Earth sciences: We're guano need to recalculate global nutrient cycles

Seabirds excrete approximately 591,000,000 kilograms of nitrogen and 99,000,000 kilograms of phosphorous globally, per year according to a study published in Nature Communications this week. This finding demonstrates that seabird droppings provide nitrogen and phosphorus inputs similar in magnitude to other important processes, such as fishing activities, normally included in the global cycles of these elements.

Nutrients in seabird droppings are an important component of global nutrient cycles. However, although previous studies have quantified the amount of nitrogen excreted by seabirds, global estimates of the amount of phosphorous excreted by seabirds have been lacking.

Miguel Huerta-Diaz, Xose Luis Otero and colleagues apply a global inventory of 320 seabird species to a model that calculates the amount of nitrogen and phosphorus excreted by adult seabirds and their chicks. The authors find that seabird droppings are an important source of nutrients, especially in the Antarctic and Southern Ocean region. They find that the droppings have an important environmental impact near seabird colonies by changing soil and water chemistry and by providing nitrogen and phosphorous in forms that are accessible to plant communities. The authors suggest that seabird colonies in polar and subpolar regions could act as exporting hot spots of these elements to the oceans. These results add to evidence from previous work showing that seabird colonies are a significant source of atmospheric ammonia in remote maritime systems.