|The effect of temperature on gametogenesis of kelp species Saccharina latissima and Alaria esculenta|
Menger, I. (2019). The effect of temperature on gametogenesis of kelp species Saccharina latissima and Alaria esculenta. MSc Thesis. NIOZ Royal Netherlands Institute for Sea Research: Yerseke. 44 pp.
Seaweeds make up for 10% of the total marine productivity worldwide, making them fundamental players in the storage of carbon dioxide and the supply of oxygen. Their high productivity and capacity of effectively storing nutrients makes seaweeds interesting for cultivation. Seaweed can be used in a wide variety of applications such as extraction of nutrients, pharmaceutical purposes and biofuel. The increasing popularity is primarily seen in Asia, although there is a growing market and interest in Europe, with the European Union as the second largest seaweed importer. In Europe, the most popular seaweeds used for cultivation are kelp species. Kelp can be used for human consumption, hydrocolloid compounds, bioremediation agents and they have great potential in serving as biofuel and feed. Another important aspect making kelp so interesting is their relatively easy life cycle. Most kelps are cultivated by direct release of zoospores onto a culture substrate, but being able to grow out kelp into a controlled lab setup, allows the manipulation of environmental conditions. This is necessary for exploitation and breeding of kelp, but also provides information about how kelp will be affected by potential environmental threats, such as climate change. Climate change causes water temperatures to rise, while water temperature is said to be one of the most important factors influencing distribution, abundance and overall health of kelp species. Studies on the effect of changing temperature on kelp species are essential for cultivation and understanding population dynamics with increasing water temperatures. Two European key kelp species that are found to be susceptible to increasing water temperature are Saccharina latissima and Alaria esculenta. It is suggested by different studies that there are differences between subspecies towards the tolerance of certain parameters during different life cycle phases. However, no experiments or statistical data can state that there actually is a difference in tolerance for certain parameters between latitudinal subspecies. Knowledge about whether there are differences in gametogenesis for certain temperatures between subspecies is considered valuable as this could provide insights in restoring and maintaining kelp forests and can attribute to selective breeding for commercial kelp production. In order to find out whether there are differences in gametogenesis between subspecies as an effect of increasing temperature. Experiments were conducted to find out wat the effect of potential climate change would be per latitudinal subspecies specifically and experiments on the difference in tolerance of the same temperature amongst different subspecies. Male and female gametophytes form each subspecies were mixed together and place in different temperature treatments. However, the experiments did not show any signs of effective gametogenesis, despite each subspecies being tested for gametogenesis prior to the main experiments. A follow-up experiment found out that the use of parafilm to seal culture plates in order to prevent evaporation could have potentially affected the gas exchange of the cultures. The follow-up experiment also found out, that the placement of the light could potentially play a role in gametogenesis. It is recommended to avoid the use of parafilm and to provide light from above onto a culture providing evenly distributed light, rather than from the side.