Future "Dead Zones" in Mission Bay

       We continued our wonderful adventure of exploring and collecting samples in Tecolote Canyon. This time around we collected water samples from various locations around the canyon specifically North Clairemont, Snead Ave., Mt. Edna, Linda Vista, and Transformer Stations. During the first day of lab, we over-filled the BOD bottles with the specified water samples and let them sit for approximately five days. The initial and final O₂ concentration (ppm) were measured with a dissolved oxygen meter in order to calculate the difference, which yielded the BOD concentration present in water samples around Tecolote Canyon. BOD stands for biochemical oxygen demand, which is the amount of dissolved oxygen needed for biological organisms in a specified body of water to break down organics and survive. The results in lab further explored the possibility of "dead zones" in Mission Bay. 

Cycle of "Dead Zones"

     

     “Dead zones” are often areas of water that contain little to no dissolved oxygen to the point where other marine life cannot survive and die or leave the habitat. The main concern with “dead zones” is that they can be man-created with nutrient pollution. Oftentimes, excess nutrients end up in oceans and rivers through waste and consequently, produce more algae within the waters that consume a great amount of oxygen that leaves less for marine life. 

From our lab data, the Tecolote sampling location with the highest initial O₂ concentration were LV#1 and NC#2 at 11.72ppm and 12.7ppm respectively.  Their final O₂ concentration was significantly smaller,but it did not affect the BOD difference (which still remained small in comparison). ME #2 and PS TT2 water samples had the highest BOD difference in concentration at 5.72ppm and 7 ppm respectively. These zones are potential “dead zones”, but considering the location of Mt.Edna #2 (higher up the canyon) the high BOD difference is mainly due to the run off of nutrients or present organics in the waste. As for the PS TT2 location, the “dead zone” is mostly likely due to run-off. One of the dangers of these possible “dead zones” is that they can continue to spread it nutrients across other water samples in the canyon and eventually end up polluting Mission Bay, which is the closest to the PS TT2 location. If these happens, fishes and marine life will no longer survive or exist in the Bay. Therefore, we should try retesting these areas of water in the future and hopefully see a decrease in BOD concentration for the sake of the Bay. 

Water Sample Sites in Tecolote Canyon with High BOD difference