WP 2: Nitrogen as a nutrient

Background

Recent evidence (mostly in North America) has emerged suggesting that base poor upland/mountain aquatic ecosystems are demonstrating a response to atmospheric nitrogen deposition even at very low inputs (e.g. Findlay et al., 1999; Baron et al., 2000; Wolfe et al., 2001; Fenn et al., 2003; Sickman et al., 2003), although some studies have been inconclusive (Burns, 2004). Unpublished research funded by NERC and the EU conducted by Monteith and Pla suggests an atmospheric pollution-related link with recent biological change in Loch Coire Fionnaraich (north-west Scotland). Preliminary results suggest that this change might be linked to nutrient nitrogen enrichment, and similar trends appear to be seen in other remote areas of Europe, e.g., Pyrenees as well as North America. Whether this is independent from or an interaction with climate change has not yet been ascertained. Furthermore, the interactions between acidification and eutrophication or oligotrophication are complex; for example, the aluminium released by acidification may inactivate P through complexation (Kopácek et al., 2001), leading to P limitation. Other work in the UK uplands has used phytoplankton bioassays to show that around three quarters of 30 study lakes are either N limited or co-limited by N and P (Maberly et al., 2002).

Hence for the first time there is direct evidence from the UK that there may be a widespread eutrophication effect of N deposition on upland waters, while the relative contribution of N deposition to eutrophication in the lowlands has never been properly quantified. A key question is therefore how N (as an eutrophier) is affecting the productivity and biodiversity of upland lakes. We have found evidence of long term shifts in diatom species composition in clean areas of the far north-west which mimic changes seen in other remote parts of the northern hemisphere. Can these be related to changing N deposition? May there be varying sensitivity to N deposition between lake types?

We will address these questions through a series of tasks employing literature review, analysis of existing datasets and a palaeolimnological scoping study at a small number of trial sites. An additional Task is then provided for expansion of validated techniques for site-based assessment of nutrient N effects to a selection of sites along the gradient of predicted impacts.

Work programme

The work programme for Work package 2 is split into four main tasks. Click on the links below for further information on an individual task

  • Task 2.1 - Literature review on evidence for eutrophication effects of N deposition in upland waters
  • Task 2.2 - Analysis of existing datasets (deposition, soils, land-cover, topography) to determine relationships between N leaching, N limitation and landscape-scale predictors
  • Task 2.3 - Split into 3 sub tasks:
    • Task 2.3.1 - Palaeolimnological analysis for evidence of biological response to N deposition independent of any acidification response
    • Task 2.3.2 - Bioassays for evidence of current biological response to nutrient N deposition independent of any acidification response
    • Task 2.3.3 - Comprehensive analysis of palaeolimnological evidence for nutrient N response in up to 6 lakes where existing catchment / water chemistry data indicate potential N limitation in Task 2.2
  • Task 2.4 - Review the case for application of critical loads for nutrient N to UK freshwaters, with preliminary assessment of critical load exceedance

References

  • Burns D.A. (2004) The effects of atmospheric nitrogen deposition in the Rocky Mountains of Colorado and southern Wyoming, USA - a critical review. Environmental Pollution 127, 257-269.
  • Baron J.S., Rueth H.M., Wolfe A.M., Nydick K.R., Allstott E.J., Minear J.T. and Moraska B. (2000) Ecosystem responses to nitrogen deposition in the Colorado Front Range. Ecosystems 3, 352-368.
  • Fenn M.E., Baron J.S., Allen E.B., Rueth H.M., Nydick K.R., Geiser L., Bowman W.D., Sickman J.O., Meixner T., Johnson D.W. and Neitlich P. 2003 Ecological effects of nitrogen deposition in the western United States. BioScience 53, 404-420.
  • Findlay D.L., Hecky R.E., Kasian E.M., Stainton M.P., Hendzel L.L. and Schindler E.U. (1999) Effects on phytoplankton of nutrients added in conjunction with acidification. Freshwater Biology 41, 131-145.
  • Kopácek J., Ulrich K.-U., Hejzlar J., Borovec J. and Stuchlík, E. (2001) Natural inactivation of phosphorus by aluminium in atmospherically acidified water bodies. Water Research 35, 3783-3790.
  • Maberly S.C., King L., Dent M.M., Jones R.I. and Gibson C.E. (2002) Nutrient limitation of phytoplankton and periphyton growth in upland lakes. Freshwater Biology 47, 2136-2152.
  • Sickman J.O., Melack J.M. and Clow D.W. (2003) Evidence for nutrient enrichment of high-elevation lakes in the Sierra Nevada, California. Limnology and Oceanography 48, 1885-1892.
  • Wolfe A.P., Baron J.S. and Cornett R.J. (2001) Anthropogenic nitrogen deposition induces rapid ecological change in alpine lakes of the Colorado Front Range (USA). Journal of Paleolimnology 25, 1-7.