Kelp forest community structure and demography in Kongsfjorden (Svalbard) across 25 years of Arctic warming
Abstract The Arctic archipelago of Svalbard is a hotspot of global warming and many fjords experience a continuous increase in seawater temperature and glacial melt while sea‐ice cover declines. In 1996/1998, 2012–2014, and 2021 macroalgal biomass and species diversity were quantified at the study s...
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ftdoajarticles:oai:doaj.org/article:798c3356279a46feaa7bc89f66f00b49 2024-09-15T17:52:14+00:00 Kelp forest community structure and demography in Kongsfjorden (Svalbard) across 25 years of Arctic warming Luisa Düsedau Stein Fredriksen Markus Brand Philipp Fischer Ulf Karsten Kai Bischof Amanda Savoie Inka Bartsch 2024-06-01T00:00:00Z https://doi.org/10.1002/ece3.11606 https://doaj.org/article/798c3356279a46feaa7bc89f66f00b49 EN eng Wiley https://doi.org/10.1002/ece3.11606 https://doaj.org/toc/2045-7758 2045-7758 doi:10.1002/ece3.11606 https://doaj.org/article/798c3356279a46feaa7bc89f66f00b49 Ecology and Evolution, Vol 14, Iss 6, Pp n/a-n/a (2024) age structure biomass coastal darkening depth zonation macroalgae time series Ecology QH540-549.5 article 2024 ftdoajarticles https://doi.org/10.1002/ece3.11606 2024-08-05T17:48:53Z Abstract The Arctic archipelago of Svalbard is a hotspot of global warming and many fjords experience a continuous increase in seawater temperature and glacial melt while sea‐ice cover declines. In 1996/1998, 2012–2014, and 2021 macroalgal biomass and species diversity were quantified at the study site Hansneset, Kongsfjorden (W‐Spitsbergen) in order to identify potential changes over time. In 2021, we repeated the earlier studies by stratified random sampling (1 × 1 m2, n = 3) along a sublittoral depth transect (0, 2.5, 5, 10, and 15 m) and investigated the lower depth limits of dominant brown algae between 3 and 19 m. The maximum fresh weight (FW) of all seaweeds was 11.5 kg m−2 at 2.5 m and to 99.9% constituted of kelp. Although biomass distribution along the depth transect in 2021 was not significantly different compared to 2012/2013, the digitate kelp community (Laminaria digitata/Hedophyllum nigripes) had transformed into an Alaria esculenta‐dominated kelp forest. Consequently, a pronounced shift in kelp forest structure occurred over time as we demonstrate that biomass allocation to thallus parts is kelp species‐specific. Over the past decade, kelp demography changed and in 2021 a balanced age structure of kelps (juveniles plus many older kelp individuals) was only apparent at 2.5 m. In addition, the abundances and lower depth limits of all dominant brown algae declined noticeably over the last 25 years while the red algal flora abundance remained unchanged at depth. We propose that the major factor driving the observed changes in the macroalgal community are alterations in underwater light climate, as in situ data showed increasing turbidity and decreasing irradiance since 2012 and 2017, respectively. As a consequence, the interplay between kelp forest retreat to lower depth levels caused by coastal darkening and potential macroalgal biomass gain with increasing temperatures will possibly intensify in the future with unforeseen consequences for melting Arctic coasts and fjord ecosystem services. Article in Journal/Newspaper Arctic Archipelago Global warming Kongsfjord* Kongsfjorden Sea ice Svalbard Spitsbergen Directory of Open Access Journals: DOAJ Articles Ecology and Evolution 14 6 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
age structure biomass coastal darkening depth zonation macroalgae time series Ecology QH540-549.5 |
spellingShingle |
age structure biomass coastal darkening depth zonation macroalgae time series Ecology QH540-549.5 Luisa Düsedau Stein Fredriksen Markus Brand Philipp Fischer Ulf Karsten Kai Bischof Amanda Savoie Inka Bartsch Kelp forest community structure and demography in Kongsfjorden (Svalbard) across 25 years of Arctic warming |
