Parameters of antimicrofouler defence after different heat wave regimes in eelgrass Zostera marina

Density of bacteria on Zostera marina, activity strength of Zostera marina surface extract against bacterial settlers and Rosmarinic acid concentration in Zostera marina leaf surface extracts, measured in May, July and August after three different heatwave regimes simulated in outdoor mesocosms at Kiel/Germany. To investigate the consequence of heatwaves on the chemical defense of eelgrass against microbial colonizers Z. marina plants were incubated in the Kiel Outdoor Benthocosm system under ambient control conditions and two different heatwave treatments: a treatment experiencing two spring heatwaves followed by a summer heatwave, and a treatment only experiencing just the summer heatwave. The capacity to deter microbial colonizers was found to be significantly up-regulated in Z. marina from both heatwave treatments in comparison to Z. marina under control conditions, suggesting defense regulation of Z. marina in response to marine heatwaves.