Here are some links with more information about what was touched on briefly in the first lecture, and covered in the October 7 lecture.
The Dead Zone:
Some important parts of it, to summarize:
- There have been other dead zones besides the one in the Gulf of Mexico
- They are caused by an overload of nutrients, which feed certain algae in an area of water, which in turn decompose and use up the oxygen supply, killing off other aquatic life.
- The nutrients which caused the one in the Gulf did not just come from the canal in Chicago, but runoff into the Mississippi from nearby farmlands (which are pretty much all over the region it flows through)
- Dead zones can be reversed and restored to their former health
Read the Wikipedia Link for history:
Apparently, it's still going strong as an exhibit, and the University of Arizona owns it now—here's a link about it, and it also has articles about more interesting questions that might be asked, and recent studies:
A current example of a dead zone is Lake Atitlan in Guatemala.
Lake Atitlan is a beautiful lake located in Guatemala's highlands. It is endorheic, meaning it does not flow to the ocean, and, volcanic in origin, it is said to be CA's deepest lake. Most of those who reside around the lake in separate villages are at least part indigenous Mayan. The communities use the lake's water to cultivate coffee, corn, and other vegetables, and for household needs including washing and waste disposal. Some support an infrastructure of Guatemalan and international tourists, who enjoy kayaking, yoga, hiking, and views of the deep blue lake surrounded by hilly mountains.
Lake Atitlan now suffers substantive and image problems due to contamination that manifests itself in explosive cyanobacteria growth. The growth of Lyngbya hironymusii, found on the lake's bottom and on substrates like rock and aquatic plants, and the growth of other plants are limited by over-blooming of free-floating Microcytis, which compete for light at the surface and form a thick surface scum. Rotting gases trapped under the mat of Lyngbya cause it to float to the surface, which further reduces the amount of penetrating sunlight. The ecosystem result: decreased oxygen level (barely two percent as opposed to the average lake level of 8 percent), imbalances in populations and a brown surface scum. The following are key parts of the process.
- An excess of nitrogen and phosphorus, caused in part by fertilizer runoff and untreated tourist and household sewage drainage into the lake, stimulates this positive feedback cycle. The amount of extra nitrogen and phosphorus is large: between 2002 and 2003, approximately 972 tons of nitrogen and 381 tons of phosphorus were added to the lake.
- An invasive species of fish introduced to the lake within the last decade is also a factor in the problem of explosive cyanobacteria growth in that it eats predators of the cyanobacteria, exemplifying trophic cascade theory.
At least one environmental NGO, the government, and UC-Davis are identified as actors addressing the problem.
Guatemala's Lake Atitlan Disaster, the explanation. Guatemalan Times. 30 October 2009.
Environment-Guatemala: SOS from Lake Atitlan. IPS. 24 November 2009. http://ipsnews.net/news.asp?idnews=49392
How Guatemala's Beautiful Lake Turned Ugly. Time Magazine. 30 November 2009. http://www.time.com/time/world/article/0,8599,1942501,00.html
Also featured in Boing Boing and NASA photo: http://www.boingboing.net/2009/11/30/deadly-algae-bloom-t.html