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Size matters: relationships between body size and body mass of common coastal, aquatic invertebrates in the Baltic Sea

BACKGROUND: Organism biomass is one of the most important variables in ecological studies, making biomass estimations one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry mass or ash-free dry mass (hereafter ‘DM’ vs. ‘AFDM’) per sample; a laborious...

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Autores principales: Eklöf, Johan, Austin, Åsa, Bergström, Ulf, Donadi, Serena, Eriksson, Britas D.H.K., Hansen, Joakim, Sundblad, Göran
Formato: Online Artículo Texto
Lenguaje:English
Publicado: PeerJ Inc. 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5270594/
https://www.ncbi.nlm.nih.gov/pubmed/28149685
http://dx.doi.org/10.7717/peerj.2906
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author Eklöf, Johan
Austin, Åsa
Bergström, Ulf
Donadi, Serena
Eriksson, Britas D.H.K.
Hansen, Joakim
Sundblad, Göran
author_facet Eklöf, Johan
Austin, Åsa
Bergström, Ulf
Donadi, Serena
Eriksson, Britas D.H.K.
Hansen, Joakim
Sundblad, Göran
author_sort Eklöf, Johan
collection PubMed
description BACKGROUND: Organism biomass is one of the most important variables in ecological studies, making biomass estimations one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry mass or ash-free dry mass (hereafter ‘DM’ vs. ‘AFDM’) per sample; a laborious and time consuming process, that often can be speeded up using easily measured and reliable proxy variables like body size or wet (fresh) mass. Another common way of estimating AFDM (one of the most accurate but also time-consuming estimates of biologically active tissue mass) is the use of AFDM/DM ratios as conversion factors. So far, however, these ratios typically ignore the possibility that the relative mass of biologically active vs. non-active support tissue (e.g., protective exoskeleton or shell)—and therefore, also AFDM/DM ratios—may change with body size, as previously shown for taxa like spiders, vertebrates and trees. METHODS: We collected aquatic, epibenthic macroinvertebrates (>1 mm) in 32 shallow bays along a 360 km stretch of the Swedish coast along the Baltic Sea; one of the largest brackish water bodies on Earth. We then estimated statistical relationships between the body size (length or height in mm), body dry mass and ash-free dry mass for 14 of the most common taxa; five gastropods, three bivalves, three crustaceans and three insect larvae. Finally, we statistically estimated the potential influence of body size on the AFDM/DM ratio per taxon. RESULTS: For most taxa, non-linear regression models describing the power relationship between body size and (i) DM and (ii) AFDM fit the data well (as indicated by low SE and high R(2)). Moreover, for more than half of the taxa studied (including the vast majority of the shelled molluscs), body size had a negative influence on organism AFDM/DM ratios. DISCUSSION: The good fit of the modelled power relationships suggests that the constants reported here can be used to quickly estimate organism dry- and ash-free dry mass based on body size, thereby freeing up considerable work resources. However, the considerable differences in constants between taxa emphasize the need for taxon-specific relationships, and the potential dangers associated with ignoring body size. The negative influence of body size on the AFDM/DM ratio found in a majority of the molluscs could be caused by increasingly thicker shells with organism age, and/or spawning-induced loss of biologically active tissue in adults. Consequently, future studies utilizing AFDM/DM (and presumably also AFDM/wet mass) ratios should carefully assess the potential influence of body size to ensure more reliable estimates of organism body mass.
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spelling pubmed-52705942017-02-01 Size matters: relationships between body size and body mass of common coastal, aquatic invertebrates in the Baltic Sea Eklöf, Johan Austin, Åsa Bergström, Ulf Donadi, Serena Eriksson, Britas D.H.K. Hansen, Joakim Sundblad, Göran PeerJ Aquaculture, Fisheries and Fish Science BACKGROUND: Organism biomass is one of the most important variables in ecological studies, making biomass estimations one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry mass or ash-free dry mass (hereafter ‘DM’ vs. ‘AFDM’) per sample; a laborious and time consuming process, that often can be speeded up using easily measured and reliable proxy variables like body size or wet (fresh) mass. Another common way of estimating AFDM (one of the most accurate but also time-consuming estimates of biologically active tissue mass) is the use of AFDM/DM ratios as conversion factors. So far, however, these ratios typically ignore the possibility that the relative mass of biologically active vs. non-active support tissue (e.g., protective exoskeleton or shell)—and therefore, also AFDM/DM ratios—may change with body size, as previously shown for taxa like spiders, vertebrates and trees. METHODS: We collected aquatic, epibenthic macroinvertebrates (>1 mm) in 32 shallow bays along a 360 km stretch of the Swedish coast along the Baltic Sea; one of the largest brackish water bodies on Earth. We then estimated statistical relationships between the body size (length or height in mm), body dry mass and ash-free dry mass for 14 of the most common taxa; five gastropods, three bivalves, three crustaceans and three insect larvae. Finally, we statistically estimated the potential influence of body size on the AFDM/DM ratio per taxon. RESULTS: For most taxa, non-linear regression models describing the power relationship between body size and (i) DM and (ii) AFDM fit the data well (as indicated by low SE and high R(2)). Moreover, for more than half of the taxa studied (including the vast majority of the shelled molluscs), body size had a negative influence on organism AFDM/DM ratios. DISCUSSION: The good fit of the modelled power relationships suggests that the constants reported here can be used to quickly estimate organism dry- and ash-free dry mass based on body size, thereby freeing up considerable work resources. However, the considerable differences in constants between taxa emphasize the need for taxon-specific relationships, and the potential dangers associated with ignoring body size. The negative influence of body size on the AFDM/DM ratio found in a majority of the molluscs could be caused by increasingly thicker shells with organism age, and/or spawning-induced loss of biologically active tissue in adults. Consequently, future studies utilizing AFDM/DM (and presumably also AFDM/wet mass) ratios should carefully assess the potential influence of body size to ensure more reliable estimates of organism body mass. PeerJ Inc. 2017-01-25 /pmc/articles/PMC5270594/ /pubmed/28149685 http://dx.doi.org/10.7717/peerj.2906 Text en ©2017 Eklöf et al. http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited.
spellingShingle Aquaculture, Fisheries and Fish Science
Eklöf, Johan
Austin, Åsa
Bergström, Ulf
Donadi, Serena
Eriksson, Britas D.H.K.
Hansen, Joakim
Sundblad, Göran
Size matters: relationships between body size and body mass of common coastal, aquatic invertebrates in the Baltic Sea
title Size matters: relationships between body size and body mass of common coastal, aquatic invertebrates in the Baltic Sea
title_full Size matters: relationships between body size and body mass of common coastal, aquatic invertebrates in the Baltic Sea
title_fullStr Size matters: relationships between body size and body mass of common coastal, aquatic invertebrates in the Baltic Sea
title_full_unstemmed Size matters: relationships between body size and body mass of common coastal, aquatic invertebrates in the Baltic Sea
title_short Size matters: relationships between body size and body mass of common coastal, aquatic invertebrates in the Baltic Sea
title_sort size matters: relationships between body size and body mass of common coastal, aquatic invertebrates in the baltic sea
topic Aquaculture, Fisheries and Fish Science
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5270594/
https://www.ncbi.nlm.nih.gov/pubmed/28149685
http://dx.doi.org/10.7717/peerj.2906
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