Identifying shell proxies and the physiological effects of ocean acidification on
bivalve molluscs
C.A. Richardson, A. J. Davies, J.D. Scourse, P. Butler and S.R.N. Chenery1
School of Ocean Sciences, College of Natural Sciences, Bangor University
1
British Geological Survey (BGS), Keyworth, Nottingham.
Global CO2 emissions have increased dramatically over the past several
hundred years (IPCC 2001) and have caused a decline in pH levels resulting in ocean
acidification globally throughout the oceans. Organisms with calcified exoskeletons
are sensitive and vulnerable to ocean acidification particularly in their early life
stages, during the accretion of their shells and hard parts and in their metabolism.
Bivalve mollusc shells are particularly suited to the study of ocean acidification as
they grow incrementally, provide an ontogenetic chronology of environmental change
and are easily collected and maintained in experimental aquaria.
The shells of intertidal bivalves contain an incremental record of their shell
growth in the form of wide tidally deposited growth increments and narrow growth
bands that have been shown to provide a detailed record of the environmental
conditions affecting shell growth (Richardson 2001). Newly metamorphosed and
juvenile mussels Mytilus edulis and cockles Cerastoderma edule will be grown in
experimentally controlled laboratory aquaria under tidal conditions with a series of
ocean acidification scenarios. The aims and objectives of the research are to assess
the influence of ocean acidification conditions on shell formation through a study of
the deposition of the shell using acetate peel replicas and thin shell sections. To
measure changes in the width of the deposited microscopic (50-100um) tidal growth
increments and to investigate the crystalline structure of the shell. The elemental
composition of the incremental growth will be studied using Laser Ablation Plasma
Mass Spectrometry (LA-ICP-MS at BGS) to elucidate whether the processes of
crystal deposition, element incorporation (e.g. as in corals McCulloch et al., 2012)
and shell formation are modified by ocean acidification conditions. Investigations
into feeding behaviour (filtration rates and shell gape measurements) will be
monitored, respiration will be measured in experimental chambers and behaviour
(burrowing, movements and byssus thread deposition) will be observed using video
cameras to ascertain whether the normal patterns of behaviour and physiology are
modified by the experimental ocean acidification scenarios.
The student will receive training in various field sampling (collection of bivalves),
laboratory (animal husbandry, sample preparation and solution-based/Laser Ablation
Inductively-Coupled Plasma mass Spectrometry (LA-ICP-MS)) and physiological techniques
as well as univariate and multivariate statistical techniques. The student will benefit from
collaboration with staff within the sclerochronology group and with analytical geochemists at
British Geological Survey. All PhD students at Bangor undertake a range of approved
transferable skill modules during their first year and students’ presentational skills are
developed through seminar programmes run by the School of Ocean Sciences and College of
Natural Sciences.
IPCC (2001). Climate change 2001: The scientific basis. Contributions of working group 1 to the
Third Assessment Report of the Intergovernmental Panel on climate change.
McCulloch, M., Trotter, J., Montagna, P., Falter, J., Dunbar, R., Freiwald, A., Försterra, G., López
Correa, M., Maier, C., Rüggeberg, A. & Taviani, M. 2012. Resilience of cold-water scleractinian corals
to ocean acidification: Boron isotopic systematics of pH and saturation state up-regulation, Geochimica
et Cosmochimica Acta, 8, Pages 21-34, ISSN 0016-7037, 10.1016/j.gca.2012.03.027.
Richardson, C.A. 2001. Molluscs as archives of environmental change. Oceanography and Marine
Biology - an annual review, 39, 103-164.
Costs: The costs associated with the LA-ICP-MS and solution chemical analyses will
be borne in house by Simon Chenery. Some small items of experimental equipment
e.g. oxygen electrodes (<£200) may need to be purchased using NERC funds
associated with the NERC quota awards. Aquaria and equipment to monitor shell
valve gape are available as well as the facilities to simulate ocean acidification
regimes. There will be small costs associated with the purchase of resin and slides for
the shell sectioning (total costs <£200) and this may be augmented by current projects
in the sclerochronology group. If available some travel costs to work at BGS and
undertake the LA-ICP-MS work will be required (5 trips @£300 = £1500).