Do seagrasses feel the heat? Assessing the potential for microevolutionary change in a marine ecosystem engineering plant in response to global warming

Bergmann, Nina (2012) Do seagrasses feel the heat? Assessing the potential for microevolutionary change in a marine ecosystem engineering plant in response to global warming (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 133 pp

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Abstract

A central question in ecology is how organisms react to changing environmental conditions induced by global climate change. This is particularly important for ecosystem engineering species, as the fate of whole ecosystems is depending upon their performance and survival. In coastal marine habitats, seagrasses are of outstanding importance as ecosystem builders. Eelgrass, the study species of this thesis, is the most widespread and locally abundant seagrass along soft-sediment coasts of the northern hemisphere. In this thesis I assessed variation among and within eelgrass populations in response to heat stress. I conducted heat stress experiments in a “common stress garden”, simulating a summer heat wave of three weeks followed by a recovery phase. I measured various physiological parameters and assessed the expression profile of selected heat stress associated genes with qPCR as well as the whole transcriptome with next generation sequencing using eelgrass with differing thermal history (a southern population from the Mediterranean Sea and northern populations from the Kattegat and Limfjord, Baltic Sea). To assess variation within populations, I used genotypes originating from a Baltic population. I found that different genotypes showed varying growth rates in control and heat treatment at acute heat stress, but that all populations lost shoots in response to the heat wave, irrespective of their thermal pre-adaptation. While populations diverged in their expression profiles of selected heat stress associated genes already at the onset of heat stress, subsequent global transcription profiling revealed that those effects were of relatively minor importance compared to massive differences in gene expression during the recovery phase between two of the populations. This is in line with findings on the genotype level within one population which showed differences in the expression profiles of selected stress-associated genes between replicated individuals only in the recovery phase. This thesis provides a basis for investigating the potential for microevolution of eelgrass populations in the face of global climate change. Both, cold- as well as warm adapted eelgrass populations responded to heat stress with shoot reduction, a finding that is in line with worldwide records of seagrass decline. On the other hand, there is considerable variation for heat stress-related gene expression within populations, a trait that is likely to be important under global change. As this variation among genotypes is the prerequisite for natural selection and adaptation, populations may succeed to persist.

Document Type: Thesis (Doctoral thesis/PhD)
Thesis Advisors: Reusch, Thorsten B.H. and Olsen, Jeanine
Keywords: seagrass, Zostera marina, global change, gene expression, heat stress
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EV Evolutionary Ecology of Marine Fishes
Date Deposited: 10 Jan 2013 12:59
Last Modified: 10 Jan 2013 12:59
URI: http://eprints.uni-kiel.de/id/eprint/19988

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