Rain dissolves fertilizer in the soil. Runoff carries it away. The fertilizer ends up in bodies of water, from ponds to oceans. Nitrogen is a fertilizer in the water. Since there is a lot of nitrogen, it causes algae to grow out of control. Pictured below is a pond covered with algae ( Figure below ). Algae use up carbon dioxide in the water. After the algae die, decomposers break down the dead tissue. The decomposers use up all the oxygen in the water. This creates a dead zone. A dead zone is an area in a body of water where nothing grows because there is too little oxygen. There is a large dead zone in the Gulf of Mexico ( Figure below ). The U.S. states outlined on the map have rivers that drain into the Gulf of Mexico. The rivers drain vast agricultural lands. The water carries fertilizer from these areas into the Gulf.
Mat was planning the company picnic. He was told he could pick between two locations A and B. He knew that several people had expressed interest in fishing and both locations had ponds that had been popular fishing areas years ago. Mat decided he would go visit each pond and see we would be best. Pond A had clear water with lots of plant life. Matt noticed a turtle going into the water. Pond B was completely covered in algae and he did not see any wildlife around the pond.
Which pond should mat choose for the picnic?