The effect of nutrient input on gross primary production in lake ecosystems in urban, suburban and agricultural landscapes
Abstract
Nitrogen and phosphorus runoff produced from human activity can significantly impair water quality and reduce biodiversity in lakes, which may have significant long-term consequences for the overall health of lake ecosystems. An important measure of lake health is gross primary productivity, which is the amount of light energy converted to chemical energy during photosynthesis by aquatic plants and algae. Under low nutrient conditions typical of pristine lakes, gross primary production typically exhibits a positive relationship with nutrient availability. Thus, nutrient supply controls primary production. Our research goal was to identify the relationship between nutrient availability and gross primary production in lakes that experience elevated nutrient availability as a result of human activity. We measured dissolved nitrogen and phosphorus concentrations in nine lakes within urban (3), suburban (3), and agricultural (3) areas in central Minnesota. We deployed dissolved oxygen sensors at a depth of 0.5m and measured gross primary production as the amount of oxygen produced over a 24-hour period in June, July, and August 2014. Our results indicate that dissolved nitrogen (0.27 – 1.75 mg/L) and phosphorus concentrations (27.47 – 96.13 μg/L) were elevated in the study lakes when compared to lakes that do not receive human-induced nutrient runoff. The rate of primary production did not differ between lakes and there was no significant relationship between nitrogen or phosphorus availability and the rate of gross primary production. These results suggest that under the high nutrient conditions observed, primary productivity was not regulated by nitrogen and phosphorus availability. Thus, under high nutrient conditions typical in urban, suburban, and agricultural lakes, the availability of other resources may play an important role in explaining rates of productivity. It is important to identify the potential factors that control primary production under the nutrient-enriched conditions now typical of freshwater ecosystems and to understand how these conditions influence the health and functioning of freshwater ecosystems.
The effect of nutrient input on gross primary production in lake ecosystems in urban, suburban and agricultural landscapes
Nitrogen and phosphorus runoff produced from human activity can significantly impair water quality and reduce biodiversity in lakes, which may have significant long-term consequences for the overall health of lake ecosystems. An important measure of lake health is gross primary productivity, which is the amount of light energy converted to chemical energy during photosynthesis by aquatic plants and algae. Under low nutrient conditions typical of pristine lakes, gross primary production typically exhibits a positive relationship with nutrient availability. Thus, nutrient supply controls primary production. Our research goal was to identify the relationship between nutrient availability and gross primary production in lakes that experience elevated nutrient availability as a result of human activity. We measured dissolved nitrogen and phosphorus concentrations in nine lakes within urban (3), suburban (3), and agricultural (3) areas in central Minnesota. We deployed dissolved oxygen sensors at a depth of 0.5m and measured gross primary production as the amount of oxygen produced over a 24-hour period in June, July, and August 2014. Our results indicate that dissolved nitrogen (0.27 – 1.75 mg/L) and phosphorus concentrations (27.47 – 96.13 μg/L) were elevated in the study lakes when compared to lakes that do not receive human-induced nutrient runoff. The rate of primary production did not differ between lakes and there was no significant relationship between nitrogen or phosphorus availability and the rate of gross primary production. These results suggest that under the high nutrient conditions observed, primary productivity was not regulated by nitrogen and phosphorus availability. Thus, under high nutrient conditions typical in urban, suburban, and agricultural lakes, the availability of other resources may play an important role in explaining rates of productivity. It is important to identify the potential factors that control primary production under the nutrient-enriched conditions now typical of freshwater ecosystems and to understand how these conditions influence the health and functioning of freshwater ecosystems.