Testing the impacts of a marine heatwave and freshening event on populations of Z. marina from the Swedish west coast
Niemi, Niklas (2022)
Niemi, Niklas
2022
Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2022060945494
https://urn.fi/URN:NBN:fi-fe2022060945494
Tiivistelmä
Marine heatwaves are increasing in their frequency, intensity, and duration. In the study area, the Skagerrak, it is common for marine heatwaves to co-occur with another stressor, freshening events, referring to a rapid decrease in salinity. Several factors may contribute to a species or population’s ability to withstand climatic stressors, such as favourable adaptations, previous exposure to a stressor, or greater genetic diversity. Marine heatwaves have already been linked to devastating losses of marine biodiversity, and freshening can be harmful to organisms, for example by destabilizing the ion equilibrium within the organism. Therefore, it is worth investigating whether previous exposure and genetic diversity may help in increasing a species’ resilience and resistance to the combination of these two co-occurring stressors.
A mesocosm experiment, simulating a marine heatwave and a freshening event, was conducted to determine the responses of the foundation species Zostera marina (eelgrass). For this, Zostera marina plants were sampled from ten different locations in the Kosterhavet archipelago and brought to the Tjärnö Marine Laboratory, located on the west coast of Sweden. It was assumed that these locations had experienced different degrees of variability in both temperature and salinity over the past, and thus, depending on their origin and potential differences in genetics or adaptations, genotypes tested from these locations might respond more robustly to the applied treatment. The measured response variables after the ten-day-long experimental period were growth, number of new leaves, and mortality of Z. marina.
Results from the experiment showed a reduction in the growth of leaves between the treatments, but no differences in the number of leaves were found. When testing the combined response of the Climate change treatment and past exposure (population), no significance was found for any of the measured responses. This could indicate that Z. marina is plastic in its response and that its original location, and the conditions the individuals experienced there, do not matter. As no genetic tests were conducted, it remains unclear whether the individuals used in the experiment were distinct populations or if they belonged to the same tolerant population, potentially explaining the lack of effect from exposure history.
This thesis found reduced growth in Z. marina individuals exposed to a marine heatwave and a co-occurring freshening event, but whether this effect was due to one or both stressors remains unanswered. Further studies should be conducted on this highly important foundation species to disentangle what stressor or combination of stressors will come to affect Z. marina in the future.
A mesocosm experiment, simulating a marine heatwave and a freshening event, was conducted to determine the responses of the foundation species Zostera marina (eelgrass). For this, Zostera marina plants were sampled from ten different locations in the Kosterhavet archipelago and brought to the Tjärnö Marine Laboratory, located on the west coast of Sweden. It was assumed that these locations had experienced different degrees of variability in both temperature and salinity over the past, and thus, depending on their origin and potential differences in genetics or adaptations, genotypes tested from these locations might respond more robustly to the applied treatment. The measured response variables after the ten-day-long experimental period were growth, number of new leaves, and mortality of Z. marina.
Results from the experiment showed a reduction in the growth of leaves between the treatments, but no differences in the number of leaves were found. When testing the combined response of the Climate change treatment and past exposure (population), no significance was found for any of the measured responses. This could indicate that Z. marina is plastic in its response and that its original location, and the conditions the individuals experienced there, do not matter. As no genetic tests were conducted, it remains unclear whether the individuals used in the experiment were distinct populations or if they belonged to the same tolerant population, potentially explaining the lack of effect from exposure history.
This thesis found reduced growth in Z. marina individuals exposed to a marine heatwave and a co-occurring freshening event, but whether this effect was due to one or both stressors remains unanswered. Further studies should be conducted on this highly important foundation species to disentangle what stressor or combination of stressors will come to affect Z. marina in the future.