In this collaboration with the Universities of Loughborough, Nottingham and University College London, we will be testing the hypothesis that long-range atmospheric deposition of nitrogen (N) is an important driver of ecological change in western Greenland. Temperature in this area has not increased during the 20th century, unlike large parts of the Arctic, but N deposition has increased since the mid-19th century, making this a suitable region for our study.
The project incorporates contemporary ecology, N deposition monitoring and the study of lake sediments. By examining ten areas along a marked precipitation and N deposition gradient we will be able to assess the influence of N inputs to lakes through seasonal monitoring and experimental work. We will use contemporary ecological experiments to determine if phytoplankton are nutrient limited, and whether this is through nitrogen, phosphorus, or co-limitation. We will measure the N content and isotopic fingerprint of rain and snow and aerosol particles. Remarkably few measurements of N deposition exist in the Arctic. Our measurements will contribute to an international focus on long-range atmospheric pollution transport. Finally, these modern studies will be coupled with analyses of lake sediments to establish longer-term trends in SW Greenland.
The Arctic is one of the most vulnerable regions on Earth and there is clear evidence that its ecosystems are changing rapidly. These changes are generally attributed to recent global warming, the effects of which are enhanced in this region. Lakes are an important component in the Arctic landscape. However, many changes seen in the lakes could also be explained by increases in fertility caused by atmospheric deposition of nitrogen. We know from the records preserved in Greenland ice cores that N is deposited in the Arctic from industrial regions many thousands of miles away. Anthropogenic N fixation (conversion of inert N2 to reactive N compounds) is now greater than its natural equivalent and changes in the N cycle are arguably as important as climate change.
Much of the evidence for long-term ecological change in the Arctic comes from lake sediments, which can be dated by natural radioisotopes. Studies show that the composition of algal communities has changed and algal productivity has increased over the past 100 years. Although many researchers think these changes are due to global warming, increased temperature is only one aspect of global environmental change caused by human activity. There are a number of other factors, some indirectly related to climate that could alter community structure in lakes, for example increased rates of weathering or acidification. However, as most arctic lakes are very nutrient poor, any increase in productivity needs an increase in nutrient availability. One important source of nutrients to remote lakes is atmospheric deposition of N. There is evidence from both alpine and arctic lakes that long-term, low level deposition of N may be affecting lake productivity and lake biology.
This project is funded through the Natural Environment Research Council (NERC), Grant NE/G019509/1.
