are other well-known dead zones throughout the world.

But it is not just the plants and animals living in the water that are affected. You can be impacted too. Swimming in or drinking contaminated waters can cause problems for people, particularly if the kind of algae that overgrows can produce toxins. In the early 1990’s people found it hard to believe that algae could produce toxins that can affect humans, but since then scientists have worked hard to track these toxic algal blooms both locally and nationally.


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