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Micromorphology of segments in Halimeda tuna and their relation to calcium carbonate precipitation
Čečmanová, Adéla ; Neustupa, Jiří (advisor) ; Němcová, Yvonne (referee)
Algae of the genus Halimeda are important representatives of green algae, thanks to their ability to calcify. Calcification is the process of CaCO3 precipitation in the form of aragonite or calcite, which is then deposited on the bottom of the sea and thus participates in the formation of sedimentary rocks. Relatively small amount of information is known about calcification in representatives of the genus Halimeda, and in particular about its storage and distribution within the plant. One of the representatives of calcifying algae is Halimeda tuna living in the Mediterranean Sea, where it forms a significant part of the underwater vegetation. These algae have a thallus composed of segments, the internal structure of which is formed by utricles - a structure in which the aragonite is deposited. The aim of this work was to find out whether the different sizes of utricles within one segment have an effect on the subsequent spatial distribution of aragonite. The results showed that the distribution of aragonite microcrystals is not dependent on the size of the utricles - it is therefore equally spread across the segment. Furthermore, we investigated whether the calcification process would differ depending on the time of sampling during the year. From our data it appears that this process exhibits some...
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Green algae of the family Halimedaceae and their role in the global ecosystem
Čečmanová, Adéla ; Neustupa, Jiří (advisor) ; Němcová, Yvonne (referee)
Species included in the family Halimedaceae are tropical and subtropical marine algae, belonging to Bryopsidales. The macroscopic siphonocladous thallus of these green algae is attached to the ground via holdfast. Segments of the thallus are able to store CaCO3, i.e. to calcificate. Consequently, dead segments of Halimeda are one of the major producers of seashore sediments. Thanks to beforementioned properties, these organisms play an important role in the global carbon cycle. Interestingly, the species of Halimedaceae are a great tool for studying the global climate change processes. Based on their strictly temperature-defined areas of occurrence in which they are able to grow and reproduce, we can easily observe the effect of increasing temperature of the seawater. Despite the significant role of Halimedaceae in marine ecosystems, these species have so far been relatively neglected in biological research. That was, amongst others, one of the main impulses for writing this thesis. Keywords: aragonite, calcification, ecology, green algae, Halimeda, sediment, segment, utricle
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