topic_facet |
age structure biomass coastal darkening depth zonation macroalgae time series Ecology QH540-549.5 |
description |
Abstract The Arctic archipelago of Svalbard is a hotspot of global warming and many fjords experience a continuous increase in seawater temperature and glacial melt while sea‐ice cover declines. In 1996/1998, 2012–2014, and 2021 macroalgal biomass and species diversity were quantified at the study site Hansneset, Kongsfjorden (W‐Spitsbergen) in order to identify potential changes over time. In 2021, we repeated the earlier studies by stratified random sampling (1 × 1 m2, n = 3) along a sublittoral depth transect (0, 2.5, 5, 10, and 15 m) and investigated the lower depth limits of dominant brown algae between 3 and 19 m. The maximum fresh weight (FW) of all seaweeds was 11.5 kg m−2 at 2.5 m and to 99.9% constituted of kelp. Although biomass distribution along the depth transect in 2021 was not significantly different compared to 2012/2013, the digitate kelp community (Laminaria digitata/Hedophyllum nigripes) had transformed into an Alaria esculenta‐dominated kelp forest. Consequently, a pronounced shift in kelp forest structure occurred over time as we demonstrate that biomass allocation to thallus parts is kelp species‐specific. Over the past decade, kelp demography changed and in 2021 a balanced age structure of kelps (juveniles plus many older kelp individuals) was only apparent at 2.5 m. In addition, the abundances and lower depth limits of all dominant brown algae declined noticeably over the last 25 years while the red algal flora abundance remained unchanged at depth. We propose that the major factor driving the observed changes in the macroalgal community are alterations in underwater light climate, as in situ data showed increasing turbidity and decreasing irradiance since 2012 and 2017, respectively. As a consequence, the interplay between kelp forest retreat to lower depth levels caused by coastal darkening and potential macroalgal biomass gain with increasing temperatures will possibly intensify in the future with unforeseen consequences for melting Arctic coasts and fjord ecosystem services. |
format |
Article in Journal/Newspaper |
author |
Luisa Düsedau Stein Fredriksen Markus Brand Philipp Fischer Ulf Karsten Kai Bischof Amanda Savoie Inka Bartsch |
author_facet |
Luisa Düsedau Stein Fredriksen Markus Brand Philipp Fischer Ulf Karsten Kai Bischof Amanda Savoie Inka Bartsch |
author_sort |
Luisa Düsedau |
title |
Kelp forest community structure and demography in Kongsfjorden (Svalbard) across 25 years of Arctic warming |
title_short |
Kelp forest community structure and demography in Kongsfjorden (Svalbard) across 25 years of Arctic warming |
title_full |
Kelp forest community structure and demography in Kongsfjorden (Svalbard) across 25 years of Arctic warming |
title_fullStr |
Kelp forest community structure and demography in Kongsfjorden (Svalbard) across 25 years of Arctic warming |
title_full_unstemmed |
Kelp forest community structure and demography in Kongsfjorden (Svalbard) across 25 years of Arctic warming |
title_sort |
kelp forest community structure and demography in kongsfjorden (svalbard) across 25 years of arctic warming |
publisher |
Wiley |
publishDate |
2024 |
url |
https://doi.org/10.1002/ece3.11606 https://doaj.org/article/798c3356279a46feaa7bc89f66f00b49 |
genre |
Arctic Archipelago Global warming Kongsfjord* Kongsfjorden Sea ice Svalbard Spitsbergen |
genre_facet |
Arctic Archipelago Global warming Kongsfjord* Kongsfjorden Sea ice Svalbard Spitsbergen |
op_source |
Ecology and Evolution, Vol 14, Iss 6, Pp n/a-n/a (2024) |
op_relation |
https://doi.org/10.1002/ece3.11606 https://doaj.org/toc/2045-7758 2045-7758 doi:10.1002/ece3.11606 https://doaj.org/article/798c3356279a46feaa7bc89f66f00b49 |
op_doi |
https://doi.org/10.1002/ece3.11606 |
container_title |
Ecology and Evolution |
container_volume |
14 |
container_issue |
6 |
_version_ |
1810294299554742272 |