The effects of ocean acidification on juvenile Haliotis iris

The world's oceans are increasing in levels of anthropogenic CO2 resulting in reductions in seawater pH and the availability of carbonate ions which are essential to calcifying marine species. Ocean acidification is considered to be a potential threat to marine populations through changes to su...

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Bibliographic Details
Main Author: Cunningham, Shaun Christopher
Other Authors: Lamare, Miles
Format: Thesis
Language:English
Published: University of Otago 2013
Subjects:
Online Access:http://hdl.handle.net/10523/4434
id ftunivotagoour:oai:ourarchive.otago.ac.nz:10523/4434
record_format openpolar
institution Open Polar
collection University of Otago: Research Archive (OUR Archive)
op_collection_id ftunivotagoour
language English
topic Ocean acidification
Paua
Abalone
Aquaculture
Shell mineralogy
Haliotis iris
spellingShingle Ocean acidification
Paua
Abalone
Aquaculture
Shell mineralogy
Haliotis iris
Cunningham, Shaun Christopher
The effects of ocean acidification on juvenile Haliotis iris
topic_facet Ocean acidification
Paua
Abalone
Aquaculture
Shell mineralogy
Haliotis iris
description The world's oceans are increasing in levels of anthropogenic CO2 resulting in reductions in seawater pH and the availability of carbonate ions which are essential to calcifying marine species. Ocean acidification is considered to be a potential threat to marine populations through changes to survival, growth and calcification. Very little information exists on the effects of reduced seawater pH on abalone molluscs, particularly the New Zealand black-foot abalone Haliotis iris. This thesis aimed to investigate the effects of reduced seawater pH, through elevating the partial pressure of carbon dioxide, on the growth, biomineralisation and respiration of juvenile H. iris. To assess the impacts of acidification, post-settlement (initial length 4-10 mm) and 30--40 mm juvenile H. iris were exposed to long-term (two separate 100 day experiments) pH levels of ambient pH, pH 7.8 and pH 7.6 across autumn/winter (6.4-11.6oC) and spring/summer (13.0-19.5oC) temperatures, and measured; survival, growth, and shell deposition, repair, microstructure, mineralogy and also metabolism in the form of oxygen consumption. The experiments were conducted using a flow-through design, and each pH treatment had three replicate 16 L aquaria containing equal numbers of abalone. Juvenile survival appeared to be unaffected by acidification, however, other sub-lethal changes were found. After 100 days of experimental exposure, the relative growth rate of shell length was 9%, and wet weight was 50% lower for post-settlement juveniles reared at pH 7.6 in comparison to ambient pH during the autumn/winter. Larger 30-40 mm juveniles exposed to ambient pH had a 1.2% greater RGRSL than pH 7.6 juveniles. During the spring/summer growth trial, growth differences among treatments were more pronounced with post-settlement ambient pH juveniles growing 160% and 1500% in shell length and wet weight respectively, in comparison to only 99% and 800% gains in post-settlement pH 7.6 juveniles. Growth was also significantly greater for 30-40 mm H. iris grown in ambient pH, although differences among treatments were not as pronounced as post-settlement growth. The pH 7.8 treatment also significantly reduced growth in both size-classes, but not as substantially as the pH 7.6 treatment. Shell deposition and mineralogy were significantly reduced by declines in seawater pH and the sensitivity to acidification was found to decrease with increasing body size. X-ray diffraction results found that ambient pH-reared post-settlement juveniles had a 15% higher calcite weight % in their shell in comparison to juveniles reared at pH 7.6. Scanning electron micrographs and XRD of juvenile shells indicated substantial dissolution of the outer calcitic layer of post-settlement juvenile shells following prolonged low pH exposure, however, larger juveniles were generally unaffected. A shell repair experiment showed that shell damage decreases growth of juvenile H. iris, and when coupled with reduced seawater pH the effects were additive, and in addition scanning electron micrographs indicated shell repair was inhibited by low pH conditions. No changes to soft-tissue growth or oxygen consumption were found leading to the proposal that juvenile H. iris suffer a growth delay and do not upregulate metabolism under long-term pH stress. The results suggest there is a shift in the energy budget of juvenile H. iris with resources invested into survival and somatic mass, however, juveniles do not upregulate metabolism to maintain normal growth or to combat shell dissolution pressure by low pH seawater. Overall, ocean acidification has the potential to cause detrimental effects to the juvenile stages of abalone, creating concerns for future aquaculture and ecosystem management.
author2 Lamare, Miles
format Thesis
author Cunningham, Shaun Christopher
author_facet Cunningham, Shaun Christopher
author_sort Cunningham, Shaun Christopher
title The effects of ocean acidification on juvenile Haliotis iris
title_short The effects of ocean acidification on juvenile Haliotis iris
title_full The effects of ocean acidification on juvenile Haliotis iris
title_fullStr The effects of ocean acidification on juvenile Haliotis iris
title_full_unstemmed The effects of ocean acidification on juvenile Haliotis iris
title_sort effects of ocean acidification on juvenile haliotis iris
publisher University of Otago
publishDate 2013
url http://hdl.handle.net/10523/4434
geographic New Zealand
geographic_facet New Zealand
genre Ocean acidification
genre_facet Ocean acidification
op_relation http://hdl.handle.net/10523/4434
op_rights All items in OUR Archive are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
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spelling ftunivotagoour:oai:ourarchive.otago.ac.nz:10523/4434 2023-05-15T17:50:53+02:00 The effects of ocean acidification on juvenile Haliotis iris Cunningham, Shaun Christopher Lamare, Miles 2013-11-15T00:43:18Z application/pdf http://hdl.handle.net/10523/4434 en eng University of Otago http://hdl.handle.net/10523/4434 All items in OUR Archive are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated. Ocean acidification Paua Abalone Aquaculture Shell mineralogy Haliotis iris Thesis or Dissertation 2013 ftunivotagoour 2022-05-11T19:16:37Z The world's oceans are increasing in levels of anthropogenic CO2 resulting in reductions in seawater pH and the availability of carbonate ions which are essential to calcifying marine species. Ocean acidification is considered to be a potential threat to marine populations through changes to survival, growth and calcification. Very little information exists on the effects of reduced seawater pH on abalone molluscs, particularly the New Zealand black-foot abalone Haliotis iris. This thesis aimed to investigate the effects of reduced seawater pH, through elevating the partial pressure of carbon dioxide, on the growth, biomineralisation and respiration of juvenile H. iris. To assess the impacts of acidification, post-settlement (initial length 4-10 mm) and 30--40 mm juvenile H. iris were exposed to long-term (two separate 100 day experiments) pH levels of ambient pH, pH 7.8 and pH 7.6 across autumn/winter (6.4-11.6oC) and spring/summer (13.0-19.5oC) temperatures, and measured; survival, growth, and shell deposition, repair, microstructure, mineralogy and also metabolism in the form of oxygen consumption. The experiments were conducted using a flow-through design, and each pH treatment had three replicate 16 L aquaria containing equal numbers of abalone. Juvenile survival appeared to be unaffected by acidification, however, other sub-lethal changes were found. After 100 days of experimental exposure, the relative growth rate of shell length was 9%, and wet weight was 50% lower for post-settlement juveniles reared at pH 7.6 in comparison to ambient pH during the autumn/winter. Larger 30-40 mm juveniles exposed to ambient pH had a 1.2% greater RGRSL than pH 7.6 juveniles. During the spring/summer growth trial, growth differences among treatments were more pronounced with post-settlement ambient pH juveniles growing 160% and 1500% in shell length and wet weight respectively, in comparison to only 99% and 800% gains in post-settlement pH 7.6 juveniles. Growth was also significantly greater for 30-40 mm H. iris grown in ambient pH, although differences among treatments were not as pronounced as post-settlement growth. The pH 7.8 treatment also significantly reduced growth in both size-classes, but not as substantially as the pH 7.6 treatment. Shell deposition and mineralogy were significantly reduced by declines in seawater pH and the sensitivity to acidification was found to decrease with increasing body size. X-ray diffraction results found that ambient pH-reared post-settlement juveniles had a 15% higher calcite weight % in their shell in comparison to juveniles reared at pH 7.6. Scanning electron micrographs and XRD of juvenile shells indicated substantial dissolution of the outer calcitic layer of post-settlement juvenile shells following prolonged low pH exposure, however, larger juveniles were generally unaffected. A shell repair experiment showed that shell damage decreases growth of juvenile H. iris, and when coupled with reduced seawater pH the effects were additive, and in addition scanning electron micrographs indicated shell repair was inhibited by low pH conditions. No changes to soft-tissue growth or oxygen consumption were found leading to the proposal that juvenile H. iris suffer a growth delay and do not upregulate metabolism under long-term pH stress. The results suggest there is a shift in the energy budget of juvenile H. iris with resources invested into survival and somatic mass, however, juveniles do not upregulate metabolism to maintain normal growth or to combat shell dissolution pressure by low pH seawater. Overall, ocean acidification has the potential to cause detrimental effects to the juvenile stages of abalone, creating concerns for future aquaculture and ecosystem management. Thesis Ocean acidification University of Otago: Research Archive (OUR Archive) New Zealand