DON AND ESTUARINE WATER QUALITY:
THE FORGOTTEN NITROGEN POOL
Eric P. Achterberg1,2, E-S Badr1 and Alan Tappin1
1
University of Plymouth, School of Earth, Ocean and Environmental Sciences, PL4 8AA
Plymouth, UK.
2
Present address: University of Southampton, Southampton Oceanography Centre,
School of Ocean and Earth Science, SO14 3ZH European Way Southampton, UK.
Nitrogen inputs into estuarine and coastal waters are increasing, with important negative
impacts on ecosystem functioning. Studies on nitrogen in natural waters have generally
focussed on dissolved inorganic nitrogen (DIN), primarily because of relative ease of
analysis and the important influence of DIN on water quality. Advances in analytical
techniques now permit the systematic study of dissolved organic nitrogen (DON). We
have undertaken a programme of research lasting 2 years in the Plym and the Yealm
estuaries (south-west England) to elucidate the inputs, distribution and fate DON. This
work has shown that DON was quantitatively significant in these waters, with DON/TDN
ratios ranging between ca. 20-70%. Highest ratios were typically encountered in late
summer.
Additional laboratory bioassay experiments have shown that a significant fraction of the
DON is bioavailable within the water residence time of the estuaries, and hence DON
appears to be a forgotten nitrogen pool with an important eutrophication potential.
Corresponding author: eric@soc.soton.ac.uk