Browsing by Subject "Baltic Sea"
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(2022)The Baltic Sea is undergoing changes due to climate change, including an increase in its temperature. This may in turn lead to changes in the traits of the species that inhabit it, including non-endemic, invasive species. Palaemon elegans is a species native to the Atlantic Ocean that has been present in the Baltic Sea since the beginning of this century. Abilities such as high thermal tolerance make it successful in colonising new ecosystems like the brackish waters of this sea. However, less is known about the behavioural traits’ adaptions to these changes. This study aims then to find out how climate change may affect the behaviour of this species. To do so, five behaviours expressed by this species were observed and analysed to see how temperature change, seabed composition and body size influence their expression. The behaviours analysed were aggressiveness, movement frequency, reaction to food stimulus, number of feeding interactions and shelter-seeking. Analyses were conducted using ten-minute videos with ten specimens of P. elegans placed in water tanks and interacting in ecosystems representations with elements typical of the seabed where this species lives, both vegetation and rocks. Student's t-tests in R were then performed to test the significance of possible differences between the behaviours studied and the three parameters that may influence their expression. The results obtained show that the increase in water temperature might indeed lead to an increase in the frequency of the five behaviours studied except in aggressiveness. On the other hand, it was found that the composition of the ecosystem does not have a significant influence overall, while body size has a major influence on feeding related behaviours. Therefore,knowing more about changes in the behavior of species susceptible to climate change can be helpful to understand how biodiversity and its distribution will vary in the not so distant and changing future and what consequences it may generate at the ecosystem level.
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(2021)Eutrophication and climate change are considered to be the worst threats to the Baltic Sea ecosystem. The goal of this work is to understand, what are the consequences of environmental change to the distribution of Fucus spp., one of the key species of the Baltic Sea. Of particular interest here is to find the role of light and water turbidity in defining Fucus spp. distribution since scenario models of the effect of water turbidity defining the distribution has yet remained less studied. Nemo-SCOBI model of physical and biogeochemical conditions of the Baltic Sea calibrated according to different eutrophication and climate change scenarios were used in species distribution modelling (SDM) to predict future distribution of Fucus spp. The SDM method that was used was a regression-tree-based machine-learning generalized boosting method (GBM). In the modelling over 30 000 species presence and absence observations and six environmental variables (temperature, salinity, light attenuation, depth attenuated wave exposition and two seafloor types) were used. Water turbidity decreased in all scenarios in the areas where Fucus spp. occur but the BSAP was more beneficial scenario than the worst case scenario. Salinity decreased more and temperature increased less in the RCP8.5 scenario than in the RCP4.5 scenario. On top of that temperature decreased in the west coast of Finland in the RCP8.5 scenario. Suitable area for Fucus spp. declined in all scenarios so that the average occurrence probability decreased 11–30 percentage points. If no climate and eutrophication objectives (the Baltic Sea Action Plan and the RCP4.5) were met the average occurrence probability declined 25 percentage points. The situation for Fucus spp. is quite alarming because even if all the objectives would be achieved the suitable environment will nevertheless decline. If no actions will be taken in order to reduce nutrients the average occurrence probability declines 11–25 percentage points. Temperature decline in the RCP8.5 scenarios is thought to be caused by increasing upwelling events in the future, which may increase nutrient amounts in the coastal waters. The weak response to light and temperature and strong response to salinity and the fact that salinity decreased in all scenarios may explain why suitable areas decreased in all scenarios. There were some inconsistencies between the results and literature since the most optimistic scenario was the RCP4.5 & worst case, where BSAP goals are not achieved. This can be due to lack of species observations in the whole environmental gradients. The prediction results in the areas where water will be clearer in the future are not reliable and presumably more positive than these results show. While the BSAP scenarios may be too pessimistic the results of worst case scenarios are more reliable.
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(2023)Zooplankton are an important link in marine pelagic food webs as they transfer energy from primary producers to higher trophic levels such as planktivorous fish. They migrate vertically in the water column, ascending to feed near the surface at night and descending to hide from visual predators for the day (diel vertical migration, DVM). Zooplankton are detected with Acoustic Doppler Current Profilers (ADCPs). These devices were developed for measuring water currents using acoustic pulses, a technique which requires particles such as zooplankton in the water column to scatter the sound. As a by-product of the velocity measurements, it provides information of these scatterers as echo intensity. This method has been used in researching zooplankton DVM, however, not in the northern Baltic Sea prior to this study. In this thesis, the data processing steps required to analyze echo intensity were examined for the specific environment of the Finnish Archipelago Sea. A one-year-long time-series was processed and averaged seasonally to investigate different patterns in zooplankton DVM. Vertical velocity data were used in estimating migration speed, and available reference measurements were combined to the data to examine the environmental factors affecting zooplankton DVM. Synchronized DVM was observed especially in autumn, however, indications of other migration patterns such as unsynchronized and reverse migration were detected during summer and winter, respectively. The primary cue behind zooplankton DVM was light, but additional contributing factors such as phytoplankton and currents were identified and discussed. The maximum migration speeds detected were approximately 10 cm/s downwards and 4 cm/s upwards. ADCP data are a good indicator of zooplankton migration in the northern Baltic Sea and in the future, it could prove beneficial in zooplankton monitoring and biomass estimates.
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