Mar 01 2010
Nutrient Runoff and Algal Blooms
In class, we uncovered 3 different issues causing ocean pollution. I want to focus on one, runoff of nutrients. It occurs only in lakes, streams, or coastal areas (the nutrients have to run off from the land), and only includes nitrogen and phosphorus.
This nutrient runoff from fertilizers and feedlot manure is also called “cultural eutrophication“– when bodies of water receive excess nutrients that then cause excess plant growth (algal bloom).
Cultural eutrophication starts out as just excess nitrogen and phosphorus entering the shores. Plants then take up the fertilizers (natural or not) and surpass normal, sustainable growth for the body of water. These algal blooms start to close off the surface and cause a decrease in the amount of light that hits the floor. A decrease in sunlight then causes a decrease in photosynthesis which usually supplies the water with dissolved oxygen. Because photosynthesis decreases, so does the amount of dissolved oxygen (D.O.) in the water.
We have seen this “overpopulation” effect in our population dynamics unit. The algae exceed the K, or carrying capacity, then comes a massive die off of the species. After the algae dies off, it leads the way for decomposers to infiltrate the body of water. The decomposers increase exponentially, again causing the D.O. to decrease even more due to respiration by the decomposers. If it hasn’t happened already at this point, many fish die because they cannot get the oxygen they need to survive.
Here is an animated version of what we learned in class:
I found an interesting article about a bay that I live by during the summer. There has been a lot of press about this issue of fertilizer runoffs from yards surrounding the bay. These things happen more often than you think and can really cause some severe damage to not only the ecosystem around us, but to businesses and restaurants revolving around the fish/shellfish industry. Enjoy! http://www.pressofatlanticcity.com/news/press/ocean/article_905b2f50-1e9f-11df-867e-001cc4c002e0.html
HABs — Harmful algal blooms
Sure this picture looks cool with the reds and blues BUT this is an example of a harmful algal bloom. These HABs can be very detrimental to a community. They produce toxins that not only effect the fish, shellfish, and marine animals, but also the marine birds and people as well. Over the years the HABs have caused more concern and prevention methods are now being looked into.
That is all we covered in class today, the other 2 ocean pollution issues are coming up this week!