Genetic Diversity in Eelgrass

Importance of genetic diversity in eelgrass Zostera marina for its resilience to global warming by Anneli Ehlers, Boris Worm, and Thorsten B. H. Reusch

Ehlers, Anneli & Worm, Boris & Reusch, Thorsten. (2008). Importance of genetic diversity in eelgrass Zostera marina for its resilience to global warming. Marine Ecology-progress Series – MAR ECOL-PROG SER. 355. 1-7. 10.3354/meps07369.

Annotated Bibliography


A german research group sampled eelgrass from the northern baltic waters to test how genotypic diversity can buffer warming waters. This is crucial as climate models show an increase in the future in harsh heat waves which could damage coastal ecosystems as the eelgrass is an ecological engineer and fundamental keystone species that provides for the food web in the surrounding waters. Through their research they were able to determine that there was a 44% loss in eelgrass shoots in 25C degree water compared to ambient water temperature. 25C is significant due to its correlation to the heatwave that happened in 2003. The researchers determined through their research that maintaining variation is crucial for building the resilience in these ecosystems so they will not collapse under sustained periods of heat.


The researchers picked eel grass from the baltic seas in random plots.  After which they created a randomized block 2×3 design where warming water and genotypic diversity were the independent variables and they studied the density of eelgrass growth.  There were 6 tanks that maintained ambient temperatures and then 6 tanks that maintained the temperature of 25C to mimic heatwave experiences in 2003. The eelgrass was put into microcosms to mimic their natural environment. They did try to include some grazing speeches like snails but were not able to include all the typical species that are accompanied by eelgrass. After Which they did a week control period and then a 4 week heating period and then another 6 week normal temperature period to mimic the heatwave of 2003. Throughout this experiment amongst other things the density of eelgrass was recorded.


The microcosms used in the experiment could have led to the discrepancies experienced in the experiment where all but one genotype in a block grew the same. In addition, the results of the experiment were not as dramatic as observed in the field. The researchers only had snail feeders which would mean isopods and amphipods were underrepresented. There was also a presence of a biofilm-forming cyanobacteria that covered 28% of the warm plots which could have skewed the results. While on the notes of warm plots, although the plants were on a diurnal rhythm the paper did not mention an oscillation of heating that might be experienced in the night time when temperatures could lower which could add to the different results than in the field. Due to a small sample size there might have also been representational issues on this front; however, the paper does say their work is still statistically significant. 


This paper did follow the idea of using realistic or previous climate events to drive their experimentation to get a better idea of outcome when genotypic diversity included into the ecosystem. With this being said they were the first to study directly manipulated water temperatures in respect to global temperatures changing with to genotypic diversity as the other independent variable. To provide their statistical analysis they used different tests but  typically used a General Linear Model platform through the Statistica software.

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