Development of vegetation and environmental conditions in an oligotrophic Danish lake over 40 years
1. Oligotrophic ‘ Lobelia ‐lakes’ are rare in Denmark. The few that have survived widespread eutrophication are in uncultivated sandy regions and are threatened by acidification and increased nutrient deposition from the atmosphere. Grane Langsø was considered the clearest lake in Denmark in the 195...
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Online Access: | http://dx.doi.org/10.1046/j.1365-2427.1998.00338.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2427.1998.00338.x https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2427.1998.00338.x |
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crwiley:10.1046/j.1365-2427.1998.00338.x 2024-06-02T08:10:48+00:00 Development of vegetation and environmental conditions in an oligotrophic Danish lake over 40 years Riis Sand‐jensen 1998 http://dx.doi.org/10.1046/j.1365-2427.1998.00338.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2427.1998.00338.x https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2427.1998.00338.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Freshwater Biology volume 40, issue 1, page 123-134 ISSN 0046-5070 1365-2427 journal-article 1998 crwiley https://doi.org/10.1046/j.1365-2427.1998.00338.x 2024-05-03T12:05:16Z 1. Oligotrophic ‘ Lobelia ‐lakes’ are rare in Denmark. The few that have survived widespread eutrophication are in uncultivated sandy regions and are threatened by acidification and increased nutrient deposition from the atmosphere. Grane Langsø was considered the clearest lake in Denmark in the 1950s, when isoetids grew to 5.5 m depth and characeans covered the deepest part of the lake bottom at 11.5 m. The goal of the study reported here was to examine whether the lake has maintained this high quality by studying the development of macrophyte distribution and composition in relation to the changes in pH, nutrient conditions and transparency over the past 40 years. 2. Aquatic mosses now dominate the vegetation rather than rooted isoetids, probably as a result of acidification (summer median pH was 5.60 in 1958–1963 compared to 5.07 in 1976–1994). Along with a reduced median pH, annual pH fluctuations have increased from about 0.3 units 40 years ago to 0.9 units today. 3. The depth limit of isoetid species has declined markedly and Nitella flexilis , which previously dominated the dense bottom vegetation in the hypolimnion, has disappeared. These changes can be accounted for by reduced light penetration and an increased cover of filamentous green algae and mosses on the isoetid species. 4. The decline in light penetration was mainly caused by increased humic content following storm falls in 1981–84, but increased nutrient deposition may also have stimulated the growth of phytoplankton and filamentous green algae. The restricted macrophyte growth in the hypolimnion during summer can account for the change from oxygen supersaturation 40 years ago to anoxia today. The reduced light penetration has resulted in cooling of the hypolimnion, thereby increasing the stability and duration of thermal stratification. This increases the likelihood of anoxia in August–September. Profound changes in the plant community and in oxygen conditions have occurred, even though the decline of pH has been small and long‐term changes in ... Article in Journal/Newspaper Nitella flexilis Wiley Online Library Grane ENVELOPE(13.385,13.385,65.539,65.539) Langsø ENVELOPE(-20.750,-20.750,75.817,75.817) Freshwater Biology 40 1 123 134 |
institution |
Open Polar |
collection |
Wiley Online Library |
op_collection_id |
crwiley |
language |
English |
description |
1. Oligotrophic ‘ Lobelia ‐lakes’ are rare in Denmark. The few that have survived widespread eutrophication are in uncultivated sandy regions and are threatened by acidification and increased nutrient deposition from the atmosphere. Grane Langsø was considered the clearest lake in Denmark in the 1950s, when isoetids grew to 5.5 m depth and characeans covered the deepest part of the lake bottom at 11.5 m. The goal of the study reported here was to examine whether the lake has maintained this high quality by studying the development of macrophyte distribution and composition in relation to the changes in pH, nutrient conditions and transparency over the past 40 years. 2. Aquatic mosses now dominate the vegetation rather than rooted isoetids, probably as a result of acidification (summer median pH was 5.60 in 1958–1963 compared to 5.07 in 1976–1994). Along with a reduced median pH, annual pH fluctuations have increased from about 0.3 units 40 years ago to 0.9 units today. 3. The depth limit of isoetid species has declined markedly and Nitella flexilis , which previously dominated the dense bottom vegetation in the hypolimnion, has disappeared. These changes can be accounted for by reduced light penetration and an increased cover of filamentous green algae and mosses on the isoetid species. 4. The decline in light penetration was mainly caused by increased humic content following storm falls in 1981–84, but increased nutrient deposition may also have stimulated the growth of phytoplankton and filamentous green algae. The restricted macrophyte growth in the hypolimnion during summer can account for the change from oxygen supersaturation 40 years ago to anoxia today. The reduced light penetration has resulted in cooling of the hypolimnion, thereby increasing the stability and duration of thermal stratification. This increases the likelihood of anoxia in August–September. Profound changes in the plant community and in oxygen conditions have occurred, even though the decline of pH has been small and long‐term changes in ... |
format |
Article in Journal/Newspaper |
author |
Riis Sand‐jensen |
spellingShingle |
Riis Sand‐jensen Development of vegetation and environmental conditions in an oligotrophic Danish lake over 40 years |
author_facet |
Riis Sand‐jensen |
author_sort |
Riis |
title |
Development of vegetation and environmental conditions in an oligotrophic Danish lake over 40 years |
title_short |
Development of vegetation and environmental conditions in an oligotrophic Danish lake over 40 years |
title_full |
Development of vegetation and environmental conditions in an oligotrophic Danish lake over 40 years |
title_fullStr |
Development of vegetation and environmental conditions in an oligotrophic Danish lake over 40 years |
title_full_unstemmed |
Development of vegetation and environmental conditions in an oligotrophic Danish lake over 40 years |
title_sort |
development of vegetation and environmental conditions in an oligotrophic danish lake over 40 years |
publisher |
Wiley |
publishDate |
1998 |
url |
http://dx.doi.org/10.1046/j.1365-2427.1998.00338.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2427.1998.00338.x https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2427.1998.00338.x |
long_lat |
ENVELOPE(13.385,13.385,65.539,65.539) ENVELOPE(-20.750,-20.750,75.817,75.817) |
geographic |
Grane Langsø |
geographic_facet |
Grane Langsø |
genre |
Nitella flexilis |
genre_facet |
Nitella flexilis |
op_source |
Freshwater Biology volume 40, issue 1, page 123-134 ISSN 0046-5070 1365-2427 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1046/j.1365-2427.1998.00338.x |
container_title |
Freshwater Biology |
container_volume |
40 |
container_issue |
1 |
container_start_page |
123 |
op_container_end_page |
134 |
_version_ |
1800756720876650496 |