Name:_ EID: Ex2- The \"patient was Green Lake, a small lake in Seattle that some

Question

Name:_ EID: Ex2- The "patient was Green Lake, a small lake in Seattle that sometimes had murky water. At its worst, a surface layer of greenish scum collected near the shore. In very hot weather, the area started smelling like rotting garbage-a characteristic that certainly discouraged people from enjoying the lake! The problems were due to the abundant growth of cyanobacteria, a group of photosynthetic bacteria. Cyanobacterial blooms (accumulations of cyanobacteria), which occur most commonly in the summer months, are more than just an aesthetic annoyance. Some strains make toxins that can be deadly to animals that drink from the lake. Because of the potential danger, when a cyanobacterial bloom occurs, lakes may be closed to wading, swimming, and sailboarding. In addition, dog owners are warned to keep their pets from drinking the lake water To control cyanobacterial growth in Green Lake, alum (aluminum sulfate) was added to the water. Aluminum combines with phosphorus and sinks to the bottom, removing phosphorus from the water column-arn action that limits cyanobacterial growth. The treatment was successful, resulting in clear water throughout the year Please write a short answerer (within 3 sentences) for each of the following questions. 1. Why do cyanobacteria blooms occur in the summer months rather than year-round? 2. What caused the greenish scum to form? 3. Why does removing phosphorus from water limit cyanobacterial growth? 4. Why did the area start smelling like rotting garbage when the weather was hot?

Explanation / Answer

Answer :

1. Cyanobacteria are photosynthetic bacteria that requires sunlight for carrying out the photosynthesis.

In summer, to capture sunlight they grow over the surface of water.

2. Greenish scum accumulated are due to both cyanobacteria and plants growing due to symbiotic association of cyanobacteria (nostoc and annabaena)

-cyanobacteria possess green pigment bateriochlorphyll

3. Phosphorus is an essential component of nucleic acid. It is required for synthesis of DNA. As cyanobacteria is showing higher growth it would require large amount of phosphorous. Hence depletion of phosphorous will prevent growth of the cyanobacteria by decreasing bacterial DNA synthesis

4. In presence of hot air and cyanobacteria, degradation and decomposition of the organic matter by decomposer get enhanced. This environment is favourable for growth of saprophytes like decomposer fungi and some bacteria.

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