The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

Advances in the state-of-the-art in the quantitative ecology of the marine megabenthos

Advances in the state-of-the-art in the quantitative ecology of the marine megabenthos
Advances in the state-of-the-art in the quantitative ecology of the marine megabenthos
This study attempts to advance the quantitative ecology of the megabenthos by (i) adopting and developing the use of mass seabed photography, and by(ii) extending body-size-based ecosystem assessment to this group. The metabolic theory of ecology (MTE) builds from simple bio-energetic assumptions of individual metabolism to make predictions about ecological processes from individual structure and functioning, to community and ecosystem dynamics. Under the ‘energetic equivalence rule’, or Damuth’s rule, the population density of living organisms is related to a -3/4 power of body mass, indicating equal resource acquisition across body-size classes. In the marine environment, meio- to macrobenthic assemblages have be usefully modelled as a notional single trophic level, suggesting energetic equivalence throughout the two fractions. That concept is tested here by extension to the megabenthos. The body-size structure of benthic assemblages was examined in four contrasting settings: two shelf-sea sites in the Celtic Sea (Greater Haig Fras marine conservation zone; Shelf-Sea Biogeochemistry area), and two deep sea sites (Porcupine Abyssal Plain sustained observatory, PAP-SO, northeast Atlantic; Clarion-Clipperton Zone, CCZ, northeast Pacific). Imagery data were collected using autonomous underwater vehicles, allowing consistent assessment of the megabenthos in the form of individual-based body-size spectral analyses, over landscape-scale areas encompassing multiple habitat types. For the well-known Celtic Shelf and PAP-SO assemblages, species specific length-weight relationships were used to derive individual biomass data. However, that was not possible for the poorly studied CCZ fauna, prompting the development of a generalised volumetric method for individual body-mass estimation. The MTE framework was used to investigate the effects of seafloor temperature and resource supply on the stocks and flows of mass and energy at these sites. The results of this study demonstrate the practical advantage of mass seabed photography in the quantitative ecological assessment of the megabenthos. The volumetric methodology developed overcomes the taxonomic, temporal, and spatial, dependencies known to impact length-weight relationships. The megabenthos body-size distributions produced were broadly consistent across sites, and generally conformed to the MTE expectations, i.e. controlled by both seafloor temperature and resource supply. These results suggest a much greater ecological significance of the megabenthos than has generally been assumed, i.e. at the PAP-SO site they account for 93% of the total metabolically active standing stock carbon biomass, and 27% of total benthic carbon respiration. Individual-based body-size spectral analyses, coupled with the MTE framework, provide a robust baseline for assessing ecological patterns, and for monitoring change.
University of Southampton
Benoist, Noëlie Marie Aline
9a06e349-0049-49dc-a616-97c43d222a2e
Benoist, Noëlie Marie Aline
9a06e349-0049-49dc-a616-97c43d222a2e
Bett, Brian
61342990-13be-45ae-9f5c-9540114335d9

Benoist, Noëlie Marie Aline (2020) Advances in the state-of-the-art in the quantitative ecology of the marine megabenthos. University of Southampton, Doctoral Thesis, 317pp.

Record type: Thesis (Doctoral)

Abstract

This study attempts to advance the quantitative ecology of the megabenthos by (i) adopting and developing the use of mass seabed photography, and by(ii) extending body-size-based ecosystem assessment to this group. The metabolic theory of ecology (MTE) builds from simple bio-energetic assumptions of individual metabolism to make predictions about ecological processes from individual structure and functioning, to community and ecosystem dynamics. Under the ‘energetic equivalence rule’, or Damuth’s rule, the population density of living organisms is related to a -3/4 power of body mass, indicating equal resource acquisition across body-size classes. In the marine environment, meio- to macrobenthic assemblages have be usefully modelled as a notional single trophic level, suggesting energetic equivalence throughout the two fractions. That concept is tested here by extension to the megabenthos. The body-size structure of benthic assemblages was examined in four contrasting settings: two shelf-sea sites in the Celtic Sea (Greater Haig Fras marine conservation zone; Shelf-Sea Biogeochemistry area), and two deep sea sites (Porcupine Abyssal Plain sustained observatory, PAP-SO, northeast Atlantic; Clarion-Clipperton Zone, CCZ, northeast Pacific). Imagery data were collected using autonomous underwater vehicles, allowing consistent assessment of the megabenthos in the form of individual-based body-size spectral analyses, over landscape-scale areas encompassing multiple habitat types. For the well-known Celtic Shelf and PAP-SO assemblages, species specific length-weight relationships were used to derive individual biomass data. However, that was not possible for the poorly studied CCZ fauna, prompting the development of a generalised volumetric method for individual body-mass estimation. The MTE framework was used to investigate the effects of seafloor temperature and resource supply on the stocks and flows of mass and energy at these sites. The results of this study demonstrate the practical advantage of mass seabed photography in the quantitative ecological assessment of the megabenthos. The volumetric methodology developed overcomes the taxonomic, temporal, and spatial, dependencies known to impact length-weight relationships. The megabenthos body-size distributions produced were broadly consistent across sites, and generally conformed to the MTE expectations, i.e. controlled by both seafloor temperature and resource supply. These results suggest a much greater ecological significance of the megabenthos than has generally been assumed, i.e. at the PAP-SO site they account for 93% of the total metabolically active standing stock carbon biomass, and 27% of total benthic carbon respiration. Individual-based body-size spectral analyses, coupled with the MTE framework, provide a robust baseline for assessing ecological patterns, and for monitoring change.

Text
Benoist, Noelie_PhD_thesis_Oct_2020 - Author's Original
Available under License University of Southampton Thesis Licence.
Download (11MB)

More information

Published date: 19 October 2020

Identifiers

Local EPrints ID: 444730
URI: http://eprints.soton.ac.uk/id/eprint/444730
PURE UUID: 0eed9dcb-383f-411e-a2fd-f99e81c9b9fa
ORCID for Noëlie Marie Aline Benoist: ORCID iD orcid.org/0000-0003-1978-3538

Catalogue record

Date deposited: 02 Nov 2020 17:31
Last modified: 18 Feb 2021 17:28

Export record

Contributors

Author: Noëlie Marie Aline Benoist ORCID iD
Thesis advisor: Brian Bett

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×