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The role of benthic macrofauna in nitrogen cycling in eutrophic lake sediment

Svensson, Jonas Martin LU (1998)
Abstract
This thesis concerns the role of sediment-living macrobenthos in the cycling of nitrogen species and nitrogen transformation in eutrophic freshwater sediments.



In my thesis I have, employing 15N-isotope techniques in laboratory experiments, shown the importance of infaunal chironomid larvae and oligochaetes on denitrification in eutrophic lake sediments. Investigated benthic organisms not only expand the sediment surface with their permanent or non-permanent burrow constructions, they also transport water through the burrows continuously. This behaviour of intermittent water-pumping activity, provides the burrows with oxygen, and in addition, mediates the supply of nitrate to denitrifying zones. The highly dynamic oxygen... (More)
This thesis concerns the role of sediment-living macrobenthos in the cycling of nitrogen species and nitrogen transformation in eutrophic freshwater sediments.



In my thesis I have, employing 15N-isotope techniques in laboratory experiments, shown the importance of infaunal chironomid larvae and oligochaetes on denitrification in eutrophic lake sediments. Investigated benthic organisms not only expand the sediment surface with their permanent or non-permanent burrow constructions, they also transport water through the burrows continuously. This behaviour of intermittent water-pumping activity, provides the burrows with oxygen, and in addition, mediates the supply of nitrate to denitrifying zones. The highly dynamic oxygen climate within and narrow oxic zones around burrows, due to their radial geometry, provides a very short diffusion path for nitrate into surrounding anoxic zones. In my studies rates of denitrification were enhanced c. 3 to 6-fold by the influence of chironomids (Chironomus plumosus) and c. 2-fold by the influence of oligochaetes at comparable biomass. The difference in degree of stimulation is explained by species-specific habitat exploitation which could also be observed between different tube-dwelling species of chironomids. Besides chironomid biomass, the degree of enhancement of denitrification by chironomids was dependent on nitrate concentration in the overlying water, and water temperature. Nitrification was also seen to be stimulated by the infaunal macrobenthos but to a lesser degree than denitrification.



It is suggested that bioturbated eutrophic sediment, under predominantly oxic bottom water conditions may act more pronouncedly as a sink for inorganic nitrogen relative to non-bioturbated sediment, and that bioturbated sediment above all, may be an important factor contributing to lowered transport of nitrogen to the coast. In order to sustain high nitrogen removal capacity in wetlands, ponds and lakes, it is further suggested that survival and establishment of sediment living animals should be faciliated. Such measures could include protection of natural habitats against pollution by pesticides, and cautiousness about introducing bottom-feeding fish in restored or recreated wetlands and lakes. (Less)
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author
opponent
  • Dr Nielsen, Lars Peter
organization
publishing date
type
Thesis
publication status
published
subject
keywords
nitrogen retention, nitrous oxide, oligochaetes, chironomids, mineralisation, nitrification, denitrification, eutrophic, sediment, lake, Macrofauna, nitrogen cycling, fish reduction., Ecology, Ekologi
pages
143 pages
publisher
Department of Limnology, Ecology Building, Sölveg. 37, 223 62 Lund, Sweden
defense location
The Blue Hall, Ecology Building, Lund
defense date
1998-12-18 10:15
external identifiers
  • Other:ISRN: SE-LUNBDS/NBLI-98/1036-143pp
ISBN
91-7105-103-1
language
English
LU publication?
yes
id
4c9307f9-afbb-4681-9874-22c39b2cbb95 (old id 39181)
date added to LUP
2007-08-01 09:21:51
date last changed
2016-09-19 08:45:05
@phdthesis{4c9307f9-afbb-4681-9874-22c39b2cbb95,
  abstract     = {This thesis concerns the role of sediment-living macrobenthos in the cycling of nitrogen species and nitrogen transformation in eutrophic freshwater sediments.<br/><br>
<br/><br>
In my thesis I have, employing 15N-isotope techniques in laboratory experiments, shown the importance of infaunal chironomid larvae and oligochaetes on denitrification in eutrophic lake sediments. Investigated benthic organisms not only expand the sediment surface with their permanent or non-permanent burrow constructions, they also transport water through the burrows continuously. This behaviour of intermittent water-pumping activity, provides the burrows with oxygen, and in addition, mediates the supply of nitrate to denitrifying zones. The highly dynamic oxygen climate within and narrow oxic zones around burrows, due to their radial geometry, provides a very short diffusion path for nitrate into surrounding anoxic zones. In my studies rates of denitrification were enhanced c. 3 to 6-fold by the influence of chironomids (Chironomus plumosus) and c. 2-fold by the influence of oligochaetes at comparable biomass. The difference in degree of stimulation is explained by species-specific habitat exploitation which could also be observed between different tube-dwelling species of chironomids. Besides chironomid biomass, the degree of enhancement of denitrification by chironomids was dependent on nitrate concentration in the overlying water, and water temperature. Nitrification was also seen to be stimulated by the infaunal macrobenthos but to a lesser degree than denitrification.<br/><br>
<br/><br>
It is suggested that bioturbated eutrophic sediment, under predominantly oxic bottom water conditions may act more pronouncedly as a sink for inorganic nitrogen relative to non-bioturbated sediment, and that bioturbated sediment above all, may be an important factor contributing to lowered transport of nitrogen to the coast. In order to sustain high nitrogen removal capacity in wetlands, ponds and lakes, it is further suggested that survival and establishment of sediment living animals should be faciliated. Such measures could include protection of natural habitats against pollution by pesticides, and cautiousness about introducing bottom-feeding fish in restored or recreated wetlands and lakes.},
  author       = {Svensson, Jonas Martin},
  isbn         = {91-7105-103-1},
  keyword      = {nitrogen retention,nitrous oxide,oligochaetes,chironomids,mineralisation,nitrification,denitrification,eutrophic,sediment,lake,Macrofauna,nitrogen cycling,fish reduction.,Ecology,Ekologi},
  language     = {eng},
  pages        = {143},
  publisher    = {Department of Limnology, Ecology Building, Sölveg. 37, 223 62 Lund, Sweden},
  school       = {Lund University},
  title        = {The role of benthic macrofauna in nitrogen cycling in eutrophic lake sediment},
  year         = {1998},
}