I believe the phosphate cycle is the main one due to run-offs from commercial synthetic fertilizers. Use of fertilizers mainly has affected the phosphorus and nitrogen cycles. Plants may not be able to utilize all of the phosphate fertilizer applied; as a consequence, much of it is lost from the land through the water run-off. The phosphate in the water is eventually precipitated as sediments at the bottom of the water body. Without an expensive tertiary treatment, the phosphate in sewage is not removed during various treatment operations. Again an extra amount of phosphate enters the water.
Here's an image depicting the phosphorus cycle:
Leaching and runoff eventually wash much phosphate into aquatic systems, where plants and algae utilize it. Phosphate that is not taken up into the food chain settles to the ocean floor or lake bottom, forming sedimentary rock. Phosphorus can remain locked in sedimentary rock for millions of years, becoming available again through the geological process of uplift.
Over all, agricultural runoff, including fertilizers and sewage, can greatly increase lake nutrient levels and speed up the process of eutrophication. This may result in algal blooms and fish kills. In some areas, exotic species of invertebrates and fish are outcompeting native species.
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