Dissertation: Effect of catchment characteristics on dietary resource use and condition of freshwater pearl mussel (Margaritifera margaritifera)
Freshwater pearl mussel (Margaritifera margaritifera) is a critically endangered keystone species that lives in oligotrophic headwater rivers. When abundant, it provides important ecosystem services due to its filter feeding activity, such as clearance of water. The study, conducted in northern Finland, aimed to understand the dietary requirements of pearl mussel, and how anthropogenic pressures affect this species. The study examined mussels and 26 environmental variables across 29 rivers. I employed fatty acid, stable isotope, mussel condition and age analyses, as well as water quality and catchment land use data.
Pearl mussel has a strong connection to surrounding terrestrial ecosystem
Organic matter originated from the terrestrial environment turned out to be the major energy source of pearl mussel, suggesting an important link to surrounding land. However, the terrestrial contribution to assimilated carbon—and the terrestrial connectivity—appeared to weaken with increasing anthropogenic pressures. On the other hand, the essential role of phytoplankton, particularly diatoms, in nutrition of mussels, to receive the essential fatty acids was also observed. However, in areas with higher anthropogenic pressures, and more productive waters, mussels relied more on phytoplankton and less on terrestrial or bacterial sources.
Condition of mussels increased when anthropogenic impact decreased
Most importantly, shell growth rate and condition of pearl mussel individuals increased with decreasing anthropogenic pressures. Better growth and condition of mussels was associated to lower productivity of water and less peatland, less forestry, less agriculture area and less ditching on catchment—as well as lower annual temperature, more northern location, more mineral soils, more conservation area, more publicly owned forest and, in general, more forests in catchment.
Conservation areas important for freshwater pearl mussel
These findings underscore the importance of pristine river environments, nature protection areas, and mitigation of human impacts through land use and catchment management practices for conservation of the species. As an umbrella species, protecting pearl mussel also safeguards a wide array of associated species, such as their obligatory host fishes salmon and trout, reinforcing the interconnectedness of riverine and terrestrial habitats. The eldest pearl mussel individual in this study had reached the remarkable age of 248 years, illustrating how unique species the freshwater pearl mussel is.
The examination of Mahsa Hajisafarali thisis:"Effect of catchment characteristics on dietary resource use and condition of freshwater pearl mussel (Margaritifera margaritifera)" will be held on 24.5.2024 at 12:00-16:00 in ³Û±ô¾±²õ³Ùö²Ô°ù¾±²Ô²Ô±ð FYS1.
The Opponent is Professor Timo Muotka (University of Oulu) and the custos is Senior Researcher Mikko Kiljunen (Ä¢¹½Ö±²¥).
The dissertation "Effect of catchment characteristics on dietary resource use and condition of freshwater pearl mussel (Margaritifera margaritifera)" can be read on the JYX publication archieve:
