On land, dead organisms are broken down by a diversity of decomposers. As the carcass decomposes, the species present on the carcass change over time. What is this situation most similar to in the marine community?
A. The decomposition of marine plants that depletes dissolved oxygen
B. The decomposition of whale carcasses that sink to the ocean floor
C. The microbe community that causes coral bleaching
D. The microbe community that causes global warming

As you know, many plant species live in freshwater. Sometimes these environments receive large amounts of mineral salts used as fertilizer in agriculture and brought to them by rainwater. Other times, in these environments garbage, domestic sewage and industrial waste are discharged, materials generally rich in organic substances. These substances are broken down by microorganisms, which release various mineral salts in water.

Under these conditions, in the presence of large amounts of mineral salts, certain surface aquatic plants can reproduce intensely, forming a "mat" over water. This algae "mat" makes it difficult for light to penetrate water, which affects the photosynthesizing activity of submerged aquatic plants. Thus, submerged aquatic plants cease photosynthesis and therefore cease to release oxygen gas. This causes the death of aerobic beings, such as fish, by asphyxiation. In addition, these submerged plants die in large numbers and are decomposed further reducing the amount of dissolved oxygen.