AQUATIC PLANTS OF THE ST. CROIX RIVER AND ITS BACKWATERS

Ally Cross, Edgewood High School, Madison, WI (advised by Jerry Kelly and Mekel Wiederholt Meier)
Ruby Herrera, Edgewood High School, Madison, WI (advised by Jerry Kelly and Mekel Wiederholt Meier)

Aquatic Plants are essential to the aquatic ecosystem. The plants provide not only oxygen for the water, but also shelter and food for the aquatic animals, and they protect the shorelines from erosion. Many factors can affect the abundance and species distribution of aquatic plant life. The purpose of the experiment was to determine the ideal environmental conditions and abundance and the type of aquatic plants in the St. Croix River and its backwaters by testing the amount of light reaching the plants, the concentration of carbon dioxide and dissolved oxygen in the water, the pH level, the water depth, the sediment composition, water clarity and the water movement at each site. It was hypothesized that aquatic plants would be more abundant where there is more light, lower amount of Carbon Dioxide, higher amount of oxygen, low water movement, low water depth, low amount of sand in the sediment, and the area would have high water clarity. It was found that submersed plants prosper with little sunlight while emergent plants require more sunlight. Also, it was noted that higher current was a cause for less plant diversity. This shows that more plants are able to grow in areas where there is a low current and only few plants can prosper in an area with faster water movement. The data also showed that more dissolved oxygen in the water resulted in more vegetation in the area. This is due to the fact that plants produce oxygen as a result of photosynthesis. It was also shown that plants flourish in shallower water. The smaller depth of the water allowed the ability of light to reach the plant leaves. In conclusion, the research helped determine the conditions that affect the abundance of plants, plant diversity, and the species that are more likely to prosper in the St. Croix River.