The effect of temperature and dissolved organic carbon on the mercury uptake in fish
Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
The rising mercury levels found in many Scandinavian rivers and lakes and its effect on the aquatic biota and their food chains is still not fully explored and likely underestimated. Since the Industrialisation in the 20th century, mercury (Hg) is a indispensable metal for today’s economy resulting in great atmospheric inputs and Hg distribution over the whole planet. If Hg reaches an aquatic ecosystem, a certain fraction methylates into methylmercury (MeHg). MeHg is a very toxic substance and might bioaccumulate and biomagnify in aquatic food chains, meaning increasing Hg concentrations in biomass at higher trophic levels. The amount of Hg that is uptaken and stored by fish can be influenced by different water-temperatures and dissolved organic carbon (DOC) input. In order to understand the effects of both factors regarding the Hg uptake in fish, this study investigates the Hg concentration in fish that were raised in different treated water pools. The experimental set-up consisted of pools that were either cold and without additional DOC, cold with additional DOC, warm without additional DOC and warm with additional DOC. I found that Hg uptake in fish increased in pools with colder temperature and additional DOC input. However, changes in water-temperature might enhance as well as diminish Hg bioaccumulation, depending on the environmental circumstances like aquatic biota or water chemistry. Furthermore the experiment showed a varying Hg uptake in fish over the sampling time from July, September and Octobre 2013. This outcome demonstrates that increasing Hg levels in fish depend on the time that is given to store and bioaccumulate this substance.
Hence, the results confirm the hypotheses of increasing Hg uptake in fish due to additional DOC input and colder water-temperature. This study also highlights the importance of further and more extensive research on the aquatic mercury cycle and especially the different environmental factors affecting the Hg uptake in fish.
Place, publisher, year, edition, pages
mercury, aquatic mercury cycle, methylmercury, temperature, dissolved organic carbon (DOC), bioaccumulation, biomagnification
IdentifiersURN: urn:nbn:se:umu:diva-104620OAI: oai:DiVA.org:umu-104620DiVA: diva2:820582
Subject / course
Examensarbete i Naturgeografi för kandidatexamen
Bachelor of Science in Biology and Earthscience