Sensitivity of A. islandica and M. edulis towards environmental change: a threat to the bivalves - an opportunity for palaeo-climatology?.

Hiebenthal, Claas (2009) Sensitivity of A. islandica and M. edulis towards environmental change: a threat to the bivalves - an opportunity for palaeo-climatology?. (PhD/ Doctoral thesis), Christian-Albrechts-Universität, Kiel, 137 pp.

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As a major green house gas, CO2 causes global warming which further induces changes in other climate parameters like precipitation and salinity. Additionally as about one-third of the atmospheric CO2 is absorbed by surface waters, the oceans become acidified. Bivalve shell production is costly and should therefore be sensitive to environmental stress. Water pCO2, salinity and temperature changes may be factors that increase physiological stress and thus, can reduce fitness, muscle strength, shell growth, shell stability and finally the bivalves’ ecological performance. The improvement of climate models requires a better understanding of climate history. The ratios of stable Ca isotopes and of divalent substituents of Ca (e.g. Mg and Sr) in bivalve shells depend on seawater temperatures and can therefore theoretically be used as archives of past seawater climates. In two 2-factorial experimental approaches (temperature vs. salinity, temperature vs. pCO2), this work investigates the influence of water temperature, salinity and pCO2 on shell growth, mortality, condition index (Ci = soft tissue weight / shell weight), lipofuscin content in the soft tissue (by fluorometry), shell stability (with a texture analyzer), shell Mg / Ca and Sr / Ca ratios (by optical emission spectrometry) and shell Ca isotope fractionation (Δ44/40Ca, by mass spectrometry) of the two bivalve species Arctica islandica and Mytilus edulis. Additionally, in a feeding assay, we tested the defence capability of M. edulis towards predation by starfish Asterias rubens. Lipofuscin accumulation, growth rates and mortalities indicate that M. edulis is rather an estuarine than a fully marine species. Independent of the respective salinity, however, condition and growth of this species are strongly controlled by temperature. In the Baltic Sea, a positive temperature effect on shell stability will presumably be stronger than a negative salinity effect. A. islandica is a species adapted to high salinity and low temperatures. This could be shown by mortalities and growth rates (salinity) on the one hand and by lipofuscin accumulation, condition index and shell stability (temperature) on the other hand. Both bivalve species that were under investigation in this thesis are largely insensitive to acidifications up to a water pCO2 of about 1400 μatm. Also, the starfish A. rubens did not change its feeding behaviour on M. edulis that were cultured under acidic conditions. Increasing temperature and decreasing salinity, in summary, will most likely shift distributions of M. edulis and A. islandica in the Baltic Sea towards the higher-saline and cooler North-Western areas. It became obvious that most of the shell chemistry characteristics investigated in this study can only be explained by a tightly biologically controlled shell formation. The DSr proxy for seawater Sr / Ca ratios (M. edulis) respectively for salinity (A. islandica) is applicable in both species. The Ca isotope (Δ44/40Ca)-temperature proxy in A. islandica has a shallow slope but is independent of salinity. Δ44/40Ca in M. edulis shells, with regard to our results cannot be used as a temperature proxy. Mg / Ca in M. edulis calcite, however, increases very consistently and exponentially with temperature, though Mg / Ca is influenced by salinity and water pCO2, too.

Document Type: Thesis (PhD/ Doctoral thesis)
Thesis Advisor: Wahl, Martin and Eisenhauer, Anton
Additional Information:
Keywords: Ecology; Climatology; Marine Biology; Mytilus edulis, Arctica islandica, temperature, salinity, ocean acidification, delta44/40Ca, Mg/Ca, Sr/Ca, lipofuscin
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-B Experimental Ecology - Benthic Ecology
Refereed: No
Open Access Journal?: Yes
Date Deposited: 15 Oct 2009 13:38
Last Modified: 19 Apr 2013 12:31

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